2012 3.0L TKS runs great with muffs, but slow on lake...

[GeorgioP07]

I saw new fuel pump but was fuel pump pressure measured under load ?

my other hobby is old cars - its a chronic issue with mechanical fuel pumps these days - the pressure output is all over the place, even on what was historically considered good brands

I stated in OP that I did not test the fuel pressure.

 

[GeorgioP07]

Jumping in late on trying to noddle this issue that is perplexing and get the OP back on the water. To help with that below is a summary to date with some items that are perplexing (perhaps only to) me.

• Bought late last season all was good and ran WOT at 35+ MPH.
• Did a bunch of maintenance items last season and still ran good at 35+ MPH (this is implied but if not the case, please correct)
• Self-winterization
• This season issues with idling > needs to be at 900 (vs 750) and does the shake and will not get above 15 MPH / 2900 RPM at WOT
• Lots of items replaced / checked including
  • New fuel pump
  • Rebuilt carb
  • Timing including the advance
  • Compression was a little higher than normal. Also I do not understand “let the gauge sit for a few minutes on each cylinder test, and there was no leaking”. And OP noted one of the plugs had a loose electrode insulator.

An indication that the test of of pulling plug wires one at a time to note the RPM drop was done BUT I am usure this has been done. There was a “spark test” in post #3 but was not a pull the plug wire and note the RPM drop that I can see. OP is going to do that test again to be sure (post # 36).

Given the rough idle + needing to be higher than usual + poor performance on the water I am leaning to a cylinder not contributing.

My suggestion:

1. Pull all the plugs and disable the coil (unplug the dizzy) and while a helper is turning the motor over, look for any spray or mist that is coming out of the spark plug holes.
2. Put back together and redo the pull one spark plug wire at a time while engine is idling and note RPM drop. Note: when reinstalling the plug wires from test 1 above, put it on enough to ensure a good connection but not fully. This will make it easier to pull off the wire. When you initially start the motor if its running rougher than normal, one of those wires needs to be seated more. Wear good insulating gloves.

And post results of above two tests. Thanks.

Just to point out to all and Thanks - I am getting on the water, its just not 100% where it should be. Maybe somewhere between 75%-85% overall right now.
In NE Ohio now, we only have about 3 weeks left before most all go into storage.
Cold starts at the dock/launch are embarrassing now. It's like a dinner bell for every backyard mechanic within a mile to come over and stare at us.
Next step is to measure the spark gap, I just received the tool today. I have it set to 1/4" or 6.4mm. I expect to see a healthy blue spark per cylinder.
Then I will idle, and pull the plug wires off, one at a time with rubber gloves, and listen for consistent RPM drop per cylinder.
If the engine stalls when I remove one of the plug wires, will post that as well.
You are correct on all the above statements. I watched somebody on YouTube let his Compression gauge sit for some minutes, and it went down slowly on its own, he later said he had a leaky valve. My gauge has a tire valve (inline). I think that the gauge only records and holds the highest values, so never mind the leaking comment.
If one of the four cylinders is not contributing, would I still see combustion residue on all 4 plugs?
I have an ounce of Marvel Mystery Oil soaking in each cylinder, 24+ hours , in case that matters.
Per Racerone's comment above, If I have to remove the valve cover to look for a stuck valve at some point, I assume that gasket needs replaced? Thanks.

 

[GeorgioP07]

Just to point out to all and Thanks - I am getting on the water, its just not 100% where it should be. Maybe somewhere between 75%-85% overall right now.
In NE Ohio now, we only have about 3 weeks left before most all go into storage.
Cold starts at the dock/launch are embarrassing now. It's like a dinner bell for every backyard mechanic within a mile to come over and stare at us.
Next step is to measure the spark gap, I just received the tool today. I have it set to 1/4" or 6.4mm. I expect to see a healthy blue spark per cylinder.
Then I will idle, and pull the plug wires off, one at a time with rubber gloves, and listen for consistent RPM drop per cylinder.
If the engine stalls when I remove one of the plug wires, will post that as well.
You are correct on all the above statements. I watched somebody on YouTube let his Compression gauge sit for some minutes, and it went down slowly on its own, he later said he had a leaky valve. My gauge has a tire valve (inline). I think that the gauge only records and holds the highest values, so never mind the leaking comment.
If one of the four cylinders is not contributing, would I still see combustion residue on all 4 plugs?
I have an ounce of Marvel Mystery Oil soaking in each cylinder, 24+ hours , in case that matters.
Per Racerone's comment above, If I have to remove the valve cover to look for a stuck valve at some point, I assume that gasket needs replaced? Thanks.

Ran the tests this afternoon:
1. Garage smoked like a KISS concert in 1978 due to 1 oz of Marvel Mystery Oil per cylinder for 24 hours +.
2. Spark gap test tool showed good blue spark at 6.35mm (1/4") on all 4 cylinders,. Once in a while the spark was yellow (does that mean that the coil is on its way out?).
3. Ran at idle, and detached each plug wire one at a time, and noticed drop of 200-300 RPM per cylinder while detached, and returned to regular RPM's as soon as re-attached. The engine sounded smoother overall after the Marvel Mystery Oil soak, but l still got shocked through rubber gloves, oh well.
I suspect that my dash tachometer is reading high, because I lowered the RPM with the idle screw at the carbourator, and the dial on the gauge did not read lower as it should have, but that is more of a nuisance at this point.
Please let me know what else I can try at this point.

 

[ESGWheel]

I do not come close to the expertise of others on this forum but thru the few years I have been active I can attest those experts and myself have only one interest > to get you back on the water with a good and safe running boat. So don’t give up on us yet!

You do have a head scratcher, and I was about to post some questions when you post # 43 popped up answering some of them. But not all and added some new ones. So here goes.

Can you explain what you mean by upon start up its like ringing a dinner bell? A video if you have one would be great. Idea here is how it behaves and sounds at start up may be an indicator of the problem.

For the oil in the cylinders > did you do this today? Why? BTW, and others may know better, but seems to me that 1 oz of liquid in the cylinder is a lot and then starting the engine (even if after 24 hrs). Reason is since the oil is not compressible, could break things like piston rings.

Also did you put oil into the cylinders just prior to the compression test? This would explain the higher than usual number and eliminate the need for my test no. 1 on post 39 but does require another test (outlined below).

Combustion residue > by that I assume you mean what spark plugs normally look like, so even if you had a weak cylinder, you would get that, perhaps not the same looking but could be there.

If one of the cylinders has little impact (no drop on RPM) when pull the wire > that is the weak cylinder. Which you apparently do not have.

It’s always best to replace gaskets as it may break or otherwise not seal properly when reused.

And while the symptoms suggest a weak cylinder the data is not. And it’s really odd doing better now. Regardless here are my suggestions:

1. Redo the compression test on a warm engine. BUT do not put any oil in the cylinders. Instead disable the spark (pull plug off dizzy) and with the throttle wide open, redo the test and post results. Here is the thinking > If you put oil in the cylinders prior to the test you did before, it may have given you false reading. Post results.
2. My other thought is the carb has blockage in the high-speed circuit. Try this old school trick prior to pulling apart the carb again > disable the ign (no spark), remove the spark arrestor and with a helper to turn over the engine, place your hand over the throat of the carb to seal it off. Crank the engine for about 10 seconds. From there it should be well flooded, so best to pull the plugs, crank it over for 30 sec and put all back together. Idea here is to ‘suck out’ any blockage. Not a guarantee but hey, worth a try.
3. Also, need to pursue Scott06’s idea about fuel delivery. Given its behaving better now, I also think this could be an issue (does not explain the rough idle). Install a fuel pressure gauge in line with the carb. I assume you have rubber hose to the carb which will make it easier > need to get a T fitting, fuel line and clamps to install. Caution: secure the gauge (zip ties) so that it can be read underway and that all the lines / gauge are not interfering with anything rotating. Also need 2 people to do this, one to drive and one to read the gauge. Idea here is to record the pressure at idle and all the way up to WOT when it starts to bog down. If any questions or help needed with this just ask.

Oh, just occurred to me to ask: when it does not get to proper speed, does the motor temporarily ramp up to 4500+ RPM and then come back down to 2500 or so?
Thanks.

 

[GeorgioP07]

I do not come close to the expertise of others on this forum but thru the few years I have been active I can attest those experts and myself have only one interest > to get you back on the water with a good and safe running boat. So don’t give up on us yet!

You do have a head scratcher, and I was about to post some questions when you post # 43 popped up answering some of them. But not all and added some new ones. So here goes.

Can you explain what you mean by upon start up its like ringing a dinner bell? A video if you have one would be great. Idea here is how it behaves and sounds at start up may be an indicator of the problem.

For the oil in the cylinders > did you do this today? Why? BTW, and others may know better, but seems to me that 1 oz of liquid in the cylinder is a lot and then starting the engine (even if after 24 hrs). Reason is since the oil is not compressible, could break things like piston rings.

Also did you put oil into the cylinders just prior to the compression test? This would explain the higher than usual number and eliminate the need for my test no. 1 on post 39 but does require another test (outlined below).

Combustion residue > by that I assume you mean what spark plugs normally look like, so even if you had a weak cylinder, you would get that, perhaps not the same looking but could be there.

If one of the cylinders has little impact (no drop on RPM) when pull the wire > that is the weak cylinder. Which you apparently do not have.

It’s always best to replace gaskets as it may break or otherwise not seal properly when reused.

And while the symptoms suggest a weak cylinder the data is not. And it’s really odd doing better now. Regardless here are my suggestions:

1. Redo the compression test on a warm engine. BUT do not put any oil in the cylinders. Instead disable the spark (pull plug off dizzy) and with the throttle wide open, redo the test and post results. Here is the thinking > If you put oil in the cylinders prior to the test you did before, it may have given you false reading. Post results.
2. My other thought is the carb has blockage in the high-speed circuit. Try this old school trick prior to pulling apart the carb again > disable the ign (no spark), remove the spark arrestor and with a helper to turn over the engine, place your hand over the throat of the carb to seal it off. Crank the engine for about 10 seconds. From there it should be well flooded, so best to pull the plugs, crank it over for 30 sec and put all back together. Idea here is to ‘suck out’ any blockage. Not a guarantee but hey, worth a try.
3. Also, need to pursue Scott06’s idea about fuel delivery. Given its behaving better now, I also think this could be an issue (does not explain the rough idle). Install a fuel pressure gauge in line with the carb. I assume you have rubber hose to the carb which will make it easier > need to get a T fitting, fuel line and clamps to install. Caution: secure the gauge (zip ties) so that it can be read underway and that all the lines / gauge are not interfering with anything rotating. Also need 2 people to do this, one to drive and one to read the gauge. Idea here is to record the pressure at idle and all the way up to WOT when it starts to bog down. If any questions or help needed with this just ask.

Oh, just occurred to me to ask: when it does not get to proper speed, does the motor temporarily ramp up to 4500+ RPM and then come back down to 2500 or so?
Thanks.

Hello ESGWheel,
I appreciate you and others hanging in there while I try to sort this out.
1. "Like Ringing a Dinner Bell" Sorry, its a slang term for when a crowd gathers. Seems like anytime I have trouble at the dock, I get a lot of unwanted attention, and irrelevant advice.
2. Adding Marvel Mystery Oil to each cylinder. I was worried about Racerone's post about having a stuck valve, that was just yesterday. I never did that before. It seemed to burn off pretty quick and quiet things down. Compression test was done 3 days ago with no oil in the cylinders.
3. Yes Combustion Residue: All 4 plugs look very good, If you were to look up one of those spark plug wear indexes, these would fall under the condition of normal wear.
4. When I rebuilt the carburetor last month, I did reuse the OEM float, because it was still good, I read reviews about those that are electronically welded plastic floats that come with these kits failing in the middle of the lake as that weld cracks, gas seeps in and they no longer float and the motor won't start no matter what. Also the kit did not come with the "Power Valve Assembly", so I cleaned and re-used the existing one after it came out of the ultrasonic cleaner.
5. The throttle lever has three positions, A, B, and C. Mine was on B. The manual says "to Move it to position A if you want to get more fuel to the carburetor" or similar, but I left it where it was on position B. I had rebuilt quite a few carburetors before, and nothing stood out in particular as difficult or weird this time.
6. I can go to buy a fuel pressure testing kit, but I read that the expected pressure for this fuel pump is only 4-7psi, and most kits that I am seeing for sale go to 140psi , so the scale is pretty far off. I read that some special GM attachment is needed but not included. That's probably why I waited this long, but if you think its time, then its time and I will order one tomorrow. If you have a model that you recommend, that would be great. The fuel pump on this motor is the one that has the intake and outlet on the same side, cause the motor mount takes up the front half, they are harder to find and more expensive. Note: I was having this problem with the low RPM's in June before I replaced the fuel pump in July (and the filter element is in the bottom).
7. With the wide-open throttle and return. On the muffs, if I rev to 4000 RPM, and then throttle back to neutral , then the RPM's come back down to idle. On the lake, the most I can rev to is maxed out at 2900 RPM's, and when I throttle back down from there, it also returns down to the previous idle.
Thanks, and I will probably have a few questions when the fuel pressure test kit gets here.

 

[ESGWheel]

A lot to take in but wanted to reply quickly before my bedtime limit on posting.

Regarding the slang about the dinner bell > I get it was slang. What I was interested in knowing is the “why” folks were gathering. Made up example: Every time I start my boat it makes a large cloud of smoke and backfires like heck which folks then come ask if I need help. So, looking for the reason folks are coming around > is it due to unusual sounds or smoke or just what?

You do not want a 140 PSI gauge. You are correct your fuel pump is low pressure as you indicated, so you need a pressure gauge like this: link If your fuel lines are metal and not rubber then need still use a gauge like indicated but cobble together the needed fittings. Post a pic of your pump / carb if need help for this.

 

[ESGWheel]

I found this thread looking for a ‘how to’ to install a fuel pressure gauge link. While his situation was ultimately bad compression in one of the cylinders, post # 18 refers to an exhaust shutter (flapper) that may be dislodged restricting exhaust flow which would have the effect of poor top end performance you are experiencing. And it could also account for the improvement you experienced > its now less restricted because it moved around.

I do not know if your engine has one, need others to chime in on that and how to check it.

 

[Scott06]

Hello ESGWheel,
I appreciate you and others hanging in there while I try to sort this out.
1. "Like Ringing a Dinner Bell" Sorry, its a slang term for when a crowd gathers. Seems like anytime I have trouble at the dock, I get a lot of unwanted attention, and irrelevant advice.
2. Adding Marvel Mystery Oil to each cylinder. I was worried about Racerone's post about having a stuck valve, that was just yesterday. I never did that before. It seemed to burn off pretty quick and quiet things down. Compression test was done 3 days ago with no oil in the cylinders.
3. Yes Combustion Residue: All 4 plugs look very good, If you were to look up one of those spark plug wear indexes, these would fall under the condition of normal wear.
4. When I rebuilt the carburetor last month, I did reuse the OEM float, because it was still good, I read reviews about those that are electronically welded plastic floats that come with these kits failing in the middle of the lake as that weld cracks, gas seeps in and they no longer float and the motor won't start no matter what. Also the kit did not come with the "Power Valve Assembly", so I cleaned and re-used the existing one after it came out of the ultrasonic cleaner.
5. The throttle lever has three positions, A, B, and C. Mine was on B. The manual says "to Move it to position A if you want to get more fuel to the carburetor" or similar, but I left it where it was on position B. I had rebuilt quite a few carburetors before, and nothing stood out in particular as difficult or weird this time.
6. I can go to buy a fuel pressure testing kit, but I read that the expected pressure for this fuel pump is only 4-7psi, and most kits that I am seeing for sale go to 140psi , so the scale is pretty far off. I read that some special GM attachment is needed but not included. That's probably why I waited this long, but if you think its time, then its time and I will order one tomorrow. If you have a model that you recommend, that would be great. The fuel pump on this motor is the one that has the intake and outlet on the same side, cause the motor mount takes up the front half, they are harder to find and more expensive. Note: I was having this problem with the low RPM's in June before I replaced the fuel pump in July (and the filter element is in the bottom).
7. With the wide-open throttle and return. On the muffs, if I rev to 4000 RPM, and then throttle back to neutral , then the RPM's come back down to idle. On the lake, the most I can rev to is maxed out at 2900 RPM's, and when I throttle back down from there, it also returns down to the previous idle.
Thanks, and I will probably have a few questions when the fuel pressure test kit gets here.

At this point I would test the fuel pressure on the water at the rpm where you feel like you are hitting the wall where it should be doing better.

if the float wasnt cracked its probably all right. Mikes carbs had at one time brass floats for mercarbs not sure if TKS is the same thing.

the 3 position lever is for the accelerator pump it can increase or decrease the volume of pump shot, which will only affect it just after stabbing the throttle, not running steady state

Wasn't sure what your spark plugs looked like, and have you cross checked the tach vs a shop tach? if you are only getting 2900 rpm under load that is way less than 75% .

The only wild card here could be if the tks module is no shutting off? but I would think your plugs would be way rich if that is the case

 

[airshot]

That is very close to what I ran in my Ultrasonic cleaner for this carburetor.
I used the Zep equivalent - Concentrated All Purpose green liquid de-greaser. Thanks,.

Did you blow compressed air thru all the small holes and passages ? Some are barely needle size so a piece of wire needs pushed thru. Just soaking won't clean out the tiny places. Also ..you should have bought a factory rebuild kit to replace all the gaskets, needle and seat for the float. Also contains the necessary settings and adjustments for your motor. Most times, just cleaning rarely works well, a complete rebuild is far more sucessfull.

 

[GeorgioP07]

A lot to take in but wanted to reply quickly before my bedtime limit on posting.

Regarding the slang about the dinner bell > I get it was slang. What I was interested in knowing is the “why” folks were gathering. Made up example: Every time I start my boat it makes a large cloud of smoke and backfires like heck which folks then come ask if I need help. So, looking for the reason folks are coming around > is it due to unusual sounds or smoke or just what?

You do not want a 140 PSI gauge. You are correct your fuel pump is low pressure as you indicated, so you need a pressure gauge like this: link If your fuel lines are metal and not rubber then need still use a gauge like indicated but cobble together the needed fittings. Post a pic of your pump / carb if need help for this.

I just ordered the 15psi gauge kit that you posted.
I will surely have to cobble some fittings together, as I read that the 2-barrel TKS carburetor was listed as using the NPT standard for inlet threads and not the AN threads. Can anyone confirm, as my quick connect to the carburetor inlet does appear to be AN upon first glance. Thanks again.

 

[GeorgioP07]

Did you blow compressed air thru all the small holes and passages ? Some are barely needle size so a piece of wire needs pushed thru. Just soaking won't clean out the tiny places. Also ..you should have bought a factory rebuild kit to replace all the gaskets, needle and seat for the float. Also contains the necessary settings and adjustments for your motor. Most times, just cleaning rarely works well, a complete rebuild is far more sucessfull.

Yes, I used compressed air, close to 50psi with a fine tip if I recall. I hesitated to use wires, since back on motorcycles rebuilds they said you could damage the white zinc metal passages if a wire was used. - Regardless, rebuilding the carb did not seem to improve or make worse the situation at all.

 

[GeorgioP07]

A lot to take in but wanted to reply quickly before my bedtime limit on posting.

Regarding the slang about the dinner bell > I get it was slang. What I was interested in knowing is the “why” folks were gathering. Made up example: Every time I start my boat it makes a large cloud of smoke and backfires like heck which folks then come ask if I need help. So, looking for the reason folks are coming around > is it due to unusual sounds or smoke or just what?

You do not want a 140 PSI gauge. You are correct your fuel pump is low pressure as you indicated, so you need a pressure gauge like this: link If your fuel lines are metal and not rubber then need still use a gauge like indicated but cobble together the needed fittings. Post a pic of your pump / carb if need help for this.

I was at the dock two weekends ago, and the motor would not cold start. Battery was at 13.5V.
We sat there about 5 minutes and a crowd had gathered after hearing the starter motor working with no ignition taking place. I had my tool bag, went over to the idle screw and gave it 1, then 2, then 2.5 turns in, and then it finally started. We had just put in 7 gallons of fresh 87 pump gas 20 minutes before that. What a pain... Thanks...

 

[GeorgioP07]

I found this thread looking for a ‘how to’ to install a fuel pressure gauge link. While his situation was ultimately bad compression in one of the cylinders, post # 18 refers to an exhaust shutter (flapper) that may be dislodged restricting exhaust flow which would have the effect of poor top end performance you are experiencing. And it could also account for the improvement you experienced > its now less restricted because it moved around.

I do not know if your engine has one, need others to chime in on that and how to check it.

Hello, I searched in my Mercury service manual for an "exhaust shutter" and nothing came up.
It does mention "Flapper", -as such: "Sometimes noises can be caused by moving parts coming in contact with other components. Examples are: flywheel or coupler; exhaust flappers rattling against exhaust pipe; crankshaft striking (pan, pan baffle, or dipstick tube)"
If you have advice as to how to check if the flapper is stuck, please let me know, short of taking the engine apart.
One other thing I noticed after rebuilding the carburetor..I could hear a pronounced "Sucking Sound" coming from the carburetor area, which I assumed was just the flame arrestor taking in air, but it seems louder and more pronounced after the rebuild.
I made sure that the new gasket at the carburetor base was tight and nuts were torqued to spec.
Are there any vacuum lines anywhere that should be checked out on this motor?
Should I generate some smoke near the base of the carburetor and see if that is getting sucked in? Are you aware of any other areas to check for vacuum leaks? Thanks.

 

[ESGWheel]

Now understand the dinner bell

Do not know thread sizes but if the fuel line from the pump to the carb is a one piece with threaded fitting on both ends, then can take that line + the gauge to a Hydraulic Hose Repair Shop local to you and explain what you are trying to do. They will hook you right up.

The flapper is part of the exhaust system. Its job is to keep water from the motor when you slow down too fast > it’s like a one-way valve exhaust can go out but water cannot ‘backflush’ up and thru the exhaust and hydro lock your engine (very bad). Here is a vid of one but on a v8 Mercruiser link

Can use stiff fishing line vs wire to chase the ports in the carb.

Here is an ‘automotive’ style multimeter that has an RPM gauge as well and is inexpensive link. Can use that to validate your RPM gauge.

I am not familiar with your motor, but I suspect no vacuum lines.

That sucking sound is disconcerting if was not there before. Can you post a video of the engine idling and capture that noise? A vacuum leak would account for rough idle / need to be at higher idle to keep from stalling and also limit top end. Instead of smoke use a can of carb cleaner and spray around the base of the carb > if the idle speed picks up there is a vacuum leak.

Also I just looked around and found this video (link) related to a TKS carb that has a sucking sound (which is normal) due to the Enrichment Valve. Does your carb have one of these?

 

[GeorgioP07]

Now understand the dinner bell

Do not know thread sizes but if the fuel line from the pump to the carb is a one piece with threaded fitting on both ends, then can take that line + the gauge to a Hydraulic Hose Repair Shop local to you and explain what you are trying to do. They will hook you right up.

The flapper is part of the exhaust system. Its job is to keep water from the motor when you slow down too fast > it’s like a one-way valve exhaust can go out but water cannot ‘backflush’ up and thru the exhaust and hydro lock your engine (very bad). Here is a vid of one but on a v8 Mercruiser link

Can use stiff fishing line vs wire to chase the ports in the carb.

Here is an ‘automotive’ style multimeter that has an RPM gauge as well and is inexpensive link. Can use that to validate your RPM gauge.

I am not familiar with your motor, but I suspect no vacuum lines.

That sucking sound is disconcerting if was not there before. Can you post a video of the engine idling and capture that noise? A vacuum leak would account for rough idle / need to be at higher idle to keep from stalling and also limit top end. Instead of smoke use a can of carb cleaner and spray around the base of the carb > if the idle speed picks up there is a vacuum leak.

Also I just looked around and found this video (link) related to a TKS carb that has a sucking sound (which is normal) due to the Enrichment Valve. Does your carb have one of these?

Alright, Once I get the fuel pressure gauge installed inline, I will spray some carburetor cleaner at the base and listen for a change in RPM's.
I watched that video of that TKS 4.3L.
That 4.3L engine in the video is quite different than my 3.0L , with his cap being behind the carburetor, and his fuel intake being on the side of the carburetor.
I do have a somewhat similar enrichment module for the TKS, it's not exactly like that one.
read somewhere that it replaced a choke and heated the gas slightly, but after watching the video, it seems more like an automatic choking system.
I did take it off and cleaned it out with carburetor cleaner when I rebuilt the carburetor.
I never much suspected carburetor flooding as a condition in this case, since I can always stop the motor and restart it pretty well once it's warmed up. Its the cold starts that are tough.
I do have that same sucking noise as in that video for sure, but I don't think it's as loud and prevalent as his, I will post a video of mine when I get that fuel pressure gauge test going. I will look at that Tachometer you posted. Thanks again.

 

[ESGWheel]

While the engine in the vid has a different configuration, the TKS carb provides the same function and thus is instructive to study it. I took some time to read up on TKS or Turn Key Start carbs. Turn Key Start as a marketing slogan to highlight that it does not require the typical ‘step on the gas’ to set the choke of more traditional / older carbs. So yes, a TKS is a ‘chokeless’ carb but uses the Enrichment Valve (EV) to do the same function. The EV does not heat up the gas. It simply opens a port to allow the mixture to enrichen. And when motor is warmed up it closes off that port. Thus, that sucking noise should go away.

So, another check to do is when the motor is warmed up, go back to idle and listen > does it sound the same? If so that EV may be bad.

 

[Scott06]

I just ordered the 15psi gauge kit that you posted.
I will surely have to cobble some fittings together, as I read that the 2-barrel TKS carburetor was listed as using the NPT standard for inlet threads and not the AN threads. Can anyone confirm, as my quick connect to the carburetor inlet does appear to be AN upon first glance. Thanks again.

usually the fuel line is 3/8" double flare like brake lines would think you can get a coupler and a short section of line cut in half & use some 3/8 ID hose to splice in your T for the gauge

Alright, Once I get the fuel pressure gauge installed inline, I will spray some carburetor cleaner at the base and listen for a change in RPM's.
I watched that video of that TKS 4.3L.
That 4.3L engine in the video is quite different than my 3.0L , with his cap being behind the carburetor, and his fuel intake being on the side of the carburetor.
I do have a somewhat similar enrichment module for the TKS, it's not exactly like that one.
read somewhere that it replaced a choke and heated the gas slightly, but after watching the video, it seems more like an automatic choking system.
I did take it off and cleaned it out with carburetor cleaner when I rebuilt the carburetor.
I never much suspected carburetor flooding as a condition in this case, since I can always stop the motor and restart it pretty well once it's warmed up. Its the cold starts that are tough.
I do have that same sucking noise as in that video for sure, but I don't think it's as loud and prevalent as his, I will post a video of mine when I get that fuel pressure gauge test going. I will look at that Tachometer you posted. Thanks again.

The TKS uses an enrichment module (valve) to richen the fuel mixture until the engine warms up, it doesn't heat the gas, it dumps more fuel in. The idea was that since no one drives carbureted cars anymore, no one knows to pump the throttle and set a fast idle when starting. This sets the choke, shoots some gas out of accelerator pump, and will quickly start a carbed engine in a good state of tune.

when cold the module/valve has a separate pathway to dump more gas in at idle, when it gets to like 135F it should shut off. I think this is the sucking sound when it starts cold.

It sort of worked, but I think the TKS is hated due to issues with the module failing, the diode failing, not being mainstream technology that mechanics are familiar with, and cost of parts.

If it was running rich your plugs would look fouled. you mention cold starts being an issue have you tried adjusting the idle mix? most of the time even cold boating weather you dont really need a choke or enrichment. I ran my 3.0 for years with the choke forced open after the element died.

 

[nola mike]

Are there any vacuum lines anywhere that should be checked out on this motor?
Should I generate some smoke near the base of the carburetor and see if that is getting sucked in? Are you aware of any other areas to check for vacuum leaks? Thanks.

Yes shutters=flappers. Maybe time to throw a vacuum gauge on it? Could show some subtle problems. It would also show an exhaust restriction, which might be tough to diagnose otherwise

 

[cyclops222]

Love a vacuum gauge.

 

[GeorgioP07]

Love a vacuum gauge.

Hmm, Not seeing any vacuum lines on this engine. The Mercury service manual mentions using a vacuum gauge connected to engine, but fails to describe how to connect the two together. The only place it mentions there is a vacuum is at the base of the carburetor. Still cobbling fittings together to test the fuel pressure. The inlet to the carburetor inlet seems to be M16 x 1.5, thread, so that is the T-adapter I ordered along with the 15psi gauge.