Mercruiser 3 L Won't Crank in Neutral

[Ed Edmondson]

I have a 2018 Mercruiser Inboard in my boat. Water got into the fuel and I had to rebuild the carburetor. Drained the gas tank, replaced the fuel water separator and placed non-ethanol 92 octane fuel in the tank, drained the fuel line all the way to the carb. until a consistent gasoline only flow was achieved. I'm sure there is no water in the fuel system now.

The engine cranked in neutral immediately after re installation of the rebuilt carb. Then died within seconds. I'm thinking this was due to the "cleaners" placed in the carburetor. The only way I could get it to crank was to place the throttle in drive position and push it back and forth quickly. Leaving it in a fixed throttle position or returning it to neutral killed the engine.

The rebuilt carb used all new parts from the kit and was cleaned and pressure purged thru all small orifices / ports. The float and set points were adjusted to the spec sheet. The electrical system has been checked from alternator all the way thru the distributor and spark plugs (all working well). Something is keeping the fuel from entering the carb. in the neutral position.

I'd like feedback on which systems could cause this (Carb enrichment solenoid valve?, vacuum system, other?)

 

[alldodge]

Howdy

Don't take this wrong, and we all want to help, but we have had several folks here lately they have said everything was done correctly and within specs, but it won't do something. If everything was within spec it would do what you want it to do. So lets start with more info about what you have and what exactly was done

What was the original motor serial number?

Mentioned enrichment valve, are you talking about a TKS carb?

Something is keeping the fuel from entering the carb. in the neutral position.

Have you checked fuel pump pressure, and if so what was it?

 

[Bondo]

Don't take this wrong, and we all want to help, but

Ayuh,.......

 

[Ed Edmondson]

Serial number is 1G412351, it is a TKS carb. I don't have a way to check the fuel pressure, however, I can see a strong stream of fuel entering the carb. with the flame arrestor off while cranking the engine and exercising the throttle as described above.

History:
This is a custom built reproduction boat (1939 Chris Craft barrellback). I built the boat from 2017 to April of 2019. I bought a packaged engine from Michigan Motorz and installed the engine myself, I also bought a ZF transmission kit 45A installed on the engine. The wiring harness and instrument panel were bought with the engine. Fuel tank, steering system, rudder, prop, etc were sourced from marine retailers to fit the boat. The boat had it's maiden voyage in April of 2019, this was to tune the systems to work together (aka, steering, transmission, & throttle) The boat was stored outside with a cover on it, however I noticed water accumulation on the deck of the boat after periods of rain. The second time out was in June of 2019, the boat was used for a couple of hours without issue. We then took the boat back out in July of 2019 and the engine wouldn't start. I placed the boat in storage for the winter and took the boat into a mechanic to fix the problem. He found water in the fuel, he drained the tank, rebuilt the carb. and was able to get the boat running well. I took the boat out in March of 2020 and ran for about an hour no problem. I took the boat back out in April of 2020, it ran for an hour and then stopped running. We had the boat towed into the marina. I drained the fuel tank and discovered water in the fuel again, I took out and replaced the fuel water separator (it had water and rust in it). I bleed fresh gasoline thru the fuel line and flushed it to a container at the fuel connection prior to entering the carb. I bought a carb. kit and rebuilt the carb. I replaced every part that came in the carb kit. I soaked the carb and cleaned all residue from surfaces, all orifices were cleaned and all were cleared of any potential debris with a thin solid copper wire inserted thru the small orifices and carb cleaner blown thru the orifices (in that order). I placed the carb back into service. With the ignition off and the flame arrestor off, I validated fuel flow to the carburetor and no water in the fuel system. I then cranked the engine and ran into the same starting problem. I removed the carb., At this point I rechecked the settings for the float (and discovered the float was about 1/8 inch off from the recommended settings), I reset it. Areas of the carb that weren't included in the carb kit I removed, cleaned and checked (aka the discharge T and ball check). I couldn't remove the shaft and spring that controls the power valve assembly since I was concerned with breaking it if I applied too much force and not having a replacement part if I did damage it. I did clean it well and operated it with carb cleaner about 30 times to make sure it was moving freely. I then reinstalled the carb, the engine started immediately in neutral (perfect start) but died within 10 seconds. I figured this was the fluids from the carb cleaning - after that, I could only crank the engine by fast shifting the throttle back and forth. I could keep it running but it was revving pretty high. I did this 4 times to validate it was doing the same thing repeatedly. If I turned the throttle back to neutral after getting it to crank this way, it died immediately, if I left the throttle in a drive position (without moving it), it died immediately.

( I hope this helps, sorry for the lengthy dissertation, trying to be through)

If I need top check the fuel pressure, what is the correct range I should be seeing? Anything else I need to checK?

Thank you

 

[alldodge]

Not finding a 1G serial number, the 3.0 carb motor last revision started at 1A020544 and up

Fuel pressure should be 3-7 psi from idle to WOT

To keep it running you have to keep pumping gas in with the accelerator pump tells me it get gas but the idle circuits in the carb are clogged up

The TKS has a module which extends and closes off the enrichment circuit after it warms up. The carb temp switch (not the motor temp) is what keeps the enrichment closed after the motor warms up. Once motor cools down, power is removed and the module retracts the shaft

This is a simplistic diagram

 

[GA_Boater]

First - Is the choke working?

Second - Does the remote control have a throttle only function? With that you can start in neutral with an advanced throttle. You shouldn't have to do the throttle wig-wag.

 

[GA_Boater]

First - Is the choke working?

Second - Does the remote control have a throttle only function? With that you can start in neutral with an advanced throttle. You shouldn't have to do the throttle wig-wag.

Missed This is a TKS carb. So making a change;

First - Is the c̶h̶o̶k̶e̶ TKS working?

Throttle question is still good.

 

[Ed Edmondson]

I validated 12 volts DC to the TKS Carb, so it could be a bad solenoid valve but the wiring and any inline devices (breaker, etc) are good.
Throttle has a remote function. I have cranked the engine with it in drive position, it fires briefly but will not continue, I can see a squirt of gasoline going into the carb in this position but it stops within 2 seconds and won't send more fuel unless the wig wag is done.
Is there a way I can check the solenoid independently, aka, take it out of the carb. hot wire 12 volts to it and make it move?

 

[alldodge]

The solenoid only shuts off the air passage which allows more fuel to be sucked in. When it closes the motor uses the idle passages

Your carb is clogged up and needs to be removed and cleaned