Fuel System Delivery Issue Mystery HELP

[KathyD19]

This is going to be a little long but I want to give all details so please bear with me.
I have a 2016 Grand Island 20 foot pontoon with a 60hp Mercury 4 Stroke Force outboard (same age as boat).
Last August, it started bogging down and acting like it was fuel starved, wanting to die. I squeezed the primer bulb and it got it going again but I had to continue doing that so we could get back to the dock. I noticed the original external gas cans looked cracked and I figured they were the issue so I bought a brand new Sceptor brand 12 gallon gas tank. Still had issues. So I began replacing things in the fuel system. Last year I replaced: all fuel lines and the primer bulb, both of the fuel filters, the spark plugs and the low pressure fuel pump. Still had the same issue.
I put it up for the winter and decided to tackle it when our lake reopened in April. I had emptied the gas and put new in, with stabilizers and injector cleaners. We got a lot of rain this Spring and the boat sits outside so I couldn't do too much more. I called two different marine mechanics to pick their brains and they said all that I had checked and replaced so far was what they would have done as well. They told me to check the VST and that it may be the high pressure fuel pump going bad. So I drained the VST (fuel looked fine, checked the screens in there and they were fine as well). I also checked the fuel pressure and it was fine on the muffs. Put it all back together and was still having the same issue but now I was getting a warning horn. I tested fuel pressure in the water as it was running and it was fine then dropped dramatically as it bogged down and threatened to die.
Gave up on solving this mystery myself and took it to an established marine mechanic. He went through everything I had done to that point and said it was all correct, but he noticed that the gas can was bulging in the heat. With the new EPA requirements, those tanks do swell up and are supposed to self-vent at a certain PSI. But he checked it and said it wasn't venting at all and that the continued swelling had blown out the gasket in the uptake seal and had allowed rain water to contaminate the fuel. He emptied all of that and ran fresh fuel through it. He wasn't getting any error codes from the computer anymore (all the code said was "fuel system" nothing more specific) but it did still have a warning beep. He was puzzled at that but said it seemed to be running fine on the muffs now with good fuel. I purchased a new tank from him, one that he "modifies" from the EPA issue so it vents properly like the old ones used to. Back home and lake tested it and it was still bogging down and had the warning beeps (they varied each time I started it up). I called the mechanic and he said the only other thing he could think would be the high pressure fuel pump was going out and needed replaced. I hauled it back there and paid for him to replace that. While I was there, so sure that this would finally be the last fix, I also had them replace the impeller since they had it there (it was fine but it had been three years....few hours but still). Back home, back in the water and running worse than ever. All kind of different warning beeps upon start up, running so rough that I wasn't sure I could get it bac to the dock to re-trailer it. Called him again and offered to sell him the boat. I am just so sick and tired of throwing money at it and never getting to use it. He said the very last thing would be to replace the ECU and that was almost $1100. There was simply nothing else left. I thought about it for a week, didn't think I could sell it to anyone else if it needed that done and couldn't be used as it was. So I went ahead and told him to order the ECU and I'd take the boat back in. He had it a week and called me to tell me good news. That as he removed the harness to hook up the new ECU, he noticed "brown, heated spots" on the harness over two of the connector areas. He said that two of the connections/pins (can't remember exactly what he called them) on the harness were loose and kind of folded over on themselves. So he took the harness off and to his bench and repaired them. When he put it back on, the motor ran great (again on muffs) and threw no more codes, had no more warning horns or anything. So that was only $350 for that repair vs $1100 for the ECU. I was thrilled. Got it home and took it out on the lake yesterday. She purred like a well-fed kitten and we putted around at a little less than 1/2 throttle for about 45 min. Then when my husband put the throttle up just a little bit, I could hear the tone in the motor change and feel the slight bog. I looked at him to see if he had throttled down and he shook his head no. It was doing it again, although more subtle this time. Whenever he would throttle up even a little, it would bog and surge, bog and surge. I checked the fuel tank cap and even loosened it just in case it wasn't venting and that didn't do anything to help. Out of routine, I pumped the primer bulb a few times to force fuel to the motor. We throttled down and headed back to the dock to give up for the day.

If you've read this far, I greatly, greatly appreciate your interest. I've done all I can do, I've thrown a lot of money at this and I don't know what else to do or what direction to go. If this will let me attach a short video I took yesterday, turn up the volume and you can hear the motor bogging/trying to recover and see me sway in reaction to the change in speed. I welcome all advice. Thank you so much!

 

[alldodge]

Moved your thread to Merc OB because it's a motor problem, not the toon

They told me to check the VST and that it may be the high pressure fuel pump going bad. So I drained the VST (fuel looked fine, checked the screens in there and they were fine as well). I also checked the fuel pressure and it was fine on the muffs.

What was the fuel pressure reading?

Back home and lake tested it and it was still bogging down and had the warning beeps (they varied each time I started it up).

He wasn't getting any error codes from the computer anymore (all the code said was "fuel system" nothing more specific) but it did still have a warning beep.

I'm wondering just what kind of scanner he has, or even if he has one that will actually read the codes. So far mechanic appears to be a parts changer and not a Marine Tech

A scanner like Rinda's Techmate Pro, or Diacom software needs to be used under load. Also connecting a fuel pressure gauge on muffs is much different when under load

The scanners in the link above is what someone needs to read info from the motor. Need either Techmate Pro kit 94070m or Diacom 94030g and kits include adapters 94029 and 94032

 

[KathyD19]

Moved your thread to Merc OB because it's a motor problem, not the toon


What was the fuel pressure reading?




I'm wondering just what kind of scanner he has, or even if he has one that will actually read the codes. So far mechanic appears to be a parts changer and not a Marine Tech

A scanner like Rinda's Techmate Pro, or Diacom software needs to be used under load. Also connecting a fuel pressure gauge on muffs is much different when under load

The scanners in the link above is what someone needs to read info from the motor. Need either Techmate Pro kit 94070m or Diacom 94030g and kits include adapters 94029 and 94032

Thank you for moving my post to the appropriate place; I wasn't sure where to post it. When I took the fuel pressure reading, both on muffs AND on the water under load, it was about 41. I don't know what specific computer he uses to check codes but he's been in business about 30 years and has a very good reputation. So I am assuming he uses something good (but again, we know what assumptions do).

 

[alldodge]

Thank you for moving my post to the appropriate place; I wasn't sure where to post it. When I took the fuel pressure reading, both on muffs AND on the water under load, it was about 41. I don't know what specific computer he uses to check codes but he's been in business about 30 years and has a very good reputation. So I am assuming he uses something good (but again, we know what assumptions do).

Not knowing how accurate the gauge used was, 41 is good enough for idle, should be closer 43 at 3/4 to WOT. Again it looks like fuel pressure is not the issue

Not putting the guy down, but there are some Marine folks that are great folks and may or may not be Dealer certified. Not that they need to be certified if they keep up with latest Tech. But only way to keep up with the latest is to be a Dealer

There is a guy here @muc which is a master retired Tech and if we can get him involved it will be great. That said if MUC comes he will want the motor serial number to start with and a bunch more to figure it out

 

[KathyD19]

Not knowing how accurate the gauge used was, 41 is good enough for idle, should be closer 43 at 3/4 to WOT. Again it looks like fuel pressure is not the issue

Not putting the guy down, but there are some Marine folks that are great folks and may or may not be Dealer certified. Not that they need to be certified if they keep up with latest Tech. But only way to keep up with the latest is to be a Dealer

There is a guy here @muc which is a master retired Tech and if we can get him involved it will be great. That said if MUC comes he will want the motor serial number to start with and a bunch more to figure it out

Thank you. I will have to go to the boat, which is currently at my dock at the lake to get the model/serial number and all for you/him. I can maybe do that tomorrow. I had taken pictures of it when I was working through all the issues myself but I deleted them from my phone and they've since disappeared.

 

[KathyD19]

Thank you. I will have to go to the boat, which is currently at my dock at the lake to get the model/serial number and all for you/him. I can maybe do that tomorrow. I had taken pictures of it when I was working through all the issues myself but I deleted them from my phone and they've since disappeared.

 

[KathyD19]

I have the Model and Serial numbers! The Model #: 1F60453LZ and the Serial # is: 1C481103

 

[alldodge]

Great hope @muc can help
Looks like a Seapro with VST

 

[muc]

I have the Model and Serial numbers! The Model #: 1F60453LZ and the Serial # is: 1C481103

The status of the motor is that it now starts and runs fine up to 1/2 throttle, but starts to surge over 1/2 throttle?

Pumping the bulb doesn't help?

No warning horn when this happens?

Do you still get the single beep when you turn the key on?

 

[KathyD19]

Yes it starts easily and runs beautifully but I don't think it made the usual beep at start up. Can't be 100% that it didn't beep, my husband isn't sure either so I'd have to start it again to see. Pumping the bulb did seem to help (it would help it level out and behave a little further then start bogging down again). No warning horn at all when it's happening now. I don't know if it's a "surge" as much as it is trying to die and slows down then tries to get back up to speed so that feels like it's surging. And in general it does NOT do it at low speed only at the mid to higher RPMs

Thank you so much for taking an interest in this.

 

[muc]

When you replaced the low pressure fuel pump, was it because testing said it was bad or just guessing? Did you use a Mercury Marine pump from a authorized dealer or off of a place like amazon?

Do you have a Mercury Marine authorized dealer near you? Preferably one on the water or close by water? Because it sounds like this will need to be in the water for testing.

Find a Mercury Marine Dealer Location | Mercury Marine

Your local Mercury Authorized Dealer is the best place to see and purchase Mercury engines, parts and accessories, or to get expert support when you need it.

www.mercurymarine.com

Unfortunately it seems you might have picked the wrong tech for this issue. They might not have the level of training this issue requires. They have raised some red flags, but they do seem honest! Most shady techs would have never mentioned the wiring harness problem and sold you the new ECM.

Depending on the answers to the above question, I'm guessing that to resolve this issue will require a scan tool, a vacuum gauge, a low pressure fuel gauge and the high pressure gauge. Is this something you will want to do?

At this point without the warning horn going off --- I don't see an "easy" fix.

 

[muc]

I was typing during your reply.

The single beep is important. Very. Please check.

Pumping the bulb and having it help might mean that you could skip the scan tool and start with the 2 fuel gauges.

 

[muc]

The slow down and increase in engine speed could be fuel or it could be the ECM going into guardian mode. This is where the scan tool or warning horn would tell if the ECM is cutting back RPM until the problem goes away and then repeating the cycle. The ECM doesn't monitor the fuel pressure.

 

[KathyD19]

Thank you again for your help with this! I will try to answer each of your questions as asked:
I feel like the marine mechanic is a "good guy"; he doesn't push me on repairs or parts and he has a ton of MUCH higher value boats on his lot to work on, rather known to be the guy who is the last resort when others can't figure problems out. Sadly I'm in a rural area of central Illinois so not a whole lot of choice for places to go as far as a certified Mercury Marine tech, let alone one on the water. But I will check the link you added! The only gauge I had was a "fuel pressure gauge" and I attached it at the Shrader valve near the VST, so I am assuming that only tests the high pressure fuel. I wasn't aware that there was a port to attach to on the low pressure pump and I don't know how to check the vacuum with a gauge. Can I use the basic fuel pressure gauge for the low pressure fuel pump as well?
I admit, I bought a low pressure pump on Amazon. I know, probably cheap Chinese crap. I can invest in getting an OEM Quicksilver one for close to $200 or the mechanic said he has good results with the Sierra brand one (for $133). My only boat experience was previously noted on here when I jumped in head first and began rebuilding a 1956 Johnson Javelin outboard a few years back. Like a boss! ) I do a lot of small engine stuff and I am currently also rebuilding a mini skid steer (also a piece of cheap chinese crap) by redoing the hydraulics and now rebuilding all four idler wheels, so I'm handy but very willing to learn.
I've been wracking my brain on this and the only thing I can think of is that if I had water in the fuel when I put the boat up for winter (it's stored in a covered shed at our local fairgrounds but not a heated enviroment) that perhaps the water in the fuel froze over the midwestern winter and that could have damaged the diaphragm in the low pressure fuel pump? Just a potential theory....

I will go to the lake tomorrow and start the motor to see if the start-up beep occurs so I can give you a solid answer.

 

[KathyD19]

The slow down and increase in engine speed could be fuel or it could be the ECM going into guardian mode. This is where the scan tool or warning horn would tell if the ECM is cutting back RPM until the problem goes away and then repeating the cycle. The ECM doesn't monitor the fuel pressure.

I just got back from the lake and checked the boat for the start-up beep. It DOES beep briefly when started. I know you said that was important so I wanted to share that with you ASAP. It starts easily and runs smoothly in neutral and low speeds. I also checked to see the brand of low pressure fuel pump that I installed last year and it was marked as EMP (Engineered Marine Products). So it wasn't Sierra or Quicksilver. If you think I should replace with one of those two brands, that's a relatively easy swap out. I just wasn't sure if I should keep throwing parts at this or wait to see if you had any other ideas.

 

[KathyD19]

I just got back from the lake and checked the boat for the start-up beep. It DOES beep briefly when started. I know you said that was important so I wanted to share that with you ASAP. It starts easily and runs smoothly in neutral and low speeds. I also checked to see the brand of low pressure fuel pump that I installed last year and it was marked as EMP (Engineered Marine Products). So it wasn't Sierra or Quicksilver. If you think I should replace with one of those two brands, that's a relatively easy swap out. I just wasn't sure if I should keep throwing parts at this or wait to see if you had any other ideas.

 

[muc]

The next steps are to determine if the engine not wanting to run above 1/2 throttle is due to engine guardian or fuel issues.

First things to do are considered the "basics".
1. Visual inspection, looking for any fuel leaks, looking for loose fasteners - especially any electrical ground or power connections, checking all electrical connectors - disconnect and check condition and terminals.
2. Remove spark plugs and inspect, use spark gap tester and make sure there is strong spark on all cylinders, compression test.
3. Dump the water separating fuel filter into a clear container and inspect.
4. Check fuel pressure - very important to check at the RPM and load the issue presents itself at - in the lake.
5. Hook up scan tool, check for codes and look at sensors for normal readings, check if engine is going into guardian while issue presents itself.

These are all the things your tech should have done. It seems like they didn't because they sold you on an ECM before finishing step one.

You don't have a scan tool and I don't know if you're up for spending the money and time that they require to learn to use them. I would call the tech and ask again what code they found, no good scan tool would just say fuel. There should be more.

You can do steps 1-4 with some time and about $100 in tools.

Here is a quick summery of guardian. Read it and see if that's what you think might be happening.

ENGINE GUARDIAN SYSTEM The Engine Guardian system monitors the critical sensors on the engine for any early indications of problems. Engine Guardian is functional whenever your engine is operating, so you never have to be concerned about whether or not you are protected. The system will respond to a problem by sounding the warning horn for six seconds and/or reducing engine power in order to provide engine protection. If Engine Guardian has been activated, reduce the engine speed. The problem will need to be identified and corrected. The system must be reset before the engine will operate at higher speeds. Moving the throttle lever back to the idle position will reset the Engine Guardian system. If the Engine Guardian system has determined the reset has not corrected the problem, Engine Guardian will remain activated, limiting the throttle. The problem must be identified and corrected before Engine Guardian will allow the engine to reach a normal operating RPM.

You asked about replacing the lift pump (low pressure fuel pump) I am very much against replacing parts without testing first. If you do that, you have no idea if you have now installed a part that is just as bad if not worse. You asked about the possibility of water freezing in the lift pump damaging it, it's possible but not very likely. I originally asked about the lift pump because there is a service bulletin about problems with engines built just after yours and sometimes those bad parts can get out in the wild or get installed on earlier engines.

Let me know how you would like to proceed and I will help as much as I can.

If you want to get started on fuel system testing, I will need a couple of picture of the fuel pressure gauge you're using. One closeup of the gauge face and one showing the hoses it has. To test the lift pump you will need a inexpensive vacuum/low pressure gauge and some correct size hose and T fittings as there isn't a test port.

One more question. Does your fuel line with the primer bulb in it or the fuel tank have an FDV (fuel demand valve)? It would have had one when you got the boat. Mercury and the EPA required it. The fact that your tech modified the fuel system illegally makes me wonder if they took the other needed steps when they did this. This engine was designed to have a pressurized fuel tank.

 

[KathyD19]

Hello again! I'll try to answer everything as best as I can (and I'll have to get back to you on a few things).
As for The Basics: I took care of most of those myself and the tech double checked when he got my boat the first time (of three times). I am the one who has been "throwing parts" at this issue mainly, trying to follow the fuel system from the beginning (the cracked plastic fuel tanks), to replacing the fuel lines and in line primer bulb which during that I inspected all of the fuel connections. The tech told me that he ran through all the electrical and used the multimeter (he said some other phrases relating to checking the electrical but I can't recall exactly at the moment) and said everything checked out.

I replaced the spark plugs this Spring, made sure they were properly gapped and my husband did the compression check when I was out of state for a week, said it was fine.
I drained the VST tank (in June of this year) into a glass canning jar before I removed it to inspect the screens/filters and the fuel looked ok to me, no noticeable water, which is why I was surprised when the tech told me that he DID find water in the fuel and that's what lead him to recheck my new replacement fuel tank, to which he noticed it was leaking gas from the gasket on the intake part when turned upside down and he presumed water had gotten in the same way during our very, very rainy Spring.
I ordered a fuel pressure gauge with an assortment of attachments from Amazon and checked first on muffs on the driveway and then on the lake under load. (It was normal range of about 41-42 on muffs and then about 45 at the lake but the needle started shaking and it dropped off when it began "the issue".


I do not have a scan tool for boats so I did not check that but the tech said he did each time. (I tried to call the shop today to be able to get more answers from him that you had asked but he was on vacation through tomorrow).

The tech did note on my invoice after I brought it in the second time (when it began giving warning beeps which it hadn't done previously) that "the motor is entering Guardian Mode"

I can attach a picture of the fuel gauge I bought from Amazon but if you need a better one I can grab it from the garage and take pictures.

Regarding the fuel tank, I actually asked him if they sold old-style tanks anymore that didn't have the EPA protective non-venting feature because I thought that was what had caused my problem initially (when he said the tank I had failed to vent, swelled up so much that it popped the seal and allow rain water to get in the fuel). He said there was info online how to bypass it yourself if you want to alter it. I contacted the Sceptor company that manufactured the faulty tank and they said it sounds like the vent port was faulty and said they would send me another cap. In the meantime, I decided to alter the cap on the replace Moeller tank myself, as I found on the web. I know in "the old days" the fuel tanks held pressure but didn't have the EPA modification on them. I do not have an inline FDV.
Let me ask you this...my original-to-this-motor plastic tank (that ended up cracking and leaking from the sun) had a fuel line hook up that had the two-prong style (attaching picture) but when I got the new Moeller tank, the tech attached a different single line connector on it for me. What is the difference between the two styles? I had only had experience with one boat and motor previously (a 1956 Johnson Javelin that I rebuilt with help from this amazing group) and it had the two prong style as well.

I will try to call the tech tomorrow and get more information from him. I honestly don't think he was trying to just sell me parts; he had actually ordered the new ECU and was going to install it when he noticed the issue with the prongs on the harness and fixed that much more cheaply than installing the new computer. He didn't have to do that, he could have just put the new ECU in, so that earned him some credit to me. My only issue is that he keeps returning it to me telling me it's running great on muffs, he hasn't taken it out on a lake to do an actual under-load test so it's always been me hauling it back home (hour round trip) and out to the lake to unload and then find out that no, there are still problems.

 

[muc]

"but the needle started shaking and it dropped off when it began "the issue".

Shaking can be normal on some engines, but should be looked into. Dropping off is something that needs to be looked into.

The tech did note on my invoice after I brought it in the second time (when it began giving warning beeps which it hadn't done previously) that "the motor is entering Guardian Mode"

This may or may not have been corrected with the harness repair.


Let me ask you this...my original-to-this-motor plastic tank (that ended up cracking and leaking from the sun) had a fuel line hook up that had the two-prong style (attaching picture) but when I got the new Moeller tank, the tech attached a different single line connector on it for me. What is the difference between the two styles?

They are just different styles. I don't have any experience with the one your tech used. My guess is that it's cheaper. I look at any fuel line connection as a source for possible leaks --- both pressure and vacuum. If you don't have a need to easily switch tanks, I would remove it and install a simple barb fitting with proper clamp.

Yes it would be nice to have more information from the tech. I totally agree they seem honest. There are many possible reasons why they have been reluctant to lake test. Possible they had a large back log of work and just didn't feel they had the time? If so now would be a great time for them to do this, August is normally a slower time in your neck of the woods. Maybe they thought that you wanted to avoid the added expense of a lake test? Your decision if you want to continue with them or go DIY.

Based on what I have read so far, my guess is you have a fuel system problem. This is something that the testing and diagnosis is mostly labor and knowledge.
You should consider getting the factory service manual, it would save you a lot of time and money in the long run.

90-8M0105570 eng JUNE 2016 is what I have.
Google 8M0105570
You will find that you have a choice of buying a paper manual for $75 to $100 or a digital version for about $25. What you should know is that the cost to dealers is $69 for the paper manual or they can download the digital version free as part of their yearly dealer fee. So this means anyone selling a digital download is doing so illegally and are most likely in a country that they feel safe breaking the laws of the USA. Buyer beware is all I'll say.

Let me know if I missed answering any of your questions.

 

[KathyD19]

Thank you again, for your thorough replay and fast response. I called the tech today and he was very open to answering all of my questions, to the best of his memory since it's been a few months since I first took it to him. He couldn't recall exactly what his scan tool said the first time he had the boat there (it's been 3 times total) but he said the second time, when it began throwing different warning beeps it said "fuel pump circuit". That's when he said he went through all of the electrical and used the multi-meter etc. Oh and by the way I asked what type of scan tool and he said it was a "Rinda's Techmate Pro".
Going forward he said I need to put the fuel gauge back on the high pressure side schrader valve and test it on the lake under load. He said whether it behaves the whole time or if it does the same thing again, he wants me to call him from the lake and tell him what the gauge is during normal running and/if during "the starved for fuel" issue. He said that it's possible the two plugs on the harness that he discovered were pushed back and over themselves could have caused damage to the high pressure fuel pump (the one I just replaced in June ) but he wants me to remove the VST and bring it to his shop for an afternoon. I purchased the new high pressure pump from him but installed it myself. He said he knows I'm "handy" but he would like to open the VST and make sure the pump is actually in there correctly, that it's not impeding the action of the float or anything else. That's totally understandable.

I forgot to ask him but I'm curious if there's a way to bench test a fuel pump, like check its electrical condition to see if it has been damaged by the harness plug issue or is it just one of those things that you "test it by using it"?

My husband is off work tomorrow then works four days (12 hour days) in a row so tomorrow is my next soonest opportunity to get out and test the fuel gauge on the lake. He needs to drive while I hang over the back seat and read the gauge. I trust him; we've been married almost 40 years and my warranty is up I'll let you know how that goes.