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50 GI over fuels engine while running over 2200RPM Help

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benjaminbr

New member
"My 1999 21’ Four winns 5.0 GI

"My 1999 21’ Four winns 5.0 GI runs and starts great when accelerating but will loose power and flood motor when cruising. With 2 or more people in the boat it takes off fine to 4200 RPM but then the RPM starts dropping as the engine loads with fuel. With an empty boat I can run at 4200 RPM for ever until I turn a sharp corner and then it again loads with fuel. When loaded with fuel I will have about 25% power left and cannot get the RPM above 2000 RPM.
The boat will run at 2200 RPM for hours without missing a beat. When this problem first started there was some backfire if to much throttle is given. Repairs listed below have eliminated this problem.

The problem can be reset by revving the motor in neutral (only to clear the motor for easy restarting). Turning the key off for 5 seconds and restarting to acquire full power again.

I usually know enough about motors to survive and I am also under guidance from a marine mechanic but does not have enough experience with Volvo Penta 5.0GI’s.
I want to fix what I can or trouble shoot the problem before sending to the marine repair shop due to the fact this repair requires water testing and there does not appear to be a smoking gun to solve this problem. Letting a marine repair shop experiment can become very expensive.

Things that were already completed:

Spark plugs, wires, rotor – cap was corroded but did not improve problem – but no more backfiring.
Fuel tank removed, drained, cleaned and new fuel filter – Suspected water – fuel filter was cloudy
Removed and cleaned high pressure pump reservoir – Found lots of fine particles – gasket edge was a little torn but not leaking – I am ordering new but I do not think it is the problem. O-ring on the high pressure line was damaged – Replaced with new

Things I am suspecting:

Replacing ignition coil – I do not believe this will work, but stranger things have happened.

Computer or sensor trouble – Due to the fact I can temporarily remove the problem with turning the ignition off.

Fuel pressure regulator that I believe is in the TBI and is not serviceable.

TBI – The most expensive part

Any help would be appreciated"
 
"I just found the problem that

"I just found the problem that was causing my 99 5.0 Gi to bog down at higher RPM and it also fixed the problem with the over fueling. I traced the problem to a plastic line that ran from the low pressure pump to the high pressure pump. My engine is a 99 5.0 Gi and most but not all Gi's run a plastic fuel line and not rubber. The fuel line is braided on the outside and made it almost impossible with out physically feeling the line for a soft spot in the plastic. I still did not know the extent until I cut the braiding material of and found that the plastic had been damaged by flexing or improper assemble. It was now permanently soft (plastic kink) in this spot and could not expand with the low psi from the pump. I would say restriction was 1/2 to 1/3 the original tube size. The trouble area for me was where the plastic met the steel connector (under the yellow guard low pressure pump side)

This would be almost undetectable by the eye if you are not looking for it. Pressure readings were fine but I suspect the low pressure reading would have showed if I had water tested. Talking to local Volvo Penta dealer this sounded new to them. On the internet I have not found anything about this problem.

I took my hose off, ground the factory crimped hose off and replaced it with standard fuel line (temporary new one is on order, over $90 for new and back ordered currently) 2 months of work, the surging and over fueling gone. Maybe the senior members can explain why the motor acted like it was getting to much fuel (sensors) instead of typical starving symptoms. This line also sits on the manifold, beside the valve covers and I suspect the heat on the fuel was another issue. I do not know if there would be any trouble codes in computer because I did not check.

I hope this helps someone in the future because I think the high rpm issues are common with the 5.0 Gi's from all the high rpm issues on these motors or simular engines running plastic fuel lines.

Also to be a smart ass, thank you for all that posted."
 
"hey ben

I read your post!

"hey ben

I read your post!

I read them all when I have a problem or when I have extra time(very rare) And have noticed many posts that seem to go unanswered. If the senior members don't get paid for their time it is a miracle that they answer any at all. I just started using the site, find it full of very helpful info, and plan on posting all of my maintenance issues and their solutions in the hopes that it might help someone else with similar problems. It is probably some combination of bad timing, maybe vacations, or maybe who wants to spend time typing on the computer if their boat is working great? Also it took me several hours to scan through the tons of info on this site before I made my first request. I didn't want El to scold me!

paul"
 
"Thanks Paul,
I fully underst

"Thanks Paul,
I fully understand your post. This is a great site. Also a great place to pick the brains of people experienced with motors. (For free)
proud.gif
It's just my joker personality. I should of put a happy face after it. Thanks for the reply and happy boating
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"
 
"He Ben, it could also be that

"He Ben, it could also be that no one had a clue
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. An engineer told me that a very lean engine will mimic an overly rich mix. This is because the lean mix will not support proper combustion so not all the fuel is burned. The unburned fuel carbons up the plugs and is also exhausted, hence the smell of fumes in the exhaust. Sounds feasible I guess."
 
is it actually true that you g

is it actually true that you guys get no compensation for the great advice found here from advanced members?

paul
 
"You may be going into Engine

"You may be going into Engine Protection Mode. This can be due to low oil pressure, high engine coolant temp, or high exhaust elbow temp. It takes a combination of one of these conditions (or preceived condtions) and higher engine RPM to set this mode, and once set it will limit RPM to 2500. It does this by shutting down one injector bank. If you have a TBI system, you can actually see that one injector has shut down when this happens."
 
"Paul, I don't know about

"Paul, I don't know about others, but I don't get (nor expect to be) paid for something I gladly do on a volunteer basis. I believe in helping others, and I guess that is what keeps me going in this forum. I have been helped many times in the past by others in several aspects of life, and (almost invariably) the people who helped me did neither expected nor wanted anything from me in exchange.

If any of my contributions to the forum did help any you to solve a problem with your boat and you feel you owe me something, then I suggest that the best way of paying it back is by trying to help others in any aspect of life in any way you can."
 
"El Pescador

Hope I didn&#

"El Pescador

Hope I didn't offend, just trying to figure how this site works. Based on the volume of posted replies and the quality of the info I foolishly assumed...It's not every day that you get to witness a job so well done and it is always a pleasure. Thanks and much appreciation for all the help. I like to think of myself as a helpful person, but you definitely take it to another level
happy.gif
paul"
 
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