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5.7Gi 300J - Engine wont idle and revs fluctuate when gear disengaged

M

munkachunka

New member
Hi all,

I am hoping you can help me. I have a 2006 Volvo Penta Gi300j that is giving me grief.


Symptoms:


Engine will not idle - it tries to start but does not fire.


I can get the engine to start by disengaging the gear and giving the engine some revs. Once started it is not happy and the revs keep pulsing (for example between 4000RPM and 1000RPM) depending on the level of throttle.

What I have done:

I have swapped the Idle Air Control and that had no effect. My engineer misdiagnosed the issues, in hindsight it could never have been the IAC as that would have only generated problems at idle.

Plugs recently changed, distributor turns although I am not sure how fast it should be turning, cap was a bit dirty and I have given it a bit of a clean. Fuel appears to be okay as I depressed the little test valve and fuel spurted out. I used a jerrycan of fuel to rule out air locks.

Many thanks, Stu
 
Did it ever run OK for you? Replace cap and rotor ... Never underestimate how much grief old cap and rotor can cause you. How old is the fuel? History on boat??? Last tuneup??? Wires how old? " Input! Need Input!!! "
 
Hi Sandkicker,

Thanks for the reply - Here is the recent history.

Engine was recently serviced (Plugs changed, oil changed, oil filter changed). During the service I also took the opportunity to clean the injectors and also removed the filter from the fuel regulator and replaced with a clip (as recommended by a service bulletin).

After putting the boat back on the water it ran fine while taking it back to the marina (30 mins plus).

2 days later I took the boat out and again it was running fine. When I tried to return home I had an issue. The engine started and was idling for 10 mins or so while I loaded up the boat. When I went to leave I noticed the engine had died. My daughter was on the boat at the time and I assumed she had fiddled with the ignition (turned it off and flooded it). I got a tow back to the marine and when I got back I decided to try and start it again. It started and ran for 10 mins with no problems.

Subsequently, two further days later I tried to take it out and it would not start. That bring me up to the point of my initial post. i.e.

Engine will not idle - it tries to start but does not fire.

I can get the engine to start by disengaging the gear and giving the engine some revs. Once started it is not happy and the revs keep pulsing (for example between 4000RPM and 1000RPM) depending on the level of throttle.

When I checked the plugs they were completely dry, IAC appears to be functioning fine (when power is applied it blocks the air flow but when the ignition is turned on it retracts to allow air flow.), no fuel leaks from the regulator return hose.

I am thinking of checking the fuel pressure with a gauge (fuel spurts out when I depress the test valve), and like you suggested, replacing the cap and distributor.

Regards, Stu
 
I am struggling to understand why it will not start when in idle but does start if I disengage the clutch and apply revs (albeit badly with fluctuating revs). What changes? Is it simply a case of more fuel and air?
 
Lets try the cheap and easy to fix stuff first. Check water separator to see if its full. Cartridge types are drainable ( into a glass jar so you can see whats up... also color of fuel, i.e., cloudy vs clear)
 
sandkicker said:
Lets try the cheap and easy to fix stuff first. Check water separator to see if its full. Cartridge types are drainable ( into a glass jar so you can see whats up... also color of fuel, i.e., cloudy vs clear)
Click to expand...

Ayuh,..... I'm runnin' the canister type fuel filter,....

Crack it loose with yer wrench, then slip a freezer baggie 'round it, spin it off, 'n drop into the baggie,...
Seal the baggie up, 'n turn it over,....
You can see any water 'n crud,.....

Also contains the mess til ya find proper disposal,....
 
bondo said:
Ayuh,..... I'm runnin' the canister type fuel filter,....

Crack it loose with yer wrench, then slip a freezer baggie 'round it, spin it off, 'n drop into the baggie,...
Seal the baggie up, 'n turn it over,....
You can see any water 'n crud,.....

Also contains the mess til ya find proper disposal,....
Click to expand...

Awwwwwh. Just when I got good at contortionist gymnastics...☺
 
Hi all,

An update of a day spent on the boat.

Changed the water separator - fuel inside it was clear, no debris and no water. It was about 7/8th full when I swapped it out (the other day when I checked it was full).
I changed the distributor and rotator and also checked each spark plug, all spark plugs firing and producing a yellow spark.

To try and identify the fault I disconnected the Throttle Position sensor. No effect when trying to start in idle. When trying to start with revs applied it would not start. The sensor does affect the symptom but in a logical way. I therefore assume the sensor is good.

I disconnected the MAT/MAP sensor on the top of the intake manifold. No affect noticed. What affect should this have?

Also - I noticed today that the higher I rev the engine the more stable it seams to be. For example - when running between 3000 and 4000 RPM it is unstable and almost dies out (when fluctuating). When I increase the revs to about 5000 it seams fairly stable and only fluctuated a little. I kept it running to get the temperature up to normal working range but when reducing the revs back to idle it dies.

thanks, stu
 
Repaired.

Hi all - For future reference the fault with my engine was the MAT/MAP (Manifold Air Temp and Manifold Air Pressure) sensor.

Regards, Stu
 
Thanks for status... Often folks post, ask questions and we never hear from them again. Very frustrating (at least for me)
 
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