Volvo Penta Fuel problem - air ? Hunting

[Lenster]

I have a Penta 2000 series engine (2 cylinder) reconditioned and professionally installed on my westerly centaur. I have also replaced the fuel tank as it was rusting and full of sludge. All fuel filers have been replaced.

My problem is that the engine will start only after cracking the bleed screw on the filter housing (or prolonged cranking) and once started it runs perfectly for about 5 mins then begins to hunt and slow until the engine eventually stops. If I crack the bleed screw during the hunting the problem goes away for a few minutes. The hunting is evident at high revs or low revs.

I am now a little short of ideas as the tank is new, filters new (and changed twice just in case there were remaining particles in the line) engine runs ok but for some reason it accumulates air somehow.

I have connected a clean fuel supply directly to the inline engine filter to rule out air ingress from the fuel lines. But the same symptoms persist.

Any ideas ???

 

[RichardS]

Could be that the air leak is actually in the engine filter, perhaps past the O-ring which seals the filter itself.

Richard

 

[Lenster]

Richard it could be but I changed that filter yesterday again to double check and the filter was well seated.

 

[Chris_Robb]

Is your tank positioned above or below the level of your fuel pump?

If it is below, it is sucking in air somewhere between the Fuel lift pump and the tank draw off fitting.

Look at every joint and tighten, including the tap which have been known to leak in air. If the tank is below, then you will not see fuel leaking as the air is being sucked in and no fuel will therefore be leaking out. If you have one of those CAV fuel filters - suspect that, they can be difficult to seat.

 

[benw]

Have you checked the fuel lift pump gauze filter. We had some bug in this part of the line and once cleared the engine ran fine. Up until finding this we would suffer the same symptoms as described. It may be historical as you mentioned sludges in your previous tank.
Ben

 

[Lenster]

Chris - I put a temporary diagnostic tank together and connected fuel direct to the lift pump so I am sure that the issue lies between the pump and the filter but don't know enough to be certain.

 

[Lenster]

Ben

No that's something I haven't checked. It would make perfect sense as this lines up with the tank issue and is the only bit I haven't checked. Mainly because I didn't know the lift pump had a filter.

Top man. Next check lined up and fingers crossed.

 

[Chris_Robb]

Did you have success running it like this? It will certainly narrow down the problem. Good luck.

 

[Sailorsam101]

If it's a new tank i would also check the tank breather. If that is blocked then it will create a vacum in the tank and nothing will flow out until air is let into it.

Try running it with the fuel filler cap off and see what happens. I have seen this exact thing before

 

[Lenster]

Chris

After an hour of fault finding and chasing leaks it would appear that there was air being drawn in via the tap. First checks seem to be all good but a lack of water prevented full testing. Fingers crossed - will feedback how the full sea trial goes.

 

[Daydream believer]

Have you checked the fuel lift pump gauze filter. We had some bug in this part of the line and once cleared the engine ran fine. Up until finding this we would suffer the same symptoms as described. It may be historical as you mentioned sludges in your previous tank.
Ben

Interesting--- I did not know of such a filter. I have a 2020MD is it the same?

 

[benw]

Not sure of other engines but we have a 2003.
It is dead easy to get to the lift pump gauze filter, switch fuel line off, unscrew the nut on top of the lift pump, break the seal and there you have it. If there is bug in there it will be obvious.
The link below may be of interest:
http://www.ybw.com/forums/showthread.php?311532-Volvo-Penta-2002-slowing-down-and-stalling

 

[benw]

I have put a photo of the lift pump and gauze in my album in case it is of any use.

 

[Lenster]

I couldn't find any access points to get to a gauze filter on mine ?

 

[scottie]

There are two versions of the fuel pump fitted to most of the Volovo own build engines IE MD1 to MD 17 and 2001/2/3/3t.
the early version has a bolt in the middle of the cover which allows access to the strainer the other which replaces it has a can like top and is a sealed unit
It's also worth replacing the washers on bleed screws if you have to disturb them as they squash.