Volvo penta fuel problem.

[rogerstown]

I hope some kind soul can offer me some advice. Penta MD2020 D, 300 hrs on the clock. Last week fitted new pre and engine diesel filters bleed the system, ran engine for 20 minutes at low revs everything fine. Lifted in yesterday engine started first time then running fine for short while then cut out, towed onto mooring. The engine is starting and will run but when throttle advanced it hunts up and down running at 3,000 rpm for a while and then down to 500 (0n the same throttle setting). With the engine running I am getting diesel at the injector delivery nuts but strangely none at the vent screw on the top of the filter mounting. Activating the hand pump leaver on the filter mounting (engine stopped) also will not produce fuel. I’m convinced its a fuel problem but what? Thanks in advance for any advice.

 

[tr7v8]

Could be an air leak, seal cockled etc.

 

[Ludd]

Air getting in somewhere(possibly filter seal not seated properly? ) or pump not sucking properly,causing insufficient fuel delivery. Could be a pinhole or split in pump diaphragm.
There might be something blocking lift pipe in tank,or if your tank is full,breather might be blocked---in fact I'd check that first.

 

[PCUK]

As you changed the filters it is almost certainly filter related. Remove both and re-check everything.

 

[rogerstown]

Thanks for the advice folks, vent seems to be ok, I am thinking the pump but filters are the most obvious; only I am in denial that having changed filters for over 40 years I got it wrong. I see pumps for sale but not diaphragms and springs; does anybody know if you can buy service kits with these?

 

[ianj99]

I am fitting an electric lift pump to my Perkins 4108 (same engine?) and removing the existing mechanical one. One advantage is that it can be switched on to help bleed the air out, and another is, no diaphragm to split.

 

[Quandary]

A boat came in to the basin yesterday after its first motorsail of the season from Ardrossan. Engine (VP2030) was not revving on the latter part of the trip. Owners changed both filters extracting some watery muck from the seperator. They know how to do this properly. I helped check fuel tank for more water or bug, very little, not enough to need more than biocide. After bleeding, on each try it was running OK under load for about 10 mins, before losing power. No sign of any fuel so we suspected air getting in on the tank side of the system, prefilter gaskets ok and no diesel weep. Checked all gaskets hose unions etc. Consulted local expert who suggested an obstruction in the fuel line, took apart fuel tap as most likely point, all Ok; then suggested governor problem but thought to be unlikely. Second specialist diesel engineer summoned who started again, at this point in time he is convinced it is air getting into the pre-filter but as I write he is still investigating. Hopefully he will have a solution tonight but I can not post again until the morning.
Since the history is similar I will update once I have a satisfactory answer

 

[chiefeng]

I had the same problem on my VP 2002. I don't know if the fuel delivery pump is the same but on mine there is a fine mesh filter in the top of the pump that was blocked solid. The symptoms you describe is more than likely air getting into the system. One way to check is to attach a clear pipe to the return from the engine to the fuel tank and put a loop in it that is higher than the engine and tank. Any air will accumalate in the loop. Also try all connections in the HP fuel system for tightness not just the filters.
For parts try Key parts, they are very helpful (no affiliation).
Hope this helps.
Rgds
Bob

 

[rivonia]

We had the same problem (same engines TWINS) It was the washer on the bleed valve letting air in .Solution NEW WASHER= problem solved.

Hope it is that simple for you.

Peter

 

[ianj99]

A boat came in to the basin yesterday after its first motorsail of the season from Ardrossan. Engine (VP2030) was not revving on the latter part of the trip. Owners changed both filters extracting some watery muck from the seperator. They know how to do this properly. I helped check fuel tank for more water or bug, very little, not enough to need more than biocide. After bleeding, on each try it was running OK under load for about 10 mins, before losing power. No sign of any fuel so we suspected air getting in on the tank side of the system, prefilter gaskets ok and no diesel weep. Checked all gaskets hose unions etc. Consulted local expert who suggested an obstruction in the fuel line, took apart fuel tap as most likely point, all Ok; then suggested governor problem but thought to be unlikely. Second specialist diesel engineer summoned who started again, at this point in time he is convinced it is air getting into the pre-filter but as I write he is still investigating. Hopefully he will have a solution tonight but I can not post again until the morning.
Since the history is similar I will update once I have a satisfactory answer

Tank vent blocked perhaps? When the engine revs drop, open the filler and listen for a hiss.

 

[bobgoode]

Same symptoms as me five years ago. Traced to a clump of diesel bug floating in the tank.

Engine runs for a while till the bug clumps on the pick up pipe and reduces flow of fuel. When engine is turned off suctions realeases the clump which drops in the tank. Starts again when engine run again.

 

[Quandary]

Tank vent blocked perhaps? When the engine revs drop, open the filler and listen for a hiss.

Promised pdate on my post about similar problem yesterday-
No, I checked that at the start when I cleaned the tank, it is about 25mm dia. on this particular tank.
The diesel engineer worked at it methodically using a small portable fuel tank to supply fuel at each stage of the system, everything worked right back until the main fuel tank. His conclusion is that there is a small pinhole near the top of the fuel lift pipe (perhaps where it is welded in) which lets air in there, this was supported by the owners experience that it ran Ok when heeled a pit to stbd when the whole pipe would have been immersed. There was a second lift pipe for the heater so he has changed it to take all fuel from it and it now works OK but there is a bit of scepticism from the boatyard man.
The tank on this boat is an impressive replacement, very tall and slim, apparently made in an aircraft factory by the previous owners, all the stainless steel is at least 5mm.

 

[Playtime]

I hope some kind soul can offer me some advice. Penta MD2020 D, 300 hrs on the clock. Last week fitted new pre and engine diesel filters bleed the system, ran engine for 20 minutes at low revs everything fine. Lifted in yesterday engine started first time then running fine for short while then cut out, towed onto mooring. The engine is starting and will run but when throttle advanced it hunts up and down running at 3,000 rpm for a while and then down to 500 (0n the same throttle setting). With the engine running I am getting diesel at the injector delivery nuts but strangely none at the vent screw on the top of the filter mounting. Activating the hand pump leaver on the filter mounting (engine stopped) also will not produce fuel. I’m convinced its a fuel problem but what? Thanks in advance for any advice.

I had a similar problem a few years ago after changing the fuel filters on a Volvo MD22 and bleeding the system as per the Volvo manual. It ran fine for more than 10 minutes and then died.

It turned out to be air in the HP feed to the injectors. This is supposed to be 'self bleeding' but obviously wasn't. I had to bleed each injector in turn and on two of them there were distinct bubbles.

Have you bled right up to each injector?

 

[grafozz]

Try opening up the fuel supply pipe to engine before the filter and , BLOW through the whole system , from the fuel filler cap , you,ll need a good pair of lungs but you will be amazed how much fuel you are able to push /purge out ! the same thing occured to me going through the Raz ! and this approach was the only thing that got the motor going .(MD2010)

 

[rogerstown]

Thank you very much for all the suggestions I guess the real answer is BOAT break out another twenty or is that ton or maybe thousand

Promised pdate on my post about similar problem yesterday-----
The diesel engineer worked at it methodically using a small portable fuel tank to supply fuel at each stage of the system, everything worked right back until the main fuel tank.

What an excellent idea thank you. (I had a boat once with the fuel tank higher than the engine a joy to work on leaks bleeding etc.) I have tested everything I can think of and all the suggestions made to me. My conclusion is that it is the lift pump, basically since I am not getting any air out of the bleed screw on the engine filter despite nearly wearing out several fingers hand pumping. I have now ordered a pump but will have to wait about a week SO I have some time and could rig up a little gravity tank just in case I missed something, this could do lots of tests including parts of the system where air normally leaks in.

"Try opening up the fuel supply pipe to engine before the filter and , BLOW through the whole system , from the fuel filler cap---" tried that section by section but not in one go straight from the filler cap, haven't got the lungs but maybe if I needed to in the Raz I would find the strength.

 

[Ludd]

Promised pdate on my post about similar problem yesterday-
No, I checked that at the start when I cleaned the tank, it is about 25mm dia. on this particular tank.
The diesel engineer worked at it methodically using a small portable fuel tank to supply fuel at each stage of the system, everything worked right back until the main fuel tank. His conclusion is that there is a small pinhole near the top of the fuel lift pipe (perhaps where it is welded in) which lets air in there, this was supported by the owners experience that it ran Ok when heeled a pit to stbd when the whole pipe would have been immersed. There was a second lift pipe for the heater so he has changed it to take all fuel from it and it now works OK but there is a bit of scepticism from the boatyard man.
The tank on this boat is an impressive replacement, very tall and slim, apparently made in an aircraft factory by the previous owners, all the stainless steel is at least 5mm.

Had just that problem(hairline crack) on a lorry once. Pull out to overtake,fuel sloshed around,crack opened up,in went the air .Pull back in ,fuel settled down,crack closed ,all a ok---till the next time! Nightmare till I twigged!