Volvo Penta 8.1 GI fuel pump issue

[cperry]

I have a 2006 Cobalt with a 8.1 GI. I was running it at about 4000 rpm yesterday and it just stopped suddenly like the ignition switch was shut off. When I tried to restart it, no luck. I was towed in and figured my fuel pump was shot since i didnt hear it cycle as it usually does when i turn the key to the start position.

Today just to be curious, I tried to start it. When i turned the key on, I heard the fuel pumps cycle on and then off and it started normally when i turned the key to start. It was idling for about 5 minutes and then shut off again with the same symptoms.

I disconnected the fuel pumps from the wiring harness and direct wired the pumps...both worked when direct wired to the battery so I figure the pumps are working properly. I next checked the wiring harness leads for each pump. No power in the on position or start position. I checked the fuses. Replaced the relays in the fuse block. Not sure if one of those is actually the fuel pump relay because 2 are labeled ignition and the biggest one doesnt have a label.

Any thoughts on what the issue may be? Is there a separate fuel pump relay somewhere else or some other component that could shut down power to the pumps?

Any insight would be appreciated!

 

[45Auto]

Re: Volvo Penta 8.1 GI fuel pump issue

Check and see if you are getting spark when it won't run. First thing to do is isolate whether it is a fuel problem or ignition problem.

I'm not sure exactly how the Volvo works, but it may have an oil pressure switch that won't allow power to the fuel pump if the engine is not turning over.

 

[rodbolt]

Re: Volvo Penta 8.1 GI fuel pump issue

power for the pump relay is supplied vi the pump fuse,cant remember but its like 10 or 15 amp.
the relay ground path for energizing it is done by the ECM.
power for the ign is the same.
easiest way to test is a rail pressure test,if it dies and you still have 50 PSI or so on the rail its not injector fuel supply.
loose 12V for the pumps, it shuts down fairly quick as rail pressure drops.
loose 12V for the ign coil or injector circuits and the shut down s instant.
loose the 5V CKP reference and the shut down is instant.

 

[cperry]

Re: Volvo Penta 8.1 GI fuel pump issue

Thanks Rodbolt. I actually have spark, just no power to the pump. When this problem occurs, there is no power to the yellow/red wire that supplies +12v to the pumps. Once the pumps shut down, of course there is no pressure to the fuel rack. Prior to the pumps shutting down, both pump pressures were within specs. The fuses are good. Any other thoughts? Could an intermittantly faulty ECM be shutting it down? Or could a intermittantly faulty alternator be the issue? I'm baffled. And if this is the case, how would I isolate the problem?

This is definitely a problem with the +12v to the pumps shutting down.