I have a 91 rs 3.1 that has always started flawlessly. Now it tries to start but stumbles and dies, no pedal action will keep it running. Code 54 was in ecu. When I turn the key to on I hear the two second fuel pump run. swapped fuel pump relay anyway no good. I'm assuming the two second action of the fuel pump is to fill the gas line to the motor. My question is, is that based on a timer or is it based on acheivement of proper fuel pressure in the line? The engine is getting gas just not enough, if there were a leak in the line I'd expect to see something along the fuel rail to the motor but i don't. I just finished replacing the intank fuel pump in my volvo 850 and was glad they allowed access thru the trunk panels. I dread having to drop this tank now. The fact it does the two second prime each time I turn the key makes me think it's sucking air somewhere and the absence of any sign makes me think it might be the coupler hose within the tank. Does anyone know whether during the initial activation of the fuel pump the cutoff signal comes from proper fuel pressure obtained or whether it's just a two second timed function. thanks

 

as per code 54 flowchart: 2 second runtime- yes, cleared code, attempted to start several times, checked for codes- ecu clean so "go to section B intermittents" not included in flowchart. does anyone know where this excerpt is from? It's got a new fuel filter and as I say the fuel pump does it's 2 second cycle each time so I would think it's not clogged unless the two second runtime with a clogged filter would just dump the overflow caused by a restriction back in the tank?

 

flowchart is from trickster post here

 

disconnected fuel line- post filter, appears to be good steady flow. 20 bucks and I'm already under car, going for new filter anyway.

 

replaced filter, cleared ecm, same problem, pulled code 54 again. just for the heck of it I disconnected the tps, no difference (although I think it operates in pre programmed 'closed loop'? for awhile anyway before checking sensors) starting to think ecm problem.

 

dropped ecm and left connected on passenger side floor, going to check pinout voltages with key in 'on' position as per-
http://chevythunder.com/fuel%20injec...20(ecm#1227730)

 

Ya know, a quick shot of starting fluid could narrow down whether the problem is fuel-related or spark-related real quick. Pumps can run but not deliver adequate fuel pressure to the injectors if the pump is worn out or the regulator is going bad.

You can still narrow down the general area of problem on a computer controlled engine using old school diagnostic methods. They just won't help you much beyond that point.

 

it does start so spark and fuel are present, but it stumbles and dies. And yes I did spray starter fluid in the throttle body and it didn't help.