I have a 780 V6 that was sitting for a few years. I got it running long enough to drive home but haven't been able to get it to run for more than a few seconds since. It has good spark on all cylinders and will run off starting fluid so I know it's a fueling issue. Cracking the fuel line at the rail it seems to have decent pressure.

​​​​​​The main pump runs (I can hear it and have confirmed it pushes fuel) and it has a near full tank so the in tank pump shouldn't matter from my understanding. When turning the key on the fuel relay will click randomly sometimes in rapid bursts and the injectors fire at random. the car turns over fine and will start up and run for a second or two before dying with the relay continuing to click at random. Sometimes it keeps going for 30-40 seconds if I hold the revs at 2-3k others it bogs and dies immediately. It has also been backfiring out the intake as it dies sometimes.

I got this car for free so don't want to throw a ton of money at it. I have a 760 diesel and 740 b230 as well and have never seen anything like this. I checked grounds and swapped known good relays to no avail. Any ideas? I'm starting to think it might be a bad ECU but am not sure how to go about testing for that.

I also tested with an external pump and tank and couldn't get it to run at all when doing so.

 

Makes a lot of sense. I was wondering why my battery kept dying. I was thinking bad battery, corrosion in the ground, maybe alternator. But the dealership told me it was the fuel pump relay they had to replace so I came on here to see what that is.




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