Weird starting problem

[EauRouge]

I did a search and I found some great electrical diagrams of the fuel system that helped with some of the diagnosing I was able to do. However, I was not able to find anything relevant or similar to what I am experiencing.

I am having a problem with my 86 930 that is not driven regularly. Not sure if the following info is relevant, but I decided to include it. I recently had some work done to replace the original fuel lines from the tank to the engine that had started to leak. Car was running perfectly when I picked it up. After sitting again for ~3 weeks, I got a chance to drive it again, but started experiencing problems where the engine would occasionally sputter under load, almost like bad gas. I put in some Techron fuel cleaner, Marvel Mystery oil, and a few gallons of fresh gas.

I let the car idle outside for ~30 mins while occasionally pushing the accelerator and revving it up. When it seemed like the car was running fine, I drove it into the garage where it promptly died. I tried to restart it, but it seemed like I completely lost power as I could not hear the fuel pump when I tried to restart it. I pulled the fuel relays, checked pin 30 for power, and found there was no power. After several frustrating attempts to diagnose the issue, I slammed the door, and found the power come back (key was still in ignition in the on position). I lost power again, but I was able to recreate the issue, getting power back after slamming the door.

I suspect something is loose or a problem with the ignition. Maybe a loose ground? Any pointers and help would be greatly appreciated.

TIA

[908/930]

Is everything else electric working? Heater blowers, Lights? Check the Yellow relay in engine compartment is sitting correctly, also check overspeed relay under driver seat.

Chance the ignition switch contacts are worn out. Fuel pump fuse have power?

[gsxrken]

Check your speed relay connector under the driver seat.
Next time your pumps lose power, pull the plug on the back of the air flow meter, and start wiggling things. If you’re lucky the pumps kick on (b/c the plug is off the meter) and you’ve found your issue.

[EauRouge]

Really appreciate the help. I was sidelined with a medical issue and have not had a chance to test out the suggestions.

[mark houghton]

Originally Posted by gsxrken

Check your speed relay connector under the driver seat.
Next time your pumps lose power, pull the plug on the back of the air flow meter, and start wiggling things. If you’re lucky the pumps kick on (b/c the plug is off the meter) and you’ve found your issue.

Yeah, wiggling things is part of the diagnostic approach. Did the same years ago and found that my overspeed relay was dirty. Just reach under the seat and bang around...shazaaam, the pumps started up. Took that bad boy out, cleaned the plug contacts, resoldered all the circuit board traces I could get to, and no problem after that.
The only prerequisite is that your car has to be dead in the shop...ideally...as apposed to on the road somewhere.

[Alan L]

The wiggle test is ideal for you. If the pumps are running, wiggle until they stop. If they aren't running, wiggle til they start. Don't forget the over boost switch on the back of the intercooler - white wire. That one can be a killer.
Alan
Edit - since slamming the drivers door fixes things, that relay under the seat would have to be a prime suspect.

[EauRouge]

Just a quick update...

After checking for anything loose and several frustrating weeks of checking electricals, by luck I was able to find the ignition switch went bad after reading some recent posts by folks with ignition switch problems. After installing a new ignition switch, I was able to successfully start the car, but it was running very rough with lots of sputtering. Just for *****s and giggles, I replaced the fuel pump relays with some Restoration Design relays I had, the car started running fine.

Thanks for the help!