94 850 Turbo keeps blowing fuel pump relays

Post by **precopster** » 07 Jul 2015, 08:29

Easy:

Remove fuel pump fuse and place ammeter across fuse terminals to measure current draw of pump circuit while jumpering positions 15 & 87 on fuel relay connectors.

What is the current draw?

draser · Post by **draser** » 07 Jul 2015, 18:03

Current measured will be less than fuse rating. Is there a pump control module on these cars?

draser · Post by **draser** » 07 Jul 2015, 18:34

There's an overload relay #2 in the electrical box where the fuse #2 is for fuel pump. The circuit also powers central locking, so see if that works when car quits.

Post by **precopster** » 07 Jul 2015, 21:11

draser wrote:Current measured will be less than fuse rating. Is there a pump control module on these cars?

Sure however what is fuse rating? Replaced with higher one to make a problem go away or a standard rated fuse for that position.

draser · Post by **draser** » 08 Jul 2015, 06:15

Several things going on here: there's this overload relay that monitors current for the pump, so when car quits you can check volts on blue/red wire that powers relay contact. Then, there's the relay coil voltage on yel/gray wire coming from ecu which can be checked when engine quits. Fuse for pump is 15 amps. There are also 2 grounds, one for relay coil in electrical box and one for pp under the rear seat. The coil gnd can be ohmed to chassis, use meter lower ohm scale, wire at relay socket is black, and pump gnd is black also. You should read zero ohms for gnd wires.

Post by **Carbon15** » 08 Jul 2015, 07:01

I'll check all of these this weekend when I'm at the garage. It would be nice if it was the pump, got a working one in the 98 that I'm striping.

Post by **Carbon15** » 09 Jul 2015, 06:07

Thanks Mike, that's good information. I guess the worst case scenario is that I pull the pump out of my parts car.

Post by **misha** » 09 Jul 2015, 07:28

It's the easiest and fastest way.

Post by **Carbon15** » 25 Jul 2015, 14:45

Sorry for the delayed response, finally got to the car to work on it. Got to the car, hot wired the relay socket, car started up and ran for five minutes. Swapped out fuel pumps, car started and ran for the usual five minutes then died. Ran a voltage check at the relay socket, got 10.5 volts, oddly the engine caught while checking the voltage. Checked the voltage at the pump, got 10.5. Tried starting the car with the repaired relays, would not start. Something is shutting the engine down, could I be looking at a bad ECU? On board diags had nothing fuel or ECU related.

Post by **Carbon15** » 25 Jul 2015, 14:49

precopster wrote:Easy:

Remove fuel pump fuse and place ammeter across fuse terminals to measure current draw of pump circuit while jumpering positions 15 & 87 on fuel relay connectors.

What is the current draw?

Is 87 in the relay socket?