Mystery: Missing Fuel Pump Relay

[StephenA]

Doggone fuel pump relay ain't where it's supposed to be...
My 92 K2500 has been stalling 5-10 secs after startup, only to restart & run fine. I hooked the lift pump directly to the battery and it ran fine. I figured to replace the pump relay and the OPS ('bout time), as I could see no voltage getting to my silent lift pump. Ordered the parts, & only the pump relay (part# 14089936)came in. I went to replace it exactly where the GM manual says it's s'posed to be, and the darn thing just wasn't there or any place else under the hood.
GM pictures point to the driver side sidewall just in front of the firewall. -Nope
Now I'm not accusing anyone of stealing it, but GM seems to think this truck is supposed to have one, & I'd love to put this new one in if I could just figure out where the (*&(*)^%$!!! things goes! :eek: :eek: Help...!

[bobt]

Hi. On my '93, it is center-left rear of engine block hidden by the glow plug controller. Try there. Good Luck.
Bob

[StephenA]

OK,OK, Bob - I found it, right where you said. I can understand my missing it, you see, it was disguised by GM... It was under a nice pice of plastic which said in BIG LETTERS IN PLAIN VIEW: FUEL PUMP RELAY!!!! Duh...
I also found the pump fuse in a nice little encloser. Fuse was OK. Relay was probably OK, but was replaced anyway; still no voltage at the fuse or pump; - I figure the OPS. It's got 12Volts going into one pin on the sender, I register changing voltage on another pin, which is the oil gauge polling for a reading I think, but nada on the grey wire going to the relay & the fuse & the pump. Got to be the OPS, right?
Amazing how my truck runs so well without the lift pump -only stalls occaisionally on startup...
Thanks Bob!
Stephen

[Turbo Al]

The OPS on these trucks is very unreliable on these trucks. I usally replace it at the same time as the lift pump just so they both get the same useage. 180,000 miles and three lift pumps/OPS. They also get a little clogged with derbis which may cause them to flutter a bit.

[StephenA]

Is it possible for the OPS to read ok on the gauge & still not send enough voltage to trigger the pump relay into coming on? If the OPS replacement tomorrow doesn't do it, I'm thinking I may have some frayed wires; or would the ignition be the problem? Pumps thumps loudly only when hotwired.
Thanks, Stephen

[gmctd]

OPS is two separate circuits - resistor to ground for oil press gage, switched +12v for lift pump. Switch contacts carbon up without affecting gage resistance.
Voltage is supplied to pump only when engine is running.

jd

[lupey6.5]

check for voltage to lift pump when cranking motor if you have juice when cranking but lose it when motor starts you have a bad ops i have a 94 w/225k i've been through 5 or 6 ops and still on lift pump#2 good luck

[StephenA]

Eureka!!! Bought the special socket & popped in the new OPS & the fuel pump ran like a banshee! No more stalling after startup. HOORAY!!!
Thanks everybody!!!!
Also, the 97 Fan Clutch with the DMAX 9 blade fan is a real easy bolt on!!! No need to widen the cowel on my truck- 1/2" clearance all around. Truck won't heat up above 210 no matter what and typically runs at 180!!!
Thanks to everybody for all the help & drawings on the bypass mod!!!! :D