electric lift pump

[orebec]

I'm Having a problem starting after the engine being turn off for a while
the lift pump is working when the engine is running. The problem is when i turn off the engine i don't hear the lift pump anymore. it used to run for for a while before shutting off. I guess that must be the problem. Also when I prime the pump by putting power to one side of the fuse on the firewall the pump runs. Someone have a clue about this problem?
Thanks

[trbankii]

It would help to know what year your truck/SUV/whatever might be...

[orebec]

It would help to know what year your truck/SUV/whatever might be...

Chevy silverado K1500 1994 diesel 6.5
also there is no 12 volts power on the truck side at the lift pump when the ignition key is at run/crank and when I just turn off the motor until the oil pressure
I think it's the lift pump relay is there a way to check this relay?

[orebec]

Chevy silverado K1500 1994 diesel 6.5
also there is no 12 volts power on the truck side at the lift pump when the ignition key is at run/crank and when I just turn off the motor until the oil pressure
I think it's the lift pump relay is there a way to check this relay?
someone can tell me where is the relay is it under the hood next to the fuel pump fuse or under the driver side dash near the handbrake?

[trbankii]

The lift pump runs through the OPS (oil pressure switch) as a safety feature. If you lose oil pressure, the lift pump stops running.

[DickWells]

You may have "fried" the contacts in the oil pressure sensor. They run the fuel pump, with no relay. After I experienced failure on the old Suburban, back years ago, I put in a new pressure sensor, and then wired a new HD relay to power the pump, with the old lead to the sensor acting to only activate the relay, and freeing up those little sensor contacts.

[arveetek]

This is an awesome product:

http://www.kennedydiesel.com/detail.cfm?ID=402

I've had this kit on my Tahoe for over 10 years now, and has worked flawlessly. The OEM oil pressure switch setup leaves a lot to be desired.

Casey

[orebec]

thanks for the link (I might think getting one if i don't find the problem)
but my problem is intermittent first the lift pump always work when the engine is running. And since I had this truck when I turn off the engine I could hear the pump running for about 10 secondes or so. Now sometimes I can hear it sometimes not. When i don't hear it I have had a hard time to start it up again likes it's not prime that is why I suspect the lift pump relay.
any more ideas?
Also How hard is it to change the oil pressure switch on a 1994 chevy 6.5 turbo diesel and where is that oil pressure switch?
thanks

[rustyk]

NAPA has a tool (3/8" drive socket) for that: #3923 Oil Switch Socket. The switch is alongside the fuel filter, and the NAPA socket overcomes the need to move the filter out of the way.

[orebec]

thanks but now I have a bigger concern I have too much pressure in the coolant system and the oil level is higher so a blown head gasket I presume. Can I find which cylinder it is by removing the glow plug and do a compression test?