Fuel pump

[6.5td1994]

I have change my fuel pump relay and the fuel pump is still not working correctly. If I by pass the relay the pump works great. I have check for good flow and everything looks to be good when I bypass the relay. I been given the impression that I should be able to hear the pump while I'm waiting fo the glow plugs to warm up, this is not the case. I have checked the voltage at the pump with the truck running and there is 14 volts at the plug. With the Key on there is no voltage at the plug.

Does anybody have any I deas I can try to fix this problem??

 

[ak diesel driver]

on the 94-95 system the fuel pump does not run while the glow plugs are on. It uses the Oil Pressure Sender (OPS) to send power to the fuel pump. It's a safety designed into the system for car wreck scenarios. The OPS is not heavy duty enough for the intended use and is a common failure item. Just because the guage works doesn't mean it's working right, there's 2 sets of contacts inside it. Most are doing the OPS relay mod and some are also tieing it into the glow system so it pre primes during wait to start.

 

[Burning oil]

x2

Throw a new OPS on it. You might consider and OPS extension hose from my site. You'll thank yourself the next time.

 

[racer55]

I like the OPS relay mod but don't really see a need for 2 relays if a 5 terminal relay is used,note I should have added a fuse in the wire from the glow relay to the mod relay:

 

[Burning oil]

I like your idea. I think the second relay would give you pump on anytime you want with use of a power source to 87a. used for priming the filter.
Your idea just replaces that with the GP input. Good idea, mind if I copy it?:hihi:

 

[racer55]

feel free

it also wouldn't be very hard to add a momentary switch in parallel with the 87a circuit using the hot side of the glow relay for filter priming.