Stevie G

Okay, turns out the lift pump is fine.
Turn the key and you can here the relay pickup.
Swapped relays and the relay is fine.
Is there any chance there is a common failure point in the harness I should check first or am I resigned to hunting for a brake in the wires the good old fashioned way?
I'm happy that the pump is fine but, I'd have been even happier if replacing the relay had done the trick.

Stevie G

Any reason I can't wire the pump through a switch?
Anybody know which wires from the power center go to the pump so I could just run new wires?

slim51015

What year truck?

Stevie G

99 dodge 2500.

bent valves

You may want to think twice about using a switch to power the lift pump. Cummins uses the ECM to control power to the lift pump. The ECM, pins 35 and 15 supply +12 volts to the pump. Two pins are used to provide enough current to the lift pump. The ECM also duty cycles the power to keep the lift pump running at about ½ speed when the engine is cranking. The slower speed keeps fuel pressure below about 7 psi to aid starting. But the reason not to use a switch is because in the event of a crash, the ECM will stop supplying power to the lift pump to prevent a fire if the fuel line gets severed. If the lift pump is powered through a switch it may continue to feed the flames.

Stevie G

so, what colors are 35 and 15.
I'd love to have it work the way it is supposed to but for now, I really need it to run.
If I new which wires to tap / replace, I'd be all set.
My manual is at my shop in NY so I have no wiring diagram.

Thanks again,
Steve

bent valves

The wires from pins 15 and 35 are both color coded Yellow with a White tracer. Both of these wires are joined at a splice marked S160 before going to the lift pump connector. My shop manual does not tell me where S160 is located, but I can give you a picture on the ECM connector on the wiring harness. The two pins marked in red are the ones you want.

Edit: Don't be fooled by the pin marked 4. It is really 41. A mistake in the Dodge manual, imagine that.

Stevie G

Thanks!!
This is the plug on the ECM on the block?
Should make things easier.