I have a no start problem on my dually. The fuel pump makes no noise when the key is turned on and there is no fuel pressure. The fuel pump relay " clicks on " when the key is turned on. I unplugged the connector at the fuel pump and probed the 4 wires. The purple wire with a white trace only shows 5.02 VDC(I think it is the 12V lead to run the pump). The 2 black wires had continuity to ground and the gray wire showed neither (+) or (-). I tried a different relay in the fuel pump relay slot, it didn't help. I also unplugged the relay and tried to jump between 30 and 87 in the relay block(also no change). I split the purple/white wire and attached 12 volts directly to the pump side and the pump didn't make a sound.
This problem happened yesterday and my battery voltage was low.(12.25 volts). I charged the battery overnight and reinstalled it, the fuel pump " whirred" when the key was turned to on, and the truck started when I hit the switch. I went to the store and exchanged the battery because it was leaking water causing the discharge, and when I put the new one in, it wouldn't start just like yesterday!
I followed that purple/white wire all the way to the ECM and there are no breaks or damaged parts of the wire. I don't think the oil pressure switch is bad. On extended cranking without starting the dash shows 20psi oil pressure. I also tried wiggling all the ground and power wires. The speedometer is pegged right now and won't zero with the key on or off. Help Please !
I'm not sure if this is related or not, but this truck has also had a (hot) hard start issue for quite awhile. It starts easily first thing in the morning (but puffs black smoke on start up and smells very fuel rich), but required extended cranking and - or - opening the throttle plate alittle to start when hot. Fuel pressure was good at 55psi.
Thanks in advance - Rick Curtin
1998 Chevy C3500
Engine size: 454
Saturday, May 26th, 2007 AT 3:12 PM