Engine/Transmission (1998.5 - 2002) What the heck is wrong with my truck?

[DPike]

Kind of a long story-1998. 5 24v. The crankshaft sensor tone ring came apart, busted off the crank sensor, and broke the block. I have since rebuilt the motor, and this is what is happening now. The engine itself runs beautiful. But when I turn on the key, the transfer pump rarely runs for 1-2 seconds like it should. It also does not always run for the 20 seconds after I bump the starter. Sometimes it does, most of the time it does not. So after the truck sits for several hours, sometime it will not start or it will start and then shut off because it has no fuel supply. If the truck starts, the fuel pump will run and stay running and act normal with 12-15 psi. I checked the voltage at the plug to the fuel pump (a stock pump relocated to the frame rail) and the voltage is 8. 6 with the key on. If I bump the starter, it will go to 12 volts.

The other problem that I am having is that when I start the truck, the oil pressure gauge will act normally, then (usually only when the motor is cold) it will drop to nothing and the check gauges light will come on. It has only come back up once so far. Usually it stays down. I pulled off the valve cover to watch it while it was running, and it still has oil pressure. I also switched oil pressure sensors and still the same problem. If the truck starts and the oil pressure gauge stays up (it usually doesn't bother if I am driving the truck) you would never know anything is wrong. Does this sound like the ecm is going bad? Is it possible that the crank sensor shorted out when it got busted off and ruined the ecm? Any other ideas? I am stumped but need to get the truck going reliably. Thanks

 

[Missouri Mule]

Does sound like the ECM. ECM controls the lift pump.

See if you got any codes stored.

 

[Sticks]

I'd install a mechanical oil pressure gauge in a "T" with the oil pressure sensor. There is a possibility that there may be a floater in the oil passage that is blocking the sensor.

My truck is also hit and miss on the "bump prime", as with several other trucks that I have worked on.

Check for fuel leaks around the quick connections. You may be having air getting in the system and the fuel is siphoning back to the tank. That would cause a no start, or dieing after starting.

I did not think a tone wheel would stout enough to break the block. WOW.

 

[DPike]

Yes I was kind of shocked myself when I found that crack in the block on an otherwise perfectly good motor. Well, It's not the ecm-I used one from another truck, and the same problem. Someone said to run a relay/wire from the battery and use power from the stock lp wiring, so I may do that and go from there. Thanks for the reply.

 

[SSolderitch]

my oil press at zero on start up happened a few times, usally fixed withg a shutdown and restart, has not happened in a long time. lost the 1 sec pre run of the pump, cured with a reflash of the ecm.