My truck ran fine before I replaced the heater core, it ran while I had the dash out with the new core in to test for leaks, then I put the dash back in and now it's not starting. It'll crank, but not start. Fuel pump is not priming, but running a straight power wire to the pump causes it to turn on, but then it still won't start with the running pump.

 

By chance did you loosen the ECU ground on the intake manifold.

This will cause all kinds of interesting things like the injectors to not open.

Did you pull the negative battery cable while you were poking around there ..
have you checked for Open fuses ??

 

I don't see any blown fuses, all I can think is somehow one of the EFI relays got shorted out while I was putting the dash back in. Intake manifold ground is attached.

 

i always disconnect the battery when I do any sort of electrical or dash work...I would stil check the ECU ground like Wyoming suggested

 

I should've disconnected battery yes. ECU ground is fully connected, tested EFI relay, main relay, open circuit relay, and whatever relay is in the engine bay fuse box, all work. EFI fuse is not blown.

 

Any codes ?

 

Not that I've been able to check for.

 

Just how did you check the relays ??

Remove them use a 12VDC power source energize the coil check the contacts for continuity ??

Check voltage into the relay on both the contact side and coil side??

If you have a shorted relay you have open circuit protection or melted wires causing a open circuit

Remember a Short is current going directly to ground

 

I checked for continuity between the two receiving power/ground posts, then took the cap off the relay, pushed the contact together and then checked for continuity between the exiting power/ground posts. All of them worked correctly. The EFI relay wasn't able to be tested like that so I tested for continuity in the receiving posts, then hooked up power and ground, it clicked, then tested continuity between exiting power and ground. It was suggested that when I lowered the steering column, one of the ignition wires could've gotten pulled out or crimped. None of them look to be, but I'll be pulling the dash back out tonight to see everything. I had switches wired to the radio/clock fuse that got shorted out and blew the fuse, taped off the power wires and replaced the fuse.

 

Found the first solution. The ignition fuse had blown and I overlooked it. It started right up after I replaced the fuse. I let it run a while and everything was fine. I put my speedometer and my radio back in, because I was going to run dashless in case something else happened. Which it did. After putting in the radio and the speedometer the truck won't start again. When I replaced the 7.5A ignition fuse I used a 10A because it was the only one I had on me, could I have just fried my ECU by using too big of a fuse? The 10A fuse is not blown now.

 

Anything is possible but I would look at the radio and dash cluster now having a open circuit due to a melted wire.

Fuse block loose and fuse not making good contact

Broken wire that makes intermittent contact now since things were reinstalled open

 

So, the last issue was the EFI relay was loose. I took it apart, which apparently you're not supposed to do, so now the cap is loose and to start the truck I have to hold the relay into the fuse block then start it. Ordering a new relay ASAP.

 

Sounds like your EFI relay is loose in the socket .

The cap covering the relay is just to keep the dirt out and peoples fingers as well

Unless you broke something the relay should work just fine with the plastic cover removed

Most of my test relays the covers have been lost years ago

It seems your getting closer in anycase

 

When you crank does the fuel pump come on? Did you plug in the circuit opening relay? Its above the ECM on pass side. Try using the diagnostic port as pet the FSM and see if the truck starts if you jump the pump circuit. Sounds like a plug didn't get plugged back in after the dash went back together possibly.