Wiggle every part of the harness especially by the idm. It could be a bad wire in the idm plug and when you changed the idm the wire made connection aging

 

Ah okay I'll do that now and see.

Also, I had a questions about the valve cover harnesses. I replaced the driver side one but used a doorman since I was short on funds like usual.

Everything appears good with it now, but I did keep my old stock one. The old stock one looked perfectly fine. Is there a way to test that harness with a multimeter? The pigtails were burnt on the driver side which have been changed out, but maybe that's all that needed to be changed. If the stock Ford gasket is still usable, maybe it's better to put that back on in place of the doorman one even though the resistance check came out good.

Edit: Just finished pulling the valve covers and the connectors look good. I don't see any indication of the wires ground out. The passenger side was the side I was more worried about since I didn't replace it but all the connectors look clean (except filled with oil on the inside but I assume that's normal.) The wires seem pretty well insulated from metal parts as well. I had the ground from the passenger side hoist bracket to the firewall a little loose on the firewall side, so it may not have been grounded well. I actually moved that ground from the hoist to one of the valve cover bolts because I lost the bolt that it went through on the engine hoist. I think that should be fine because the bolt goes into the head which is grounded out from the motor. I'll put everything back together and throw in the new IDM I suppose.

 

Could this be a problem,

My multimeter read about 4ohms on the driver side injectors through the UVCH, and about 3 ohms on the passenger side (also on the UVCH.) This pretty much matches what I tested yesterday, but I read a post saying the ohms should not be higher than 3. My multimeter isn't that accurate and I believe it reads high, so the ohms could be close to 3 or lower for all I know (because measuring one ground next to another gives a reading of 1 to 2 ohms usually.)

Would a higher ohming injector solenoid possibly kill an IDM? Based on my multimeter and it's accuracy, I don't think my injector solenoids are out of range, but I suppose it could be possible.

 

lower ohms will draw more amps, unless its a coil and then impedance kicks in and makes it a higher non measurable value like speakers are rated

 

Injector solenoid has a normal ohm of 2.9
From the 42 pin ohm can be 3.5-5 ohm

 

I spoke kinda soon. My multimeter does actually work on the lowest setting, its just the pins are very sensitive and sometimes don't read. I just re-ohmed them from the IDM plug and got a reading of 3.3 to 3.5 on all 8 injectors. I suppose they are close to the actual value so I don't think they are the fault of the failing IDM then.

I'll still search around for a short, but I think everything is checking out so far. Maybe the grounds were a little bad or I just had two bad IDMs.

 

My next step would be checking grounds.
Using your meter put one on the battery and the other on the ground you want to check. In a perfect world it should read open. Anything 1.5 or higher if consider a poor ground

 

Thank you that sounds good. Also thank you for all the suggestions while I've been figuring this out! I was checking the grounds against different parts of the body, but what you said sounds like a better idea.

As far as I know, there is a ground strap on the passenger side that goes from the firewall to the motor, both batteries have a ground to the motor and fenders, there is a ground from the chassis harness to the core support near both headlights, and there is a ground wire near the IDM.

Is there any other main one I might be missing?

 

Well I ended up forgetting about some electrical things I wanted to fix. The 3 wire plug on the alternator had one burnt commector and was a poorly spliced in replacement. I bought a new plug and soldered that one in. Also, the passenger side negative battery cable to fender was in bad shape. It looked as if it got so hot it was near melting before. I cut off the end of the negative clamp and put a new one on, as well as upgraded the wire from a 6 gauge to 4 gauge.

As of now, everything seems good. I had an initial code of p1668 and p0340, but I cleared them and they haven't come back yet. The truck seems to run a little better on this new IDM as well for the small driving I did. I sure hope I fixed my issue!

 

Hopefully you tracked it down then. A problem with projects like this is running down the gremlins that pop up until everything is dialed in

 

Haha thanks! I figured there would be some things, I just didn't think I'd having issues with parts getting ruined... just issues with them working properly.

If what I did ended up working, then I should be good to go!

 

Hopefully all is good

 

Quick question. I read people with the newer diesels have had their FICM fail due to bad alternators.

I have a 130 amp alternator on my Bronco now, which I had on the 302 as an upgrade, I just swapped pullies. I believe the alternator from my parts truck was also a 130 amp, so I'm guessing the stock alternator is 130 amps for these motors.

However (with both alternators) the battery light stays on until the glow plugs are off. Is this normal, or is there a possible issue with my charging system? I know the wiring to the alternator had some burnt pins (before the swap), and I recently changed that after my second IDM failed. I just want to make sure it's normal for the battery light to be on when the glow plugs are on.

 

Not normal at all

 

^^^ If terminals on the alternator itself were burnt/damaged, most likely the corresponding terminals on the connector are damaged. Check/replace it, and solder / heat-shrink the splices. Also reference the EVTM and check the corresponding connection on the other end of that wire (IIRC, it connects to the main power junction at the starter relay).

Your belt may also be loose.