The Diesel Stop banner
1 - 11 of 11 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter · #1 ·
I’ve got a 2000 f250 that’s been having some startup problems in the “cold” (40-50 degrees)
I’ve tested all my glow plugs, they all work. I do have 2 GPS and one of them is not getting ground to the little terminal therefore not actuating. Does anyone know exactly how the PCM works to supply the ground to the solenoid? I see that the 2 ground terminal wires go into a bunch of loom with other wires. Do those two wires stay separate all the way to the PCM or are they spliced together in the loom? My thoughts are if the one solenoid is getting its ground then the PCM should be working....? Hopefully someone knows more about it than me.
 

·
Registered
Joined
·
35 Posts
Since your truck has two solenoids, you have the auxiliary intake heater -- kind of a useless appendage, unless you live way up north. You can see the heavy wires running from the large glow plug in the intake to the solenoid -- ignore this solenoid, and focus on the other one. The second solenoid is for the glow plugs in the cylinders.

Use a test light and see that there is 12 volts on one side of the large terminals - key off - this is the battery feed. Now, disconnect one of the small terminals, and key on - time is short so hurry . Use your test light on the small terminal and the post where it came from -- which one has 12 volts? This will determine which wire is hot and which is ground.

The "hot" is supplied form the switched battery circuit, the "ground" is supplied by the PCM. The ground is timed depending on temperature - ambient and -- (hmm, coolant or oil, need to check)

When all of the wire purpose is figured out, then you can test at key on (for a few seconds) the small PCM ground and the large solenoid output post. The small ground and solenoid output should operate at the same time. To test the small ground, you will need to put the test light clip on a positive battery post.

The control wires you asked about are separate from the PCM
 

·
Premium Member
Joined
·
4,497 Posts
HydroTek,

Good catch. Two Relays means the AIH is still there.

I don’t know if it makes much difference for airflow to have the element installed but I pull my AIH mostly to de-clutter the top of the engine a little.
 

·
Premium Member
Joined
·
4,497 Posts
I am pretty sure the AIH was designed to lower emissions rather than a cold weather starting aid. The AIH does not get power until after the engine is running and is OFF while cranking.

Also, the AIH Relay is designed to not come on while the GPs are cycling so the test that the OP ran really does not isolate the GPR is bad.

OP, the AIH Relay is forward of the GPR (the GPR is closer to the firewall.)
 

·
Administrator
Joined
·
24,971 Posts
There should only be one wire going from the small terminal to the PCM.
Here's the wiring arrangement: Red wire from fuse block to small terminal, violet/orange wire from other small terminal to PCM. Large gauge black/orange wire from fuse link to one large terminal. Large gauge brown and yellow wires from other large terminal to GP's. Three small gauge blue fuse links connected to the same large terminal as the brown and yellow wires. Connected to these three fuse links are white, white/violet, and white/lt green, all going to the PCM. These are voltage monitoring wires that tell the PCM whether the GP's are active. There are three of them because it's a holdover from when there was a shunt on the output of the PCM, and they were connected to the center, and each end of the shunt in order to measure current to each bank of glow plugs. It may be that if you have two wires connected to the small terminal going to the PCM, it's not letting the PCM connect to ground. Testing the GPR can be done by following the instructions in the Hard or No-Start link in my signature (expand it to see the link.)

ArcticDriver is correct about the IAH (Intake Air Heater) relay. It only works at low ambient, AFTER the glow plugs are off, and only if the accelerator pedal has not come off idle. It's purpose is to reduce smoke on extended idle.
 

·
Premium Member
Joined
·
4,497 Posts
IAH. IAH. IAH.....

I always confuse it with Alaska Industrial Hardware.
😀
 

·
Administrator
Joined
·
24,971 Posts

·
Premium Member
Joined
·
1,221 Posts
I would pull that air heater out unless you live way up north
And.....removing the IAH makes for a really slick spot to add your tubing/boost gauge

Vehicle Automotive tire Motor vehicle Automotive lighting Automotive exterior
 

·
Registered
Joined
·
33 Posts
I’ve got a 2000 f250 that’s been having some startup problems in the “cold” (40-50 degrees)
I’ve tested all my glow plugs, they all work. I do have 2 GPS and one of them is not getting ground to the little terminal therefore not actuating. Does anyone know exactly how the PCM works to supply the ground to the solenoid? I see that the 2 ground terminal wires go into a bunch of loom with other wires. Do those two wires stay separate all the way to the PCM or are they spliced together in the loom? My thoughts are if the one solenoid is getting its ground then the PCM should be working....? Hopefully someone knows more about it than me.
Clean your battery terminals and cables and the connections to the starting solenoid. I replaced everything on my 01 until I discovered only one battery was running the starter. It needs both. Check the voltage on battery cables, not on the posts. Both batteries were new and just installed but cleaning posts and clamps solved the problem. I now have every conceivable thing new on my truck for thousands of dollars and all I had to do was clean battery cables that looked fine. Good luck.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top