GPR not functioning

[82fordtruck]

I was having a hard starting issue that I thought was related to injector O rings. After a month in the garage, and new O rings all around, with new UVCH plugs - the glow plugs are not kicking on at all. I had the whole engine harness taken off to work on the UVCH parts (had to repair and solder in some splices by the plugs). I am not finding a positive signal for the GPR on the stud.

Can anyone tell me where this comes from and where the other connections are made for it? I'd like to check the connections before tearing back into the wiring harness.

Also - the truck was starting before, after a minute or so of cranking in cold weather. Will a powerstroke fire with NO glowplugs at all in freezing weather?

 

[82fordtruck]

Nobody can help?

 

[Agnem]

Sorry, but I don't know off hand. Now if you want to know about cracked injector cups, I'm your guy.

 

[93turbo_animal]

I don't know about your wiring but I do know a PSD will not start with out glow pugs or ether even when fairly warm

 

[BigRigTech]

The GPR has a large and small positive wire all the time, the PCM controls the other small wire - it grounds it to close the relay and this puts power to the GP's....Take a test light and check the two small wires for power, if neither will bring the light on then you have lost your 12+ to control side of the relay, the other side just needs to be grounded to make everything work....The last PSD I saw with this issue cost my buddy $600 for a new PCM from Ford. he had a no start issue - but previous to that the GP's were new as was the relay but they didn't work....The old PCM was not closing the ground like it should.

 

[82fordtruck]

The GPR has a large and small positive wire all the time, the PCM controls the other small wire - it grounds it to close the relay and this puts power to the GP's....Take a test light and check the two small wires for power, if neither will bring the light on then you have lost your 12+ to control side of the relay, the other side just needs to be grounded to make everything work....The last PSD I saw with this issue cost my buddy $600 for a new PCM from Ford. he had a no start issue - but previous to that the GP's were new as was the relay but they didn't work....The old PCM was not closing the ground like it should.

I tested it more yesterday and I have 12v at both small terminals between the terminal and ground. I have no idea what this means.....


Tonight I am going to disconnect from the relay and retest the wires and coil separately. All gp's tested fine and I did some work to the UVCH.


Also - it will fire down to about 0 degrees but it takes a minute or two of cranking to do it in really cold weather. This week since I know the gp's are not working I have been using ether and it's been incredibly easy - only a quick shot in the morning and it's not needed the rest of the day.

 

[BigRigTech]

You have 12V on both sides for how long? With the key will it light a test light on one side only once it stops clicking or all the time....You need to figure out which side should be the small ground and ground it for 10 seconds to see if the truck will start.

 

[yoslick]

PCM sends the signal, I'd definately ground the non hot side small post and see what happens, your other choice would be to run a hot wire via a heavy duty push button on the dash so you could control the relay manually for as long as you wanted.... cheeper than a new PCm if thats the problem.....

 

[82fordtruck]

PCM sends the signal, I'd definately ground the non hot side small post and see what happens, your other choice would be to run a hot wire via a heavy duty push button on the dash so you could control the relay manually for as long as you wanted.... cheeper than a new PCm if thats the problem.....

I am really curious what is going on. Both sides test 12v to ground when the truck is on, but if I disconnect the wiring from the relay I can get 12v signal from the truck. I tried jumping the relay and it will not click at all - so it would seem it is bad. I am getting .6 ohms across the two small terminals.

I'm real confused here but wondering if the coil isn't damaged in some way causing the PCM to do something funny.

I plan to get a new GPR and try it but I managed to leave the truck on all night running the battery down all the way - and then my battery charger broke......so I have no way to start the thing.

 

[BigRigTech]

Replace the relay and see what happens....If it still won't click then put seperate power and grounds to the small posts to see if you can close it.