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GPR Tests and what each step means ?

1529 Views 10 Replies 2 Participants Last post by  SirJeff
I read through alot of the posts but the answers weren't very definite ...

Truck : 1994 Ford XLT F250 Diesel

My WTS doesn't light up and the glow plugs aren't activated because the truck is hard to start in the mornings now that its around 70F (20C) or colder in the mornings ... After a few cranks it does start though !

This happened all of a sudden !

I tested the GPR with the following results :

KEY OFF
1st Large Pole = 12V
2nd Large Pole = 0V
1st small wire = 0V
2nd small wire = 0V

KEY ON ( I seem to hear a clicking sound but can be anything ??)
1st Large Pole = 12V
2nd Large Pole = 0V
1st small wire = 0V
2nd small wire = 0V

KEYON After 2 minutes
1st Large Pole = 12V
2nd Large Pole = 0V
1st small wire = 0V
2nd small wire = 0V

What would be defective :
PCM ?
GPR ?
Selenoid ?
Other ?

Thanks !

IT APPEARS LATER IN THIS THREAD THAT POSTER IS WORKING ON AN IDI. POST RELOCATED TO IDI FORUM FROM OBS POWERSTROKE FORUM.

Dave / Believer45



Jeff
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I read through alot of the posts but the answers weren't very definite ...

Truck : 1994 Ford XLT F250 Diesel

My WTS doesn't light up and the glow plugs aren't activated because the truck is hard to start in the mornings now that its around 70F (20C) or colder in the mornings ... After a few cranks it does start though !

This happened all of a sudden !

I tested the GPR with the following results :

KEY OFF These are all correct
1st Large Pole = 12V
2nd Large Pole = 0V
1st small wire = 0V
2nd small wire = 0V

KEY ON ( I seem to hear a clicking sound but can be anything ??)
1st Large Pole = 12V Correct
2nd Large Pole = 0V Should have voltage
1st small wire = 0V Should have battery voltage
2nd small wire = 0V Should be grounded for up to 2 minutes

KEYON After 2 minutes
1st Large Pole = 12V Correct
2nd Large Pole = 0V Correct
1st small wire = 0V Should have battery voltage
2nd small wire = 0V Should have battery voltage from the other post
through the relay coil

What would be defective :
PCM ? Possible
GPR ? No
Selenoid ?
Other ? Check fuse #22 under hood it is a 30 amp maxi fuse, it could also be a wiring problem from the fuse block to the relay. With you not getting the ground from the PCM it sounds like a wiring problem in the harness.

Thanks !

Jeff
Some things for you to check. But when the #22 fuse usually blows the truck will not run at all. Does the WTS light ever come on when you are trying to start the truck?
For the diesel fuse #22 is for the glow plug relay control and fuel heater. There are no fusible links in the circuit. If you are getting voltage through the fuse then I would suspect a problem with the wiring from the fuse block to the relay. Also when you turn the key on you should get a ground from the PCM to the relay to activate it. Since you are not getting either the ground or the key on voltage that is why I suspect the wiring harness.
Did you buy this truck used? The reason that I ask is that you should only have one wire on each small post and it sounds like somebody did some home wiring. One will have power on it when the key is on and the other is for the ground.

You should have a red/lt green wire that will have voltage on it from the fuse pannel that also go to the fuel bowl heater on the filter housing. The ground is supplied by a purple/orange wire from termial 101 of the PCM. And those are the only two wires that should be connected to the small terminals of the relay.
It is possible that you have a IDI (indirect injection) instead of a Powerstroke which is DI (direct injection). Can you see the glow plugs and injectors on the outside of the valve covers? If so it is a IDI the Powerstroke's glow plugs and injectors are under the valve cover and can not be seen unless you pull the cover.
If you can see them then it is a IDI engine. In 94 Ford put 3 different diesels into the trucks. A 7.3 IDI non turbo, a 7.3 IDI turbo, and the 7.3 DI or Powerstroke. The Powerstroke was only available with a 5 speed transmission.

So if yours is a IDI then we can get a moderator to move this post to the IDI section and they will be a lot more help. Just click on the report post icon down below your user name and just ask for it to be moved.
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