Ok so I have read the glow plug sticky and I have been posting on the "7.3 idi hard start" thread and starting a new one in hopes of new ideas and more visibility.

I would like to first off start by saying THANK YOU to STARMILT, FARMERT, GREYWYND and the others that have been trying everything they know to help me out.

I have a 1990 F-350 7.3L with no clue how many miles (the odometer only has 5 digits, so been rolled over at least once).

I was having a problem starting on cool (not even that cold) days, unless I plugged in the block heater. I replaced the glow plugs (with Motorcraft) back in April and we used this truck on average once a month to pull my wife's horse trailer. I bought a GPR111 from Napa and looking to replace the old relay, I was told (after my first failed attempt) that I needed the GPR109 so I have switched. See the pictures.

Before I replaced it the WAIT TO START light would come on and the relay would click some and then it would start up, as long as it was plugged in or just driven. I have wired it up and now when I turn the key the WTS light turns on and stays on and there is no clicking. I waited some time and tried to start it up just to see and the engine tries to turn over but it won’t start, as if the GPR is not warming up the plugs.

With the key on, the WTS light on and power going to the relay, I ran a wire from the negative post of the battery to the small terminal post on the relay with the white wire and it energized the relay and was clicking quickly.

I have searched some and it seems that I can't find anyone on here that has the same problem. I have looked at the glow plugs and they look to be fine and are providing resistance via Ohm-meter. I have been working on this for three days now (not all day mind you), but I am completely puzzled as to what is wrong.

I apologize for the length of this post but I wanted to provide all of the details in one thread.


Original GPR:



This is a picture of the GPR111 wired up and the GPR109 has been wired up the same way:


As for the wiring, I have wired as so:
Small white wire (ground?) to small terminal.
Large yellow wire under metal strip to Glow Plugs on large post
(2) Small red wires to small post.
(2) LARGE Yellow wires connected together with 1 BLACK connector to large post.

I pulled off the controller as well and looked at the wires to see if they were cut or anything and everything looks to be intact. Obviously, I can't see inside the controller without taking the whole sealed unit apart.


At this point, I have NO CLUE what is going on and becoming very frustrated, especially since there is no way I can drive it to a mechanic. Once again I am VERY grateful to the help I have received thus far and I am hoping that with more visibility I might be able to get a solution.

 

to me it looks like your new relay is put on the controller the wrong way.

if you look on the top of the relay there is that molded section that kind of "sepperates" the posts. you will see that one of those dividers is longer than the others. that long divider is in a different spot now than in the pic of the original relay.

IIRC from what i learned about relays in school they need to be set up exactly rigt or they won't turn on or they could stay on all the time when energized wich sounds like what is happening.

rotate the relay and see what happens. i bet that is the problem. good luck.

 

@'94IDITurbo7.3: This is the case for the GPR111 but when I replaced it with the GPR109, the longer divider/plastic section, whatever you want to call it, is in the same spot as the original relay. I will try to get a picture posted tomorrow if it makes a difference. As I mentioned above the #2 picture, that is of the GPR111 and the GPR109 is wired in the same way, basically on the same posts as far as large posts & smaller posts. The only real difference that is noticeable between the GPR 109 & the GPR111, that I can tell, is that on the 111 the terminal posts are rotated about 90degrees.

 

pic of the gpr109 wired up please.

 

The GPR is just a big relay. Applying 12v to one of the small terminals, and ground to the other small terminal energizes the solenoid in the relay, connecting the two large terminals together. The GP controller controls the relay by connecting & disconnecting the ground side of the solenoid in the relay via the white wire.
DieselRugger, you said you connected a ground wire from Bat Neg to the small terminal on the relay with the white wire and the relay energized. Try running that ground wire to the ground wire from the controller. This is to make sure the controller has a good ground...

 

Controller without relay attached (if this helps at all):


GPR109 Hooked up:






@ Phy: Last night when I had the key on and the WTS light on and power to the relay, I ran a wire from the negative post on the battery to the small post while the white wire was still connected to it. So I should test the ground on the controller (white wire) by disconnecting it from the relay and run the white wire from the controller directly to the negative post on the battery?

 

Are you sure you don't have a starter relay?

 

Im pretty sure, it is a GPR109, should I also replace the starter relay? Would it start to go bad around the same time? Is there only one of them, the one on the passenger fender well?

 

NO, parts store have a knack for giving customers the starter relay when customer asks for a GP relay. It looks the same, but different internally, so the customer gets all mad when nothing works. This happened to me, thats why I'm wondering.

On naponline, GPR 110 is the correct one.

 

Where is your grounding wire? I don't see it.

 

Now the GPR110? I was told from Napa GPR111, I was told on here that for the 1990 I needed GPR109. What is the fundamental difference between them? I am asking because I am trying to figure out what would cause the WTS light to stay ON and not heat the plugs.

The black wire from the controller goes back and is grounded. I never loosened or removed it, but yes it is hard to see, but it has not changed.

 

Did you test your wires? are you sure the solenoid is not bad?

 

I doubt that the solenoid is bad since when I had the GPR111 on and the GPR109 on, I am having the same problem. Now it seems that the problem is that the WTS light stays on and it seems that it is not warming up the GPs.

Which wires do I need to test and how? It seems that there is power going to the solenoid since when I have power doing to it and I run a wire from the white wire post to the negative post of the battery it energizes the relay.

Does any of this sound like it could be the starter solenoid?

 

When you ground the white terminal, does it transfer voltage to both large terminals.
Going by memory (which isn't the best) there is a ground wire that is under the controller at one of the bolts, that holds it down, that is very important. Some members have even grounded it straight to the battery and claimed it worked better than they ever did.

 

No, I mean leave the white wire on the relay, and run a ground wire to the black ground wire from the controller. As many have said, a poor ground there and strange things happen...
The white wire isn't the ground for the controller, the controller connects the white wire to ground to operate the relay when it wants to send power to the plugs.