Glow Plug Relay Help

[mjonesjr]

I am having trouble with my glow plug relay. I have put a new relay on the truck, however I am still not getting any action to my glow plugs.

The factory wire that is supposed to trigger the relay is getting 12v (battery voltage) when the ignition is turned on. It is on the "S" terminal of the relay. Should it be on the "I" side of the relay?

 

[mjonesjr]

I am getting 12v with key on on both the small red and small brown wire going to my relay. I am not getting any voltage to the glow plugs.

If I ground the relay on one side straight to battery, it will hum and put voltage to the to the glow plugs.

 

[Tom S]

The glow plug relay is switched on the negative side by the PCM. Take a look at the thread by estrogen hostage. I posted up quite a bit on there.

 

[mjonesjr]

I read through that Tom, good info, but I have a few more questions.

1. Do I see it right that the brown wire going to the glow plug relay is the one the PCM grounds?

2. Where in the PCM connector does the brown wire go into?

3. Should the relay be active no matter the temperature ?

4. Is there a sensor that the PCM sees ambient temperature to ground the wire?


Reason I ask is, the relay clicks when I turn the key on for a split second like an ambient air temperature sensor isn't showing it cold enough to leave it engaged.

 

[Tom S]

I read through that Tom, good info, but I have a few more questions.

1. Do I see it right that the brown wire going to the glow plug relay is the one the PCM grounds? I think so going off memory The + wire had a tracer

2. Where in the PCM connector does the brown wire go into? I can research that if you need to determine which pin it is.

3. Should the relay be active no matter the temperature ? I am not sure on that. PCM base code effects that. I think they will come on for a short time no matter what.

4. Is there a sensor that the PCM sees ambient temperature to ground the wire? I think the PCM uses the intake are sensor at a minimum.


Reason I ask is, the relay clicks when I turn the key on for a split second like an ambient air temperature sensor isn't showing it cold enough to leave it engaged.

That is what I have for you without digging out the books.

 

[mjonesjr]

I traced the brown w/ red or orange stripe wire from the relay to the PCM and it ohm'd out good.

I read that if you disconnect the oil temp sensor that it will activate the relay for the total of 2 minutes. Well I tried that and the relay never went active.


Any ideas?

 

[Estrogen Hostage]

Between the two of us we'd have one normal operating truck.....


I'm confused though. You say it clicks momentarily when it's turned on. That to me sounds normal. My glow plugs haven't been working for a year and a half and during summer it starts like any other truck. Why do you think you have a problem?

 

[mjonesjr]

It clicks momentarilly when I turn the ignition on.

This morning it was 45* outside and it still just clicked real fast. When I tried to crank the engine over, it just cranked real hard. Once I jumped the ground off the battery to the wire that is supposed to ground out for about 25 seconds, it cranked like it was 100* outside.

 

[Estrogen Hostage]

I'd say you can eliminate a bad relay since it pulls in with the jumper wire, and the wiring from the PCM since it clicks some. I'd get it on a scanner and see what the IAT, EOT, and CTS readings are. If they are all good try a new PCM.

 

[mjonesjr]

I've ran the codes via a hand held code reader and nothing came up.

Is there any other type of scanner that will show?

 

[Tom S]

AE, one the little scan gauges, or a pro grade tool.

 

[mjonesjr]

AE, one the little scan gauges, or a pro grade tool.

Do you have a link to one or know where I can get it scanned?

 

[Tom S]

http://aeroforcetech.com/products.html

Complete Performance a site sponsor is a dealer.

 

[mjonesjr]

I did a little wire tracing today.

The purple/orange wire at the GPR ohmed out to 3 wires at the PCM connector. Those wires seem to be ground wires.


The purple/orange wire is grounded when the key is off and the PCM puts 12v to it when the key is turned on.



I need to pull the harness apart on the engine now to see if I have any wires burnt together.

 

[Tom S]

I did a little wire tracing today.

The purple/orange wire at the GPR ohmed out to 3 wires at the PCM connector. Those wires seem to be ground wires.


The purple/orange wire is grounded when the key is off and the PCM puts 12v to it when the key is turned on.



I need to pull the harness apart on the engine now to see if I have any wires burnt together.

I think you are wrong in the PCM supplying power to that wire.

 

[mjonesjr]

Something is powering that wire. With the key in the run position (truck running or not) the purple/orange wire has battery voltage on it (1 lead to battery ground, 1 lead to purple/orange wire on GPR.

 

[Tom S]

I believe that is key on power not PCM power. The PCM supplies the ground to activate the relay.

 

[mjonesjr]

I wonder why it isn't grounding out then.

 

[Patrick Feeley]

It could just be the PCM. I had a similar issue with my 94 IPR power circuit. It turned out to be the PCM (of course the last pinpoint test in the series for the P1283 DTC was "replace the PCM and retest"). The PCM did everything else (like communicate with my diagnostic scanner software, run KOEO tests). Make sure that when you are checking the P/O wire that it is disconnected from the GPR and that the PCM connector is also disconnected. That way you won't get any readings backwards through the GPR coil and fuel heater circuit. With those disconnected, you should not get any "association" with other PCM grounds. Cheers!

 

[mjonesjr]

I will have to check the P/O wire tomorrow with the PCM unplugged and the GPR unhooked.

I have nothing hooked up to the fuel bowl heater, no fuel bowl present since I did the regulated return. I have all the wires that plugged into the fuel bowl electrical taped up so they wont hit anything. The only part of the wiring harness that I am using is the IRP plug for obvious reasons.

How would the P/O wire get a back reading through the fuel heater wire when it isn't in the same circuit?


I have used a code reader to pull any codes in the PCM; none showed up.



I am going to try to find a good PCM. I know I will need one from either a '96 or '97.