Do these trucks have a problem with glow plug relays?

[IDIDieselJohn]

Sure about that?

The solid state controller came out in 1987.... on the last year 6.9's. My 6.9 is an 87 so it's got the "7.3 style controller"

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[Diesel_brad]

Yes. You have the exception to the rule

 

[Freightrain]

Ok, time to highjack a thread.......;p

Our '95 PSD at work is having starting issues. The WTS light comes on for about 8-10 seconds and turns off. Truck huffs white smoke but won't start(like a typical cold diesel). Cycle the key a few times does nothing.

Yesterday while I was fooling around under the hood I left the key on. After a few minutes I reached around and it fired up nice and clean like it used to. I've done some reading of posts about glowplugs and controllers to familiarize myself with what does what.

Truck has 270K+ miles, we've only had it just over a year and have no history of what has been done to it. It was someones service truck(F250 std cab/8ft bed), as it runs perfect but not pretty looking.

I'm guessing I have to pull valve covers to remove glowplugs, as I see the wiring harness under the cover. Never had to wrench on a PSD, so it's new to me. Our '99 F450 stakebed has 250K miles and never been under the hood except for minor stuff

I realize this might not be the right year forum, but thought since we're talking the same stuff I'd try.

 

[82F100SWB]

Psd's run the timer for the light and the relay separately. There is no controller like an IDI, it's all dune by the ECM.
You could have a bad relay, or a dying ECM. I've been through 2 GPR's on my 96 in the last year, I have not been able to get a good quality one for quite a while.
I suggest turning the key on and watching the voltage, as well as listening for the relay to click. If the relay is closing and opening as it should, check the voltage on the load(glow plug) side of the relay. It isn't uncommon for the contacts to fail and the relay to still click and eventually make contact.
The glowplugs in a PSD are quite robust, and 99% of the time the relay fails multiple times before the glows finally do.

If the relay isn't cycling at the proper time and closing(or at least getting signal to) in conjunction with the wts light coming on, you probably have a failing ecm. This is why I have my 96, the first signs of it malfunctioning were the relay not cycling at the proper time(it would close the GPR 5-10 seconds after the WTS went out) and it never really acted any differently for quite some time(year and a half+) then it randomly died on the side of the road, the po got it going after a bunch of fooling around, it made it home, and never started again.
I swapped out the ecm, and it has been fine since.

 

[Freightrain]

Thanks for the heads up. I have listened for "clicks" and do hear it under the hood. Guess maybe it has burnt the contacts up? Likely, as a few times, randomly, it has kicked off like it should. Then times it just cranks and smokes

Guess I'll pull the cover off and start checking for voltage at the relay.

The scary thing is it's having trans issues(randomly). Sometimes it just goes into neutral for no reason. I hope that this is not another ECM issue manifesting. Not sure if it's related to ECM or not?(not sure with all the computer controlled crap). Old days the tranny went out, simple. Now it could be anything.

Thanks again.

 

[82F100SWB]

That sounds like a bad relay to me. I plan on eventually swapping mine over to a contactor, but, I'm still in warranty on the one on there.
As for the transmission, that could be a MLPS(Manual lever position sensor, would have been a NSS on a C6) going bad, or out of adjustment, or a failing transmission. I'd lean towards the position sensor first, most likely it is going south.

 

[Diesel_brad]

Freight train. Check the voltage at the RELAY. there should only be a .5V drop across the 2 big posts. If it is bad there are only 3 REPAYS I would get.

A IH one

a Ford one(repackaged IH in an Ford box and $50 more )

OR a Western plow RELAY. I have yet to have one of there fail, but you need to modify your mounting bracket, O and they are ONLY $12

 

[RLDSL]

I replaced my glow plug relay with 275,000kms on my '90 7.3L. Saturday I went to go start my truck ant the WTS light goes out immediately. I tried again sunday morning, same thing. This is exactly what happened to me last time my glow plug relay went. Are these trucks known for this? I can't believe in only 10,000kms the thing went.

Chances are your new relay is fine. It cycles by sensing resistance in the tips of the glow plugs. The resistance changes as they heat up. If you have burned out plugs , it throws off the reading drastically so the relay can't tell how long they are really burning. If you have 2-3 or more burned out glow plugs, then it is very common for a healthy relay to short cycle like that. You need to get rid of the garbage glow plugs before you wind up having to do surgery on the thing, and get a set of Beru / motorcraft plugs in there ( beware, there have been a few recent incidences of ford dealers having other brand plugs packaged in motorcraft bags so best to just buy Beru plugs, do a search on here, there are plenty of sites listed like ryderfleetproducts.com that sell them cheap)

 

[ninjai]

Okay it's me again... After rereading bits of this thread my joy has come to a close.

I just tested all 8 plus with a multimeter and every single plug hit 11.98v (shouldn't it be like.. 12.5?).

I guess I now need to pull all the plugs and test them as someone else in this thread said(can't remember who said it, but said voltage was right but some weren't glowing)?

So how do I test this then? Do I pull the glow plugs out, and turn the key to see which ones heat up? I mean.. I'm sorta of confused here because my WTS light shuts off _immediately_, so I suspect none would glow red.

I still have my suspicion that it's the GP relay/controller again. Still waiting for it to arrive... ordered it off ebay from the US (I live in Canada) about 2 weeks ago.

 

[IDIDieselJohn]

You pull 'em out, and get a good battery on hand, or remove one from the vehicle, and test the plug in your hand directly on the battery.

 

[ninjai]

You pull 'em out, and get a good battery on hand, or remove one from the vehicle, and test the plug in your hand directly on the battery.

Is that different than testing them from the top? Cause I used the multimeter on the top of the plugs

 

['94IDITurbo7.3]

Chances are your new relay is fine. It cycles by sensing resistance in the tips of the glow plugs. The resistance changes as they heat up.

so if everything associated with the glow plug system is working correctly, when the engine is warm the glow plugs should not come on b/c for lack of a moe technical description the tips of the glow pugs are telling the controler that the engine is warm?

 

[ninjai]

I'm getting more and more confused. Should I install the new controller when I get it? All my plugs show 11.84v or something close to that number (.94? I can't remember). I was testing voltage, should I re-test with resistance? What resistance should I expect from good plugs?

 

[ninjai]

Okay guys... I just talked to Ford. I decided that I am going to replace both my relay/controller AND my glow plugs, just to do it all at once and so I can use motocraft plugs instead of my autolite ones (as per recommendation by many IDI 7.3L owners).

The guy asked me if my truck was turbo charged. I said "yes... if that makes a difference". and he told me it does. Why? What would glow plugs have anything to do with turbos? Don't they just pre-heat the cylinders to aid in starting, and do nothing when the engine is running?

That aside, I'm going to try and do all 8 plugs and my relay on Sunday and that should be the end of it.

 

[RLDSL]

Okay guys... I just talked to Ford. I decided that I am going to replace both my relay/controller AND my glow plugs, just to do it all at once and so I can use motocraft plugs instead of my autolite ones (as per recommendation by many IDI 7.3L owners).

The guy asked me if my truck was turbo charged. I said "yes... if that makes a difference". and he told me it does. Why? What would glow plugs have anything to do with turbos? Don't they just pre-heat the cylinders to aid in starting, and do nothing when the engine is running?

That aside, I'm going to try and do all 8 plugs and my relay on Sunday and that should be the end of it.

Makes a difference... since when? Sounds like brainchild is trying to sell you powerchoke parts. The only difference on teh 7.3 IDI between the turbo and non in teh glow plug setup is where the controller is mounted and the harness for the plugs, but the controller and plugs are the same