Howdy,

I recently plated a '86 Ford F-250 6.9L Diesel 4spd 4X4 that has been around in my family since new. It was running well enough to pass the local AirCare emissions test easily.

I parked it a few days ago and the other morning I went through the starting ritual and found that the glow plug indicator light did not come on. I did not opt for a hard-start, its an old truck after all and I just knew it was an indication of a greater fault.

Prior to parking, the glow plug light was intermittently coming on during urban driving. I noticed it and set to getting to the bottom of this fault. Then the glow plug light failed and the game was on.

A test of the relay that sits on the right front fender well showed no volts on the left or rearward terminal post (yellow/brown wire) and a little over 12v on the right terminal post; with the key turned to the on position.
The relay clicks at a two or three second interval, no volts on the left terminal despite the sounds.

On an initial inspection of the glow plug harness I found the connection boot to the top of the switch (coolant temp sensor below) at the rear of the engine behind the air cleaner, was easily removed, too easily. It appears to be loose and it connects via what appears to be a similar end of a spark plug, a threaded connector that sits under the screw cap end that the spark plug boots connect to like the threaded ones on my motorcycle that connect directly without the screw caps.

I thought to crimp the harness female cap end but I don't want to damage the boot. Applying Dielectric paste did cross my mind but it is not a place that gets very wet at the moment (just you wait).

So what would you advise? What diagnostic steps would you recommend?

Regards,
Tim

 

There are some stickies at the top of the forum about both glow-plug styles. I would start there with a thorough read through. I believe they cover troubleshooting, as well as alternate methods for getting the GPs hot. Other than that im not a whole lot of help as i still havent hooked up my GPs lol

 

Thanks for the reply hairyboxnoogle. I've read the sticky and will use it to help myself along.
I've scoured the web and have found wiring diagrams for the GP circuit and am trying to post them here.
But at the free level it does not permit. AAARRUUUGH!

Lets see if my avatar will accept it.

Regards

I've posted it in my Albums.

 

I think its 25 or 30 posts then you should be able to.

 

I'm having the same problem. My glow plugs do work though, you can hear them cycle and starts easier after cycling 2-3 times. Just no light, ever.

I've also read through the stickies, and to tell you the truth the one for the older style we've got really isn't that great. Half the thread is irrelevant, and some of the information is unclear.

I was actually hoping that someday we could get a more straightforward one up there, with just the important stuff

 

I have to agree with you about the stickies.

 

Hello all,
Yes indeed, that familiar rat-a-tat-tat is back, glow plug light doing what it is supposed to.
I grabbed that sunshine this morning and started my diagnosis. Armed with my ancient tablet I re-red the sticky on '86 or lesser 6.9 glow plug,relay, etc. and set a 2X10 across the engine bay, threw a halved moving blanket on it and lay down with my multimeter, test light, and alligatored wire.
This simple combo allowed me to test the glow plugs two ways, the relay in two ways too, as per sticky instructions.

A Tip of My Hat to Festus Hagen for his post and his step by step instructions.

Read them carefully. I had my tablet handy to view his work, otherwise I'd have printed a handout of his post and had it handy as I worked through it.

The BRT (Big Red Truck) had been sitting for the last more than few years under my sons care. He diligently, periodically started her and kept the batteries solid. I took her over recently and rolled up my sleeves, expecting the unexpected.

I suspected the problem lay with the relay from the start. The glow plugs had been replaced not long before she'd been put down last. So I was not surprised to have the test light, light on all eight. The average ohm reading was 1.1 across the board.
I turned my attention to the relay and found that it was lighting the test light and clacking in rythm as it should ( with the purple wire connected) but no voltage appeared when testing the output terminal (large rearward terminal post), problem found.

I picked up a Borg Warner starter relay (in a box with a Lordco logo too) for $33.00 Cdn, taxes in, at VAP. The one presented to me at NAPA had no instructions and diagrams and was missing the added spacers, nuts and lockwashers. They were asking fourty-eight loons for it w/o tax. I fled.

Problem solved, I hope.
The glow plug indicator lights as it should, truck starts and runs smoothly. I did notice a bit of chatter coming from the engine front so I killed the engine and decided to check the radiator (call me clairvoyant) and yup, no coolant.

A gallon and a half of Prestone later, I drove her to her space and will see about starting her up tomorrow, looks like rain. :

I had some premix antifreeze hanging around for my bike and had to flip down to the local Canadian tire to pick up another gallon hoping that this would suffice. And it did.

I have this sneaking suspicion that the guy who appears on the Cdn Tire currency is none other than Mister George Tirebiter.

Regards,
Tim

 

Can I ask you a couple questions while we're on the subject, Tim?

I don't have a test light, can I use my multimeter to test the relay? If so, where exactly would I want to put the wire to test it? I'm having trouble finding thorough enough instructions for me to follow, I'm a novice to say the least. I read in the sticky something about jumping a positive lead but I didn't understand what they meant by that either.

Zac

 

Yes you should be able to test the relay with your multimeter in place of a test light, however, I'd advise you to get one as they are cheap. Look around in the sellout bins at your local suppliers, or even ask a clerk.
Cheap like Borscht.

See: https://www.ford-trucks.com/forums/9...d-style-3.html
At the bottom of the page. Under:*** Pre '87 Controller, Relay test. ***

1st, does your meter have an audio continuity test? Does it beep when you touch the red ( + ) and black ( - ) leads to each other?

This is helpful when checking if items are properly grounded, the beep just makes things easier.
Your truck body has a negative ground, that is, the electrons flow from the positive to the negative. Marker lights and such need only one wire to supply the electrons as the fixture is grounded to the body.
Checking items for proper grounding solves many headaches.

I once had a '76 Mercury Capri that received a mild tap in the grill while parked during a heavy snowfall. The other drivers insurance picked up the tab. I took it to a Ford dealer and had the grill replaced.
On that model the turn signal indicators attached to the grill and the leads to them were two wire.
I got the car back and found that the signals were flashing double time; back to the dealer who blamed it on the flasher unit under the dash. Not wanting to pay Fords price I headed out to the wrecker and installed what I found.
Same problem. Another after market unit from a friend who worked for a supplier. Same problem.

Standing there in the driveway with my bro I said that I'd checked everything but the ground. And he said let us check that. So I did and what I found surprised me.

 

Thanks, Tim. My meter doesn't have a beeping function, didn't think I'd need it or any of the other fancy stuff so I just got a basic one.

I read the instructions for the relay test again and they don't seem so bad now.. how do I know where the output terminal of the relay is?

I'll look around for a cheap test light.

 

Hi Mozzles,
The output terminal post is where the white and orange wire connect on the rearward side of the relay. The one that has two or more wires connecting to it.

Damn if I can't post the pictures that I took. Silly Forum rules just gettin' in the way.

Cheers and good luck.

Let me know how it turns out. Too many times posts go unresolved. The problem is fixed and the fixer does not post their final result after asking and getting assistance. Selfish and rude, really . . .
edit: here is an picture example of what not to do: https://www.ford-trucks.com/forums/1...250-6-9-a.html

The picture shows the relay but was taken wrong. How people can take a picture that is not from the viewpoint that you get while looking under the hood and use it as an example while asking for help is just beyond me.
Wake Up! You're sleeping. If I didn't know any better I'd think they be Trolls.
The top of the picture shown is frontward. Although I may wrong as I do not recognise the black sphere which some have said was part of the cruise control; ain't got one, don't want one.