New to the forum, and diesel fords :)

[8v-of-fury]

Hi, my name is Jeremy! I am new to this forum and am also new to diesel ford trucks. Not necessarily new to diesels though I am a Die-hard Volkswagen diesel fan and haven't much experience working on the old Ford's.

(sorry if some of this doesn't make sense, it applies to the diesel vw forum I am apart of and posted there because every ford forum i found was lousy.. until i found this awesome site!)

The truck in question is a 1987 F-350 with a 6.9 N/a IDI with 695k on the clock.

It's my gf's moms work truck. They have owned it for 8 years and have done nothing to it. And rightfully so it hasn't needed anything, until now. My gf's dad worked on it and kept it going good, but he recently passed on and now its up to me to keep this beast going because one day I hope for it to be mine Smile They don't run it all winter long because they claim it will never start, now this leads me to believe her father in his mechanical wisdom wasn't much of a diesel guy. I checked the resistance at the gp's and i think I got around 5.5, I thought the number was supposed to be like less than 1 or something? Also, I noticed that some of the gp's wires weren't even connected! Not only that but when you turn the key to activate the gp's the light goes off after 3-5 seconds! No wonder this thing could never start in the winter!!! It must still have decent compression to start the way it does..... ? I measured the voltage at the plugs as well and got a steady 8.4V Sad when i got it going for the first time this winter on Friday i hadn't found out about the gp's yet so i just used a battery charger set to 60A so i could crank the engine up to temperature. When i went to go out this morning to try it again (i was at their place for a few days) I thought to myself.. what about jumping the gp's? so i did that while i had my gf crank her, it fired up in about 10 seconds as opposed to Friday's 45-60 seconds. So it does seem that at least 7 of 8 (due to broken wire) are working.

Question being, where is the GP relay on these things? Also why would it only stay on for 3-5 seconds? It was about 5 degrees Celsius out today i would expect at least 10 seconds of gp's to attempt a start on an engine of such size and age.

I think that if I reconnect the broken GP, use Vince's guide to "pimping" to make sure they are getting as close to 12V at each plug, it will run a lot better. I mean they don't drive it in the winter anyway, but having the gp's actually work in the summer I'm sure will help prolong the life of everything.

The weird thing about this thing is, is that it was used before they got it, to haul a fifth wheel to B.C every year! for like 10 years. I am really surprised with how this truck runs.. Once it gets started it runs like a tank.

WOW this is a long post, I hope you liked reading my blabbering Laughing

What do you guys think? some cheap ways to maintain and keep this old girl going for a few more years?

Thanks a lot guys.

Jeremy

 

[david85]

Welcome to the forum (got your PM)

Here's some backround on the system you are dealing with:

The controller for the glow plugs is located on the back of the intake manifold.

You are dealing with an electronic controller that works completely off of resistance feedback in the wires from the glow plugs. As the glow plugs heat up, the resistance increases (true for any electrical circuit). After the resistance reaches a certain value, the controller cuts power to the glow plug relay (controller and relay are one assembly in this case). When the resistance drops below a certain value, it turns on again.

Once the engine is running and generates enough heat to keep the glow plugs hot, the controller will no longer cycle the plugs anymore even though power is still being sent to the controller. This design allows for a simple after glow feature that keeps the glow plugs warm even after the engine first starts. This prevents stalling in really cold weather and also reduces emissions.

Now since the system works off of feedback resistance, any corrosion in the wiring connections can give the controller a false reading and it will turn off too early thinking the glow plugs are hotter than they really are. If you have only 7 glow plugs that are good and you are only getting up to 5 seconds of glow time, this could be your problem.

Once you locate the glow plug controller on the top rear of the engine (removal of air cleaner is needed), you can trace the heavy wires back across the engine harness and inspect the connectors for signs of corrosion or even burning. The major one that often causes problems is the main engine connector near the dipstick tube.

My 1986 uses a different system, but it is similar. Here you can see how I bypassed the main engine harness connector, and soldered the wires directly after I found corrosion in the connector (the two thick orange wires that are against the black plastic ball).

 

[8v-of-fury]

Wow, thank-you for your super fast reply to my PM!

So assuming I understand what you said, if one wire to one GP was completely disconnected, then the whole GP system would be flawed. Also if the WTS light comes on and is sensing resistance, then that is ok to reuse. Ultimately what it would need is new GP's and new wiring from the Relay to each GP. Sadly I nor they have the funds to fork out that kinda cash for a work truck only used in warmer weather you know? So what it looks like i may have to do for a quick fix, is to set up a Switched relay system that will draw directly from the battery to each glow plug. Until we can afford all new GP's.

Do you see any disadvantage to setting it up with a manually controlled relay? I know in Vw diesels they set it up like that so that they can decrease the amount of voltage drop, you can check out the very common VW setup here:
http://vincewaldon.com/index.php?option=com_content&task=view&id=30&Itemid=28

This man is very reputable among the Vw community and has some good write-ups as well. But I'd like to hear what you guys think it would be like on a 6.9 as opposed to a 1.6 What do you think? good or bad?

Thanks again.

EDIT: Also There is a difference in Volkswagen diesels, they turn off their Gp's when a coolant sensor, sense that the head has gotten to a sufficient temp.

 

[david85]

There is one thing about the controller that I forgot to mention. It will automatically sense when one glow plug is bad and compensate with a shorter glow time. So if one plug dies, it will compensate and keep working, if two or more quit, it shuts down to prevent the remaining plugs from burning.

NO you don't have to replace any wiring. What you have to do is inspect the wiring and the clip-in connectors specifically, for signs of corrosion or burns (often both in the connector I mention earlier). If there is corrosion in any of the connection prongs inside, all you have to do is deal with that connection by itself. Replacing the whole wiring harness is not needed. What I did is simply cut the wires off at both sides of the connector and splice them together. no new wires needed, just some solder and heat shrink tubing.

If the engine still has good compression, good fuel system and is timed good enough, then it should fire without glow plugs provided its block heater has been plugged 3 hours prior to cold starting. Mine will start below 0C with nothing but the block heater plugged in. It sounds like the engine is otherwise tuned well, so it should start off the block heater alone.

Manual control for the glow plugs will work on these trucks as well as on any other vehicle but the OEM control system is pretty good and is worth trying to fix. I have my original controller (my older truck uses a crude Bimetal switch that is less reliable) but I also have a manual over ride. You can send 12V directly to the relay on the controller instead of adding another relay if you want to go that route.

If you decide to buy glow plugs eventually, come back here and we can direct you to some online suppliers that can get you the right kind at a good price. You MUST NOT use autolite, champion, wellman or any other aftermarket brand as they can fall apart in the engine when they burn up. I would know because it cost me an engine rebuild last year The brand you want is BERU, made in germany and is normally only available though ford or international for a few pints of your blood. However there are webstores in the states that carry them at a much better price even after exchange rate, shipping and brokerage.

Another option is to just replace the single glow plug by getting one at a local ford dealer (~$30). Not ideal, but if you are tight on cash is acceptable.

 

[8v-of-fury]

If this truck is tuned well I'll be a monkies uncle

It was worked on by a couple "back-yard-mechanics" that worked on gas engine cars

The reason I wish to replace the wiring is so I can run 10 AWG to each glow plug to ensure I am getting 12V at each plug. These 8 wires will be fed by a buss that will have 4 AWG to a ford starter solenoid then to the battery. The switch on the dash will be able to activate the solenoid, allowing 12V at full amperage to flow directly to each glow plug. I was reading on another forum about how people notice that they only read 5-7V at their plugs, and they keep it that way because they think its better? why would that be better? these are designed to be run at 12V are they not? Running them at 12V should make them be able to reach optimum starting temps in less than half the time.

Why would people want to run them at less then optimal voltage requirements?

you make very good points David, thank-you. I think the only problem with running the stock wiring right now.. is that I am certain the Gp's have not been changed in the last 8-9 years, and god knows how many km's and starts they have on them. I will reconnect the broken wire when I am at the gf's next and see if it makes the WTS light stay on for longer. I will also try plugging it in over night and starting it with no GP usage to see how tight the engine really is. Judging by the broken wire, the lack of WTS light staying on for more than 3 seconds in cold weather, and the way this thing started last summer in warm weather.. i'd say this GP circuit has been out for a while...

 

[Knuckledragger]

The glow plugs are 6V, so the 5-7V readings are accurate. Feeding 12V to them is the reason that they heat up. Adding larger gauge wiring will not be of any benefit.

Glow plugs are relatively inexpensive and very easy to change. Fix the wire and get new plugs.

 

[8v-of-fury]

Ahh.. I see. Why are they only 6v?

They are unlike VW GP's Whereas they get 12V.

Good to know, they are getting optimal voltage then. Thank-you.

Also, I will fix the wire. No money to be fixin a run down truck right now.. there house needs a new well, roof, and plumbing

Sadness that all this has to happen right after the death of their father/husband.... makes me cry

but nonetheless.. thank you! i will reconnect it and see if it makes the relay stay on as long a it is supposed to.

 

[david85]

The original design of glow plugs on the 6.9 and later 7.3L IDI (pre powerstroke diesels) was for 6V, but they are used in a 12V system to make them heat up faster for convenience of people that are used to gas powered vehicles. This makes them more at risk of burning up so you have to turn them off in time to make sure you don't burn them out. Thats why you have an automatic solid state electronic controller to manage the glow plugs. Its a compromise system that was intended to balance fast starting, reliability and cost savings all at the same time.

In reality, you should be getting closer to 10V at the glow plugs (unless its really cold out) so you still have loss in the system somewhere if you are only seeing 7V. 10V is acceptable considering the glow plugs will draw about 200amps and that will pull the voltage down even direct off the battery. Its to be expected. Don't replace the wires that feed the glow plugs themselves. Those are fuse link wires and need to stay there unless they are burned or badly corroded. If you alter any wiring between the controller and the glow plugs, the automatic system may not work right anymore (remember the resistance feedback).

The wires I am refering to are the 10 gauge wires that feed the relay on the controller........ THEN from there the power is distributed to the individual glow plugs via fuse links wires. This is a factory wiring diagram for the 1987 model year.

You must be registered for see images attach

A weak connection at the main engine connector of these two heavy gauge wires (yellow according to above picture) will eat up amps and volts on the circuit and throw everything off. In theory it could also develop into a fire hazard if it gets bad enough.

 

[Agnem]

The 7.3L style glow plug system is very reliable and highly desireable to us 6.9L style system guys. If you want to go with a manual glow plug system, by all means do it, and mail me your controller and harness please!

 

[dyoung14]

my 86 still has the factory screw in the head controller and still works perfectly, which suprised me.

 

[8v-of-fury]

my 86 still has the factory screw in the head controller and still works perfectly, which surprised me.

Well I am sure it most likely still works like a charm, I mean we are talking about good ol' Fords here Its just that I am worried that one or two will be burned out, creating enough resistance to cause the system to see too much resistance and not turn on the gp's at all. If there is too much resistance to work, then i will put in some custom wiring not deleting the original harness, but working along side it. As you said, Using the switch to apply 12V directly to the Glow plug Controller. It really is too bad the truck is like 50kms away.. id be in it right now working on it if i had the choice lol

Do the 7.3 use a different style GP? I think i read that they use like a ZD9 as opposed to like a ZD1A1 or something obscure like that.. and one has bullet connectors and one has spade connectors.. What would make the bullet connectors more desirable over spade connectors? and what else about the system is different?

 

[dyoung14]

Well I am sure it most likely still works like a charm, I mean we are talking about good ol' Fords here Its just that I am worried that one or two will be burned out, creating enough resistance to cause the system to see too much resistance and not turn on the gp's at all. If there is too much resistance to work, then i will put in some custom wiring not deleting the original harness, but working along side it. As you said, Using the switch to apply 12V directly to the Glow plug Controller. It really is too bad the truck is like 50kms away.. id be in it right now working on it if i had the choice lol

Do the 7.3 use a different style GP? I think i read that they use like a ZD9 as opposed to like a ZD1A1 or something obscure like that.. and one has bullet connectors and one has spade connectors.. What would make the bullet connectors more desirable over spade connectors? and what else about the system is different?

yes fords are very good trucks, especially when they have the best diesels engines in the world shoved down into them, cough(idi)


yes 7.3 has what looks like a bullet tip connector, old style 6.9 has spade connector, but i think 87 6.9 has the 7.3 style glowplugs and controller, 7.3 style is easier to trouble shoot than the 6.9 wiring

 

[david85]

The change over year for the newer glow plug system was 1987, so 6.9s build in that year had the newer ZD9 glow plugs. 86' and older still had the thread in controller on the head (like mine).

 

[Agnem]

my 86 still has the factory screw in the head controller and still works perfectly, which suprised me.

So does my 83'. Scary I know. My theory on why the 6.9 controllers fail so much, is their location. I believe they get rained on a lot if they are out in the weather. Right under the cowl seal, which to some extent is an oxymoron.

 

[dyoung14]

so far i havent had any problems with mine, all my glow plug system if still like it was from the factory except it has new plugs, anyone else still got the stock controller in the head working?