Hey guys, I need some help on my glow plug solenoid. The two hot leads from the starter solenoid are 13v to the post on the glow plug solenoid. When the key is on I am only reading 5 to 7 volts on the opisite post that goes to the glow plug harness. What should it read? What does this indicate? Note that before starting failure it was hard to start. Took 5 seconds to start or more. I would appreciate any help Don

 

waldrop4,
Welcome to FTE and the IDI diesel forum.

Voltage drop will have the voltage on the glow plug side of the relay lower when the glow plugs are heating.
200 amps through rather small AWG wire.

That said, there are two places you need to look.
First look at the chassis to engine connector, circled in red in this picture.



That picture is on a 6.9 engine, so your is a little different.
In the picture the large AWG wires, orange color will be either yellow or tan on yours.
There will be two, both on the same end of the connector, You connector will be either black or white if I remember right.
Anyway, look for signs the connector has been hot, deformed or burnt looking plastic.
If you see that, the connector terminals are not making a good connection.
The only fix is to splice the wires aroung the connector, very common problem.
Caution, the wires are always hot, direct connection to the battery positive post.

The other possibility is the relay contacts have burnt up.
The relay from an 86 6.9 engine will bolt right on top of your controller, just make sure you get all the wires back in the same locations.



1986 6.9 glow plug relay, about 30 dollars at NAPA.

Incase you don't see them, the small green controller wire is on the terminal at the end of the metal strip labeled GLOW PLUGS, the small yellow wire in under the other end of the strip on the large terminal of the relay opposite the battery terminal.

 

I have bypassed the wires coming from the starter solenoid and wire nuted them together. I also replace the glow plug solenoid and checked my wires according to the diagram that Dave sent me. I did get it started but it took rolling it off a hill and popping the clutch. It would start right up after I drove it around easy. The next morning I went out to check it and it still wont start on its own. The glow plug light comes on then it starts cycling really fast. Is that normal. Or could it be the IP not doing its job? I kind of rulled that out because it wouldnt even start with a little squirt of either before I finally pushed it off a hill to start it. Thanks any help would be appreciated,
Don

 

How long does the glow plug light stay on solid for the first start of the day?

You should be looking at 8 or 10 seconds.

Start the engine as soon as the light goes out.

 

Dave, I tried this morning and the light stays on for 2 seconds then there is a clicking noise from the glow plug solenoid. It clicks about 2 times a second. I have referred to this as the glow plugs cycling. thanks for your reply
Don

 

Two seconds is the glow plug controller telling you that you have burnt out glow plugs.

If you don't start the engine, after the initial 10 seconds, the controller will cycle the glow plugs to keep the cylinders warm, which is normal.



Two methods to check glow plugs, ohms is a better test, but an automotive circuit tester is faster.

Fast test, clip the ground clip of a test light to the positive battery terminal.
Remove the first glow plug wire connector and touch the tip of the tester to the glow plug terminal.
If the tester lights, the glow plug is probably good.
If it does not light, the glow plug is bad.
Continue until you have checked all 8 glow plugs.


More accurate test if you have a fairly good ohm meter.
The glow plug resistance should be between .5 and 1 ohm when the engine is cold.
Check resistance between the threads and electrical connection.
This test can be done with the glow plug installed, touch the hex on the barrel with the probe that would be on the threads.

If you try this test with a cheap meter, the normal resistance is so close to a dead short, it will probably just show a short or 0 ohms.

The 87 thru 94 uses Motorcraft/Beru ZD 9 glow plugs.

Champion, Autolite, Wellman are all junk, don't use them.
Bosch I have heard more bad stories than good ones.

 

Dave I installed two more glow plugs which made eight new ones. And guess what? The light stayed on 10 seconds and fired right up. You are ausome thanks a bunch. You taught this okie a few more tricks. God Bless, Don

 

Just glad you are back on the road.

 

Hi on my 86 6.9L when I turn the key on the wait to start light doesnt come on and I do not hear clicking. Does anyone know what this could be?? Any help appreciated!

Also what brand of glowplugs should I be cautious of?? Thanks

 

The 86 system is a bit different.

You probably need a glow plug controller or the relay is dead.

This is the controller.



It screws down into the coolant jacket at the rear of the drivers side head standing straight up and down.

This is the glow plug relay.



Mounted right behind the passenger side battery down on the inner fender well.
To test the relay, remove the purple wire on the small terminal and jump 12 volt power to that terminal.

When you do, you should hear the relay click and have power on the large terminal that has the two large orange wires on it.
The small black wire under the orange wires in the picture goes to the wait to start light in the dash.
The old style system does not sense burnt out glow plugs like the new system does, so you need to check them.

Motorcraft/Beru ZD1A is the only glow plug you should use.

 

Thanks for the quick response I was looking at it closely today (been sitting outside for months and had mouse nest on back of engine so I cleaned it up and let it dry) and found that someone did a poor job of putting a pushbutton for the glowplugs. I found several wires unhooked at the rear of the engine and found the plug that goes over the top of the controller up by the air-cleaner! Gonna mess with it again tomarrow so ill let you know how it goes. Thanks again

 

When you look at the wires unhooked for the controller, be aware that it is common for the controller to fail and turn the glow plug on.

So if you plug it back in, the glow plugs may come on as soon as you turn the key on and stay on until they burn up.

I am also aware many people try to hot wire the glow plugs direct.
Since the glow plugs draw 200 amps when heating you must use the relay when converting to manual control or you risk an electrical fire.

Best way to convert the old style system is find a power source (fuse panel) that is only hot when the key is on.
Run a wire from the source to a momentary switch, then come off the other terminal of the switch with a wire that gets run out to the relay and connected to the purple wire terminal.

Then to operate, turn the key to on, hold the momentary switch for up to 10 seconds, then start the engine.

When the temps are extremely cold, after starting the engine may stumble, a short afterglow of glow plugs will smooth it out and keep it from stalling.

 

I plan on putting things back to factory and taking the manual switch that the last owner installed off. Thanks again

 

Watch the glow plug light.
If it comes on while driving your glow plugs are short for this world.

Since the glow plug controller has been in the head for 23 years, many break off when you are trying to remove them.

If it does break off, head comes off to get the remnants out of the head before you drive the truck again since it screws into the coolant jacket.

Mine was removed when the engine was out for rebuilding and a pipe plug now resides in it's location.
Not a big deal for me, I am the only one that drives my truck and I have been around manual glow plugs since the 60's.

 

Ok ive been looking for the controller but I cant locate it. Do you have a diagram or pic of where its located. If the plug wasnt off of it I probably could have found it.