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This is my first post so sorry it is a little long. I recently obtained a 1987 F350 6.9L that was abandoned on one of our properties. I was told that it last ran at least 5+ years ago but I am not sure. Once we got it towed home, I checked the fluids (which all looked good) and installed two new batteries and tried to get it started. After hearing a single click when trying to get it started, I replaced the starter solenoid, hit it with some starter fluid and it started right up. I drove it around my property and it runs great with the exception that it seems to want to hold onto 1st gear (its an automatic) and the tach doesn't work. I was able to stop it and start it multiple times over the course of about 45 minutes and it fires right up as soon as I turn the key.
When I try and start the truck the next morning, it would just crank and crank without firing. I hit it with some starter fluid and it fired right up. I read every thread, and the sticky, I can about the glow plugs, glow plug controller, glow plug relay, bypassing the controller etc. so I started by replacing 7 out of the 8 glow plugs with Motorcraft ZD-9s. I could not get the glow plug closest to the driver's seat out as it is so stripped that I can't even put a socket on it (this glow plug does test ok with a test light.) 3 of the 7 plugs that I removed were bad so I assumed that was the issue. I tried starting the truck and it would still just crank and crank. I broke out my multimeter and tested the glow plug relay and glow plug connectors on the harness. When I turned the key to the "run" position, I got the attached results with my multimeter. The end result is that there is no power getting to the terminal with the squiggly metal piece so there isn't any power going to the glow plug connectors or glow plugs themselves. I am able to get power to the glow plugs and start the truck when it is cold by jumping the two big posts on the glow plug relay with a screwdriver. On a side note, the "wait to start" light does stay on for about 5-10 seconds when I put the key in the "run" position and sometimes I hear a buzzer but I don't think I hear the buzzer every time.
With these results, I thought I would try installing a momentary switch to manually turn on the glow plugs. I removed the white wire from the glow plug relay and attached a 12 gauge wire to the terminal on the relay where I removed the white wire. I did not remove the blue wire that leads to the "wait to start" light. Before I go drilling any holes in the dash to install the switch, I test the bypass by taking the loose end of the 12 gauge wire (which is still about 25 feet long) and hold it to the ground terminal on the driver's side battery for 7 seconds while the key is in the "run" position. I could not find a ground in the cab or in the engine bay so that is why I placed the wire on the battery ground terminal. When I place the wire on the ground terminal I am getting some sparks from the loose end of the wire and I thought I could hear some type of noise from the glow plug relay. I disconnect the loose end from the battery ground terminal, run back to the cab and when I try and start the truck it still just cranks and cranks and does not fire. I tried does this about 4 times. I again take a screwdriver and jump the two big posts on the relay for about 3 seconds and the truck fires right up. I take out my multimeter and test the terminal with the squiggly metal piece and it is still not receiving any power when I ground out the new bypass wire I installed.
Is it possible that the relay is just bad so the bypass won't even work? Am I missing something obvious? I am at a loss here. Any help would be appreciated.
If your relay is bad, you can buy just the Relay. Tell the parts guy you need a Relay
for a 6.9 IDI. 83 - 86 use them.
If you ask for the relay for your 87, they will sell you the whole Controller set up.
I think a GP Relay is about 30 bucks.
Make sure it is a GP Relay and not a Starter Relay they give you.
Iam no expert on the Controller you have as I have a 86.
Yes, the controller will cycle the relay continuously if one or more plugs are bad or not properly connected. It also cycles normally under certain conditions (temp) as an attempt to lower exhaust smoke when first running (thank the politicians for that).The Wait To Start light gets +12 from under the dash and the controller provides a ground. You can disconnect the wait to start light connector attached to the controller by the firewall and ground it to see if the light comes on. The actual bulb sockets can get flakey from corrosion and that can cause flickering. I always clean all the sockets with contact cleaner, WD40 works also.If you hear the relay "flickering" or your testing the light is OK, then the controller might be defective. The whole scheme shortens the life of the plugs with them coming on sometimes when the engine is pretty warm and the after-start cycling.Just like many others on this forum, I eliminated the controller.Disconnected all of its wires coming out of the controller and tuck them behind .Small +12 wire from truck wiring harness remains connected to small terminal on relay.Push button on dash has one terminal grounded, long wire of other terminal goes through firewall near steering column and connects to the other small terminal on relay. Relay is receiving +12 from harness when key is on, push button supplies ground to make it close. Also, connect the Wait To Start wire I mentioned earlier to that same terminal as the push button, and it will illuminate when button is supplying ground to it and solenoid.I suggest leaving controller unit in place to serve as a mount for relay and the big wavy Ballast that's on it. Do Not bypass or eliminate that Ballst resistor or too much current will be supplied to plugs and harnesss.
glow plug controller gets shut off by engine temp sensor around 110 degrees engine temp.
if your controller is cycling the plugs once engine is warmed up, than the temp sensor is failing.
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