I've got an 83 F250 6.9 diesel. All glow plugs are good but 60% of the time the red "Wait To Start" start light doesn't go out and she won't start for love nor money. The remaining 40% of the time in summer weather the red "Wait To Start" light goes out she starts everytime. Now that the weather is staying in the mid 20's I'm plugging her in. She is starting everytime now no matter if the red "Wait To Start" light continues to burn or goes out.

Which component in the glow plug system do you feel is causing the problem?

Thanks for your help,

Rick
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Check for good grounds first.

 

Try running a separate ground from battery to the contoller. Had to do this on my 93 and have had no problem since with this issue.

 

The way most of the old system glow plug lights were wired your glow plugs are heating when the light is on. If the light does not go out the glow plugs are probably toast.

The old system has a temp sensor in the rear of the passenger side head that senses coolant temp to turn the glow plugs on. It also has a timer circuit to turn them off. This will continue to cycle on and off till the coolant reaches a little over 100 degrees.



This picture is the glow plug relay located on the passenger side inner fender.
This one has been wired on by an owner so the butt connectors in the purple wire and the green wire are not there.

The purple wire on the right side of the relay activates the relay to turn the glow plugs on.
The top terminal has two orange wires that go to the glow plugs harness. The black small wire on that terminal is what lights the "Wait to Start" light.
The red wire goes to a terminal that can not be seen that has battery voltage at all times.
The small black wire to the left of the orange wires is a ground for the relay coil.

The ground for the wait to start light is under the dash near the light.
If the ground for that light is bad and the light is back feeding the light, the light could be on because it is grounding to the glow plug harness.
If that ground is good, the only way for the light to be on is power is applied to the glow plugs and they are heating.

Do you notice any other dash mounted electical devices that are not working when the glow plug light is on?
I think the radio and possibly the cigarette lighter also uses the same ground as an example.

What many of us with the old style system have done to fix problems with the controller and glow plug system is convert to manual glow plugs.
Find a power terminal in the fuse block that has power only when the key is in the run position.
Run a wire off that terminal to a momentary switch and then out to the terminal with the purple wire.
Remove the purple wire and attach the wire from the push button.
Now turn the key to on, push the switch for 10 seconds, start the engine.

Hope you can follow all the info in this, if you have any questions post back.

 

Hello Dave:

I can't thank you enough for your detailed reply to my glow plug problem. For awhile I was wondering if I would get a good strong response. I do understand most of what you have written to me but would ask if you could private message me your telephone number so I could call you to clarify a few things. I can't say I'm much on writing back and forth, being from the old school of "let's talk about it." I have unlimited long distance so that wouldn't be a problem for me. Please let me know the best time to call. I'm in the eastern time zone. If you don't feel comfortable with sending along your phone number, I have an 800 number that rings to my home. It's not free but I need the help and I understand that you may wish to keep your privacy. Many thanks again Dave

Kind regards,

Rick Cato
888-822-8517

 

Dave's da Man

 

Hello Dave:

I can't thank you enough for your detailed reply to my glow plug problem. For awhile I was wondering if I would get a good strong response. I do understand most of what you have written to me but would ask if you could private message me your telephone number so I could call you to clarify a few things. I can't say I'm much on writing back and forth, being from the old school of "let's talk about it." I have unlimited long distance so that wouldn't be a problem for me. Please let me know the best time to call. I'm in the eastern time zone. If you don't feel comfortable with sending along your phone number, I have an 800 number that rings to my home. It's not free but I need the help and I understand that you may wish to keep your privacy. Many thanks again Dave

Kind regards,

Rick Cato
888-822-8517

 

Thanks for the heads uo on the grounds.

cato47