Glow plug controller
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Glow plug controller
I have searched my manual twice and can find no information on the Glow plug control circuit. I have an 1987 F250 and the wait to start light comes on and stays on. My truck will only start when using starting fluid. I don't know what to replace. Any help will be appreciated.
I'm wondering if I can't just trace the line to the glow plugs and install a hold-to-power switch to power the Glow plugs.
I'm wondering if I can't just trace the line to the glow plugs and install a hold-to-power switch to power the Glow plugs.
Logistics Pro
Joined: Jun 2005
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From: AZ
I've got to assume you are in Antartica if you need the glowplug system to start the truck this time of the year 
. OK, first chase the penquins 
away from the front of the truck. Find the relay for the glow plugs
and jump the big posts with a screwdriver for about 30 seconds or so with the key on. Then try to start her up...if she starts without the smoke you have found your problem...a new glow plug relay is your answer. If it doesn't make any difference you'll need to ohm out the glow plugs through their harness.
ON EDIT: I just now noticed that you have an `87....you might want to post this to that group...
. OK, first chase the penquins away from the front of the truck. Find the relay for the glow plugsand jump the big posts with a screwdriver for about 30 seconds or so with the key on. Then try to start her up...if she starts without the smoke you have found your problem...a new glow plug relay is your answer. If it doesn't make any difference you'll need to ohm out the glow plugs through their harness.
ON EDIT: I just now noticed that you have an `87....you might want to post this to that group...
Last edited by nlemerise; Jul 14, 2007 at 02:44 PM.
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Thanks, Neal. No penguins here in Tennessee. 94 degrees F.
Isn't there more than a glow plug relay to control the circuit? My "wait to start" light comes on and stays on. Even when I drive 100's of miles, the light is still on. I just replaced all the glow plugs because I thought that was causing the failure-to-start problem. Soon after I did that, the "wait to start" light started staying on, but not immediately after replacing them.
Isn't there more than a glow plug relay to control the circuit? My "wait to start" light comes on and stays on. Even when I drive 100's of miles, the light is still on. I just replaced all the glow plugs because I thought that was causing the failure-to-start problem. Soon after I did that, the "wait to start" light started staying on, but not immediately after replacing them.
Logistics Pro
Joined: Jun 2005
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From: AZ
I have no idea how the circuit is set up on a 1987...On the newer PSD's I can tell you that all your key does is send a low amp signal to the relay which closes a contactor inside and lets high-amperage to go from the battery to the glow plugs. On the newer trucks, the "wait to start" light is independent of the glow plugs. When you turn the key the PCM uses a few sensors (temp, barometric pressure) and decides how long the glow plugs should be on, irrespective of how long the WTS light is on or not.
So, I go back to diagnosis...jump the relay on your truck and see if it starts more easily. My guess it is the relay that is bad, because as you said, you changed the glow plugs already.
So, I go back to diagnosis...jump the relay on your truck and see if it starts more easily. My guess it is the relay that is bad, because as you said, you changed the glow plugs already.
Tuned
Joined: Feb 2007
Posts: 461
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Neal,
I see that you have a '99 as I do. I have heard that the glow plugs will only energize if the engine is below a certain temperature. 60 degrees? Is this true?
On my Mercedes, the dome light dims as the glow plugs activate. Once the plugs turn off the light brightens and I then start the car, even though the "wait to start" light may have turned off 30 seconds earlier.
My truck starts fine as glow plugs are seldom needed in Florida, and the "wait to start" dummy light works as it should, but I don't see the dome light dim as it does in the Mercedes. My thought is to check the relay, but will the relay be engaging at these warm temps?
It's not really a concern other than I want the cylinders as warm as possible when my veg fuel is initially sprayed in.
I see that you have a '99 as I do. I have heard that the glow plugs will only energize if the engine is below a certain temperature. 60 degrees? Is this true?
On my Mercedes, the dome light dims as the glow plugs activate. Once the plugs turn off the light brightens and I then start the car, even though the "wait to start" light may have turned off 30 seconds earlier.
My truck starts fine as glow plugs are seldom needed in Florida, and the "wait to start" dummy light works as it should, but I don't see the dome light dim as it does in the Mercedes. My thought is to check the relay, but will the relay be engaging at these warm temps?
It's not really a concern other than I want the cylinders as warm as possible when my veg fuel is initially sprayed in.
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