6.9 diesel glow plug problem
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6.9 diesel glow plug problem
I am new to the site and have a question right off the bat! I have an '84 3/4 ton 4X4 with of course the 6.9L. Last hunting season I started having trouble starting the rig in the cold mornings up in the woods, I figured one or two glow plugs was bad and after hunting season I checked out all the plugs with a test light and discovered they were ALL bad. I replaced them all and the rig ran fine for several months. Recently it has been hard starting even in our 90 degree weather. I took a stab at a bad glow plug and discovered all of them were bad!!! $90!! I looked in my nearly worthless Chilton's manual and saw a brief statement about a relay in line with the plugs. What I am wondering is if I replace the relay and glow plugs again will this solve the problem? Can there be anything upstream of the relay that will burn it up and my glow plugs again? Also, where might the relay be located? I know this is a lot to ask, but it is about to start getting cold again and I don't want to only be able to drive where I can plug the truck in. (When plugged in it starts great of course) thanks in advance---Kevin
Hotshot
Joined: Feb 2004
Posts: 11,697
Likes: 3
From: Marengo, Iowa
Sounds to me as the controller is either putting too much voltage to the plugs, or staying on too long. The system is set up to go on for about seven seconds, then altrenate on off for a little longer. I rigged up my sister's truck with a momentary switch, a big name for a toggle switch that is sprung off, you have to hold it on. All it takes to do this is hook the purple wire in the solenoid on the fender well, not the one for the starter, the one down flat, and ground the black wire. Hook the toggle from a fused power source from the box, or put a fuse in the line and bring a wire in from the accessory post under the hood. My old man's 84 is next on the list, that's why I can quote colors to you.
Tuned
Joined: Nov 2002
Posts: 348
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From: Benson, AZ
I did the same thing to my truck. Here is a diagram of the glowplug momentary switch setup.
https://www.ford-trucks.com/user_gal...oid=49492&.jpg
scott
https://www.ford-trucks.com/user_gal...oid=49492&.jpg
scott
Post Fiend
Joined: Nov 2003
Posts: 21,285
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From: Nutter Fort, WV
KSA you must install MOTORCRAFT/BERU glow plugs to get any kind of life out of them.
Cheapest price for them is at Autozone.
The momentary switch will be a step in the right direction also.
I use my plugs first start of the day in the summer, the rest of the day it starts fine without the glow plugs.
In the winter if it sets for less than 3 hours I usually do not need to use them either.
Cheapest price for them is at Autozone.
The momentary switch will be a step in the right direction also.
I use my plugs first start of the day in the summer, the rest of the day it starts fine without the glow plugs.
In the winter if it sets for less than 3 hours I usually do not need to use them either.
Tuned
Joined: Nov 2002
Posts: 348
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From: Benson, AZ
Your best bet is to just replace the relay on the fender. The cost is not that much and then you know you have a good relay.
scott
scott
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Joined: Aug 2004
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From: Fairfax, VA
Still Having Problems with my Glow Plugs
I'm new to this site and wish I had discovered it a long time ago. I am the proud owner of a 1985 F-250 3/4 with a 6.9L diesel. I love the truck and have and have a lot of questions to ask but the most pressing is the difficulty I am having starting the truck. When I first got the truck (a gift from my dad) it had 72,000 original miles. I was having problems starting it so after some research discovered that 6 of 8 glow plugs were burnt out. I replaced them and also the glow plug relay. It fixed the problem. Recently I noticed the wait to start light was not illuminating in the cab and it was cranking a lot before it started. I decided to bypass the controller. I wired it the switch in accordance with the diagrams I linked to several postings on this site. I still have not fixed the problem. Since the wait to start light was not not coming on before I wired the switch I am beginning to think it's the relay. How can I check that? Also what would cause it to go bad after only about 18 months? Thanks for you help fellas.
Tuned
Joined: Nov 2002
Posts: 348
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From: Benson, AZ
Ok the easiest way to check the relay is to have someone hit the switch and use a test light to check the relay. Make sure the ground wire is hooked up to the relay. You can also listen for a click from the relay when you hit the switch.
Senior User
Joined: Aug 2004
Posts: 100
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From: Fairfax, VA
Got it Working
Thanks for the help. I did a little thinking and figured the problem with my glow plugs was the relay. I invested $16 in a new one and bam it workls like a charm. I also set installed a bypass switch in the cab which is a great idea. I don't think I'll be having any trouble starting my truck this winter!
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