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Discussion Starter · #1 ·
Greetings all,

So our 99 F250 SD with the 7.3 has been having a hard time starting this winter, and it has just been getting worse. 3 years ago we replaced the glow plug relay and that fixed the issue. Same thing last year. And it looks like we need to replace it again this year. Is it normal for these things to have such a short life span?

As we were looking around the engine we noticed this dangling down by the wheel. What is it? Is it supposed to be plugged into something?

Thank you for any help you can give.
 

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Do you have an aftermarket intake system? That looks like your intake air temperature sensor, which would have been plugged into the side of your stock air box.
 

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That is the oxygen temperature sensor. It is supposed to be inserted into a hole in the air box to measure air temp. Looks toasty. Might need to replace it. At least clean it. That relay should last for about a million years. Just kidding. They last a long time. Test all the glow plugs individually. You can do that from the plug on the valve cover. Do not probe the wires, unplug it and probe the pins. The two outside pins on each side of the plug are the glow plugs. They should be around .9 t0 2.7 ish ohms. If they are open, they are dead. For the relay, I would look for shorts and test all the wiring. Check voltage drop across large terminals as well. When you first try to start, does your voltage drop real low indicating the plugs are heating?
 

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Yes. It plugged into the back of the stock air box (and the Ford severe duty AIS) - its job is to report to the PCM the ambient temperature of incoming air. It could affect cold starting if it was damaged. Best way to find out is use a scanner to see what the PCM is receiving and compare that with actual ambient temperature. Do that before you get the motor warm.
 

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My new AFE had a spot for the sensor. I've found the only effect it has on the cold start is it controls the rpm on the high idle by how cold the air is. So at most it would not idle up. His issue is that relay and or the plugs.
 

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That relay should last for about a million years. Just kidding. They last a long time.
Really?? You're talking about the GPR? If it's stock, you're lucky if you get a year out of them. I've had them go bad within a couple months. The Stancor relay I finally replaced mine with has been going strong for 4-5 years.
 

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Really?? You're talking about the GPR? If it's stock, you're lucky if you get a year out of them. I've had them go bad within a couple months. The Stancor relay I finally replaced mine with has been going strong for 4-5 years.
Terrible luck you have. I have the same glow plug relay that came with the truck in 2002. Never been changed. If you lose a relay every year, your issue is not the relay but what the relay is operating.
 

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Terrible luck you have. I have the same glow plug relay that came with the truck in 2002. Never been changed. If you lose a relay every year, your issue is not the relay but what the relay is operating.
My glow plugs have been changed only once, on the original engine, and they were all good at that time. Did it because I changed injectors. With the replacement engine (that got the Stancor transferred to it) came with 6 bad glow plugs that I forgot to have changed when the engine was sitting on the shop floor. So it's not the glow plugs that are the problem. The fact is that OEM GPR's are under-designed. If I had a choice, I'd spend 15 minutes to change a GPR than 2-3 hours to change glow plugs. Actually I do have a choice, that I took - install a sufficiently robust relay.
 

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Terrible luck you have. I have the same glow plug relay that came with the truck in 2002.
Same here, I'm just waiting till it goes out to order the stancor relay but that thing is tough.

Maybe Canadian built are tougher :grin2:
 

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You didn't really indicate the symtoms of the hard start beyond having to replace the GPR twice in the past 3 years. That is not normal. Find out why the GPR is failing; also pull the batteries and load test them if you haven't do so lately.

My '99 has never had new GPR or plugs put in.

Check the hard start link at the end of klhansen's signature box. Good info even if you never use it.
 

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Same here, I'm just waiting till it goes out to order the stancor relay but that thing is tough.

Maybe Canadian built are tougher :grin2:
Hahaha, I'd love to go with that, but my truck is from Texas :surprise:
 

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Well that explains everything, doesn't it. ?
 

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I'm having issues with my truck as well (02 f350 7.3). Plugged in all night and went to start it in the morning took me three tries to get it fired up. New injectors, mechanic said my glow plugs are good, GPR is good and batteries are good. Just bought this truck a couple months ago so I'm new to diesels. Any idea what could be goin on? Is it normal to have difficulty starting sometimes when it's cold out even when plugged in? Maybe my plug on the truck isn't working? My solution has been plug it in AND put a heated mattress pad under the hood haha. Fires right up then. Anyways, would love to know what you all think could be goin on
 

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Its entirely possible your heater isn't working. The heater itself is fairly robust - the problem usually is in the cord. I would suggest you plug it in for a couple hours, then UNPLUG IT and slide under (right behind the front left tire) and reach up and feel the area around where the oil filter attaches. That orange cable sticking out at a right angle is your heater. If that area isn't warm, you can bet your heater isn't working.

Nick is in Maryland. If you still can't get it running - PM him (Maryland Dieselnick) - he'll get you going.
 

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Discussion Starter · #19 ·
Thank you all for the responses.

We changed the relay and no luck, still won't start.

The voltage drops a little when I turn it on, but not a whole lot.

The batteries are about two years old. I think they are doing ok as they don't not work, they just engine just doesn't start (if that makes sense).

We checked the fuses, all appear ok.

The Glow plugs are 3.5 years old. They replaced the stock ones and the mechanic who did it had a lot of trouble. Could they be damaged?

Thank you all for the responses and help.
 

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check this for the procedure how check the GP's and GPR. http://www.thedieselstop.com/forums/f47/hard-no-start-check-here-first-75094/

did you check the fuse with a multi-meter? sometime fuse look good but they're not

having the battery load tested would be a good thing. Also make sure ALL connection are clean.

look RPM when cranking, you need about 150 RPM to get the engine started
 
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