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Discussion Starter #1
1995 7.3, 108k miles. Has baby swamp injectors and a Hydra tuner, AFE big boost air filter. A couple days ago, it was about 20 degrees out and the truck started up as usual without being plugged in, 2 GP cycles. After sitting for 9 hours a work, no start. It would crank but not fire. Cycled glow plugs again, started to fire then just cranked. Repeat. Then it started and ran fine. Replaced the fuel filter, no gel in the filter. Put more white powerservice in, added some truck stop number 2 diesel. Same issue. Plugged it in for 2 hours, started right up. Glow plugs? Relay? Where would you start? This is my first diesel, learning as I go.
 

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https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.powerstrokenation.com/forums/17-1994-1997-power-stroke-technical-info/374226-glow-plug-resistance-test.html?amp=1&ved=2ahUKEwizp4iT1sXgAhX2HjQIHW_NChIQFjAGegQIBhAB&usg=AOvVaw2uyYeQj4gRkNjEHc7YYL_O&ampcf=1&cshid=1550506427151


Read this thread, good GP test info. There are some good threads on here about testing the GP Relay, but I'm not sure which relay you have.

Sent from my E6810 using Tapatalk

Having troubles getting a good link, use the search bar and search glow plug resistance test.
 

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After thinking about it today, it sounds like a couple of glow plugs may be bad, but not sure. Test them if you are in doubt, as for checking the relay, the way I check mine is I hook a voltmeter between the two large posts on the relay, key off should read battery voltage, key on/glow plugs on should read .5 volts or less. A reading of more than .5 volts means your relay is working, but the contacts are getting bad, and not supplying good voltage to the glow plugs, and should be replaced soon. If it reads battery voltage constantly, and clicks when the key is turned on, the relay is junk. If it doesn't click, or reads battery voltage at all times, it is time to test the relay controls. But I don't think you will have to go there yet.

Things to consider: on a cold truck, the glow plugs should stay on for almost 2 minutes when you turn the key on, no need to cycle the key, the WTS light is not hooked to the GP's. I turn the key on and count 45-50 seconds then she starts, down to about 8 degrees. ( Bugman learned me that trick, before I joined the forum. Thanks Bugman!)

I have only used this test on relays, which do not have a shunt on the GP relay, if yours has the shunt, I'm not sure this test will work. (The shunt looks like a piece of accordion sheet metal bolted under one large post on the GP relay)

I am just assuming the connections on your relay and batteries are clean and snug. If not, fix that first!

If you replace your relay, HillHavenFarm posted a link to a good source! I still have a stock relay, but will upgrade when it needs replaced.

Hope it helps, just my .02

Sent from my E6810 using Tapatalk
 

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Thank you for the suggestions, I'll try to pick up a voltmeter in the next day or so to check the relay first. A lot of the truck is still original. The glow plugs were done about 2 years ago but I don't know if the relay was replaced.
 

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Get a digital volt/ohm meter.

Do you know what brand of glow plugs that were used? A lot of the aftermarket ones will burn out quickly or get stuck in the head and break off when you try to remove them.
 
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