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7.3 PowerStroke Glow Plug Question

I have a 97 PSD. When the key is turned on, the "Wait to Start" light lights as it is supposed to. It generally goes out in about 10 to 15 seconds and the engine starts with about 1 to 2 seconds of cranking. This is in South Florida in the morning at about 80 degrees.

I just took a trip to the Carolinas and had a problem when I tried to start as soon as the "Wait to Start" light went out in about 15 to 20 seconds.

Back in Florida and reading my service manual, indications are that the glow plug relay would stay energized for about 60 seconds at sea level with an oil temp of 60 degrees. I just tested the relay at about 70 degrees and the "wait light" still goes out around 15 seconds, but the relay stays energized for a total of 50 seconds. My question is, where does the "wait light" get it's voltage from? It obviously is not the downstream side of the glow plug relay which is the way the older IDI engine relays were wired, or it would have remained on for the total time the relay was energized. Why does the light go out long before the glow plug relay opens? I am under the impression that the relay is controlled by the PCM which relies on a barometric sensor and another sensor that reads oil temp. I am assuming that when I was in the mountains, had I just left the key on for about a minute the engine probably would have started easily. That would have been about 45 seconds longer after the "wait light" went out.

Is my "wait to Start" light functioning properly? If so, what starting procedure do you guys use when the temp is below about 40 degrees? Does your "Wait to Start" light remain on for a much longer time?

TIA

Reply to
CrazyMan
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My friend has a Powerstroke. We tested and found a number of dead glow plugs. It was hard to start when cold. Other than that, no problems. We're in Tucson, the problem showed up on a camping trip to the high country.

Al

Reply to
Big Al

I don't know about all that testing of electrical currents, but in my experience (2 Powerstrokes, both 2000's) I have had the glow plug relay go bad on both. I think it's a pretty common failure from what I've read on the Deiselstop.com website (

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,Great website if you haven't been there). One easy way to tell if it's your relay is to just turn the key to the "on" position (wait to start & other dash lights will be on) and just sit there for a couple of minutes. If after a couple of minutes the dome light suddenly gets brighter the relay is working. If the light stays the same the relay is probably shot. This test may be easier to do in less than full daylight......

A relay is about $40 at your local International Truck dealer, and is right on top of the engine, about a 10 minute job. Very easy to do, and that's where I'd start if I were you.

My understanding is that the glow plug relay energizes the glow plugs for about 2 minutes each time the truck is started. It takes the first 15 seconds or so for the glow plugs to get good & warmed up (i.e glow), that's why we have the "wait to start" lights, but the glow plugs stay energized for a couple of minutes aftre the engine is started to help get the fuel to burn in a cold engine. I truly believe that my glow plugs work every time I start a cold engine regardless of ambient temperature. BTW, I live in Atlanta.

For what it's worth, my truck starts right up without waiting for the "wait to start" light to go off until the outside temp gets down into the 30's or so, so unless it's colder than that I don't even wait. Just get in & crank 'er up. If below 40 or so I wait for the "wait to start" light to go off then crank and never have had a problem except when the relay was bad. When the relay failed, I had a heck of a time getting it started in cold weather & when it finally did start made a gawdawful cloud of smoke until it warmed up....

Hope this helps.

Reply to
johnH

Thanks for your reply. As per my earlier post, I have already determined that the relay is functioning. The real question still boils down to why the "Wait to Start" light goes out way in advance of the relay disengaging and if this is normal operation.

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energized

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Reply to
CrazyMan

yes it is normal

the WTS lamp stays on for an interval dependent upon outside temperature

this gives the GP's time to heat the air in the cylinders to an acceptable level

the colder it is outside, the longer the WTS lamp stays on

GP's remain on while cranking to help keep cylinder temps up

Reply to
TranSurgeon

So what you are saying is that if I have trouble starting in cold weather, I should just continue to wait after the WTS light goes out before cranking. The WTS light only stays on about 20 seconds at 50 degrees but the GP relay remains energized much longer.

temperature

acceptable

degrees?

Reply to
CrazyMan

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