Glow plug system issue

[stackedpstroke]

Well its been getting cold in texas and my truck has been giving me trouble starting up in the mornings. I have to crank probally 4 5 second intervals before itll start

Today i had time to check it out and i thought i found the problem. My glow plug solenoid wasnt clicking on. So i ran up to napa and replaced it. I also tested all my glow plugs and they checked out fine. But the solenoid still isnt getting power

Now after jacking around with the truck i found that the two red wires coming off the relay never get power ( im assuming they activate the solenoid) Hince my glow plugs not working.

Anyone know what might be the problem?

[kanuck15]

seems like a bad connection id trace those wires

[SBSyncro]

I'm having the exact same problem. I just replaced the solenoid and after the new one was failing the "voltage test" at the GP side of the relay, I checked the wires coming from the pigtail. One of them shows 12.8v whenever the ignition is turned on, the other does not show any measurable voltage when the GP "warm up light" is on on the dash.

Is there a timer control circuit somewhere that controls the operation of this wire getting voltage? According to my service manual (which is *(%$^ difficult to find information in):

"PCM controls relay's operation by sensing engine oil temperature, PCM voltage, and barometric pressure."

Is it possible/likely that one of these sensors is faulty? I'm assuming that if the barometric pressure sensor was faulty then the fuel injection system would be working very poorly, which it is not once warmed up. The only problem I'm really having is cold starting (no GP operation at all)

Thanks.

[kanuck15]

its all in the pcm

[CHUCK]

the relay on the right fender feeds 12v to the GPR. Check and make sure the wire is good between there. It should be on the large post closest to the frt. Should be 2 other leads there also, 1 from the battery and 1 to the alternator.

I cant recall if its a fuseable link... 1 or 2 of them are....

[SBSyncro]

Are you talking about the large gauge "feed" wire, or the smaller wire that "activates" the relay?

Here's an update to my situation... Hopefully this doesn't turn into one of those "why you should pay a professional to do it right" kinds of threads....

I started testing voltages and noticed that one of the two small wires to the GPR was getting voltage when the key was turned to the "run" position (when the GPs should be warming up). It wasn't turning off after the light in the dash did, but I'm not sure about whether that light is "smart" or not (or just a dumb timer that isn't actually aware of the GP voltage status).

"Aha" I thought - the PO must have installed the relay with these wires crossed up. So I reversed them (putting on on the "I" terminal and the other on the "S" terminal on the opposite positions that they'd been.

I pulled the terminal plug to the GPs and turned on the key to the "start" position and checked the voltage to the GPs via the terminal connector. Sure enough, I was getting voltage!

So, I plugged the connecter back in, put away the tools and fired up the truck. It started easily, since now the GPs were getting hot.

I ran her around the block to warm up the engine, planning to check to make sure the GP relay had shut off by the time the engine was warmed up.

Well, I got about 1/2 a block down the street and the truck wouldn't shift for a looong time then WHAM! it shifted hard, then shift back. Suddenly the truck is running like CRAP and I notice the "OFF" light on the overdrive button is flashing.

So much for that idea...

I pulled back into the driveway and switched the wires back to their original position and took her back out for another drive around the block. Unfortunately, the problem is still there - shifting VERY rough and running very poorly while flashing the "Overdrive Off" button.

Now I'm wondering if somehow I fried the PCM by swapping the wires....

[SBSyncro]

Update (and good news). Man, I cannot believe the electrical system in this car - I'm starting to wonder if maybe some Brits were involved in the design....

I discovered that I'd blown the fuse for the dome light today while changing out the assembly (Fuse #8). Swapping the 15 amp fuse from the turn signals (#7) fixed the problem. Sheesh, what a relief!

Now, back to the original problem of getting this GP relay to work...

[Goose]

Keep in mind that your glow plugs dont always kick on.

[SBSyncro]

Originally Posted by Goose

Keep in mind that your glow plugs dont always kick on.

Yup. Apparently the PCM looks at oil temp & air pressure (barometric) to determine how long to fire them.

Anyone know the max time they will run before shutting off? Under which conditions?

[bdpprocessors]

Ok so i replaced the relay and it worked fine for a few weeks but now im having issues again.

When i turn the key. The wire going to the Plugs never gets Power. The two small red wires are always posotive. (shouldnt one be negative and then switch to posotive so the relay deactivates? ).

So What im thinming is that whatever tells these wires to switch from pos to neg is bad. What controls this?

Or does anyone know of another possible problem It could be?