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I have the LED mod and several weeks ago, my LED stopped indicating and the truck would not start in cold weather unless I jumped the terminal on the relay. I replaced the relay and while I was tightening one of the small lugs, the one towards the nose of the truck, I felt it break. The truck acted just like it had been for the weeks prior, if I didn't jump the relay, it wouldn't cold start, so I assumed, because I had broken that small lug, it wasn't getting the signal to turn them on.
I had a patient who is a mill right make me a little tool that helps me with the jumping. I like it way better than using a screw driver. It's stainless and has a wooden handle.
Pretty cool little gem, but I wanted to fix the issue, so I got another relay today, got it installed, and pfffttt....still no glow plugs. I had to jump it.
So what now? obviously the GP's themselves are working, as the truck starts when I jump them. But for some reason no signal is getting to the relay. What do I need to check to see what is going on between the PCM and the relay?
I have the LED mod and several weeks ago, my LED stopped indicating and the truck would not start in cold weather unless I jumped the terminal on the relay. I replaced the relay and while I was tightening one of the small lugs, the one towards the nose of the truck, I felt it break. The truck acted just like it had been for the weeks prior, if I didn't jump the relay, it wouldn't cold start, so I assumed, because I had broken that small lug, it wasn't getting the signal to turn them on.
I had a patient who is a mill right make me a little tool that helps me with the jumping. I like it way better than using a screw driver. It's stainless and has a wooden handle.
Pretty cool little gem, but I wanted to fix the issue, so I got another relay today, got it installed, and pfffttt....still no glow plugs. I had to jump it.
So what now? obviously the GP's themselves are working, as the truck starts when I jump them. But for some reason no signal is getting to the relay. What do I need to check to see what is going on between the PCM and the relay?
I have a 24" Single Jumper Cable with Clamps in my Box I use. I made it about 10 years ago maybe from someone's trash
So what now? obviously the GP's themselves are working, as the truck starts when I jump them. But for some reason no signal is getting to the relay. What do I need to check to see what is going on between the PCM and the relay?
Now you're getting to temps where the glow plugs don't come on anyway, you might have to use ice on your IAT sensor to make them work. I am under the impression that the PCM sends ground to the GPR and that the two wires are always hot (the feed from the battery and the small wire that works the relay). Then when the relay is activated it powers the other side, which feeds the glow plugs. Do you have power to that other small wire? And you could have gotten a bad GPR even though it is new. If all that checks out then you need to determine if your PCM is sending ground to the relay when needed.
The small post with the red wire gets its power from the PCM relay and should be hot with the key on. The other small post with violet/orange wire grounds from PCM to activate. Hook a test light to the battery ground and test small posts with key on. One will light up and the other will activate the GPR when touched. Both small terminals will be hot if there is no ground signal from the PCM. If only the red one is hot, the relay latching circuit is bad. You will have to do this on a cold engine to be sure the PCM conditions are met for GPR operation.
Jason, on the two SMALL posts on the GPR, one is a 12V feed with ignition on, and the other is switched by the PCM - when glow plugs are needed, the PCM switches it to ground; all other times it has 12V (with ignition on). So, if the PCM is demanding glow plug operation, with your voltmeter you will read 12V between the two small GPR posts. All other times, metering between the posts will show 0V (both posts have 12V, so a 0V reading with the voltmeter from small post to small post).
I believe EOT and ambient temp (I assume from the IAT) are the inputs the PCM uses to calculate glow plug duration. Even at 50-60 degrees, with cold oil, glow plugs will be kicked on for a short period.
Thanks guys, definitely having some sort of issue with the communication of need for glow plugs to be on. I will meter it and get back to you, maybe tomorrow morning. I know it's getting warmer, but the truck still needs the plugs to start, it is still going down low enough at night to need a little assist from the plugs, and as I have stated in the past, you would be surprised how much they come on even in warmer temps. That LED mod will really be informative for those of you that haven't done it yet.
I notice my add on digital battery volt gauge that GPR will come at least once in the morning even in moderate outside air temps. The voltage drops on the gauge and duration will change as the truck warms up. Once the truck is at normal operating temp I don't notice the volt gauge drop at all and the wait to start light does not come on.
I read that duration is controlled from oil temp and altitude by the pcm..
So, I have another issue that I have to deal with first. I am blowing the 30amp site glass fuse for the starter motor...just was 40 minutes from my office looking at a house for my brother and sister in law in Pasadena, Md., and went into the house looked around. Came out and tried to start it and no starter. Looked at the fuses, number 113 (If I recall correctly) was blown, swapped the one next to it for the wiper motor, turned the key, saw and heard it blow. Called a tow truck, then my dad to come get me and take me to work. looks like it was good timing for my daughter to be in Florida for the week. I get to drive her Wrangler...:/
Two key heavy-current items going out at the same time? I'd make sure both your battery grounds to the block are good. A lot of arcing could feasibly blow a fuse - but my suggestion is more precaution than troubleshooting.
My 2002 diagram shows a fuse #61 going directly to the starter solenoid. A bad fuse there usually means a bad starter solenoid, a bad connection on the plus or negative side, or a burned up starter relay. There is no fuse on the starter itself - it needs way too much power for a fuse.
I believe it's a 30amp sqaure fuse with a site glass on my 2003under the steering column number 113 if I recall correctly. Next to the bottom left corner. The bottom left corner was 105 again, if I recall correctly and was for the wiper motor, also a 30 amp square fuse with a sight glass, right next it was the blown one. I switched them, went to turn the key and heard and saw it blow. The truck was sitting at an up angle front to back and the wheel was turned to the right not all the way to lock out, but more than half way. Last week it did the same thing, but I didn't realize it was a fuse, and it was at a down angle and the wheel was turned to the right. Replaced the fuse, all was well for 6days, and then Monday, wham it did it again.
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