electrical issues

[JohnC]

yes, it appears to be tight and bolts securely to the frame.

That is not the one I meant. There are a number of sensor grounds as well as the main PCM ground that bolt to the engine. Any bad connection here will result in major drivability issues.

[derekja]

Well that's certainly the kind of symptom it exhibits. Today as I was checking things over again it behaved slightly differently. Instead of refusing to start, it started and then shut down a second later. (literally a second, maybe two at the outside. It definitely caught and then acted like I'd turned the key off. Did this 3 times.)

On the RH rear intake stud there are 4 wires, one big braided strap down to the frame, and three smaller wires to different parts of the wiring harness. All are securely attached as far as I can tell. (edit: well, all are definitely securely attached to the stud, what I can't tell is what happens to the wires once they go into the harness, but the plastic casing on the harness doesn't appear damaged anywhere...)

It is still reliably giving me the heater circuit DTC code. Is this sufficient evidence to conclude that my short or other wiring problem is in that area or could it be a ground well removed from there and that's just the first component effected?

Possible next steps:

1) replace the glow plug relay. (~$60, but easy to get to)
2) pull off the fuel filter and heater to look for a short beneath it. (no money involved, but I'm so not looking forward to all that disassembly to get down there...)
3) keep looking for other ground issues. (but I'm not sure where to start)

What else should I check?

Thanks again. Sorry to keep running around in circles on this...

--Derek

[JohnC]

OK, I get it. I'm pretty sure the braid belongs on a bolt on the back of the cylinder head, but I doubt if it would make any difference.

I don't have any info on the '98, but there were more than 3 wires on there in '95, specifically, PCM ground PD6; ECT, IAT and Crank position sensor; MAP sensor; Baro sensor; and Trans temp if it's an automatic.

[derekja]

Still pulling my hair out over this. I've found some issues, but not the one I need to solve, apparently. Here are the things that are off the list:

1) glow plug controller/heater circuit. I replaced the controller yesterday and cleaned all the plugs on the heater circuit. I cleared the code and it didn't come back. Yay! One problem down.

2) slow cranking, turbo smoke issue. That appeared again as soon as I got the glow plug stuff back together. A friend had a load meter and the RH battery tested bad. In fact, the side terminal connection appeared fine on the outside but was all corroded inside the battery. Kind of a dumb design, so I replaced the battery with a top connection one and the starting issue went away.

I'm left with the most mysterious issue, though. It is now manifesting itself as an intermittent shut down. Once I replaced the battery it ran for about 4 or 5 minutes and I was getting all self-congratulatory and then boom, just like I'd turned the key off. No codes set. Went to start it up and it wouldn't do so, no starter click, nothing. Went to lunch and came back, same behavior. Tightened battery connections, checked fuses, messed around a bit and it started just fine. Ran for 15 minutes with no problems. I turned it off and put away my tools. Ran it one last time and predictably, the same behavior. Shut off like I'd turned the key off, this time only 30 seconds or so after I started. Started up fine this time and then did it again.

One additional data point, when it is running the battery meter usually reads about 14 volts. Sometimes, though, it mysteriously drops down to 12.5 or so. At the same time as this happens, carcode suddenly loses the ODBII connection. The voltage comes back up, the carcode connection comes back.

I still think this sounds like a ground issue. I don't know what else to check, though. I've checked the grounds off the engine to the wiring harness, the big braids down to the frame, the battery connections, the connection from the battery to the body. Where else could I be missing?

Sigh. Thanks.

--Derek

[TAG]

Boy this one sure sounds like a bad ignition switch to me. As intermittent as it is it might be tough to diagnose. Maybe throw one in pray?

[derekja]

Ack, except they want $160 for an ignition switch! Yikes. Hard to throw that money at it without some surety that that's where the problem is. Got some calls out to the salvage yards around, though...

I was looking at that, unplugging the ignition switch and looking for bad contacts and stuff and I came across another theory.

So I have that security light on. It's code reads "B2948 antenna power short to battery or security system sensor power circuit high"

I wasn't aware that there WAS an aftermarket security system in this truck. It had never been mentioned to me and I never saw any evidence of it. But there is. There is a little black module with "hornet" on the side and getting on the net I find that this is an aftermarket security company. Thinking there's a sensor reading high and shutting the truck down rather rudely sounds like just the kind of thing a security system might do.

Sound a reasonable theory?

[edit. nope, don't think so. Talked to Hornet technical support and they deny that there is any mechanism in their security system to shut down a running vehicle. Rats, I liked that theory, too...]

[Turbo Al]

Do you have a lot of keys on your key ring?? Believe it or not we get a lot of bad switches because people put every thing but the kitchen sink on there key rings.
Al

Also check replaced the battery grounds? Eazy to check them is to put jumper cables on to battery to ground and see if it continues to run -- these things corrode inside and it is hard to find.

Al