Right on!

Ouch on it taking out the glow plugs too. My two controllers were both taken out by a faulty alternator that supplied unrectified AC current to the controller through the sensing conductor (one of the controller's six wires). It was a very expensive learning curve - heck your $3.65 doesn't even cover the sales tax on my repair bills!

But I'm sure glad that the bypass switch works well for you.

Best regards,
JT

 

I was just thinking. Ya, Ya, I know, you thought you smelled something that smelled just like diesel smoke . But seriously, how the heck did you ever figure that out??

 

 

I studied the Haynes Diesel Repair Manual; it says "...when a diode in the alternator fails, battery voltage can get to the GP Controller even with the key in the "off" position and the engine stopped. This battery voltage is usually supplied to Pin #1 in the GP Controller from the alternator after the engine starts. In effect, this voltage "tells" the controller that the engine has started and shuts off the glow plug heating cycle."

I used my multimeter to check for voltage with the engine running and the blown alternator was cranking out 17 - 20 volts unrectified AC to Pin #1 which cooked it like dinner. With the engine off, it displayed battery voltage which at the time was around 12.9 VDC.

That agreed with the manual's assessment. Besides, I couldn't think it was anything that I did that caused it to blow...

JT

 

good diagnosting!

 

Really good diagnosing! I'm going to try and find a copy of that Haynes Diesel Repair Manual. A lot fewer problems with the manual switch though, no diodes, yada yada, to worry about. Simpler, cheaper and just as easy to use.
Take Care

 

The Haynes Manual is a good investment for the $22.00 price. It covers the GM 350 CID (5.7 liter), 379 CID (6.2 liter) and 397 CID (6.5) diesels in precise detail. Also covers the Ford 420 CID (6.9 liter), 445 CID (7.3 liter) and the 445 CID (7.3 liter Power Stroke) diesels, but no Dodge/Cummins. There are no wiring schematics however, as the manual does not get into any chassis issues.

I am still having a problem with the starting circuitry. When I turn the key to the "Off" position, the engine keeps on running. As a general security measure, I had installed a simple kill switch in the fuel shut-down solenoid wiring (the pink wire terminating on the top cover of the fuel injector pump) just before the GP controller blew - just in the nick of time I guess.

I have been using the kill switch to shut down the engine, but it still isn't right. The first kill switch was a cheap rocker style, and when the batteries went flat, I found a 3 amp drain somewhere in the start circuit. I replaced the kill switch with a higher quality toggle switch, and that reduced the drain to under 0.5 amps, perfectly acceptable with clock, gas sniffers & monitors, and a high end stereo sucking a little memory power.

I have just changed the ignition switch this afternoon in hopes that it was the faulty component and in the future, I will be able to shut down the engine with the keyed ignition switch rather than the kill switch.

I mention this only because there is a chance that other 6.2 liter owners might have a no-shut-down situation with the key after installing a manual glow plug bypass switch. Maybe it's just coincidental that this problem surfaced in my vehicle at the same time that the GP controller fried, but I cannot say for certain.

Once I replace my start batteries under warranty (this will be the third time in less than a year), I should know the answer to that question, and I will post the results on this forum.

Anyway, glad yours is working so well - I look forward to mine returning to reliable status soon.

All the best,
JT

 

I’ve had my GP controller bypassed for over 10 years with no problems, so if I had to guess, I would not think that your fuel solenoid problem is related to the GP bypass. When you finally find the problem, tack a post up here and let us know what happened.
Take Care

 

Installing the kill switch in the fuel solenoid power circuit was only a safety measure at the time; I believe the GP controller & no-shut-down situation are simply coincidental events that were sent here to confuse and upset me!

A have a couple of quick questions for you:

1. when you installed your bypass switch, did you disconnect the GP controller's connection from the controller, or did you leave it fully intact?

2. does your engine shut down with the key, or does it keep running like mine does which necessitates the use of the kill switch?

The reason I ask is because this seems to be a frequent problem with other owners, according to what I have read on the Internet and what is contained in my Haynes Manual. Unfortunately, I haven't found the answer to why that has happened to so many others.

I am curious about your installation because if you left the controller connected, and your engine shuts down with the key normally, then that suggests that I have another unrelated problem somewhere in the ignition circuit, i.e. the ignition switch, which I have just replaced. I can't test it yet because the electrical drain caused my brand new start batteries to go flat for the 4th time, and they no longer hold a charge. They are to be replaced under warranty next week (I hope...) but I can't do any more troubleshooting until I get the beast running again.

If the new ignition switch will shut down the engine normally, then I won't need to use the kill switch for that purpose anymore, but will still use it for general security purposes. On the other hand, if the new ignition switch does not shut the engine down normally, then I am doomed!

I concluded that the combination of a blown GP controller and the previously faulty alternator (which was replaced for the second time a month or so ago...) had something to do with the no-shut-down situation as the key used to function normally prior to the first faulty alternator blowing the first GP controller. When the second faulty alternator cooked the second GP controller (the one that is installed now but is not connected...), I lost track of what faulty component was blowing other faulty components, and arrived here dazed and confused without a clue about what is really going on!

The good news is that Fleetwood RV, the manufacturer of Pace Arrow motor-homes, came through for me this morning with an email that had an 11 page attachment of the complete electrical system, both the chassis 12 VDC and the coach 110 VAC systems. They are copies of the electrical engineer's hand drawn schematics with each component identified by number with a complete legend and index, and many, many notes - perfect for a lay person novice electrician like me.

So I am only certain of one thing right now, and that is by the end of the day, the score-sheet will read: JT one, and the Pace Arrow no score! It will take my continued persistence to make it to that day, but I've been there before and know what I have to do.

I look forward to posting a final report that brings closure to this miserable situation once and for all... Otherwise, my 6.2 runs really well, and is a pleasure to operate. I get over 20 miles per gallon combined highway/city driving, and who could complain about that for a 12,000 pound plus vehicle?

Thanks for your support and encouragement! And I apologize for the length of this message.

JT

 

A1. No, I never took the old failed controller out or unplugged it. So it is fully intact. I figgured it was dead and I'm kind of lazy, so I just cut a piece of old 120V extention cord, pealed the ends and connected at the relay end one wire to the 12V hot terminal feeding the GP relay and the other to one of the small side terminals on the relay. I found the correct small terminal just by hunting and pecking until I touched the one that made the relay click. The other end of the extension cord just attached to the two switch terminals. I also installed an in-line fuse. I think that is exactly as you described in your earlier post.

A2. Yes, my engine shuts down with the ignition switch.

You know, being dumb, I never thought about it, but I suppose it is possible that GM wired the shut down solenoid through the GP controller to minimize wiring or something. I loaned the truck to my nephew for a few days, but when I get it back, maybe I take a look to see what I can see.

Take Care

BTW, Your fuel economy is amazing for a 12,000 vehicle. My 6.2 barely gets 20 mpg in my Sub and that is if I keep it at not much more than 55mph.