Question: Any tips on tracing electrical power loss after various repairs? - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
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Old 07-01-2017, 05:36 PM   #1 (permalink)
researchguy007
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Any tips on tracing electrical power loss after various repairs?

1982 Silverado originally with 6.2 L diesel and banks power kit. Mysteriously lost all engine oil five years ago and replaced engine with Marshall rebuilt 6.5L. I bought the truck about seven years ago only because it is set up to run WVO and I thought the price of fuel was going to go through the roof. I listened to the wrong experts but that's a whole another discussion.

If I'd known how hard it is to obtain, filter, and keep running WVO, I would never have bought the truck. After finally completing the construction of the appropriate infrastructure, I started running pretty cleanly filtered WVO (contaminants filtered out down to about a micron) a couple of weeks ago. Contrary to some people's reports, at low speeds the engine ran rougher than with diesel. But it had full power, especially at full throttle -- indistinguishable from diesel.

After turning the engine off and then immediately restarting it, it started fine as well. So I went up the nearby mountain for a shakedown cruise and hopefully a hike. When I got to the little mountain community, I flipped back to diesel 10 minutes before stopping the engine, which is even more time than "they" say is needed.

After eating breakfast for an hour or so, I came out and the truck wouldn't start. It cranked great. I tried again about four or five times, letting the starter cool in between times. I didn't significantly lose battery power until after a good minute or more of total cranking.

A tow truck driver towed me to his shop down the hill and tested all my fuses with a test light. He didn't find any bad ones. The truck is so old, many of the labels are faded and illegible. I've tried to find a clear picture or graphic of my exact fuse box, to no avail. Obviously some of the labels are abbreviated, and different functions are combined in the same fuse. So this stage of the troubleshooting involved some stupid guesswork on my knees with a flashlight. Pointless. Just test every fuse.

The tow truck driver had already tested for power at the coldstart solenoid, and there wasn't any. That's why he tested the fuses. So then he connected a jumper wire, allegedly to the cutoff solenoid on the injection pump.

We could hear a click when he connected the jumper, with the engine off but the ignition on. That did seem to confirm that the solenoid was not already on for some reason.

Before I left, I asked the driver if I was going to have to disconnect the jumper to get the engine to turn off when I got home. He said yes. I decided to test his theory. His prediction was incorrect. When I turned the ignition key off with the jumper still in place, the engine died just like it should. So then I disconnected the jumper wire and the engine started and ran just like it should. WTF? The truck wouldn't even cough while cranking before, and now in apparently the same electrical condition as before I call the tow truck, it starts fine?

I told the above story with my injection pump/injector rebuilder, BECS Pacific in San Bernardino. The guy there told me that two independent problems could conspire to cause this kind of failure. First, if the WVO is old, poorly filtered, or for whatever ever reason has too much sludge, it can make the coldstart advance valve stick, despite power going to it through the ignition switch. He said that an old ignition switch might not be sending enough power. The jumper wire direct from the battery would send more power and overcome the sticking. He also said that the coldstart advance switch could be bad. He suggested replacing one or the other or both. I didn't think the truck had cooled off enough to need a cold start advance, but whatever.

I couldn't find the coldstart switch. It isn't at the right rear of the engine where everybody says it is on my vehicle. Maybe the 1993 engine doesn't have a place to insert such a switch. Maybe it doesn't need it because of the electronic control, or whatever.

After a lot of searching around I found a wire ending in an insulated female blade connector, hanging on the right side of the engine between the second and third injector. The other end of that wire led to the coldstart solenoid. So much for that theory. I have evidently never had a coldstart solenoid working on this vehicle since I got the new engine!

Needless to say I didn't use WVO again, planning on replacing both switches before I tried that again.

I made a few trips during the next week. On one of those trips, when I got back to the truck, it wouldn't crank it all. All the lights on the dash looked strong. Dead starter! Okay, so the five-year-old starter got killed by all that cranking up on the mountain the week before. Nice. I thought I had been gentle enough with it, but no.

Got towed home again (thank goodness for Geico roadside assistance coverage) and replaced the starter. Had already bought a new ignition switch, so I went ahead and bit the bullet, brought the steering wheel down and replaced that switch as well.

If one solenoid-controlled valve can stick because of WVO sludge, then so can the other. So I decided to replace the coldstart advance switch. People here have said they cost $100, but I found one for $67 at O'Reilly's. At 85į it is open, and after 10 seconds with an ice cube pressed against it, it is closed. I've forgotten exactly what temperature is supposed to be to the cutoff, but it seems to be basically working okay.

Since I couldn't figure out where the old switch (if any) is located, I bought brass plumbing and installed the new switch into radiator/heater hose that is running to the sleeve heater for the WVO. That will probably leave the engine in a coldstart advance condition a little longer than it needs to be after startup, but there's no other easy place to install the switch. There is not enough room between the water pump and the crossover pipe, top center of engine (I tried). And I sure don't want to cut threads into the head. No time for doing everything that that would require.

So I cut the wire that supplies ignition-switched power to the cutoff solenoid and spliced in a wire leading to the coldstart advance switch. On other blade of the switch, I installed a wire back to the coldstart solenoid, with a pigtail over to the high idle solenoid. Proud of my work -- or at least relieved that it was over with -- I turned the key. Pretty good cranking for a few seconds, but no startup! And the cranking slowed much faster than it did two weeks ago on the mountain. So the batteries -- one of which is new and the other of which is about four years old -- collectively aren't holding a charge worth a damn.

I disconnected the glow plug relay (since I won't need the glow plugs heating up and using power for a while), hooked up the battery charger, turned the ignition key on, and tested for power around the ignition pump. Nothing at the coldstart solenoid connector and nothing at the cut off solenoid connector! All this work and I've broken something else!?

Now I am wishing that I had tested for power at the cutoff solenoid just before starting all this work. But after I installed the starter in the ignition switch, the truck started up. So I obviously had power to the cutoff solenoid then.

I have generally not had any luck doing wire tracing. It always seems a lot harder than it should be. Old green wires look black, I end up getting hooked on something and ripping it out, etc. But I don't know what else to do. It would help if I could read the fuse box labels, but I can't. I think I have a test light somewhere so I guess I can just test both sides of every fuse and if both sides light up, then the fuse is good, right? And if there's no power on either side of a given fuse, then either that circuit isn't needed for ignition, or the problem is with my ignition switch or its connector.

I would strongly prefer not to have a Frankenstein truck that requires all these aftermarket switches that I have to remember to use and turn off. That's why I went to the trouble to install the coldstart advance switch in the first place, instead of using the $5.00 toggle switch solution many people here have used when their coldstart advance switch goes bad.

Sorry for all the words, but I don't believe in handicapping my would-be helpers by giving them incomplete information.

Any help would be greatly appreciated! Don't be afraid to point out the obvious, I'm probably missing it.

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Old 07-01-2017, 05:49 PM   #2 (permalink)
researchguy007
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–And I figured it out!

1. The truck just needed a little more cranking since it hasn't started in a week or so.

2. After I killed my first engine with the oil leak, I installed an oil pressure cutout switch which has to be pushed in while cranking, or else you have to crank long enough to let oil pressure build up to above 5 psi at the top rear of the engine. I was holding that momentary switch in when cranking, but I wasn't doing it when testing for power at the IP. Kinda hard to reach both places at once. Forgot about that switch when testing.

Woo-hoo! On the road again!

I appreciate everybody being here and reading. This is an incredibly useful forum!

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Old 07-01-2017, 05:51 PM   #3 (permalink)
boneheaddoctor
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I'd start by downloading the proper Electrical diagrams from the FAQ fir your year truck. I'd also get a Digital volt meter..they can be bought very cheap, with a coupon, even free at times from Harbor Freight. You can only go so far and do so much with a test light.
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Old 07-01-2017, 05:54 PM   #4 (permalink)
boneheaddoctor
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I see you responded as I was writing my response. I still stand by my answer...it applies to anyone who owns and works on their own older vehicle.
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Old 07-01-2017, 06:13 PM   #5 (permalink)
researchguy007
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Quote:
Originally Posted by boneheaddoctor View Post
I'd start by downloading the proper Electrical diagrams from the FAQ fir your year truck. I'd also get a Digital volt meter..they can be bought very cheap, with a coupon, even free at times from Harbor Freight. You can only go so far and do so much with a test light.
I'll definitely download the diagrams, thanks for the tip!

I have a decent digital meter. But a light can be easier to use when you have to put the leads just so, you're holding a flashlight at the same time, and/or the old eyes just don't see up close so good no more...
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Old 07-01-2017, 07:27 PM   #6 (permalink)
davester
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If you are loaded down with extra cash, you can get something like the Autel PowerScan PS100. I've got one and find it handy for tracing electrical problems with my truck. It can test for power and ground, has a light to see where the tip is, powered by either clip on battery connectors or cigarette lighter, can ground/power the tip on demand, bunch of other stuff. It's much easier to use vs a regular meter where you always seem to need 3 or 4 hands to hold everything just right to get a reading.
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Old 07-01-2017, 08:52 PM   #7 (permalink)
researchguy007
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> Autel PowerScan PS100

Looks like a great tool -- and affordable enough for what it is.

I was wondering if the technology for testing DC current has improved since I last checked. I have some fiberglass-wrapped steel heater wire that I need to tape alongside the injector lines and hook up. But it's been so long since I bought it, I forgot its current rating. I think it should be well under 40A because I bought one of those standard old GM 40A relays to power it with. But it would make sense to make sure before I waste a fuse and/or the relay. I bought a 200A alternator a couple of years ago because I was planning to hook up a lot more power devices to the truck. I think it's about time I got my money's worth out of that thing.

Anyway ... If I could accurately test resistance down to fractions of an ohm, I could apply Ohm's Law to calculate the current draw at 12.8V. But I have neither that nor a tester that can handle more than 10A. There's supposed to be a way to use a shunt, i.e. a conductor of known/specified resistance in parallel with the part to be tested. But I don't know where to get a conductor of known/specified resistance. Nor do I have a 12V source that can supply 40A, other than the alternator itself in the running vehicle, which kinda defeats the purpose. My battery charger only goes up to about 8A.
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Old 07-01-2017, 09:02 PM   #8 (permalink)
researchguy007
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Corrections to my last post:

1. A shunt is evidently to be connected in series the part to be tested, not in parallel. This makes sense, as you want to reduce the current going through it.

2. My tester shows fractions of an ohm, but they bounce up and down quite a bit when I'm just holding the leads against something by hand. I guess I could try wrapping the heater wire around the leads and see if it stabilizes the reading. Tired of working out in the heat for the day.
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Old 07-02-2017, 01:06 AM   #9 (permalink)
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>>> "So I cut the wire that supplies ignition-switched power to the cutoff solenoid and spliced in a wire leading to the coldstart advance switch"

Not a good idea.. IP needs all the voltage it can get especially at cranking.

"cold start solenoid" is not what the solenoid is or does.. Most vehicles do not need it. It has no effect on cranking ability. It was basically designed to slightly advance the IP at cold idle. Seems up north people were cranking them in the garage and the white smoke was not wanted. GM's "fix" was to slightly advance(1-2 degrees) the timing.
So disabling the solenoid has no effect on your vehicle cranking.

I use a PowerProbe for electrical diagnostics. Had it for years and the thing is amazing for finding problems. Just like testing your fuses. The thing has an audible beep that can instantly tell you whether the fuse is good or bad. Also has a distinctive sound for ground. Really speeds up testing circuits.
https://www.ebay.com/i/292033482620?chn=ps&dispItem=1
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Old 07-02-2017, 10:13 AM   #10 (permalink)
researchguy007
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Quote:
Originally Posted by DieselPro View Post
>>> "So I cut the wire that supplies ignition-switched power to the cutoff solenoid and spliced in a wire leading to the coldstart advance switch"

Not a good idea.. IP needs all the voltage it can get especially at cranking.

"cold start solenoid" is not what the solenoid is or does.. Most vehicles do not need it. It has no effect on cranking ability.
I appreciate you taking the time to give me this caution.

First, it would seem strange that the coldstart solenoid would cause a significant voltage drop relative to what the IP needs.

Second, it would seem that it would cause that voltage drop no matter where it was getting its power from, since obviously the twin batteries are the only power source. Hopefully the resistance of the wires in the circuit that I spliced into is insignificant.

Third, my engine does seem to need it, because it's been getting harder and harder to start, even before I ran any WVO through it. It's always been hard to start in the winter, even here in Southern California. I live in a close-packed retirement park and it's embarrassing to leave in a cloud of blue smoke every morning. People are walking their dogs and if I don't see them and wait for them to pass before I start up, they end up having to have to avoid or tolerate the smoke cloud.

I do have a problem, in that I probably need to replace the older battery. Just after driving up the mountain, when the engine wouldn't light up, I had plenty of cranking power, but after just a few days, it didn't. But that wouldn't have anything to do with a small decrease in voltage at the IP.

I will ask around and see if there seems to be a consensus about what you are saying. One thing I've learned about cars, computers, and everything else, is that opinions vary, even among people who should absolutely know what they are talking about. Personal experimentation seems to be the only definitive road to truth. I sure wish that weren't so.

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