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6.2 No Start, No Turn Over

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buff_dog70

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I just finished replacing the water pump, on my 1982 GMC Jimmy 6.2 diesel. When I was doing that work, at first I did not disconnect the batterys positive terminals. When I loosened the alternator to remove the belt. The alternator moved and I believe grounded the positive terminal on the alternator to the engine. I remedied the situation asap but, now the engine will not start, also noticed check engine light do not work. Any suggestions to get back on the road? Also no click when key is turned. Did I burn something up? Relay, fuse? Or is there something wrong with the key mechanism on the steering column?
 
Most likely you fried a fusible link--probably the one of two (or both!) located in the thick red wires that bolt under the positive battery cable at the starter solenoid..there may be another fusible link at the red wire coming out of the altenator that might be buried in the wiring harness,but usually if that one pops,the only think you'll notice is the altenator wont charge--the other two mentioned kill all power to the cab,and depending on which one blew,you might have nothing working in the cab,or just some accessories and no ignition...
 
Did some troubleshooting, and cause some trouble.

I did some trouble shooting, the only power off the batteries, is off the postive terminal (large wire) down to the starter solenoid. Attached to this main lug is two wires that go into the wire harness (colored red). There appears to be fuseable link material that is in tact. I removed the starter for ease of access. I attached 12V to the other wire that gives the signal to engage the starter solenoid with the starter not attached. If I go in the cab it and turn key, the power is now restored to the guage panel. So I think the lack of power must be coming from the upstream side of the ignition (on the way in). In the process of putting starter back on I broke one of the main bolts in the block. So that going to take a while to remove the broken end (stuck in the block. I been studying the wire diagram, and I plan to do some more troubleshooting tommorrow, Merry Christmas.
 
Sometimes fusible links "look" OK,but are indeed burnt inside or only have a strand or two left making the connection...the purple wire at the solenoid is the one that engauges the solenoid when you turn the key to crank it,that wire should only have juice while cranking....there may be another fusible link or two in the thick red wire located on the junction block on the firewall,next to the power brake booster also,if that one blows it will afftect the power going to the cab too,and some of those junction blocks had a "shunt" connecting the two threaded studs on it,that can blow like a fuse too..not every truck had that however..
 
I blew one on Big Ugly a few years ago and it really didn't look that toasty.

I replaced it with a 50amp maxi fuse holder. Also heard of folks using breakers like semi's use.
 
Thanks for advice

I will start replacing the OK looking fuseable links tommorrow. But can they be blown enough that they won't start the vechile but enough to hold 12V when I check with a voltmeter? I will say the picture in my manual shows it melted down, none of them look like that.
 
buff_dog70 said:
I will start replacing the OK looking fuseable links tommorrow. But can they be blown enough that they won't start the vechile but enough to hold 12V when I check with a voltmeter? I will say the picture in my manual shows it melted down, none of them look like that.
Click to expand...

Sometimes the wire looks OK but inside it's just ashes, you can tell by holding the wire and bending it or squeezing it.
The insulation doesn't always burn and it hides what is inside.
 
Partial Fix, poor idle lots of white smoke.

I got the Jimmy turning over and running. Replaced a fuseable link that turned out to be burned out. It showed no outward signs of failure. Jimmy starts and kinda of runs, lots of white smoke, not sure if it is firing on all cylinders, and idles terrible when cold. I still don't have power to my A/C heater controls. I think this might also be attached to the cold idle advance on diesels. I'm going to replace a glow plug I know to be bad and trouble shoot the lack of power to the A/C. Check all the fuses, they all seem good. Got some pics of the failed fuseable link. Iceman was totally correct on how the fuseable link didn't appear failed.

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Did some more trouble shooting, alternator trouble?

Fixed the problem with diesel advance. Appeared to be a dirty connection off the thermal switch mounted on the engine block.

Now when I start the engine still white smoke but probably just cold, still doesn't idle very good, might change the fuel filter. Any way I changed the fuseable links and replace with a 20 amp in line fuse. When I start the vehicle, once the engine starts turning, I notice the voltmeter guage (on the dash) goes from around 12V but once the alternator kicks in with the engine turning, the voltmeter pegs to above 18V, then drops to nothing. The inline fuse I put in place of the fuseable link (protects I believe the 16ga wiring) is blown (20 amp). Going to trace, probably pull alternator and have it check, think it might be the voltage regulator in the alternator. Not sure if I can change the voltage regulator or have to replace the whole alternator if it turns out bad.

Also think the relay on the A/C box that might be blown. Thats why the fans not working. Ordered a new one. Added some pics.

Should have removed the postive terminal when I was changing the water pump and I wouldn't have any of these problems.

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Last edited:
buff_dog70 said:
I did not disconnect the batterys positive terminals.
Click to expand...
buff_dog70 said:
The alternator moved and I believe grounded the positive terminal on the alternator to the engine.
Click to expand...

money-to-burn.jpg
 
Check and see if the altenator is getting 12V to both of the wires on the 2 prong plug with it running or the key in the "on" position..it needs 12V at both wires in order to energize the feld coil and make it charge,but if it lacks 12V at the white or tan wire on that plug ,it can still "self energize" when the altenator reaches about 2000 rpm,and it will suddenly "kick in" and start charging...the red wire in the two prong plug senses the voltage,and "tells" the regulator how much amps and volts to put out--if that wire is dead,it will likely go to "full charge" mode,and could be what your experiencing now..

You may want to check the glow plug wires before replacing the glow plugs,unless your certain it IS a bad glow plug...I've found many 6.2's have the glow plug wires get gangrene and corrode,and it reduces the voltage to the glow plug,if any at all gets thru them--the insulation will look like your blown fusible link and will feel "empty" where the wire failed...sometimes a test lamp might show voltage,but the wires are too corroded to let sufficient amperage pass to heat the glow plugs up--an old headlamp bulb is enough of a load to test if the wires are passing enough juice,if the lamp dont light or is dim,chances are that wire is corroded or burnt inside...

They sell 12V xircuit breakers ,I'd use them before a fuse on the main power wires--you definately dont want a fuse blowing while your on the highway,shutting everything down suddenly!...even a breaker could do the same though,so a fusible link wire is the proper way to fix it...I moved the twi thick red wires that go under the starter solenoid stud under the positive battery cable on my truck,and instead ran them to the positive battery terminal--I've had these wires burn up where they are routed thru the metal conduit near the exhaust,and the fusible links are inside that conduit,making it hard to inspect or repair them...GM used to run them to the battery terminal until 73,why they changed it to such a stupid design,I dont know...now all I have for wires at the starter solenoid is the positive battery cable,and the purple wire that activates the soleniod when you crank it over--a lot less chances of burnt wiring or failed fusible links that way...I left the fusible links intact and had to lengthen the wires in order to reach the battery positive terminal...
 
Still having trouble.

I replaced the alternator. It tested bad at the auto parts store. Tested the prongs on the alternator they tested good.

Put a circuit breaker (20 amp) in the inline fuse (where I replaced the fuseable link) because I kept blowing the 20 amp fuse.

I started the Jimmy, (engine running) the Circuit Breaker kept clicking on and off. The water in the fuel light went super bright going on and off as the Circuit Breaker clicked on and off.

The new alternator seemed to have not solved the problem.

Not sure what to do?

Friend suggested checking to make sure batteries are good. He suggested that if the battery is bad the voltage regulator might send too much voltage trying to charge a bad battery.

So I pulled the batteries and I going to check them tommorrow and if bad replace.
 
Only thing that I can think of right now is I put a 40 or 50 amp fuse in place of that main fuseable link. smalltruckbigcid explained it to me as the peak loads going through there required it.
 
Test light is slightly pointing towards problem

I tried a bunch of different things today to troubleshoot. The guage/idle fuze is blowing. It will blow after turning the ignition to on (engine off, this also applies power to the circuit, but it does not blow immediately, takes 20-30 seconds then it blows. Has no effect on starting the car, but the dash guage quit working after it blows. This is a 20 amp fuse.

Also started the car, without the alternator belt on. Surging problem that blows the fuselink which I replaced with a 20 amp circuit breaker seems to not fail.

Thinking there might be two independent problems, tommorrow, I'm going to trace wires from alternator to see if there is an short there. Only seems to blow when the alternator is turning and putting out juice.

The guage fuze blowing, not sure how to proceed? Pull the dash guages out and look for a short. Why does it take 20 seconds to blow?

Test light is a great tool wish I had bought one years ago.
 
Short on the ignition side

I went through the wiring harness coming out of the battery and heading to the firewall and ignition switch. I ran a wire directly from the alternator output to the battery, (cuts out it going to the voltage regulator in the dash I think) both the 20 amp fuzing blowing for the guage/idle goes away in the fuse box, and the 20 amp Circuit breaker I replace on the fire wall seems to not be shorting. Think there must be a problem with either the guages (short) or does the idle effect the solenoid movement on the top of the injection pump for cold start?

Still having a problem idling, but the maybe its just cold, lots of white smoke. Have to go on travel a week, but I will address when I get back.
 
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