Strange problem needs expert help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

wlee · 08-08-2002, 07:17 PM

A friend of mine who owns a ’71 Custom 10 with a 350 automatic called the other day to see if I could help him get it started. It seems his son left the lights on and ran the battery down . . . sounds simple enough, but he didn’t discover the problem for 6 days, so the battery was REALLY flat. The first thing he did was to hook up a charger and try to start it again . . . here’s where the information gets a little fuzzy. He doesn’t remember if he used the 30amp charge function or the 50 amp quick charge . . . probably doesn’t matter, except that there was some damage done to the dash circuit board. (I’m assuming he left the key on while the battery was charging)

When I got there, I put in a new battery and checked the terminal at the fender for continuity – everything was OK . . . tried starting & got nothing. That’s when the owner said he could ark across the solenoid & the truck would start – at that point I checked the connection at the key, and when I re-attached the plug, the heater fan came on, so I thought I’d found the problem, but the truck still won’t start with the key. I found the problem with the dash circuit board while I was checking the ignition switch – when I reconnected the switch the dash circuit started smoking. The trace from the ammeter burned, and I’m not sure why. I replaced the circuit board & reconnected the battery – no smoke, so I guess there isn’t a short anywhere, but the engine will not start with the key. You can turn the key to “ON” and jump the solenoid and the engine starts – then it will stop with the key turned off.

My question is – do you guys think the ignition switch start contacts could be burned or am I dealing with something else?? Any help will be appreciated!

dwaite72lnghrn · 08-08-2002, 07:49 PM

Do you have a meter or test light to see if the voltage is leaving the switch or getting to the starter?

*Zkast* · 08-08-2002, 07:52 PM

I'll just touch on a few things here.
Using a test light, check your soleniod wire AT the starter just to verify no power during crank mode, we already know there is no voltage there but it never hurts to be 100% sure. Also check your fusable links since your there already. These will be on the starter post along with the battery cable.

Next(at the ignition switch) check for voltage on the soleniod wire coming FROM the ignition switch if you have voltage move on to the neutral safety switch if there is one. If you have power coming from those two area's, you have just verified a break in the wiring from the firewall to the starter.

If there is no power coming from the ignition switch, odds are you have a bad switch if all other accesories are working ok.

It's a simple circuit that we should be able to track using your testlight.

O'l Buck · 08-09-2002, 01:16 AM

my 72 has a big purple 10 gauge wire from the switch to the starter "S" terminal....i had a problem that it wouldn't start with the switch, so I cut the wire, and jumped it to the battery, and it cranked and started fine.......I found the starter bolts were just a little loose and a bunch of oil and crap was keeping it from getting a good ground. Evidently the bad ground in combination with the voltage drop across the switch was enough to keep it from doing anything.........

I cleaned up the starter, tightened the bolts, hooked the switch back up and haven't had a problem since.

BTW...this is after I fried a 15A push button switch that i hooked up until i had a chance to find the real problem

the moral of the story is.........bad grounds are a PITA

wlee · 08-09-2002, 08:49 AM

Thanks Guys!! I'll do some voltage investigation this weekend - I have a "new" Ignition switch ready to install in case the problem is that simple. Seemed strange to me that all this started from a dead battery - I feel like the problem may have happened during the charging process. If the key was on during a 50 amp charge, wouldn't it send a dangerous amount of current through the system? I'll let you know what I find

08-08-2002, 07:17 PM	#1
wlee Just an Old Mr Goodwrench Join Date: Feb 2002 Location: Green Ridge, MO USA Posts: 259	Strange problem needs expert help A friend of mine who owns a ’71 Custom 10 with a 350 automatic called the other day to see if I could help him get it started. It seems his son left the lights on and ran the battery down . . . sounds simple enough, but he didn’t discover the problem for 6 days, so the battery was REALLY flat. The first thing he did was to hook up a charger and try to start it again . . . here’s where the information gets a little fuzzy. He doesn’t remember if he used the 30amp charge function or the 50 amp quick charge . . . probably doesn’t matter, except that there was some damage done to the dash circuit board. (I’m assuming he left the key on while the battery was charging) When I got there, I put in a new battery and checked the terminal at the fender for continuity – everything was OK . . . tried starting & got nothing. That’s when the owner said he could ark across the solenoid & the truck would start – at that point I checked the connection at the key, and when I re-attached the plug, the heater fan came on, so I thought I’d found the problem, but the truck still won’t start with the key. I found the problem with the dash circuit board while I was checking the ignition switch – when I reconnected the switch the dash circuit started smoking. The trace from the ammeter burned, and I’m not sure why. I replaced the circuit board & reconnected the battery – no smoke, so I guess there isn’t a short anywhere, but the engine will not start with the key. You can turn the key to “ON” and jump the solenoid and the engine starts – then it will stop with the key turned off. My question is – do you guys think the ignition switch start contacts could be burned or am I dealing with something else?? Any help will be appreciated! __________________ 1969 CST 20 Longhorn 1970 CST 20 Fleetside 1991 Jaguar Sovereign 1992 Mazda Miata

08-08-2002, 07:49 PM	#2
dwaite72lnghrn Registered User Join Date: Jun 2002 Location: central pa Posts: 1,525	Do you have a meter or test light to see if the voltage is leaving the switch or getting to the starter? __________________ 72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne

08-09-2002, 01:16 AM	#4
O'l Buck Recovering Truck Driver Join Date: Mar 2002 Location: Orleans, NE USA Posts: 1,883	my 72 has a big purple 10 gauge wire from the switch to the starter "S" terminal....i had a problem that it wouldn't start with the switch, so I cut the wire, and jumped it to the battery, and it cranked and started fine.......I found the starter bolts were just a little loose and a bunch of oil and crap was keeping it from getting a good ground. Evidently the bad ground in combination with the voltage drop across the switch was enough to keep it from doing anything......... I cleaned up the starter, tightened the bolts, hooked the switch back up and haven't had a problem since. BTW...this is after I fried a 15A push button switch that i hooked up until i had a chance to find the real problem the moral of the story is.........bad grounds are a PITA __________________ 67 K-20 350, SM465, Eaton rear, 4.56 no spin option 00 Dodge 2500 4x4, 24V cummins, 5 speed Chad South Central Nebraska

08-09-2002, 08:49 AM	#5
wlee Just an Old Mr Goodwrench Join Date: Feb 2002 Location: Green Ridge, MO USA Posts: 259	Thanks Guys!! I'll do some voltage investigation this weekend - I have a "new" Ignition switch ready to install in case the problem is that simple. Seemed strange to me that all this started from a dead battery - I feel like the problem may have happened during the charging process. If the key was on during a 50 amp charge, wouldn't it send a dangerous amount of current through the system? I'll let you know what I find __________________ 1969 CST 20 Longhorn 1970 CST 20 Fleetside 1991 Jaguar Sovereign 1992 Mazda Miata

08-08-2002, 07:52 PM	#3
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	I'll just touch on a few things here. Using a test light, check your soleniod wire AT the starter just to verify no power during crank mode, we already know there is no voltage there but it never hurts to be 100% sure. Also check your fusable links since your there already. These will be on the starter post along with the battery cable. Next(at the ignition switch) check for voltage on the soleniod wire coming FROM the ignition switch if you have voltage move on to the neutral safety switch if there is one. If you have power coming from those two area's, you have just verified a break in the wiring from the firewall to the starter. If there is no power coming from the ignition switch, odds are you have a bad switch if all other accesories are working ok. It's a simple circuit that we should be able to track using your testlight.



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