Engine dies when turning on accessories...

[akcoastie]

Hello from Alaska. I'm new to the forum and have a question about my 1986 CUCV Blazer. I apologize if it was answered in another thread but I didn't see anything that quite covered this issue. When the truck is running and I turn on the heater, lights, and wipers the truck shuts off. When I say it shuts off I mean it just flat out dies like someone flipped a circuit breaker. This is not a lot of fun if you are driving on an icy road in traffic as you may imagine. A little background on the truck... I have two good batteries that are staying charged at 100% (13.2 volts), both alternators seem to be charging, and it doesn't happen all the time. Occasionally I can get it to happen but it isn't all the time. When I turn on the lights, blower, and wipers both Alt lights will flash and then the truck just dies. Alt 1 seems to light slightly before Alt 2. Any ideas?

 

[Barrman]

Since you are new, you get welcomed first. Welcome!

The CUCV trucks are basically Chevy trucks with a few things changed. They are also 1973 vintage wiring practice since that is when the body style first came out. They were a huge improvement over the previous truck wiring, but pretty darn bad by todays standards.

Your problem is probably caused by a bad ground. I would suggest crawling under the dash and looking at the top of the parking brake pedal bracket. There is a ground there with 6 connector pins waiting for more wires to be plugged in. There should be 1 or maybe 2 wires there now. Pull them off, pull the bracket off, clean everything including the brake pedal bracket and put it together again. Your problem could be solved. Make sure the 3 bolts that hold the brake pedal bracket to the truck are actually tight. 2 of them you have to go under the hood to get to next to the thru firewall plug.

If that doesn't fix your problem. Go to the other side under the hood and look at the heater blower motor mount. If it is loose or the ground for the blower motor isn't working right, it could be your problem.

If that hasn't fixed it. Start at the batteries and clean every single ground and positive connection as you work your way through the bus bars on the firewall to back under the dash. You will probably find several connections where you say to yourself "How did this thing run with the corrosion so bad?" every other connection you pull apart.

 

[MakersTeleMark]

That would be my guess as well, but I wonder why it would kill the engine?

 

[marchplumber]

Welcome aboard. Grounds, grounds, and MORE grounds! As the a fore mentioned responders stated. ENJOY the truck, and welcome to the site!

God bless,
Tony

 

[akcoastie]

Thanks guys! I'll tear it apart and see what I can find. So far I have replaced everything from the batteries to the starter and to the bus bar just cleaning things up and I will just continue along that path until it all starts working. That ground on the parking brake may explain why my fuel gauge inexplicably stopped working... Kodiak is a wet, wet, wet place and I brought this truck here from Camp Lejeune area. It probably needs a good coating of silicone dielectric on everything anyway!

 

[MakersTeleMark]

Your symptoms are all linked to one or two fuses from the fuse panel by your left foot (for starters). Get in the cab, start there, before you concur the engine bay. Yours is definitely originating from a poorly grounded fuse box.

No need right now to tear anything apart. What you want to do is reinforce and clean up. Start with the easy stuff (duh, but sometimes, not so duh).

Good luck and post up. I'd be glad to help, and I imagine a bunch of others as well. But start there.

 

[kabar1]

Since you are new, you get welcomed first. Welcome!

The CUCV trucks are basically Chevy trucks with a few things changed. They are also 1973 vintage wiring practice since that is when the body style first came out. They were a huge improvement over the previous truck wiring, but pretty darn bad by todays standards.

Your problem is probably caused by a bad ground. I would suggest crawling under the dash and looking at the top of the parking brake pedal bracket. There is a ground there with 6 connector pins waiting for more wires to be plugged in. There should be 1 or maybe 2 wires there now. Pull them off, pull the bracket off, clean everything including the brake pedal bracket and put it together again. Your problem could be solved. Make sure the 3 bolts that hold the brake pedal bracket to the truck are actually tight. 2 of them you have to go under the hood to get to next to the thru firewall plug.

If that doesn't fix your problem. Go to the other side under the hood and look at the heater blower motor mount. If it is loose or the ground for the blower motor isn't working right, it could be your problem.

If that hasn't fixed it. Start at the batteries and clean every single ground and positive connection as you work your way through the bus bars on the firewall to back under the dash. You will probably find several connections where you say to yourself "How did this thing run with the corrosion so bad?" every other connection you pull apart.

+2

 

[akcoastie]

I do have some water coming in by that fuse panel every time it rains. The floorboard is always wet there. I have previously checked all the fuses to replace the blown ones and tightened up the mounting for the fuse panel. It is really nasty under there and to be completely honest I should probably replace the whole mess under the dash. I'll start with the simple as you suggested though. I seem to remember some of the grounds looking pretty bad.

 

[MakersTeleMark]

Can I maybe suggest, once you've figured out your electrical, that you close the floor vent? Jeebus, it's got to be 2' above the ground. Why so much water, and if so, maybe isolate it in a sealed box?

 

[dependable]

I agree grounding may be the root of problem. Make sure a thick gauge ground is connected from terminal lugs to motor and the one in front of front battery is connected to chassis. What is probably loosing power to make it shut off is the 12v power supply to IP (the pink wire).