Runs terrible and hard start after bad bump

[sKnNyPpY]

So I got back from a two week road trip and was excited that Black Betty fired right up after having alternator problems and doing the rear flip. I took her across town to feel how everything was after the drop and hit a railroad track too hard. Heard a loud clang (exhaust?) and she started running rough/missing. Made it home with a loud backfire and she didn't want to start. Jump started quickly and seemed to run ok except when I turned on lights/ac. This morning tried to start and she tried but heard a metal clanging and didn't fire up, just werrwerrwerrrrr.

It could be a coincidence about the bump, because I didn't use lights or ac until coming home. I didn't change the regulator when I changed the alternator and the battery is holding a charge as it sat for two weeks and fired right up.

Could it be:
exhaust leak (already had one, may have made it worse)?
starter (may have taken a hard knock)?
regulator (probably needs to be changed after alternator anyway)?
tranny (please God no)?

Any ideas would be great. This is a 71 GMC 350 with a 3 speed

[domeier]

It could be the primary carb float got bent or stuck? Or, a plug wire got knocked loose, or maybe the choke engaged? Must have been one hell of a bump!

[sKnNyPpY]

Thanks domeier, I'll check the carb. It is due for an overhaul anyway. I'm thinking the bump might not have had too much to do with it, just exposed an existing problem waiting to happen. I've had the truck for less than a year, and besides plugs, filters, and fluids the engine has been neglected as far as tune ups go. The exhaust manifold is leaky and the wiring is all dry rotted so I'm replacing things one at a time.

[sKnNyPpY]

Could this be from crappy gas? I just filled up not too long before this happened.

[domeier]

I don't think it's bad gas, unless you filled it with diesel. I did that once to a work truck when I was nursing a bad hangover. Bossman was not pleased!

[sKnNyPpY]

Took the air cleaner off and changed fuel filter and she reluctantly fired up, then ran strong on the automatic choke for a few minutes, but died the minute I tried to go anywhere. Starter wouldn't even make a noise when I turned the key, but I have power to the cab lights and a/c, etc. Had a small wire to the starter severely melted and snapped off and tried to run a patch...nada. Changed the voltage regulator and a broken grounding strap... nada. Dropped the starter and had it bench tested and it worked fine, haven't put it back in yet. I'm trying to back trace the wire from the starter to find any fuses/ fusible links but this stuff is new to me.

On another note the plastic diaphragm housing (?) in the Quadrajet looks split and there is a screw that doesn't seem to be able to adjust anything kind of next to it. Rebuild/ replace seems to be in order, if I can get her to turn over/ start.

[domeier]

Check your battery terminals where the wire attaches to the post clamp. They can do a partial corrode/burn under the insulation and leave enough wire to run accessories but not the starter.

[sKnNyPpY]

Reading up on fusible links. I think I burned one out from the battery last week replacing the alternator and just patched it not realizing what it was. I need to peel back a lot of electrical tape and see whats going on under there. Is there a fusible link going to the small wire on the starter? The small engage (?) wire (not the small starter turning wire ) was really brittle and I was just tried to patch it. THANKS!

[domeier]

Originally Posted by sKnNyPpY

...I need to peel back a lot of electrical tape and see whats going on under there. Is there a fusible link going to the small wire on the starter? The small engage (?) wire (not the small starter turning wire ) was really brittle and I was just tried to patch it. THANKS!

Getting the wiring straightened out is always a good thing. No FL on the purple wire (key switch-to-starter) wire, or the yellow, (starter-to-coil) wire. You don't need the yellow wire any more if you have HEI ignition. There's a manual on this site somewhere, has all the schematics.

You can do a dirty test of your batt-to-starter big wire by momentarily grounding the hot pole on the starter to the frame with a big screwdriver or wrench - you should get a bigass spark. If not, the cable's bad. Don't do this with an open fuel line, or gas rags nearby!

You'll need a multimeter or test lamp to check the purple wire - 12v with key in start position.

I think you're right: The big bump and running bad/not starting are maybe coincidence.

[sKnNyPpY]

Guess the hit took out the battery. I added a fusible link where there was supposed to be one, stripped back and replaced a lot of cracked wire and ring end connectors, re-installed the starter and jumped her. Started right up, ran like crap. After everything replaced or checked including alternator and regulator, the only thing left was the battery (that some Auto partZ store said was good, house brand gold top woulentyaknow) New battery, vroom and we're good.

HOWEVER, I knocked into the fuel gauge pressure sending line and snapped it off without realizing it. When I jumped started it, oil shot out from behind the distributor cap all over the windshield, roof, and even into the bed of the truck. Easy fix, but what a freaking mess. Cleaned her up and she's running like a champ. All the things I did needed to be done, but damn if it would have been nicer to have known the battery was crap before all the trouble.

[domeier]

But look at all the fun you had!

[Square_78]

I've had all sorts of weird electric problems caused by a bad battery. Apparently the plates inside the battery can short out causing weird things to happen. I was sure the ECU on my grand Cherokee was toast because my gauges were going wonky and truck wouldn't run properly. New battery and problem solved. Old battery even tested fine but wasn't quite holding its charge. Easy fix. I bet that bump slammed the battery hard enough to jar something loose inside it.
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