Need Help- Truck Won't Start!

[Shaun1162]

So after my last thread (http://67-72chevytrucks.com/vboard/s....php?p=5728562) I thought my electrical problems were solved... Guess I jumped the gun on that one. I've searched alot on this site and the rest of the net, but haven't found anything quite like this...

So after a new battery, new alternator, and a tune-up the truck ran fine. Drove it around the yard quite a bit. I had problems with the carb and decided I should rebuild it... So before taking it off I went to start the truck and move it out of the way. Had to dump gas down to get it run, but on the last time trying to crank it over it just died (not like a battery dying- just wouldn't crank). Figured it was something simple like a battery cable, so I just left it there, took the carb off and rebuilt it.

Today, I come back, put the carb on, and nothing. The dome light in the cab works, and when I turn the key the dash lights come on (Choke, Brakes, and Seat belts, along with the buzzer for the belts), but as soon as I turn the key to crank the engine it all dies. The first couple times I heard a faint clicking from the starting, but nothing at all now. When I try to crank it all the lights go out, including the dome light. If I close the door, let it set for a second, open the door and try cranking it again- the same thing happens. I used a test light on the fuse block and everything lights up, until I try to crank it and then all power goes dead.

Headlights also don't work at all. They won't turn on with key on or off. The dome light, windshield wipers, and radio work with the key on, but again go dead when I crank it.

I've cleaned the battery to engine ground on both sides, as well as the ground wires going to the radiator support and the frame next to the engine.

With a test light, I have power at the starter, and I've tried to jump the starter with a screwdrive on the solenoid, and it sounded like the starter wanted to engage the first couple times I did it, but now it does nothing.

I've tried all of this with just the truck's battery, as well as jumping it from a running truck..... I could see a bad starter being part of the problem, but why won't the head lights come on, and why do I lose all power after trying to crank it? Maybe it's in the ignition switch?

Any advice is greatly appreciated! These kinds of problems get kind of fustrating...

Forgot to add- Truck is a 78 GMC with a 6 cyl 250 and a SM465 four speed.

[bobbybyrns]

Sounds like a bad connection some where or maybe a bad starter or cables to the starter the main battery cable that goes to the starter? a few things pick up power right there dont know if the head lights do or not thats some thing to think about

[KQQL IT]

Or a burnt fusible link.
Posted via Mobile Device

[DesertCat]

Step 1 - make SURE your battery is FULLY charged. Just because dash lights illuminate doesn't mean you have a charged battery (headlamps not lighting is another big clue that the battery is low). Test lights aren't much help with this kind of thing.

You said "So after a new battery, new alternator, and a tune-up the truck ran fine. Drove it around the yard quite a bit."

I would fully charge the battery and if it starts then, take it straight to the local parts store to get the battery/charging system tested (assuming you don't have an volt or amp gauge).

Also remember (and believe me I have learned this many times in electronics) that "new" or "rebuilt" doesn't necessarily mean that it is good or works. If I had to guess, I would say your alt isn't charging.

[chengny]

Some things to think about:

Starter internally shorted to ground. Either in the motor circuit or the solenoid.

Sometimes whacking it with a hammer will temporarily get it to crank.

Main battery cables (negative to block and positive to starter solenoid) failed internally. Not common but does happen - look great from the outside but inside the copper is reduced to a couple of strands.

Is the battery holding it's charge or do you have to keep on charging it up?

Look closely at the main cable that runs from the battery positive to the starter. Check for insulation failure and shorts to ground.

[sqzbox]

Originally Posted by KQQL IT

Or a burnt fusible link.
Posted via Mobile Device

If itwas the fuseable link on the fireall, you would have no power anywhere on the vehicle.

[Phillip Pennartz]

Get a voltmeter and measure your battery. It should read about 12 volts dc. While you
are still holding the leads on the battery ,have somebody try to start the truck. If the
voltage reading goes down a lot, then you have a battery that doesn't have enough capacity to start your truck.it could be dead or have bad cell. Swap your battery with one that is known to be good. Unless you have another problem this should get you started. Measure the battery voltage again with the engine off , again should be 12vdc, Start truck and again measure voltage level. It should be around 14.3 or slightly higher if alternator is working.

[Shaun1162]

Well took your guys advice and finally got it figured out...

Charged the battery last night, truck did the same thing today. Hit the starter a few times witha hammer, and got some clicks. To be sure, I went and got a battery out of another truck that I know was good- got a couple clicks that time too. Sooo... I had a couple used (but good starters) on the shelf, so I put one in it, now nothing.

Then for some reason I decided to hook one end of a jumper cable to the battery, and the other right to the starter. Turned right over like it was made to! Still can't beleive that's all it was... Cleaned both sides of the positive cable yesterday and looked it over, still can't see where it went bad..

But hey at least I know how to change a starter now

Thanks guys!

Now I just have to figure out what I did wrong when I rebuilt the monojet carburetor...

[gchemist]

If the cable ends are open, corrosion has started to build up inside the cable. I see it all the time. Cut the ends off to make a better connection. If you see green inside the cable, corrosion is really bad. I knew a girl that changed her starter and then called me. I changed it again. I finally found the problem, corrosion inside a $10 power wire cable!! Could have saved two starter changes and expensive Toyota Landcruiser starter.

[86c20]

you live in new hampshire then i would say corrosion. i live on an island its the first thing we check in a older truck and it is always right after you do something else to it lol.do yourself a faver and run power to starter then ground to starter then ground to frame and then batt to frame. you will never have a problem with power or ground to the starter and it will spin like no tomorrow. i di it this way after haveing a few melted wires. no more problems for me

[Shaun1162]

Glad I'm not the only one who's learned this the hard way

I'll definately be getting some new cables made up...

Thanks again guys!