The Stovebolt Site Forums The Shop Area Engine Shop I Don't Know What is Wrong with it

Ok, let me start by saying, I been having problems. First I bought my 1976 chevy C-20 about 3 weeks ago. I had a grounded wire which I fixed and the truck was running fine. About a week ago while I was driving it stopped running and hasn't since. I have replaced the spark plugs, fuel pump, rotor, distribtor cap, the ignition coil and module and still nothing. So I put in a new distribtor, well its not a new one but one that came from the same type of truck and same engine size and still nothing. I have tried everything and it will crank but will not kick over. I had a friend look at it and he is also stumped. What can I do to get it running or what have I missed? Please let me know, I am really lost.

Others are a whole lot better at this than me, but do you have spark? Disconnect a spark plug wire, pull back the rubber collar, hold the metal end near the block, have someone try to start it and see if a spark will jumps to the block.

Is the carb getting fuel? The old way would have you disconnect the line from the carb, put the end in a bucket and have someone crank the starter with the coil wire disconnected. You don't want it starting, but I guess that's the original problem! Stop cranking as soon as any gas shows up in the bucket. There's potential fire hazard here so maybe someone has a better way.

If it has spark and fuel, it must start, right?

If the truck has over a hundred thousand miles on it pull the distributor cap and see if the rotor spins and how it spins,if it spins erratic you might have jumped time and are you getting any fuel to the carb.

You haven't mentioned if it's a 6 or a V-8. Either way, check to see if the distributor is rotating when you crank the engine. The 8 is much more likely to have valve timing problems, since it uses a timing chain instead of gears. The timing gears on a 6 either work, or they don't, as a failure usually involves a few teeth stripping, and the cam doesn't move at all. A V-8 will sometimes jump a few teeth, resulting in late cam and distributor timing. If it runs at all, it won't get out of its own way!
Jerry

First thing you always do is diagnose if it's a spark problem or a fuel problem. If it has both, something will happen. It will either run, try to run or back-fire. Do you have spark at the plugs? Do you have HEI? V-8 or I-6?

Its a 454 Engine and there is no spark? the rotor spins and it looks normal, We changed the distribtor cap and rotor and that didn't do it, so I changed the whole distribtor and still nothing. Like I said it cranks and thats it.

Some of those GM's have an anti-Knock computer (for the lack of better words). There is a pulse out of the distributer that goes to the computer and then back to the coil, not sure which wire it is, but if you check the wireing diagram you can bypass the computer, just by taking the pulse out of the distributer and connecting it directly to the coil, my friend next door ran his truck for 3 years with no knock computer just have to set your timing for the grade of gas you use most often.

Go back to where Hotrod mentioned the timing chain. The GM V8s are bad to jump timing teeth and absolutely will not start or run until the chain and/or gears are replaced.

There is a definite procedure for checking this out so get yourself a manual.

Well I tested the distribtor with a test light and I am getting spark going in, but no spark coming out. Tomorrow I am going to check the ignition wire and the timing chain. If it is the timing chain, is it cheap to fix and easy to do also?

GM HEI distributors are notorious for breaking the wires off of the pick-up coil at the bottom of the distributor. Also, sometimes aftermarket modules (especially cheap ones) are bad right out of the box. I would check the wire between the dist. housing and the pick-up coil for breakage or corrosion. this wire is always bending because of timing advance.

Use a 12 volt test light at the battery wire going into the distributor cap. With the ignition switch on, you should have voltage there. Then move the test light to the "Tach" terminal right next to the battery wire. It should also have steady voltage with the key on and the engine stopped, but it should change to a pulsating flash on the test light while cranking. If it stays steady while cranking, you've got a bad module or pickup coil. If it's flashing while cranking, the pickup coil and the module are good. If there's still no spark, it's a bad rotor or coil. The older rotors had a bad habit of burning a hole in the center, and sending all the spark to the distributor shaft, none to the plugs. Since you've changed the rotor, that's probably not the problem unless you put another bad one in.

Checking the pickup coil:
Unplug the yellow 2-wire connector from the module, and use a low-reading digital voltmeter on the AC volts scale. While cranking, you need at least 1/2 volt at the plug terminals. With the distributor out of the engine, this voltage can be checked by simply spinning the distributor shaft. The voltage is generated by magnetism without any input from the vehicle electrical system. You can also check out the whole ignition system with the distributor removed. Use the whole distributor, cap and all, with the plug wires removed. Be sure the 3-wire plug from the distributor housing to the cap is connected. Just put 12V power to the Bat. terminal on the cap and ground to the distributor housing, with the distributor mounted in a vise. Take the coil cover off, and spin the shaft. Sparks will jump from the plug terminals to the coil housing. Quick, easy, and it checks out the whole system. Those sparks are about 50,000 Volts, so don't get bit!
Jerry

Since you've changed distributors & then added tune-up parts, it might not be the distributor. The GM HEI only needs 1 wire, a switched 12 hot to operate. I've seen situations where a malfunction in the keyswitch or starter soleniod can cut power to the HEI when cranking. Check to make sure the distributor is getting 12 volts in "start" and "run" positions of key. How many wires go from vehicle harness to distributor- One, two, four, etc? Regular HEI needs but 1 wire. The spark knock models used a bunch more wires between dizzy and truck harness. The ESC controlled dizzys didn't have built-in spark advance, it was done in the computer. And like other posters say, when they went bad, they went baaaaad.

You can check condition of timing chain with a compression tester. If you've got good compression, over 110 PSI, the timing chain and valvetrain is likely OK. Since rotor is spinning, a jumped chain wouldnt kill the spark. It might spit and pop, but not just "quit" and do nothing. I've seen chains jump and timing gears disintergrate from wear, a furd 302 and a chevy 307, and they'd both still kinda run, but badly. Changing the chain requires removal of crank pulley, water pump, timing cover, etc. Not a fun job.

I would like to let all of you that tried to help me with my truck that with countless hours and the effort and suggestions from all of you that it is now running. What was the problems. The fuel pump went out and when I but it in, it missed the rod inside it. Second with the new distribtor, a wire was burned out. I had a shop look at that and replaced it. So once again thanks to all of you that helped and I raise my bottle of beer to you. Thank You