Weak Spark

Wondering if anyone can help me out here. I have a 66 Chevy van, with a 230 straight six in it. I have a new HEI with coil on top, new spark plugs and new wires.

I had it running about 5 months ago and it purred perfect, started right up not even a blink of a eye.

Now I went out there today to get it running and it won't fire. Sits there and just turns over. I pulled a plug and grounded it and it has a really weak spark.

What can be causing this? I went through with a amp meter and check the starter and solenoid and reads over 12 VoLts through the key positions.

I have a full 12 volts on the battery. Then a full 12 v on the starter and when I turn the key and check where the wire from the starter connects to the HEI it also has a full 12 volts. I have the battery cable (-) connected to the same spot as I did last year. I pulled the cap off to make sure it had good contact, nothing was rusty or anything.

The only thin i changed was I went from a top load battery to a front load because I moved my battery location.

The voltage will proboly drop to about 9.5 or 10 volts during cranking. Thats normal. The HEI will produve a full 45,000 volts with as low as 8 volts input to the red wire. Check the voltage at the HEi while cranking and when you do that have your meter ground lead on the distributer base. You could be having a poorly grounded distributer.

If thats not it than you need to look into the distributer. not likely a primary circuit problem unless the coil has developed a short. Look for burn marks or blueing on the sides od the coil near the steel coil laminated inductive core.

Most likely a problem with the secondary circuit, ie bad rotor or cap. is there condenstion in the cap? that can happen after sitting. is the rotor show signs on its underside of burn through?


M1D

I dont know that the distributor gets power when the ignition switch is in the crank position,,,,I would turn the key on and energize the starter at the solenoid,,,,also lay the cap over, take a ground wire and test for spark at the coil output terminal in the middle of the cap on the inside, which is before the spark has to jump through the rotor, cap and plug wires and see what you get,,,,is the inner plug on the cap making good connection?

So I am still battling this problem, this is probably why my van will never see the road.
I ordered a new coil and put a new module in it and still doesn't do anything. I checked and it has 12 volts to the hei with the key turned on., 12 v to the starter so I know it's getting power.

The last thing I am going to try is changing the pickup on the bottom on the HEi and if that doesn't work I will be trashing this one and buying a brand new Petronix one.

Run a wire straight from battery to power HEI. See if that helps. If it does it's in the wiring. If not the distributor is messed up.

Here is what you may be missing.....In the days of point-fired ignition, the positive wire to the coil was either a resistor wire OR it had a ballast resistor wired into it..... A second, non-resistance wire hooked to the coil positive terminal comes directly from the accessory terminal on the starter solenoid to give the coil full 12 volts while cranking..... When installing HEI, the resistance wire needs to be replaced with a non-resistance wire from the ign switch to the coil positive....

so where you checking for spark?,,,,,,did you take a ground wire and see if the spark is strong at the middle terminal inside the cap as you crank the engine,,,,,,,if it aint sharp there, the distributor aint working right,,,,,,,,

AzDon wrote:Here is what you may be missing.....In the days of point-fired ignition, the positive wire to the coil was either a resistor wire OR it had a ballast resistor wired into it..... A second, non-resistance wire hooked to the coil positive terminal comes directly from the accessory terminal on the starter solenoid to give the coil full 12 volts while cranking..... When installing HEI, the resistance wire needs to be replaced with a non-resistance wire from the ign switch to the coil positive....

I was just thinking this.

Have you replaced the resistor wire???????????

donivan65 wrote:so where you checking for spark?,,,,,,did you take a ground wire and see if the spark is strong at the middle terminal inside the cap as you crank the engine,,,,,,,if it aint sharp there, the distributor aint working right,,,,,,,,

never seen this done before.....cool

If,,,,,,he is saying there is weak spark at the spark plug,,,,,,I flip the cap over and see if spark jumps to ground from that center coil terminal when I crank the engine,,,,,,,,,,,,,,no spark means it most likely is a primary problem,,,,,,,wiring or control unit,,,,,,,,if you get spark there, then the spark aint getting through the rotor, cap or plug wires,,,,,,,,its just a starting point to check, to get you looking in the right direction,,,,,

Alright so I did the checking the spark from the bottom of the cap and it has plenty of spark there. So it is not letting it through the cap for some reason.

hook a jumper to the rotor and see if spark jumps from that center terminal when you crank the engine,,,,,if it jumps, rotor is shorted,,,,,,

Alright so I put a jumper on the rotor and watched it spin as it was still connected the the lower dist. It did not give off any spark off the rotor.

Then i put the jumper on the bottom of the cap and it sparks a lot like it should.

spark has to go from that button down to the rotor,,,,rotor turns and sends spark to each spark plug terminal in cap and out to each plug wire to each spark plug,,,,,,check other plug wires for spark with the cap back on and all hooked up in case you got a bad wire,,,,,the engine has to be in time for the spark to make it to the plug,,,,,,broken timing gear would not let the spark out to the plug at the correct time,,,,

What are the chances of the spring button beneath the coil pack in the cap not making the correct connection ? Might worki upside down and not installed?

so,,,,,,it ran fine 5 months ago and now it wont start???? grounding a plug aint a real good way to test for spark,,,,,plugs dont spark real good,,,,,,,put it all together and take a plug wire off and use a jumper wire to see if you got spark out of the cap,,,,,,,I think spray some carb cleaner down the carb might put some life in the engine,,,,,,its probably a fuel problem,,,,,,,,,,,

I will check the spring underneath the coil.

I did test the bare cap when I had it all together and i did make a spark. The carb is all rebuilt and ran perfect before this. It's like it just cranks and cranks and doesn't even want to burp or anything. I will go over everything agian and see what I can find. So frustrated right now

And I know it's getting gas because when I open the carb to full throttle and look down the barrel I can see gas sitting down on the intake. Something must not be right and not allowing it to ignite

so when you put #1 on its compression stroke and the timing mark at 6 degrees before top dead center, is the rotor pointing to the #1 spark plug wire?,,,rotate the distributor a little and see if the engine trys to start,,,,,,

I just got back from the shop and rest the timing. It's burped once and then it stopped. Checked to see if I have spark on the bottom of the cap and I did. Put it all back together and pulled a plug wire off and put a test light by it and it had no spark.

And now the starter on the engine took a crap so now I need a new one of those

what about that connector and wires connecting the cap to the distributor,,,,,,you seem to have problems when you move the cap around,,,,,,,whats wrong with the starter now,,,,,will it crank when you jump from the battery cable to the S terminal on the solenoid? how about tap the starter underneath with a hammer to free up stuck brushes in it,,,,,,,,

Alright so I banged on the starter and now it seems to be working agian. I should replace it either way.

I tried wiggle around the wires on the cap and seems to do nothing. I can get a really faint spark when I pull a spark plug wire off and hold a tester on the cap. I don't know if I should just try to replace the cap and rotor. It's like I litterly replaced eve thing so far and not getting anywhere . But there is a lot of spark at the bottom of the cap in the center.

Sounds like your not getting a good contact between the cap and rotor. try cleaning the contact area on the rotor with emory paper and bend it up a little to make better contact.

Alright i see what you mean. I bought a new rotor today so hopefully this will cure the problem. Fingers crossed