HEI won't start

[RPM]

Help me out here, I am about to go nuts. Got this T bucket here. 350 motor with an HEI in it. The car has set fro about 3-4 months. It ran and drove into where it now sets. It looks to have a new MSD HEI in it. So I went to start it today and the battery was dead, charged it up no big deal. Well it won't start, NO SPARK.

We have 12 volts to the switch, we have 12 volts out of the switch, in both the run and crank positions on the key switch. The distributor does turn and everything about the motor seems fine. We have 12 volts at the switch going to the BAT terminal at the cap. I removed the cover to make sure the plug in is connected, it is.

We have no way to test, modules, coils or pick up coils. From past experience, when a GM hei failed to fire after it had run perfect, most times it was the module. So I had another dist laying about so I robbed the module from it. No fire. Took the original module to the auto parts store, the guy said the module was bad. OK Got a new module installed it. NO fire. So I went and bought a complete MSD NEW distributor. Installed it no fire. Ran a jumper from the battery to the BAT terminal on the cap, still no fire.

The motor spins fine so I have rulled out a ground issue. It does have several grounds on it as well. Cleaned and tightened those grounds also.

Tried the MSD tech line and they are closed today for a holiday. What Holiday?

 

[Hotrod46]

Ron
Does it have a tach connected to it? The tach may be bad and is grounded out.

Sounds like you've checked everything else.

Mike

 

[RPM]

No tach. I have seen that before.

 

[Northstar T]

How exactly are you testing for spark? have you connected a timing light? if so, did it trigger the timing light?

Russ

 

[RPM]

I have a new spark plug and I pulled a plug wire and put the plug on the intake manifold. Any other HEI would light that plug up big time.

Even with a shot of starting fluid the engine won't even sneeze.

 

[Northstar T]

So I take it you did NOT connect a timing light to it then? A spark plug laying on the manifold is a very poor way of determining if you have acceptable spark for several reasons. it's not grounded well, and the electrode gap is such that it's very hard to see a spark as you crank the engine over even if there was one. even if you do see a spark that doesn't mean that spark is adequate to fire once it's reinstalled and under compression, as it requires MUCH more voltage to fire a given gap under compression than it does that same gap in free air. As memory serves, a .166 gap in free air requires comparable voltage to fire as a .032 gap under compression.
so hook up a timing light, and wile you're at it, hook up a test light to the distributor hot lead and ground. give er a crank and report back if you see the light at either the test light or timing light.

Russ

 

[bigfrank330]

Hey Ron
Hook a test ligt to the TACH terminal
It should blink while cranking if the primary circuit is OK
If it does blink Check the Ignition coil resistance Batt term to Tach terminal should be approx 1 ohm
Secondary terminal to Batt term should be 15,000 ohms
Please let us know if this helps
Frank

 

[RPM]

OK the test light to the BAT terminal is on when ign is on also when cranking. Test light on TACH terminal is on when Ign is on also when cranking. Hooked up a timing light it does not blink, at all.

So now what? I have another new MSD that I got last night. Try it I guess.

 

[RPM]

Another new MSD dist. Still no fire. Found my volt meter. 14.1 bat volts. I have bat voltage at the terminal inside the cap. Drops to 10.5 when cranking. I think I am headed to the junk yard, to get a stock HEI.

 

[T-Test]

I have seen camshafts break in to and would spin the distributor but not crank, no valve action. It's hard to believe that many distributors/ coils/ modules are bad.

 

[sstock]

Ron, Just for sh!ts and giggles, you do have the polarity of the battery correct?
In backwards you would still read voltage but there would be nothing in the secondary winding of the coil IMHO.

 

[Northstar T]

Ron, Just for sh!ts and giggles, you do have the polarity of the battery correct?
In backwards you would still read voltage but there would be nothing in the secondary winding of the coil IMHO.

excellent thought. there just aren't many things that can go wrong with an HEI system.
in fact, now that you mention it, I've seen a battery go totally dead, then be charged up reverse polarity also…… NAAAaaaaa. Ron wouldn't do that…………

Russ

 

[Francis Blake]

Second try I thought I posted earlier but it aint there. Does the msd need an ignition box.

 

[RPM]

Ron, Just for sh!ts and giggles, you do have the polarity of the battery correct?
In backwards you would still read voltage but there would be nothing in the secondary winding of the coil IMHO.

BINGO we have a winner. The cables are both black and I got them switched. Found it when I had the original dist in it, still would not fire. Installed the new HEI with the polarity correct and it fired right up and runs great. Now the buyer should be here in just a little while.

 

[donsrods]

Gee Ron, I have NEVER done anything like that. Ok, I do things like that all the time. Glad you found your problem.

Now that this thread is solved I thought I would hijack it and pass along something I learned that might help others. We went to a car show the other night and were talking to a guy who owns a T bucket. He was saying he has been chasing a problem where when he shuts off the key the motor keeps running for a few seconds. He has tried everything.

I asked him if he has an electric fan and he said "Yes." I told him that was the problem, until the fan stops spinning it is a very efficient generator and is feeding current back into the system. He thought I was nuts and started up his T and disconnected the fan plug. When he turned the key off the motor stopped running immediately. The reason I knew about this is because my own 27 has that issue and if I shut off the fan switch before turning the key the motor, lights, and electric fuel pump stop immediately.

A diode in the power wire will fix it too, allowing juice to only flow into the fan, not back out. But I am lazy, so I just shut my switch off first.

Don

 

[Francis Blake]

Don the same thing happened to my sons truck,and after some head scratching I figured it out so we installed a switch.

 

[sstock]

Good post Don, that is so prevalent. painless wiring even has it on their FAQs

 

[Northstar T]

Gee Ron, I have NEVER done anything like that. Ok, I do things like that all the time. Glad you found your problem.

Now that this thread is solved I thought I would hijack it and pass along something I learned that might help others. We went to a car show the other night and were talking to a guy who owns a T bucket. He was saying he has been chasing a problem where when he shuts off the key the motor keeps running for a few seconds. He has tried everything.

I asked him if he has an electric fan and he said "Yes." I told him that was the problem, until the fan stops spinning it is a very efficient generator and is feeding current back into the system. He thought I was nuts and started up his T and disconnected the fan plug. When he turned the key off the motor stopped running immediately. The reason I knew about this is because my own 27 has that issue and if I shut off the fan switch before turning the key the motor, lights, and electric fuel pump stop immediately.

A diode in the power wire will fix it too, allowing juice to only flow into the fan, not back out. But I am lazy, so I just shut my switch off first.

Don

Which is why Ign switches have separate Acc posts and Ign posts

Russ

 

[RPM]

Here is how we found this. Went to connect a jumper wire from the ground post on the battery to the dist base to make sure we had a good ground. When my buddy touched the jumper wire to that base it sparked like a welder, and it should not have. Then we got to checking stuff. This car has the battery in the bed and not much room. Both cables are black and I got them switched.

But hey at least I came back and told what it took to fix, so the next guy might learn from my mistake.

 

[donsrods]

Yep, it is rare to ever hear back what the OP found that fixed his problem. I have seen tons of threads with people offering lots of suggestions, then you never ever hear what the guy found. Thanks for letting us know , Ron.

Don