HEI, how to test for spark... or test module... - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

 
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post #1 of 14 (permalink) Old Dec 28th, 15, 3:55 AM Thread Starter
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HEI, how to test for spark... or test module...

I have an HEI in my car. Its just a temp setup.

Today, I tried to start it with a wire directly to the battery (and to the BAT terminal on the distrib). It sounded like it was trying to start (stumbled), but it was only while cranking. I adjusted the distributor (tried more initial advance and then some retard, etc), but couldn't get it to fire again, at all, no stumbles even... No backfires, etc.

So I am looking for how to diagnose if its the module, etc...

Again, this system is totally "hot wired" (its just temporary). I have a wire to the distributor and a wire to the starter, both directly from the battery + terminal... These wires are NOT in the stock harness, just separate wires. The distributor worked before (in this same engine), but I have had it apart for a few years.

BTW, it has fresh fuel, and I was suing some starting fluid as well... Clear filter and float site plug... Carb was used on another project a few months ago. Engine ran okay, and it sounds like it has compression, not like its spinning/turning over with plugs out...

Thanks

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post #2 of 14 (permalink) Old Dec 28th, 15, 7:44 AM
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Re: HEI, how to test for spark... or test module...

Engines need air, fuel and properly timed spark to run. First was the distributor installed with the #1 piston at tdc? Second hook a timing light to the #1 spark plug wire and see if it flashes during cranking. If you have spark then check for fuel by looking down into the carb while you operate the throttle by hand, to see 2 solid streams of fuel spraying in.

If you don't have spark there are many threads on checking the module and pickup.

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post #3 of 14 (permalink) Old Dec 29th, 15, 4:35 AM
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Re: HEI, how to test for spark... or test module...

could be the way you are wiring it. what I did was to use a toggle switch for a good on/off power to the HEI. get the 12v wire from hei to one side of switch, the other side of switch the wire goes to battery. then I got a starter switch, hooked one lead up to battery and the other lead to the S terminal on starter. when you are ready hit toggle switch on for
12V, then hit the starter switch and engine will start and run ok if all else is good. once I was done with testing I hit the toggle switch off, to cut juice to HEI, and turn engine off. this is a temp set up and had it like that for a while til it got wired permanently.
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post #4 of 14 (permalink) Old Dec 29th, 15, 4:42 AM
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Re: HEI, how to test for spark... or test module...

forgot to mention, you can easily eliminate the toggle switch but I felt safer using it instead of a test wire with alligator clips on either end. tested the engine, carbs, HEIs to good effect.
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post #5 of 14 (permalink) Old Dec 29th, 15, 1:16 PM Thread Starter
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Re: HEI, how to test for spark... or test module...

Quote:
Originally Posted by 68Cpe307 View Post
could be the way you are wiring it. what I did was to use a toggle switch for a good on/off power to the HEI. get the 12v wire from hei to one side of switch, the other side of switch the wire goes to battery. then I got a starter switch, hooked one lead up to battery and the other lead to the S terminal on starter. when you are ready hit toggle switch on for
12V, then hit the starter switch and engine will start and run ok if all else is good. once I was done with testing I hit the toggle switch off, to cut juice to HEI, and turn engine off. this is a temp set up and had it like that for a while til it got wired permanently.

forgot to mention, you can easily eliminate the toggle switch but I felt safer using it instead of a test wire with alligator clips on either end. tested the engine, carbs, HEIs to good effect.
Yeah,

Same setup, except no button on the starter, I just tough the wire to the battery post... I actually started and ran my other Chevelle with the same setup a few months ago ( along with an electric fuel pump)... I pulled all the wires/toggle switches off that car, and switched them to this car. Swapped the carb over to this new engine too.

This engine ran before, same distributor even, but its been down for a few years... I just R&R'd the cam to check the grind, and put it back together with lots of cam lube...

I actually had to bypass the ignition toggle switch the other day, but I found no current was getting through. After bypass, that's when I heard it stumble a few times ( started but wouldn't keep running), but after playing with the initial timing ( advanced a bit- nothing, then retarded it a bit, nothing, right back to where it was and still nothing). it no longer does anything, so I was thinking "module"?...

The distributor clamp is pretty tight. I can barely turn it with both hands, and it should still be grounded with all the metal contact...

I probably won't get back to it until Thursday or Friday...

The wiring harness is out of the car, and I need a way to move the car up my driveway so I can get another car into the work area (to pull the engine)...

Thanks.

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post #6 of 14 (permalink) Old Dec 29th, 15, 4:12 PM
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Re: HEI, how to test for spark... or test module...

It's more likely that the coil would go out before the module. There are some tests you can do but the loaded tests at the Auto Store testing machines are best for this.

Are you certain that the distributor is installed correctly with TDC #1 firing position with rotor pointing to #1 plug post. Easy to make the mistake of 180 degrees out so watch your valve sequence with the valve covers off to make sure.

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post #7 of 14 (permalink) Old Dec 29th, 15, 7:59 PM Thread Starter
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Re: HEI, how to test for spark... or test module...

Quote:
Originally Posted by 65chevelle300post View Post
It's more likely that the coil would go out before the module. There are some tests you can do but the loaded tests at the Auto Store testing machines are best for this.

Are you certain that the distributor is installed correctly with TDC #1 firing position with rotor pointing to #1 plug post. Easy to make the mistake of 180 degrees out so watch your valve sequence with the valve covers off to make sure.
Yes, I checked TDC compression stroke using the valves as a guide... I also verified the timing mark on the balancer and timing pointer.

The engine tried to start, stumbled a bit, and I could here it coming from the exhaust, but standing next to the engine, there was not popping thru the carb like should occur if 180 out... Been there, eyebrows finally grew back

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post #8 of 14 (permalink) Old Dec 29th, 15, 8:11 PM
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Re: HEI, how to test for spark... or test module...

Do you have spark at the plugs?

Maybe it's just flooded

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Last edited by Dean; Dec 30th, 15 at 11:05 PM. Reason: TYPO
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post #9 of 14 (permalink) Old Dec 30th, 15, 9:06 PM
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Re: HEI, how to test for spark... or test module...

A simple check to determine if the module is completely dead is to:

Get a simple test light.

If possible;

Disconnect the tach signal wire from the "TAC" terminal on the HEI distributor. (assuming you have a tach connected to it to begin with).

Connect the test clip of the test light (carefully) to the tach lug connection on the distributor and stick the probe end of the light into the power wire connection at distributor (the "BAT" terminal)--leave the main power wire connected to the distributor of course.

Have an assistant crank the engine.

The test light should be rapidly flashing representing the module is switching properly. This simple test will not tell you if the module is on it's way out, but will tell you whether it is in fact dead and not providing the needed coil switching.

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post #10 of 14 (permalink) Old Dec 31st, 15, 12:27 PM Thread Starter
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Re: HEI, how to test for spark... or test module...

Great info Joe...

Currently no tach hooked up...

Quote:
Originally Posted by Coppertop View Post
A simple check to determine if the module is completely dead is to:

Get a simple test light.

If possible;

Disconnect the tach signal wire from the "TAC" terminal on the HEI distributor. (assuming you have a tach connected to it to begin with).

Connect the test clip of the test light (carefully) to the tach lug connection on the distributor and stick the probe end of the light into the power wire connection at distributor (the "BAT" terminal)--leave the main power wire connected to the distributor of course.

Have an assistant crank the engine.

The test light should be rapidly flashing representing the module is switching properly. This simple test will not tell you if the module is on it's way out, but will tell you whether it is in fact dead and not providing the needed coil switching.

Once you go RAT, you never go back...
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post #11 of 14 (permalink) Old Dec 31st, 15, 6:13 PM
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Re: HEI, how to test for spark... or test module...

And if you perform this test and find out there is indeed "no switching", we can tell you how to check the reluctor coil as well to verify it is sending the proper signal to the module to tell it to turn off and on.

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post #12 of 14 (permalink) Old Dec 31st, 15, 7:56 PM Thread Starter
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Re: HEI, how to test for spark... or test module...

I had a chance to work on it this afternoon...

Hooked the test light to the "Tac' terminal and then to the negative post of the battery... At first there was no flashing, but when I took the cap off and flipped it over, I saw that my alligator clip was on the plastic divider, and not the terminal... Reattached it, and when tried, the light flashed...

Hooked an old plug to one of the plug wires, and held it against the ground cable/bolt on the block... NO spark at all when cranking...

So I grabbed an old used Cap/coil and was going to swap out the coil, but instead decided to swap the entire cap despite having some corrosion and "wear" on the posts... I retested with one plug, and I got spark!

Swapped over the rest of the wires to the old cap, and it fired right up!

First time I had started this motor in 4+ years, but it seemed to run pretty good (I R&R the intake and water pump, Fuel pump and cam this past summer). Whew...

Thanks everyone, and thanks Joe/Coppertop for that tip...

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post #13 of 14 (permalink) Old Jan 4th, 16, 4:02 PM
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Re: HEI, how to test for spark... or test module...

So it was indeed the coil. Typical for HEI as I mentioned earlier.

One thing to remember about those modules is that they require some type of thermal interface material "TIM" on the bottom where they contact the distributor or else they will quickly over heat and destroy themselves in short order.

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post #14 of 14 (permalink) Old Jan 4th, 16, 4:32 PM Thread Starter
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Re: HEI, how to test for spark... or test module...

Quote:
Originally Posted by 65chevelle300post View Post
So it was indeed the coil. Typical for HEI as I mentioned earlier.

One thing to remember about those modules is that they require some type of thermal interface material "TIM" on the bottom where they contact the distributor or else they will quickly over heat and destroy themselves in short order.
Yeah... I think it was just the coil

It was from a Summit $89 special (HEI with cap and coil). Lasted in my Chevelle for a few years until the rivets broke... Then had the cap sitting in a box for a few years more... The distributor itself is an OEM HEI, and the cap/coil were a little old and "worn"... But thankfully they still function...

I was going to just swap the coil to the "newer" cap, but it was all rusting inside (this is the one that was "good", the burned out one looked nice)...


For now, I just needed something that works. I ran 12V from the battery, to a toggle switch on the dash, and I use that to turn on the ignition... Another "momentary" toggle switch for the starter solenoid. Enough to start the car and move it around...

Once you go RAT, you never go back...
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