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78 Won't Start HEI Problem

1

1978L48jafo

Guest
I have a no spark condition with a HEI coil that is vibrating when the key is turned on. I suspect the module or ECM does anyone know a way to prove? Manual lists something specialized from GM to test. Note I repleace the stock with a HEI rebuild kit a few years back a company called performex???? any suggestions would be appreciated it started fine all winter long and then has issues come spring :bash
Thanks
John
 

minifridge1138

Well-known member
Joined
Feb 2, 2007
Messages
908
Location
USA
Corvette
1982 Black Fastback
I was doing a top end rebuild on my engine. When I got to the distributor, I decided to have the module tested. I just took it to my favorite auto parts store (Advanced Auto is 1 block from my house so it is my favorite) and they tested it for me. Turns out, that it was fine at low temps, but as it warmed up it started failing. The test was free and a new module was $35 i think.

Good Luck!
 

10752

New member
Joined
May 11, 2006
Messages
4
Location
Florida
The Pertronix units have aquired a pretty poor reputation for reliability.

Here is a total test procedure for hei. You may consider going back to that GM module. Cheap and reliable. Your 78 shouldn't have an ecm.

HEI Test

1. With the ignition on, connect a test light to the coil positive (+) post or HEI BAT terminal.
LIGHT ON: Go to step 3.
LIGHT OFF: Go to step 2.
2. Check for continuity or voltage drop in the ignition switch and in the circuit from the switch to the coil positive (+) side or HEI BAT terminal, including any aftermarket ignition modules or ballast resistors. On conventional ignitions, also check for continuity in the bypass wire from the solenoid R terminal. Repair or replace as necessary.
STARTS: Stop—you’ve found the problem.
NO START: Go to step 3.
3. Remove a spark plug wire and insert an extension. Using insulated pliers, hold the spark plug wire ¼-inch away from the engine block while cranking the engine.
SPARK: The problem is not the ignition system. Check the fuel system, spark plugs, timing, and internal engine condition.
NO SPARK: Go to step 4.
4. Remove and inspect the distributor cap for cracks and carbon-tracking. Visually inspect the distributor mechanism for moisture, corrosion, or burns. Repair as needed.
STARTS: Stop—you’ve fixed it.
NO START: Go to step 5.

5. Check the coil.
CONVENTIONAL COIL: Go to step 6.
HEI (IN-CAP COIL): Go to step 9.
6. Set an ohmmeter to the low scale. Connect the leads across the primary terminals. Coils requiring ballast resistors should have about 1-2 ohms of resistance. Those not requiring a ballast resistor should have about 4-5 ohms of resistance.
OK: Go to step 7.
NOT OK: Replace coil.
7. Switch the ohmmeter to the high scale. Connect one lead to either coil primary terminal and the other lead to the secondary cable tower. A stock-style coil should read between 4K and 8K on the scale. Some aftermarket coils may have lower values; consult the appropriate specs.
BELOW 4K OR OVER 8K: Replace coil.
WITHIN SPEC: For points systems, go to step 8. For electronic systems other than HEI, consult the system manufacturer for further troubleshooting steps.
8. Using a voltmeter, connect one lead to ground and the other to the distributor side of the coil. Remove the high-tension wire from the coil and ground it. Bump the starter switch to open and close the points; the voltmeter reading should be 1/3 to ½ the battery voltage during cranking as the points open and close.
READING AT OR NEAR ZERO: Replace the points and condenser.

9. Set an ohmmeter to the low scale. Connect the leads across the HEI’s "BAT" and "TACH" terminals.
ABOVE 1 OHM: Replace coil. If vehicle still doesn’t start, go to step 11. 0-1 OHM: Go to step 10.
10. Switch the ohmmeter to the high scale. Connect one lead to the "BAT" terminal and the other lead to the coil contact in the inside-center of the cap. Switch the first lead to the "TACH" terminal and recheck.
EITHER TEST READS 6K to 30K: Coil is OK. Go to Step 11.
BOTH TESTS READ INFINITY: Replace the coil. If the engine still won’t start, go to step 11.
11. Remove the green and white leads from the HEI control module. Connect the ohmmeter from ground to either lead.
INFINITE:
Go to step 12. LESS THAN INFINITY: Replace the pickup coil. If the engine still won’t start, replace the module.
12. Connect the ohmmeter across the green and white module leads.
READS 500-1,500 OHMS: Repeat Steps 11 and 12 while moving the vacuum advance with a screwdriver. If reading is still OK, replace the module.
DOES NOT READ 500-1,500 OHMS: Replace pickup coil. If the engine still doesn’t start, replace the module.

:)
 
1

1978L48jafo

Guest
Thanks, tested the module at auto zone, it took a while the young lady did not understand how to setup the machine and then wanted to hook up backwards....;-) but it was bad and she started right up.
John
 
1

1978L48jafo

Guest
Thanks I wish my manual would have had a bit more. I will print and keep for future use.
John
 

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