Low Spark HEI Distributer
Thread Starter
Instructor
Joined: Feb 2011
Posts: 234
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Low Spark HEI Distributer
Hello All,
Hope all are safe. Strange problem just started. The engine will not start. I tested the spark plug by putting spark plug in spark plug wire, grounding the metal of spark plug to engine. Very low spark, sometimes no spark. I installed a new coil and ignition control module, cap and rotor but same thing. I tested the positive wire to the distributor with multimeter and got 12 volts and when the engine is cranking 9 volts.What else could it be? Does the distributer need to be replaced? Any thoughts are greatly appreciated.
Thanks
Hope all are safe. Strange problem just started. The engine will not start. I tested the spark plug by putting spark plug in spark plug wire, grounding the metal of spark plug to engine. Very low spark, sometimes no spark. I installed a new coil and ignition control module, cap and rotor but same thing. I tested the positive wire to the distributor with multimeter and got 12 volts and when the engine is cranking 9 volts.What else could it be? Does the distributer need to be replaced? Any thoughts are greatly appreciated.
Thanks
Tech Contributor
Joined: Jun 2004
Posts: 20,860
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Hello All,
Hope all are safe. Strange problem just started. The engine will not start. I tested the spark plug by putting spark plug in spark plug wire, grounding the metal of spark plug to engine. Very low spark, sometimes no spark. I installed a new coil and ignition control module, cap and rotor but same thing. I tested the positive wire to the distributor with multimeter and got 12 volts and when the engine is cranking 9 volts.What else could it be? Does the distributer need to be replaced? Any thoughts are greatly appreciated.
Thanks
Hope all are safe. Strange problem just started. The engine will not start. I tested the spark plug by putting spark plug in spark plug wire, grounding the metal of spark plug to engine. Very low spark, sometimes no spark. I installed a new coil and ignition control module, cap and rotor but same thing. I tested the positive wire to the distributor with multimeter and got 12 volts and when the engine is cranking 9 volts.What else could it be? Does the distributer need to be replaced? Any thoughts are greatly appreciated.
Thanks
Pro
Joined: Jul 2021
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Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
Two things to check...
1. Repeat the test using a different plug wire - I know a bad plug wire is unlikley as the car isn't starting - but it's a cheap and fast test.
2. Check that the Module is properly grounded. We always worry about the V+ side - but all of with later model Vettes (should) have come to realize that grounds are typically a lot more problematic than power supply wires. You can check for grounding quickly by running a jumper from the control module ground to the batt neg terminal or to something like the alternator case.
If neither of the above look to help - you have a couple of options. You can try to replace the Ignition Module again. There are a number of stories on CF about brand new modules being bad. Or you can try to replace the entire distributor - and see if that resolves the problem. Full up HEI distributors are available through number of sources for pretty reasonable prices.
1. Repeat the test using a different plug wire - I know a bad plug wire is unlikley as the car isn't starting - but it's a cheap and fast test.
2. Check that the Module is properly grounded. We always worry about the V+ side - but all of with later model Vettes (should) have come to realize that grounds are typically a lot more problematic than power supply wires. You can check for grounding quickly by running a jumper from the control module ground to the batt neg terminal or to something like the alternator case.
If neither of the above look to help - you have a couple of options. You can try to replace the Ignition Module again. There are a number of stories on CF about brand new modules being bad. Or you can try to replace the entire distributor - and see if that resolves the problem. Full up HEI distributors are available through number of sources for pretty reasonable prices.
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Thread Starter
Instructor
Joined: Feb 2011
Posts: 234
Likes: 15
It's a stock 1975. I upgraded the motor with a standard 350 from BluePrint.Was told that when cranking the voltage to the battery will drop down to 9 and that was normal. Installed a third Module & grounded but same issue.
Can anyone explain how to takei ohms reading for the pick up, and where the pickup is located?
Thanks
Can anyone explain how to takei ohms reading for the pick up, and where the pickup is located?
Thanks
Race Director
Joined: May 2006
Posts: 18,703
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It's a stock 1975. I upgraded the motor with a standard 350 from BluePrint.Was told that when cranking the voltage to the battery will drop down to 9 and that was normal. Installed a third Module & grounded but same issue.
Can anyone explain how to takei ohms reading for the pick up, and where the pickup is located?
Thanks
Can anyone explain how to takei ohms reading for the pick up, and where the pickup is located?
Thanks
did you check the S terminal on the starter solenoid?
Last edited by MelWff; Jul 21, 2021 at 11:05 PM.
Pro
Joined: Jul 2021
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pickup is below the weights & springs ... has "teeth" & two fine wires. To R&R it, You MUST remove dist from motor and pull gear off shaft, then pull shaft from housing.
you can take an ohm reading with it in place ... unplug it from module and probe the two fine wires (after 46 years, its white wire is now probably yellowish-brownish)
pic & details here .. it's Standard Ignition pn LX-302
https://www.rockauto.com/en/moreinfo...t=7176&jsn=263
While cranking, make certain you have 9-12 VDC AT DIST CAP
FYI LX302T is the budget cheapo version, while LX302 is the good one.
you can take an ohm reading with it in place ... unplug it from module and probe the two fine wires (after 46 years, its white wire is now probably yellowish-brownish)
pic & details here .. it's Standard Ignition pn LX-302
https://www.rockauto.com/en/moreinfo...t=7176&jsn=263
While cranking, make certain you have 9-12 VDC AT DIST CAP
FYI LX302T is the budget cheapo version, while LX302 is the good one.
Last edited by ebbnflow; Jul 22, 2021 at 12:12 AM.
Tech Contributor
Joined: Jun 2004
Posts: 20,860
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
A factory HEI module is designed to work down to 6v. If there's an aftermarket module in it now, then it's anyones guess what it does at anything less than 12v.
Drifting
Joined: Oct 2020
Posts: 1,566
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From: Wisconsin
Could he not eliminate the voltage as an issue by isolating the dizzy to a 2nd known good battery to ensure 12v at cranking? Make sure connection can be easily disconnected to shut down the motor.
Never tried it, so proceed with caution.
Never tried it, so proceed with caution.
Drifting
Joined: Aug 2019
Posts: 1,334
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Sure. But if the starter is cranking at normal speed, I'm not concerned about the 9 volts.
Thread Starter
Instructor
Joined: Feb 2011
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Ok found the issue. Did all posted and still would not start. Got a new distributer and still nothing. I took carb cleaner and put a 1 sec spray into #2 chamber and its wanted to start. Then pumped the gas pedal 8 times and it almost started. Think the fuel pump is not pumping enough pressure to the carb. When I look down the carb the jet spray is not strong and the more you pump the weaker the spray gets until almost nothing. Why do you think?
Drifting
Joined: Aug 2019
Posts: 1,334
Likes: 225
Ok found the issue. Did all posted and still would not start. Got a new distributer and still nothing. I took carb cleaner and put a 1 sec spray into #2 chamber and its wanted to start. Then pumped the gas pedal 8 times and it almost started. Think the fuel pump is not pumping enough pressure to the carb. When I look down the carb the jet spray is not strong and the more you pump the weaker the spray gets until almost nothing. Why do you think?
Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
I've seen Q-Jet Fuel filters that were truly horrid. It's a lot faster (and cheaper) to change a fuel filter than a fuel pump.
Of course - you could hook up a pressure gauge to the fuel line, put some gas in the carb, start the car and measure the fuel pump pressure.
Of course - you could hook up a pressure gauge to the fuel line, put some gas in the carb, start the car and measure the fuel pump pressure.