I have a few questions concerning what MAY be a spark related problem in a "cranks but no start" situation. On a different forum there was a remark that spark has a more difficult time in high compression engines than in low compression. My engine is approx 11.5:1. It's a TPI swap into a Caprice wagon. Any truth to that situation?

Additionally, I've been trying to set base timing with an new Actron timing gun. As stated it will crank but not run, There is no ability to "idle" at this point. Although I can see spark when I take a plug against the block, it not like lightning bolts. I can't get the gun to show any blip at all in this vehicle. I get it to read in other vehicles, but they are running, not just cranking.

Is the fact that I can't see a flash from the gun during cranking indicative of a spark so weak that it won't trigger the inductance coil of the gun?


I'm the fourth owner of this vehicle, A previous Kicker demo car from the 90"s. I have no idea how many times the B+ wires have been tapped into, and am thinking of rewiring the battery to key, and key to coil direct, bypassing the connectors from dash to engine harness along the way.


Your thoughts and answers are most welcome. Thanks

 

It sounds like the ignition coil is weak. I do not believe compression has anything to do with spark relation to compression. Make sure that the engine is getting fuels also. These would be the basic starting point for you. If these basic checks/fixes does not help, then you will have to start checking other items that will be more time consuming.

 

My apologies for not pointing out this the second new Accel remote coil. The entire Ignition system has been replaced twice with exception of wiring from battery to key to coil.

Seems like that's the only thing left, but not seeing a flash at the gun is frustrating. So the question remains,do others see a flash while purely cranking? The point is that I don't. Being that's the case, is "no flash" a telltale sign of weak spark, so weak that the inductance gun is not being triggered?

It only takes one last little tiny wire to get continuity and volts at the coil. At what level is a gun triggered? Is it a question of volts or amps? (or both). Is it reasonable to think I'm below that level or do I misunderstand how an inductance timing gun works?

 

The gun won't necessarily trigger with a weak spark. Seeing a spark on a plug isn't the best test, it might fire in free air but not in the compressed mixture in the chamber. Try a calibrated spark tester, they're less than $10 at your local parts store.

 

I'd say you have a problem somewhere with your ignition system. My guess would also be a bad coil since the plugs do spark, just not enough.

My engine is around 14:1. I use a huge MSD coil and a Holley ignition. I don't ground the plug to check for spark but I have used a timing light multiple times on other engines to see if the plug is firing. If there's enough energy to fire the plug, the timing light will flash. It's a good way to determine the location of a miss. A fouled or damaged plug won't fire. Cranking an engine over should produce enough spark energy to flash a timing light.

The magnetic pickup inside the distributor collapses the field in the coil which creates a high voltage. Power from the coil goes into the center of the cap then gets distributed to the proper plug at the proper time as the rotor goes around the cap.

Any number of things can create low plug voltage. Bad coil, coil hooked up backwards, not enough voltage to the coil. Bad plug wires. Bad cap and rotor.

You should be getting a minimum of 15-20,000 volts to the plugs.

Quick and easy test, drop a large cap HEI distributor into the engine. Supply it with a good switched battery source and see if the engine fires up. That will eliminate your aftermarket ignition/coil/distributor system.

 

have you checked to make sure you have 12 volts goin into it?