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Old 12-19-2005, 09:18 AM
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Should Timing Light Blink While Cranking?

After removing and reinstalling my HEI distributor, I can't get the car started, except for one short time when it started, ran rough for a few seconds and died.

To check for spark, I have:
1. Connected timing light but get no blinking while cranking
2. Removed plug and grounded electrode - got faint blue spark in well-lit garage

Do you think I have sufficient spark?

John

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Old 12-19-2005, 11:46 AM
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yes the timing light should be blinking....and ground the sparkplug with the sparkplug wire on it and see it it "arcs" if not the car will not run
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Old 12-19-2005, 05:34 PM
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Doc here,

If you are getting full voltage during crank to the HEI coil, you should get a strobe on the timing light.

BE sure the light is Power AND Ground at THE BATTERY...not the engine block...your block ground may also be the reason it won't fire and run!

Is the An upgrade to HEI from Points or replacing an engine that had points before? If so, you may have a Resistance wire or resistor on the coil Battery (+) wire feeding the HEI still..you will have to remove this in order for it to run or run correctly. HEI's do not require Ballast resistors.

A Quick test is run a jumper to the battery from the BATT terminal on the HEI cap (coil power) and crank it, If it fires and runs OK, you found the problem.

If not, Pull the Module and take it to the parts store and have it tested (several times to heat it up) and replace if needed..If you get a new module, HAVE it tested also...these have a HIGH fail rate out of the box..like 1 in 3...and when you leave the store, it's your problem. When replacing the module, DON'T forget the heat sink compound or you'll be buying another module within a week..same applies to replacing the used good one.

Test the coil..Measure the primary side of the coil, ( Probes on BATT and TACH) It should read on a DVOM set for R X 1 , less than an ohm...then measure the secondary side of the coil, (Probes on BATT and Carbon rotor pickup under the cap) Set for R X 10k or higher, It should read between 6000 and 30,000 ohms..If these readings are too far off, replace the coil.

If you installed a Fresh SBC...You might require a Secondary ignition wire from the Solenoid,(losing power in crank mode) OR, You may also have Ground issues, Set up ground buss as follows:

Run a properly gauged Ground cable from the battery to any handy bolt at or near the starter, From that same bolt get a Battery cable at the parts store, that has two 3/8 ring terminals on each end and attach it there and to the Frame.

Next get some 10 gauge wire and ring terminals and run that from your bolt on the block to the Firewall, and another to the Alternator bracket or mount bolt.

If the Bracket and alternator is power white remove them both and their hardware, sand or pressure wash them until clean semi shiny metal, dry and reinstall.

You have electrolysis there..and it will also eat a water pump impeller up faster than any acid..The Alternator Bracket and Alternator housing is Aluminum and the block is Steel..(what were they thinking?)

When you go to reinstall the brackets, go to the hardware store and get some aluminum wire compound, and coat everywhere the mount hardware meets steel (bolts, mount surfaces Ect..)

Next get some Wire Braid, (Radio Shack) and install braid from the radiator support to the frame, Fenderwells to frame , hood to firewall, Doors to door posts, gas flap to body, tailgate / Trunk to body.

At each point the wire is grounded, Burnish ALL the paint and grease off to bare metal. Use a proper star-washer and lock. Use sheetmetal or Tech screws where no screws are available.

It sounds like a lot of work, but after you assemble all the parts, it's only a few hours to do..and you'll end up with a system that will work reliably for many years to come..and can eliminate that from your troubleshooting list.

Doc


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Last edited by docvette; 12-19-2005 at 05:36 PM. Reason: Cuz I can...
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Old 12-20-2005, 08:32 AM
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Doc.

The car ran okay before pulling the HEI distributor, which was an old used unit of unknown history. But, the mechanical weight pins were half way worn through, so I pulled it to just replace the core drive shaft and mechanical weight assembly. I left all the original electronics in it -- of course they were disturbed and wires wiggled while I had it out -- but I did make sure they were all connected before reinstalling, and sanded the ground connections at the capacitor.

I have pulled the distributor back out and made the following checks:
1. The pickup coil has 765 ohm resistance between the two contacts at the module connection
2. The coil has 12.4K ohm resistance between the secondary terminal and the ground terminal
3. The coil has infinite resistance between the secondary terminal and the tach terminal
4. The coil has less than one ohm resistance between the primary terminals (tach and bat).

I think these indicate the pickup and coil are good.

Is there a way to test the module?

I feel confident I have the cam and distributor phasing correct (timing mark at 14* and rotor aimed at #1 post, same as it was when I removed the distributor).

After reinstalling a second time last night, it cranked and I did get a couple of single hits, but again the battery started getting low after a few minutes of trying. I have rotated the distributor probably 15* each direction. Pulled #3 plug and it looked good (tan, not wet).

Problem has to be with the distributor since car has consistently started with a little pumping of the gas (QJet) in the past.

Module?

John
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Old 12-20-2005, 08:35 AM
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Doc,

Forget to say, the timing light is connected to a separate battery on the garage floor, not to the car battery. It is a dial back light and the digital readouts work, but no flash when cranking.

Also, checked volatage at the bat connection to the distributor and it is 11.9 volts with car not running.

John
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Old 12-20-2005, 11:43 AM
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Doc here,

I think The coil may be is shot...

IT should read on the BATT to TACH terminals...less than one ohm.

IT should read between the BATT and Carbon rotor pickup on the underside of the cap, 6000 to 30,000 ohms...

Hard to tell from your description...did you measure between the rotor button pickup and the Batt terminal? These are the only two readings you need to make..And if so..12.5 k is kinda marginal..(weak spark)..For a Stock HEI.

Pull the module and take it to the autoparts store, they can test them for free..have them do it several times to heat it up..and if you need one, have that one tested too..they have a high OBF rate ..like 1 in 3, and if you leave with it, it's your problem.

When you replace the old module, or install the new one, DON"T forget the heatsink compound, or you'll be doing it again in a few weeks. Wipe the old stuff off the advance plate, and apply a generous (but not sloppy) amount to the new module.

Your Dialback light may not work that way, try using an older redundant "No Frills" timing lamp ...


Doc
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Old 12-21-2005, 02:13 PM
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Doc,

Module checked good at Advance Auto so bought a coil although the old coil passed my resistance checks at home.

Installed coil, turned key, Vrroooommm!

Thanks Doc.

John
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Old 12-21-2005, 04:30 PM
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Quote:
Originally Posted by JohnTN
Doc,

Module checked good at Advance Auto so bought a coil although the old coil passed my resistance checks at home.

Installed coil, turned key, Vrroooommm!

Thanks Doc.

John
Doc here,

Thanks For posting back with the fix...will help the next guy!

I had a feeling it was the coil...

Resistance Checks while indicating good on Coils will not show internal "Arc Over" or jumping from one winding to another...You need a scope for that..but it will kill spark just as fast without showing bad readings.

Glad to hear your running now!

Doc

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