Ignition System Problem Diagnosis/Service

Michael Mayben

Michael Mayben

IHPA Tech Moderator - Retired & No Longer Online
We'll use this thread to discuss fault diagnosis and suggested repairs for common ignition-related issues in regards to various IH product applications.
 
Hey I have a 1975 Scout with a 345. I just put an engine in and I cannot get it 2 start. I set the distributor 2 the number 8 cylinder wen it was on the compression stroke and the harmonic ballancer Mark was lined up on the o degree Mark and I still cant get it 2 start. Im getting gas 2 the carb and im getting fire 2 the plugs but wen I crank it over it backfires. I thought it was the timing but ive been working on it 4 a week now and tried just about everything on it. I had a few guys come help me with it and they couldnt find out wat was wrong either. One guy told me it could be my ignition box?

Thnx,
derek
 
Ya I read that just before I posted this. At first I was timing the engine on the number one cylinder because im used 2 working on sbc but I had a guy that has rebuilt a few 345s and he helped me time it 2 the number 8 cylinder and we got a compression tester 2 tell wen it was on the compression stroke and set the distributor on the number 8 and its still backfiring. I have replaced the rotor, cap, coil, plugs, and wires. The only thing I havent worked on or replaced is the carb and the ignition box 4 the electronic ignition.
 
Loosen the distributor hold down to allow distributor rotation. It'll stay in place just fine when the engine starts.

While having a helper crank the motor over, slowly rotate the distributor body fore and aft. It'll either get better, or get worse regarding the "popping"! I suspect ya just have not found the sweet spot for initial base timing.

When you say "ignition box" I assume you mean it has a Holley "gold box" system? Did you do anything to the distributor guts while it was out? Have you verified that the mechanical advance mechanism in the distributor is free to operate and not "stuck"? Did the ignition system operate properly before the engine swap? You didn't do a "duraspark" conversion on the gold box distributor did you??? If so, there is no telling what ya got as "phasing" that conversion is tedious!

Try rotating the distributor and get back to us. We need mucho more info so we can understand the big picture!
 
Ya it has the Holley gold box. I tried turning the distributor while it was cranking and it didnt change any. I have not touched the box. The only thing I did 2 the distributor when it was out was change the rotor and cap. I never heard it run. I bought it 4 cheap from an old man that had it setting in his barn for 8 years. And wen I started looking at the engine it had a crack in the block so I bought a rebuilt engine and stuck in it.
 
Ok derek...so if I understand correctly, then this vehicle and engine we're not running when ya got it. You swapped motors and now are trying to fire it for the first time.

It's very possible the rig was parked because the ignition system was giving problems. Personally, I'd not deal with that gold box system right now. I "think" you simply wanna make it start? You can deal with the gold box system later.

Easiest thing is to swap in a points distributor out of another engine that has had the dwell "point gap" set. Then just "hot wire" it using the existing coil which is the correct item (if stock primary resistance value) for the breaker point system also. You must use a 1.8ohm ballast resistor in the "hot wire" setup, other wise the breaker points will overheat/fail fairly quickly.

If your oem wiring harness also has the "resistor wire" inside (many of those rigs used the earlier wiring harness), then ya don't even need to hot wire it, just connect the wire from the breaker points to the negative side of the coil and go! If the wiring is botched, then just use the hot wire technique to make some fire! With the resistor wire, you do not need to add a ballast resistor in the ignition "run" circuit.
 
Alright. Well I went out a while ago and took the spark plug out and put the plug wire on it while it was out of the engine and cranked it over and the plug was sparking across just fine.
 
So double check your distributor stab! At this point I'll wager it's 180* out. But just put the crank at tdc on #8 compression stroke again! Then see which cap terminal the rotor is pointing too. Make that one #8 plug wire and completely re-wire the cap...again...the firing order is 1, 8, 4, 3, 6, 5, 7, 2. And the distributor turns clockwise! So the plug terminal in the cap that is to the right of the #8 terminal is #1!

Don't forget...thus is not a chryfordrolet!
 
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