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Intermittent spark??  Rating:  Rating
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 Posted: 08-19-2005 04:56 pm
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Joel
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Ok, I thought I had carb troubles. But, it's not a fuel problem (yet) it's fire.

The car was running berry berry poorly. Actually, according to my mechanic friend, only on 2 cylinders at idle. We pulled the plugs and two of them were barely putting out any spark.

The plug wires were pretty mickey moused by the PO(S). So, yesterday I put new plug wires on (thank you Greg!!). Now I don't have to heel and toe to keep the car running when I stop. . .nice. Now the car will actually idle quite nicely most of the time.

But - it's still not 100%. Same symptoms just to a lesser extent. Idles a little rough, hesitation on acceleration at low RPMs (kind of stuttering actually), etc.

I have not pulled the plugs yet and checked but I think I'm still going to find a weak spark on cylinders 1 and 2. Before when I pulled the wires with the car running - on 1 and 2 the car didn't run any differently!!

The car has pertronix. What do you think I should check/replace next? Distributor cap looks to be in decent shape. I cleaned the contacts a little but they look pretty good.

Ideas?

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 Posted: 08-19-2005 05:38 pm
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Mark Rosenbaum
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Sounds to me like you had/have two problems: first, bad plug wires, which you fixed; and second, something wrong with the front carburetor, which remains to be addressed.  When were the carb balance and mixture adjustments last made?

On the other hand, problems with the rotor and distributor cap are not always easy to spot, so if you have new spares on hand, you can try substituting them (both at the same time) for the parts currently on the car.  Bad plug wires allow the development of very high voltages inside the distributor, and this can cause carbon tracks which are often hidden from view.  And humidity inside a distributor, whether or not combined with such carbon tracks, can cause a broad assortment of peculiar problems.

If you were still using points, I'd suggest checking the points gap for all four dist. cam lobes, but you mention having a Pertronix.  As a fairly remote possibility, perhaps two of the magnets in the rotating part have broken or are covered with something that would affect the device's operation, thus giving a weak or untimely spark. 

You may also have low compression on cylinders 1 and 2.  If you haven't done a compression test recently, it's certainly in order now.

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 Posted: 08-19-2005 06:21 pm
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Joel
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ok. i'm definately thinking along the same lines. i was thinking about getting a new rotor and dist cap - they're cheap and i can keep the old ones as spares. the car is actually driveable now so i'm pretty happy. before it was a real PITA. also the motor is pulling MUCH stronger now (funny what adding a coupla cylinders can do for you).

we did test the compression when we realized that two cylinders didn't seem to be running right - thankfully all was well. i wasn't running the test (i was cranking the car) so i don't know what the numbers were - but they were fine.

re the front carb - i don't know when they were last balanced/adjusted. actually the carbs are one of the few things that intimidates me a little. . . i had a stromberg on an old mercedes i used to drive. auuughhh.

anyway, i checked the fluid level in the carbs when first got the car - the front one was dry. so i topped it off with fluid and it seems to be ok. not losing any fluid and has pressure on the plunger, good seal, etc. also, we sprayed around the carbs looking for vacuum leaks and didn't find any - so that's a positive sign as well.

right now, i'm still convinced that it's a spark problem. tonite i'll pull each plug wire then each plug individually and check the spark.

but, i think the 1st step is probably to get the rotor and cap. i guess i'll cruise thru the postings - i'm sure i saw someone describe how to pull the distributor somewhere.

thanks for the comments. sorry i couldn't make the margarita party on saturday. i was busy monkeying with the car and doing house stuff. perhaps next time the car will be running right and i can make it up. i'm also going to miss the get together here in SD. i'll be in Japan that week. i was really hoping to see some other cars.

Last edited on 08-19-2005 06:22 pm by Joel

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 Posted: 08-20-2005 12:03 am
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Joel
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update: after driving the car to work today. the problem has returned. and is almost as bad as before. i have not started screwing around yet.

something vibrating loose that i'm retightening up everytime i pull the dist cap and fudge around with the wires?

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 Posted: 08-20-2005 05:40 pm
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Judson Manning
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Joel,

If two cylinders are running poorly, I'd again look at the ignition system.  I've seen too many Pertronix installed wrong.  Check where Pertronix gets +12V, your's may be wired to the back side of the ballast resistor and only getting 8VDC.

Judson

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 Posted: 08-20-2005 07:25 pm
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Joel
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Hey guys.

The system is NOT pertronix as I had thought. It's actually a brit system - Lumenation. And I goofed - when I pulled the dist i seem to have broken off one of the little fans that interrupts the light source (don't ask). I'm betting that one of those leetle dohickeys isn't easy to find here. So, i'll probably be ordering a new pertronix system - I think I need the coil too - as I think the Lumenation system has some kind of a coil that they claim is only supposed to be used w/ their system.

I'll be reading up on it and let ya know.

Honestly, it might make me feel better just to buy the damn pertronix and do it myself. . .:-)

Thanks for all the comments. I'll keep ya posted.

Joel

Last edited on 08-20-2005 07:27 pm by Joel

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 Posted: 09-01-2005 04:15 am
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Joel
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Ok, some of the discussion for this post is in the ditribution of distributor probs thread.

Bottom line is my baby is running again!

I busted the edge of the dist where the clamp holds it on. But there's still enough to hold it in place.

I found tdc (or close anyway) from the marks on the cam gears. I found that the pulley marking the timing isn't original. The new one has a nice 'scratch' to mark the timing - obviously an upgrade from the PO(S).

I removed the Luminination system and put in a new pertronix with new coil, cap, rotor, wires - the whole shebang.

After cranking a couple of times I realized it wasn't right. I had the wires going clockwise instead of 'anti-clockwise'. Anyway, rectified that and cranked again. I had checked which plug the rotor was pointing towards but she'd spit and maybe run for a second or two but wouldn't go.

So, I got very scientific and rotated the dist one way to see what would happen. Sure enough she fired. So I turned it until she would idle and then fiddled with it with a timing light.

Now, she idles. She wouldn't idle before so I'm happy. She still seems to be missing a bit. But, I need to gap the plugs and make sure everything is tightened down and do the timing when I have an extra pair of hands. So, I'm sure it will be fine for now.

And, now I've got other problems I'll post in other threads - gas tank discussion anyone???

Thanks for all the great posts everyone - much better than trying to get by with just the manual.

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 Posted: 09-16-2005 01:00 am
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Joel
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Back to the drawing board. With the new wires, plugs (gapped at 40-45), rotor, cap, coil and pertronix there is a MARKED inprovement. However, it's still not right. The car will idle but if I pull wires 1 and 2 while she's idling - no change. ie, it's not firing on the front 2 cylinders.

The acceleration is much better now - but still stutters from 1500rpm to 22-2500. I'm guessing that's about the point where she starts to get enough juice to fire the 2 front cylinders and the stuttering is intermittent firing.

Wiring to the coil seems to have an extra wire. . .I have not traced them all down b/c they are all in the harness.

On the positive side (+) there is one red wire from the pertronix. One that looks like it was red (before being wrapped w/ electrical tape - the original plastic is quite soft - maybe it got very hot once??) and goes thru the firewall. The other wire is white and goes into the wiring harness up by the engine. THe other wire (white with black trace) also goes to the harness and goes to the negative side of the coil.

The negative side of the coil has the aforementioned white with black trace that goes to the harness. ANd, the black wire from the pertronix.

The previous Lumination system had a very expertly (NOT!) jury rigged wire that went from the fuse box over to the heat sink that was mounted on the firewall - part of the Lumination system that I completely replaced with Pertronix.

So - it's a little better but still not right. Ideas?

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