View Full Version : Evil Electronic Gremlin

11-15-2004, 08:23 AM
What is the most likely gremlin stinking up my truck’s electronics? I cannot get No. 1 & No. 7 spark plug wires to spark the plugs.

289 V8
new copper core spark plug wires
new plugs, gapped correctly
new coil
new ballast
new distributor cap
new points and condenser, gapped correctly
engine timed correctly (or as close as I can get it from the “coil” wire – N0. 1 not working)

11-15-2004, 08:29 AM
You mentioned that you've changed everything but the rotor. ;) They have a bad habit of the contact loosening. Was it doing the same thing before you changed all the goodies?


11-15-2004, 09:35 AM
Hi Sonny,

Thanks for replying. I forgot to mention the rotor is also new. I don't recall exactly what was wrong before but I do remember it ran poorly. The thing just has ne stumped! Maybe it's a bad distributor!?!

11-15-2004, 10:25 AM
Is this a Delco distributor or a Prestojunk?
To be a "Bad Distributor", you'd have to have a really slopped out shaft, cam lobes for 1 & 7 gone, or maybe - maybe - a bad ground to the plate the points mount to. There's no other mystical, voodoo parts of the "distributor" that you haven't replaced already, given the list you put up. Distributor's just a hunk of metal with a shaft spinning in it.[:0]
Do you have any of the plug wires bundled together? Did you change all this stuff to cure this problem OR did this problem only start once you changed everything? Isn't this the truck that just had it's Pertronix module retrofitted with the points?[?]

Miscreant at large.

11-15-2004, 11:41 AM
It's a Delco.

Good advise. I will check the ground. The engine (distributor included) only has 96K original miles on it. I guess it's possible for the cam lobes to be gone on 1 & 7!?!

I've been chasing this problem for quite some time - that's why there are so many new parts:-)

No, no Pertronix in this truck. I've owned it since 1978 with points and all.

11-15-2004, 04:27 PM
Pop the cap off, remove the rotor and wiggle the distributor shaft to and fro. It may well give a tiny bit but it shouldn't SLOP back and forth. If it did, that would mean the bushings in it were shot.
Is this a "window" type Delco or non-window?

Miscreant at large.

11-16-2004, 07:40 AM

I have tried to wiggle the distributor shaft around and it doesn't have any slop. It's a non-window Delco.

11-16-2004, 11:29 AM
OK, well, I was only being facetious about any cam lobes being gone. I doubt that could ever happen under normal circumstances. I'd like to hear exactly how you're determining that there's no spark to 1 & 7.Is this with the plug wire pulled off and lying close to metal, with the plug out - wire attached - and laying on the engine .... Running or just cranking? [?]

Miscreant at large.

11-16-2004, 11:35 AM
When I put the timing light on 1 and also 7 the light will not flash. It does flash on all other spark plug wires. 1 & 7 plugs are wet with fuel all the others look okay. Both 1 & 7 spark plugs spark next to a ground resting on top of the engine while cranking.

11-16-2004, 12:34 PM
Try a continuity check on the two bad plug wires. It's possible new wires could come with an 'open' in them. Try the same with the plugs, ditto. Check continuity in other wires to make sure your set-pu is working.

Tom Bredehoft
'53 Commander Coupe
'60 Lark VI

11-16-2004, 01:08 PM
Man-o-man you DO have some gremlins. But I'd have to say that the problem is that your gremlins are mechanical. The timing light spark test isn't very reliable and the reason why is, the timing light shows actual spark plug firing, not high voltage electrical energy in the wire going to the plug. What's happening in your case is, fuel is being drawn in, fouling the plugs immediately, so the timing light would show no spark, (I'll bet they're Champion plugs too). The proper test is just like you did, it must be done with the plugs dry, serviceable and laying against a ground on the engine. If you get a healthy blue spark, the cylinder should be firing properly. If it's a yellow spark, it's a good indication of a weak/bad condenser or even the coil, (a problem somewhere in the high voltage side). The whole secret to it is, the plug has to be fired at the right time.

Have you done a compression check? If you're getting a good blue spark when you ground the plugs on the engine, it's a good indication that you don't have all the things that have to be happening and aligned at the right time in cylinders 1 & 7. That's why I'm saying it's a mechanical problem in the valve train timing itself, (timing gear, distributor drive gear, etc....) I'd NOT expect to find a problem with the engine cam lobes on 1 & 7 themselves, although it IS an outside possibility. I'd definitely recommend a precise TDC check using a dial indicator.

Just thought about One more thing to look at...... What does the timing look like with the car running? The reason I ask is to make sure that the distributor is installed correctly. Yep, I know it sounds silly, (because it IS running right?). BUT, I've done this myself, in a hurry or not paying attention. Dropping that distributor in our Stude V8 with the engine in can be a real ball buster. You can drop it in a tooth off, re-assign the wire positions on the cap, (move 'em "forward" or "back" one hole), and the car will run. The problem is that it runs like chitt, especially if it has a weak valve train, weak compression, etc., and you can forget timing it by the timing mark.


12-06-2004, 02:55 AM
Have you made any progress on this problem yet?

I'm wondering if perhaps you somehow managed to get the #1 and #7 wires interchanged, which would cause both plugs to fire at the wrong time.

Can I suggest you double-check the firing order is right, do a compression test on the affected cylinders, and try new plugs in those holes?

There is a little gizmo you can make that may prove useful when troubleshooting a problem like this. Get a block of hard plastic about 3/8" thick, about the size of business card. Drill a 1/2" hole in the middle of the flat side. Then from each long edge, drill about a 1/8" hole to intersect the big hole. You will tap these holes for 10-24 screws, so use the right tap drill size for 10-24, obviously. Take a pair of 10-24 x 1 1/2" screws, grind a point on them, and run them into the holes you've tapped, so the points face each other with a gap of a little less than 1/4". To one of these screws, solder a short length of spark plug wire with a terminal to fit your spark plugs. To the other, a short length of wire having a spark plug terminal on its end; the actual fitting off the end of a spark plug (find an OLD plug with a brass terminal you can solder). Slip some fuel line tubing over the exposed part of the screws for safety's sake.

You've just made a small spark gap that can be inserted in series with any spark plug of your choice. If there is spark in the wire with the engine cranking or running, you should see (and hear)it at the gap. And if the plug is fouled, often this will help the engine actually run better by allowing the coil voltage to build to higher value before any spark current flows. (Quite often, an engine with a spark miss will pick up and run smooth when the wire to a fouled plug is pulled just a little way off the stud.)

Hope this helps,

Gord Richmond, within Weasel range of the Alberta Badlands