Weak Spark???? Car Sounds Like a Tractor!

[Satellite72]

So due to my #5 and #7 plug wire/boot touching my headers, dispite putting a plug wire sock on them to keep it from melting, I decided to go and buy two generic plug wires with 90 deg boots on them at Autozone to fix the problem. So I crimped the distributor terminals and put them back on the car. I then took it for a ride down the road... at first everything was running great but no more then a mile down the road I could feel that it dropped a cylinder, and then it felt like one or two more dropped. I just barely limped back home on what seemed like 4 cylinders. After inspecting the wires it did look like the rubber on the #7 wire was a little bit loose... sounded at the time like it might be the culprit.

Now today, I got a couple more terminals and re-cut the wires back some and crimped the new terminals. Just to be sure, I checked the resistance on both wires and they checked out fine. After putting them back on, we cranked it up to give it a test.... it still sounds like a darn tractor. I pulled those two wires one at a time as it was running and they were both sparking, so I know that it is at least getting down to the plug. I also felt around on each header to feel if some were hot and some not (determining which fired or not). I felt like some were hotter then others, but they all were still warm kinda hot to the touch and by that I mean even some of the otherside of the block. This makes me wonder if something I've done is causing a weak spark all around?

Anybody got any suggestions? Thanks.

 

[70rr-brian]

What is you ignition system? Stock? MSD? I assume if stock being a 72 you at least have electronic ignition? Sounds electrical in nature.

 

[Satellite72]

The ignition system is stock 72 model stuff including electronic ignition. I know its surely getting plenty of fuel and passing off lots of rich un-burned fuel at that... my wife was complaining about the exhaust smell on my cloths when I walked in the house last night. lol.

 

[67 coronet]

check your timming and firing order just to be sure.timing can cause fuel smell in exhaust.several things can cause week spark,coil going bad,pickup going bad,and module going bad.hard to say.mechanical where can cause what you are talking about as well.(in the valve train)

 

[Satellite72]

I know for sure that the firing order and plugwires are in there correct locations and that the distributor is still tight in its original position, so I would think that the timing hasn't been moved accidentally. I've never checked a coil before, so If I were to check the coil, what kind of volts should I expect out of the coil?... and would I need to check the positive post of the coil or the plug-to-distributor connection? Thanks again.

 

[69Bee]

Coil Spark:

Blue = Strong spark

Orange = Weak spark

I had an aftermarket coil go out on me once. I spent hrs trying to figure it out, went back to the barracks to sleep on it, and around 2am, decided to try the original coil, and bingo, worked fine.

 

[tpodwdog]

Coil Spark:

Blue = Strong spark

Orange = Weak spark

I had an aftermarket coil go out on me once. I spent hrs trying to figure it out, went back to the barracks to sleep on it, and around 2am, decided to try the original coil, and bingo, worked fine.

YA DONT REALLY NEED TO GET ALL TECHNICAL WITH OHMS AND VOLTS AND SUCH....DO THIS :

pull off a plug wire from ANY spark plug
shove a screwdriver ...preferably a #2 philips...in the boot
ground the screwdriver to the valve cover or a good ground....start the car.....
if its orange,,,,,weak coil
if its blue....good coil...and your prob MORE THAN LIKELY ...is somewhere in the dizzy....or the module!

ORRRRRRRR.....pull the boot off of a spark plug....shove an old spark plug in the boot...and ground it to the valve cover or a good ground and watch the spark jumping.

DO NOT REMOVE A PLUG FROM THE ENGINE..... AND START THE ENGINE....use an old plug.

orange = bad coil
blue= good coil

 

[Satellite72]

Ok, thanks!... That sounds easy enough. I'll try that tommorrow and see. I hope it's an easy fix like the coil.

 

[HEMI-ITIS]

Also,remove ditributor cap and check for cracks or traces of crossfireing.

 

[Satellite72]

Well, I think I can rule out a weak spark now... when I pulled off the plug wire I actually got it to ground to the valve cover through the rubber plug boot. The spark appeared to be blue, seemed to be a consistent pulse and was about 3/4" in length when grounded.

I had to get some work done out in the garden yesterday, so I didn't have that much time to fiddle with the car. These where my findings though; It still is running weak and sounds like some cylinders are hitting less than others. I'm also seeing that it won't hardly keep an idle without the choke on (manual). It would want to die when I pushed the accelerator (this is only a problem when its been running for after 15 sec). I'm going to assume for the moment that the fuel pump is doing its job... the fuel line felt firm when the car was running and soft when not running. Lastly, I could spray some starting fluid into the carb and it would pick up rpm's and run better till it was burnt up.

Does that sound like a restriction in the carb causing it to run lean?.... maybe the float is having issues? I can smell exhaust, so that kinda confuses me into wondering if it is rich or lean.

btw this is a 1405 Edlebrock, 600 cfm on a 318.

Thats the verdict for now... as always I'm happy to get some input. Thanks for all your previous help.

 

[tpodwdog]

did you pull the cap and inspect it like HEMI-ITIS suggested? sure sounds to me like its in the distributor... either cross firing... or timing.

i had a ford truck . 6 cylinder. i was driving it on the interstate and the more gas i gave it ,,,,the slower it went. it turned out to be the drive gear on the distributor turned on the shaft and sheared the little roll pin that held it on. i dont know if yours has a roll pin. maybe someone that knows small blocks can verify that... if it does have the roll pin holding the drive gear on.....pull the dizzy....and inspect it !

 

[Satellite72]

Topdog... your trip in your truck does sound familiar to when it first started this mess. I meant to add that I did in fact pull the cap off the dizzy to inspect what was going on. I couldn't find any cracks in the cap and the terminals appeared clean. I also took off the rotor and wiped it down (it seemed fine too). Even though I didn't use a feeler gauge, the relucter and pick up coil gap looked correct and they were both clean as well.

I think I may replace the cap and rotor just for the heck of it... then I'll borrow a timing light to see if the timing has shifted.

I wouldn't have thought about a drive gear malfunction... thanks for the tip... I'll look into that one as well.

 

[67 coronet]

if the car runs better with choke closed or when you spray carb spry in it then you either have a vacuum leak or are straving for fuel.put your hand over the carb while it is idleing.if it smooths out or reves up then you probly have a vacuum leak.if that happens,try spraying around the out side of the carb base,and along the intake(where it bolts to the heads)if the car runs smoother,you found your leak.

 

[1971RR]

So due to my #5 and #7 plug wire/boot touching my headers, dispite putting a plug wire sock on them to keep it from melting, I decided to go and buy two generic plug wires with 90 deg boots on them at Autozone to fix the problem. So I crimped the distributor terminals and put them back on the car. I then took it for a ride down the road... at first everything was running great but no more then a mile down the road I could feel that it dropped a cylinder, and then it felt like one or two more dropped. I just barely limped back home on what seemed like 4 cylinders. After inspecting the wires it did look like the rubber on the #7 wire was a little bit loose... sounded at the time like it might be the culprit.

Now today, I got a couple more terminals and re-cut the wires back some and crimped the new terminals. Just to be sure, I checked the resistance on both wires and they checked out fine. After putting them back on, we cranked it up to give it a test.... it still sounds like a darn tractor. I pulled those two wires one at a time as it was running and they were both sparking, so I know that it is at least getting down to the plug. I also felt around on each header to feel if some were hot and some not (determining which fired or not). I felt like some were hotter then others, but they all were still warm kinda hot to the touch and by that I mean even some of the otherside of the block. This makes me wonder if something I've done is causing a weak spark all around?

Anybody got any suggestions? Thanks.

You sure your wires arent crossfiring? If you got a spark through the rubber boot I would upgrade my wires. I got some cheap wires once. At night, there was a very cool light show under the hood with the wires arcing across each other. And this was with wire separators installed. Was pretty to watch but ran like poo.

 

[Satellite72]

Problem fixed!!!

I originally overlooked any fuel problems because it was clearly getting some fuel anyways.... the problem though was that it wasn't getting enough. After looking over the fuel system, I decided to change out the fuel filter... that was the problem. I had let my tank go pretty low and of course the fuel pump sucked a lot of tank sediment into the fuel filter resulting in a lack of steady fuel delivery. I still don't completely get it, but nevertheless she's back up and firing on all 8!

Thanks for all the help!!

 

[tpodwdog]

Wooooooooohooooooooooooooooooooooo....i love a happy ending!