I wonder if anyone can help me resolve an issue with my truck.


I have a 1968 Ford F100 unmodified 6 in line 300 CID with a 1 BBL Holley 1940 carburetor. A while ago I installed a Pertronix Ignitor II and I noticed that sometimes when I start the truck it makes a single POP sound from what it sounds like the distributor area, it happens as soon as the ignition key is turned. The truck starts, idles and runs fine, but I noticed that when the sound happens it takes slightly longer to crank.


The conditions have to be right for this to happen, it appears it has a greater chance to do so when the weather is hot and the truck has been parked for a shorter period of time after a short trip.


The sound almost appears what would be an electrical short, but I am not sure. It is not coming from the carburetor, but from the driver side of the engine bay.


I opened the distributor to look at the Petronix module and I noticed there is a black smudge on it, I'm not sure if that is indicative of a short of some kind, but I thought I'd attach a picture in case it can help determine what is happening.


Any help in resolving this issue would be appreciated.

 

Could there be arking?
It pops before you crank it, correct?
Maybe try to look under the hood when it's dark outside.
The black smudge is where the rotor is contacting the cap

 

Do you mean it cranks slower? Or that it cranks longer before starting?

 

@JEFFFAFA, it cranks longer before starting, not slower.


@TeachNlive4ever, the tricky thing is that it doesn't do it all the time and when it happens it's mainly during the hotter part of the day and I don't have a garage. Maybe I'll take it over to my girlfriend, she has a garage. The problem is when I show up at her house I end up doing a bunch of chores and fix it projects which take up most of the day.


Actually I'm beginning to think it's not the distributor, but maybe the truck vapor locks and when I start it, somehow it pops at the fuel pump which is right next to the distributor.

 

The silicone sealer is not allowing crankcase fumes to escape from under the cap. They are explosive. Marine engines have special flame arresting screens to keep a flame from leaving the distributor housing.

 

Looking at your pic. it may also be in need of a new dizzy cap. What's the reason for putting silicone on the dizzy cap?

Clean all that stuff off of the dizzy plus remove the carbon build up from the rotor best to replace it along with the new dizzy cap.

Ps lady friends with a house always want their men friends to come over as fix it men.
Once they know you know how to do repairs they have a never ending list..

Been there do that as that what they think of us is Mr. Fix it Man:

Orich

 

I think Kenny is on to something here. Back when I was in High School I knew a kid that claimed his truck had started when the key was cycled to the run position. For this to happen the engine would have to stop at exactly the right spot to have compressed fuel and air in the cylinder. Then the key is turned to the run position and the ignition will spark.

 

Kenny might be on to something. But because it takes longer to start, AKA fire, sounds like the spark isn't happening the 1st "X" amount of revolutions. Like it's coil related. Hey OP, pull the coil wire out of the coil and see if some oil leaks out of the coil.

 

The material on the edge of the housing is dielectric grease, I had put it there thinking maybe the current inside the distributor was arcing and causing the noise at startup. I didn't know that cap had to breathe the crankcase fumes out, so I will clean it all up and clean the rotor and the cap contacts and report back. Thank you all that took the time to respond.

 

Also check that the wires our not rubbing the inside of the dizzy side case wall. Double check that screws & nut connections our tight an the ground wire is good.

Also the dizzy cap inner carbon button that rubs on the rotor is not cracked any.
Orich

 

I did a tune up gotta bad coil. Drove me crazy assuming all the parts were good. Can do many things in and pop/bang is one

 

I think I was able to resolve the problem. It was a combination of things.

First off, the battery was bad so I changed it with a new one and after I did so, the loud “pop” at startup disappeared. However, I noticed there was a more muffled sound when starting the engine which was probably masked by the louder one, which sounded to be more of a backfire from the carburetor. While trying to resolve this, I came to thinking that I had gotten in the bad habit of running the truck with a gas tank between ¼ and ½ full on a regular basis, which I suspect caused a condensation accumulation in the tank. So I tried to see if filling the tank completely and adding some water removal additive would have any effect and it seems to have eliminated the backfire from the carb at startup.

I also bought a new gas cap since the old one was not sealing properly and maybe that helped some.

Finally, my Pertronix went out right around the same time, so I got a new one and the truck drives much differently than before.

I can’t peg what of what I did helped in getting this fixed, but I thought I’d post a follow-up to this thread in case anyone has the same issue, for a list of things they can try.

Thanks to everyone who responded to me and I hope this post can help anyone who develops the same issue.

 

Glad to hear the good news.

 

In regards to the Pertronix module quitting, did you have the Pertronix's ignition hooked up with the original resistor (AKA Pink) wire? Or did you hook up the ignition with out a resistor?

 

Without the resistor. You think that had something to do with it going out?