1965 L79 Just started back firing

[Forrest Gump]

They’re a good brand but coils can give up. Easiest just to try another coil.
It’s when you said it runs okay for a few minutes then starts to misfire points toward something getting hot and starting to fail.

 

[teamzr1]

A couple of weeks only and I use Shell super or Esso Supreme.

At least from the look via photo, I would drain out and not use
Rust and some water ?

 

[Mr. Cricket]

At least from the look via photo, I would drain out and not use
Rust and some water ?

No it's crystal clear, the photo I uploaded looks deceiving. Will pick a coil up today put the wheels back on and give it a try later.

 

[62 C1]

Also check your manifolds haven't com loose. The header to the exhaust connection is simple to check and can shake loose and cause backfires. Less likely to have come loose but worth check is the header to head connection.

Going back to the distributor also get an airline on it and blow out dust. I have seen rust dust caused by previous condensation cause internal shorts.

 

[62 C1]

Also coil you can check out the high low circuits against the published spec with a multimeter when cold and then put the body of it in freshly boiled water and check the warm readings

 

[Mr. Cricket]

Also coil you can check out the high low circuits against the published spec with a multimeter when cold and then put the body of it in freshly boiled water and check the warm readings

Ahh just seen this having slammed the garage door shut and sulked away.

Manifolds both tight with no movement or gaps.

Got the wheels back on and the car back on the floor so removed the dizzy cap and checked for any slack in the dizzy - none. Used a warm air blower on the dizzy to make sure there was no moisture beyond what the eye can see. Removed the air cleaner and could see that the carb was delivering fuel as I would expect when pressing the accelerator but gave the carb a couple of taps with a rubber mallet anyway. Changed the Pertronix flamethrower coil for one I had already. Cranked it and nothing.. I knew if I'd have pressed the go pedal to the floor and held it, it would likely have spluttered into life but by then the new battery that I fitted on Saturday was getting week. That's now on trickle charge and I'll try the coil test tomorrow. The points are electronic and probably Pertronix as well but nothing showing to confirm. I've seen mixed reports on the Corvette Forum about these so maybe worth changing?

Having moved here last year I've been scoping out garages and found one that works on older stuff so dropped in today and delivered a sausage n egg McMuffin and asked if he would do a home visit if I don't get it done soon. The offal, grease & cheese mixture was too much to resist and he said he would at weekend. I would though prefer to get it done and learn a bit on the way if possible..

Cheers,

Stuart

 

[Mad4slalom]

Ahh just seen this having slammed the garage door shut and sulked away.

Manifolds both tight with no movement or gaps.

Got the wheels back on and the car back on the floor so removed the dizzy cap and checked for any slack in the dizzy - none. Used a warm air blower on the dizzy to make sure there was no moisture beyond what the eye can see. Removed the air cleaner and could see that the carb was delivering fuel as I would expect when pressing the accelerator but gave the carb a couple of taps with a rubber mallet anyway. Changed the Pertronix flamethrower coil for one I had already. Cranked it and nothing.. I knew if I'd have pressed the go pedal to the floor and held it, it would likely have spluttered into life but by then the new battery that I fitted on Saturday was getting week. That's now on trickle charge and I'll try the coil test tomorrow. The points are electronic and probably Pertronix as well but nothing showing to confirm. I've seen mixed reports on the Corvette Forum about these so maybe worth changing?

Having moved here last year I've been scoping out garages and found one that works on older stuff so dropped in today and delivered a sausage n egg McMuffin and asked if he would do a home visit if I don't get it done soon. The offal, grease & cheese mixture was too much to resist and he said he would at weekend. I would though prefer to get it done and learn a bit on the way if possible..

Cheers,

Stuart

bit of a long shot but could it just be being obstreperous because you have taken it away from the sunny west country and removed it T’ North ! ?
Hope you get it sorted, reckon it will be something simple if she was running fine. Had a coil breaking down on a “78 “ years ago , that would just back fire and stop when it got hot.

 

[62 C1]

did you find the problem? Always good to know the solution.

 

[Mr. Cricket]

bit of a long shot but could it just be being obstreperous because you have taken it away from the sunny west country and removed it T’ North ! ?
Hope you get it sorted, reckon it will be something simple if she was running fine. Had a coil breaking down on a “78 “ years ago , that would just back fire and stop when it got hot.

ahh yes the frozen north..

The garage is currently 3 deg C but the other two are fine. Air Conditioning being fitted next week will cure the frigid temps and that's the benefit of owning a mechanical company.

So I tested the coil and should be getting 1.2 - 1.4 ohm on the primary and 6.5 - 9.5 on the secondary but actually got 0.7 & 09.05 so deduced the coil is fubar. Couldn't find one locally as I wanted to match the Pertronix flame thrower so ordered one from USA that came today and I just fitted it. Now the brand new battery I fitted two weeks back is very low so that is now on charge ready for a go at it later after a CCCUK committee meeting starting in half hour. Bet y'all jealous of my Friday night eh?

 

[Mr. Cricket]

did you find the problem? Always good to know the solution.

Hopefully know later and I'm 50/50 on it being as simple as a new coil

 

[Oneball]

Bit late but Aldon in Brierley Hill sell the Flamethrower coils and also the ignition modules etc.

 

[Mr. Cricket]

Committee meeting over, new flame thrower, fully charged battery and ZILCH. Cranks but nothing. Going to pull all leads tomorrow and check them. Can I check continuity on leads or not? Will pull the Pertronix points as well. Reminder, this was running sweet then did a 180??

 

[teamzr1]

Does the clutch pedal have a safety start switch ?

Have you checked vacuum and timing, as GM specs show ?

 

[Mad4slalom]

Committee meeting over, new flame thrower, fully charged battery and ZILCH. Cranks but nothing. Going to pull all leads tomorrow and check them. Can I check continuity on leads or not? Will pull the Pertronix points as well. Reminder, this was running sweet then did a 180??

that was disapointing . , it womt be leads, recokon it s more likely something in the pertronix thingy in the distributor. Have heard of them packing up on the vw forum when i fitted one to my buggy .

 

[Forrest Gump]

Check that you’ve definitely got fuel in the carb - operate the throttle and see the fuel squirt. Maybe the fuel pump has packed up.
Check if you are getting a spark when you crank it - pull an HT lead and test with another spark plug grounded.
If no spark, check you have 12v at the coil. You know the coil is good so must then be the dizzy itself at fault.

 

[Oneball]

Is it misfiring (doesn’t always ignite the cylinder) or backfiring (loud bang from the exhaust)?

 

[Roscobbc]

I use a MSD Billet distributor......perhaps acknowedged as being the best available.......although perhaps not in one respect. They seem to have a weak spot - the centre fixed carbon electrode in the dizzy cap. When running a high output MSD ignition system too the spring tension on the rotor arm needs to balance having sufficient sprung pressure to allow efficient transfer of the significantly increased energy from the MSD HT ourput....... yet not have too much 'wiper' pressure to prematurely wear the carbon electrode and creating 'arcing' within the distributor cap (and a continual reducing spark transfer). Not saying that's your issuse but if using the Pertronics unit perhaps worth checking out dizzy cap?

 

[Mr. Cricket]

Does the clutch pedal have a safety start switch ?

Have you checked vacuum and timing, as GM specs show ?

View attachment 20877

that was disapointing . , it womt be leads, recokon it s more likely something in the pertronix thingy in the distributor. Have heard of them packing up on the vw forum when i fitted one to my buggy .

my thoughts too so will pull that today

 

[Mr. Cricket]

Is it misfiring (doesn’t always ignite the cylinder) or backfiring (loud bang from the exhaust)?

It started back firing from the exhaust when it started to warm up. Now it won't fire at all

 

[Mr. Cricket]

Check that you’ve definitely got fuel in the carb - operate the throttle and see the fuel squirt. Maybe the fuel pump has packed up.
Check if you are getting a spark when you crank it - pull an HT lead and test with another spark plug grounded.
If no spark, check you have 12v at the coil. You know the coil is good so must then be the dizzy itself at fault.

yes I can see fuel flowing into the carb from the drivers seat