Okay maybe it’s not a fuel delivery issue

[Doug&Deb]

I thought my problem was fuel related since turning on the electric pump seemed to help. Tonight that helped but not completely. When I got home I let it idle for a while and it seemed to occasionally cut out slightly. I’m starting to understand how Donald feels. This isn’t fun right now. By now I should be driving the wheels off and I’m leery of going anywhere in it. My diagnostic skills suck so I’m searching. Plugs and wires are very recent. Gap is correct and dwell is correct. All connections are clean and tight. Cap and rotor are also almost new as well as coil points and condenser. What am I missing. Also compression is 90 across the board. Not ideal for 13,000 miles on a rebuild but that’s another story.

[Hickory]

I never trust these new condensers. I would try another just because they are junk and they are cheap. I have found a lot of fuel problems end up being ignition issues. Make sense. Improper ignition causes different vacuum which is how a carburetor operates so some times they are related.

[Sniper]

Hook up a tach to the coil and see if it spazzes when you hear the hiccup.  Sounds like an intermittent electric open to me.  You can run some temporary jumpers from the battery - post(assuming still 6v positive ground) to the coil - post, if that cures it the issue is between the coil thru the ignition switch to the generator.  Though if it were on the gen side of the ignition switch I'd expect the lights to flicker in time with the hiccup.

 

If the jumper does nothing then you will need to do a very close visual inspection of the lead from the coil to the points, as well as the wiring inside the distributor as that circuit might be intermittently shorting out causing the problem.

[kencombs]

1 hour ago, Hickory said:

1 hour ago, Hickory said:

I never trust these new condensers. I would try another just because they are junk and they are cheap. I have found a lot of fuel problems end up being ignition issues. Make sense. Improper ignition causes different vacuum which is how a carburetor operates so some times they are related.

 

That's one of the reasons I opted for the slant six mod for my build.   80ish Dodge PU slant six distributor donated its innards and it will be mated to a GM HEI controller.

 

No resistor or condenser needed, with the right 12v coil

[Sniper]

2 minutes ago, kencombs said:

That's one of the reasons I opted for the slant six mod for my build.   80ish Dodge PU slant six distributor donated its innards and it will be mated to a GM HEI controller.

 

No resistor or condenser needed, with the right 12v coil

 That swap is on my list, actually I have all the parts, just haven't done it.

 

Link to a thread on how to do it

 

https://www.jalopyjournal.com/forum/threads/mopar-flathead-6-distributor-upgrade-48-desoto.653565/

[kencombs]

1 minute ago, Sniper said:

Hook up a tach to the coil and see if it spazzes when you hear the hiccup.  Sounds like an intermittent electric open to me.  You can run some temporary jumpers from the battery - post(assuming still 6v positive ground) to the coil - post, if that cures it the issue is between the coil thru the ignition switch to the generator.  Though if it were on the gen side of the ignition switch I'd expect the lights to flicker in time with the hiccup.

 

If the jumper does nothing then you will need to do a very close visual inspection of the lead from the coil to the points, as well as the wiring inside the distributor as that circuit might be intermittently shorting out causing the problem.

Or, hook a timing light the coil output lead.  Watch closely for a pattern miss.   If not there, try each plug wire in turn.  

 

Best case, find a local car nut with an old fashioned ignition scope.

[kencombs]

1 minute ago, Sniper said:

 That swap is on my list, actually I have all the parts, just haven't done it.

 

Link to a thread on how to do it

 

https://www.jalopyjournal.com/forum/threads/mopar-flathead-6-distributor-upgrade-48-desoto.653565/

Mine is all back together, but the engine has not been installed.  Later this summer, I hope.

 

Got to remember to finish the full flow oil filter plumbing before starting too!!

Edited April 21, 2023 by kencombs

[Sniper]

9 minutes ago, kencombs said:

Best case, find a local car nut with an old fashioned ignition scope.

 

They make a scope adapter that allows you to use your laptop to do that.  Been mulling over getting one, though I have an O'scope I could use as an ignition scope.  Hmm, things to think about.

[Doug&Deb]

I’m beginning to suspect the coil since the problem only occurs after the engine has been at operating temperature for a while. It’s fairly new also but with quality being what it is lately who knows. I will try the other things suggested though. 

[Pete]

9 hours ago, Sniper said:

 

They make a scope adapter that allows you to use your laptop to do that.  Been mulling over getting one, though I have an O'scope I could use as an ignition scope.  Hmm, things to think about.

 

Sniper, do you have a link for that laptop scope adapter?

 

Pete

 

[Sniper]

2 hours ago, Pete said:

 

Sniper, do you have a link for that laptop scope adapter?

 

Pete

 

 

Here is one I have been looking at Hantek

 

You still need adapters to measure spark wave forms though,

 

A handy guide to help.

ignition_waveforms.pdf

Edited April 21, 2023 by Sniper

[Kilgore47]

At 13000 miles your engine probably needs a valve adjustment.  When I got the P15 the PO said the rebuilt engine had about 10000 miles on it.  Sounded like a sewing machine.  It would idle fine for 30 to 45 seconds and then start loping.  Tap the gas and it would idle fine again for a little bit. Adjusted the valves and now it idles good.  

 

Lots of good suggestions here and it could be any of them.  In a previous post someone suggested fixing one thing at a time.  If you fix several things at once and the problem goes away - you won't know which one caused the problem.

 

Just keep going and you'll figure it out.  BTW my engine has about 90 pounds per cylinder also.

[Doug&Deb]

I’m going to start calling my car Damian. I think it’s possessed. I changed the coil to see what that would do and no luck. It completely shut off on me. I kicked on the electric pump and it fired right up and ran fine the rest of the way home. I’m changing engines soon so I’ll just drive it with the electric pump on all the time.

[Sam Buchanan]

29 minutes ago, Doug&Deb said:

I’m going to start calling my car Damian. I think it’s possessed. I changed the coil to see what that would do and no luck. It completely shut off on me. I kicked on the electric pump and it fired right up and ran fine the rest of the way home. I’m changing engines soon so I’ll just drive it with the electric pump on all the time.

 

Some of us got tired of messing with an antique mechanical pump, tossed it and run electric all the time......

 

Sounds like you definitely have a mechanical pump problem, the symptoms are textbook.

[Doug&Deb]

I’m inclined to agree but why does it take a while to act up? Until it’s been at operating temperature for a while it runs fine. That’s what made me think coil. I’ll take a look at the mechanical pump. I’m too timid to go with only the electric pump. It’s a cheap Airtex and I’m not very trusting of the Chinese junk that’s available.

[Sam Buchanan]

4 minutes ago, Doug&Deb said:

I’m inclined to agree but why does it take a while to act up? Until it’s been at operating temperature for a while it runs fine. That’s what made me think coil. I’ll take a look at the mechanical pump. I’m too timid to go with only the electric pump. It’s a cheap Airtex and I’m not very trusting of the Chinese junk that’s available.

 

Then don't run the off-shore junk, get a real pump:

 

[Los_Control]

IMHO, just seems to early to have issues with vapor lock.

The symptoms you described could be vapor lock .... just not warm enough here in Texas to see this.

But with a warm engine heating the fuel ..... Who knows.

 

Because I never driven my truck yet I never seen vapor lock. I'm adding a return line to the fuel tank to prevent it .....  Before it happens.

 

What you describe sounds exactly like fuel turning into vapor.

Todays fuel is absolutely crap ..... Are you sure it is just not your fuel heating up inside your fuel line & turning to vapor?

[Doug&Deb]

I’ve not had problems like this before. We’re in the low 80’s and I’ve driven in much hotter temperatures. I do occasionally have fuel percolation on hot starts which is why I installed the electric pump. It’s driving me nuts because I can’t replicate the problem in the garage. Sam, what brand is your pump? That’s a clean setup you have.

[Sam Buchanan]

13 minutes ago, Doug&Deb said:

I’ve not had problems like this before. We’re in the low 80’s and I’ve driven in much hotter temperatures. I do occasionally have fuel percolation on hot starts which is why I installed the electric pump. It’s driving me nuts because I can’t replicate the problem in the garage. Sam, what brand is your pump? That’s a clean setup you have.

 

I'm still 6v so it's a Carter P4259:

 

https://www.amazon.com/Carter-P4259-Line-Electric-Fuel/dp/B000CIS4IU/ref=asc_df_B000CIS4IU/?tag=hyprod-20&linkCode=df0&hvadid=312454010291&hvpos=&hvnetw=g&hvrand=17773229802414862486&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9012652&hvtargid=pla-568638290350&psc=1&tag=&ref=&adgrpid=61179236814&hvpone=&hvptwo=&hvadid=312454010291&hvpos=&hvnetw=g&hvrand=17773229802414862486&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9012652&hvtargid=pla-568638290350

 

It's installed on the frame rail just ahead of the rear axle. I haven't needed a regulator or return line. It can be wired for either neg or positive ground.

Edited April 22, 2023 by Sam Buchanan