Ignition system problem? Help!

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cosworth

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At a loss trying to figure out this problem, had to step away from the car for a bit and now im back at it. Any ideas would be appreciated. Below is an explanation of the symptoms and things ive tried or replaced sorry for the long post.

After first getting the car in running and driving condition I could drive the car on 1-1.5 hour drives with no issues, only difference is I was running a borrowed carb which I gave back and swapped to another used one (at this time I have ruled out the carb on a different car) Tried to drive the car the 1 hour drive got almost home and it started acting like it didnt want to idle and from a stop would try to backfire if I didnt flutter the pedal, no biggie thought maybe carb was getting hot so I put a spacer and changed jets and idle jets in the carb. Went for a short drive and just driving down the highway the car began to backfire and sputter blew every vaccum cap off barely got her home. Tinkered with adjustments and no matter what I did it just got worse and worse till it just wouldnt crank at all. Next morning cranked right up and idled fine in the driveway for 15 mins. Tried new Ballast and new Ignition Module and at this point I can let the car idle in the driveway for 20-30 mins and runs fine just it just falls flat and dies. It will re-start but has no power if i rev it. Ive done this several times trying to pinpoint a problem...

Car doesnt get hot, it is getting fuel, runs and revs great till its run for approx 20-30 mins. If I can pinpoint the ignition system as a problem ive considered using a MSD box I have several I could slap on it.
 
cosworth said:
At a loss trying to figure out this problem, had to step away from the car for a bit and now im back at it. Any ideas would be appreciated. Below is an explanation of the symptoms and things ive tried or replaced sorry for the long post.

After first getting the car in running and driving condition I could drive the car on 1-1.5 hour drives with no issues, only difference is I was running a borrowed carb which I gave back and swapped to another used one (at this time I have ruled out the carb on a different car) Tried to drive the car the 1 hour drive got almost home and it started acting like it didnt want to idle and from a stop would try to backfire if I didnt flutter the pedal, no biggie thought maybe carb was getting hot so I put a spacer and changed jets and idle jets in the carb. Went for a short drive and just driving down the highway the car began to backfire and sputter blew every vaccum cap off barely got her home. Tinkered with adjustments and no matter what I did it just got worse and worse till it just wouldnt crank at all. Next morning cranked right up and idled fine in the driveway for 15 mins. Tried new Ballast and new Ignition Module and at this point I can let the car idle in the driveway for 20-30 mins and runs fine just it just falls flat and dies. It will re-start but has no power if i rev it. Ive done this several times trying to pinpoint a problem...

Car doesnt get hot, it is getting fuel, runs and revs great till its run for approx 20-30 mins. If I can pinpoint the ignition system as a problem ive considered using a MSD box I have several I could slap on it.
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Do you have an electric fuel pump you can run temporarily?
Having to feather the throttle sure sound like a fuel issue.
Have you chked the fuel filter/s? since they will act like that when they start plugging up.
When it sits, some of the crap falls off the element and when it builds back up from running it will starve it for fuel again.
I pull them off and cap both ends with my finger and shake it, then dump the fuel out of the inslet side. (crap will come out if it dirty)
I will sometimes blow through them also, to see if it seems restricted.
 
Thanks for the Idea I will give it a try. But I dont think fuel delivery was an issue I have a clear inline filter that looks completely clear, ive checked the inlet screen in the carb several times fuel tank and lines are less than a year old.
 
Filter wouldn't be completely clear if it has fuel in it.

What car is it ? model, etc.. there are places on some where the heat from the engine can cause intermittent electrical failures.
White harness connector at back of right valve cover is one.

Could be flooding too. That will cause no start today and start right up tomorrow ( or after the plugs dry ).
 
Car is a 1974 Duster 318 M4. Previous owner hacked the engine harness up I got a replacement from Waggs. I will try both of these suggestions.

At this point if somebody said standing on my head while rubbing my belly would do the trick I would give it a shot.
 
cosworth said:
Car is a 1974 Duster 318 M4. Previous owner hacked the engine harness up I got a replacement from Waggs. I will try both of these suggestions.

At this point if somebody said standing on my head while rubbing my belly would do the trick I would give it a shot.
Click to expand...

Chk the connector between the distributor and the harness.
I have seen heat cause intermittant connection there, and removed that plug from my system because it drove me nuts till I found that's what it was.

I went with fuel because you said you had to feather it to keep it running.
Could there possibly be another inline filter under the car somewhere?
 
There are no other filters in the system other than the sock in the tank. The line is brand new steel fuel line. Didnt run a bypass line.

The connector is kinda jacked up at the distributor from being unplugged, it is the original distributor for what I can tell.

Ill give all of these a shot and report back.
 
This sure "sounds like" fuel to me.

One thing you can do is get a spark tester, start the car cold, determine that it runs "OK" and shut it down. Use the spark tester to examine the spark when cranking the engine, and take a GOOD LOOK.

Next time the car screws up, shut it off and retest the spark, and see if the spark seems deteriorated from cold.

"Rig" yourself a fuel pressure gauge temporarily BUT SAFELY!!! so you can monitor fuel pressure at the carb.
 
Your talking about one of the lights that goes inline between the plug wire and spark plug?
 
I prefer (and you can make one) the ones that look like a big gap spark plug, but I also have one of these, which is adjustable

[ame="http://www.amazon.com/Lisle-50850-Ignition-Spark-Tester/dp/B0002STS44"]Lisle 50850 Ignition Spark Tester : Amazon.com : Automotive[/ame]
 
I agree that you need more diagnostic tools, because it is almost impossible to judge whether a spark or fuel problem by "feel". I don't know how long the cheap in-line spark testers w/ neon bulb from Harbor Freight can run, but I once drove with one in-place 10 miles home because I wasn't going to take it out once I got the car started (XR700 ignition module had failed). Next time you have the exhaust pipe off, weld in an O2 bung so you will be ready for an O/F indicator. They are cheap and come with a plug.
 
BillGrissom said:
I agree that you need more diagnostic tools, because it is almost impossible to judge whether a spark or fuel problem by "feel". I don't know how long the cheap in-line spark testers w/ neon bulb from Harbor Freight can run, but I once drove with one in-place 10 miles home because I wasn't going to take it out once I got the car started (XR700 ignition module had failed). Next time you have the exhaust pipe off, weld in an O2 bung so you will be ready for an O/F indicator. They are cheap and come with a plug.
Click to expand...

And here's a cheap way to get a bung:

It's called a nut

http://www.forabodiesonly.com/mopar/showthread.php?p=1969675332
 
Ok finally got some time to tinker with the duster.

1. Choke is all the way open when the car finally dies.
2. Put a spark tester in line and ran it, again ran absolutely great till bam its dead no sputtering just flat out dies. I did notice the first time that the fuel filter was half empty so perhaps it is a fuel problem... Fuel pump is brand new. Going to get another fuel pressure regulator to try my electric pump. Tried it inline tonight but as expected its too much for the carb and leaks by the needle valves.

Spark looks fine the entire time its running so I think ignition is ruled out.
 
Maybe fuel "percolating"?? The spacer usually fixes that though....
After car dies, do you chk for spark immediately after??
 
Next time it dies, while loosening the gas cap, - listen .. if you hear/feel suction at the cap, perhaps the gas tank vent has been plugged, causing vacuum in the tank,, and will run till the tank vacuum exceeds fuel pump suction,, and dies,, for a while.. hope its this easy..

Did you plug any hoses when you took the old carb off ??

When it blew off the vacuum hoses,, did you plug something you shouldn't have.
 
I checked the spark right after it died and looked good. I never thought about a blocked vent.. This car would have had a charcoal canister which I dont use anymore and I put a single feed fuel sender/pump so no return. And best I remember It doesnt have anything else on the tank or fuel neck. Im going to let the car run with the gas cap off tomorrow who knows worth a shot.
 
Tried running with the gas cap off, no luck still dies.

I looked harder at the spark now that I had some spare hands to keep the car running while I looked at the spark tester and it seems like the car is missing I dont see spark when I think I should and when I do its very difficult to see.

Ballast and Ignition module are both less than a month old.
 
Coil would be highly suspect in this case then.
Possibly even just the voltage to it is way low.
 
Gonna try swapping the coils out once the car gets to the point it wont run, ill check the voltage at the coil wires as well. If nothing changes I can temporarily wire in my MSD box to see if that solves the problem or not.
 
TrailBeast said:
Coil would be highly suspect in this case then.
Possibly even just the voltage to it is way low.
Click to expand...


^^^ I think we have a winner. Let the car run till it died and immediately swapped to a different coil and she cranked right back up. I let the car run on the new coil for awhile then swapped to the old coil and let it run till it died again.
 
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