/6 runs great, randomly stumbles and dies...???

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72Dodge

72Dodge

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I know some may want tons of details, understandably, I'll do what I can, but to start, I'll keep it brief (OK, too late, I wrote a lot).

History: /6 in 72 Dart sat for about 15 or so years indoors without being started at all apparently. 112k miles. I get it, get it running, convert to electronic ignition, change all plugs, ballast resistor, cap, rotor, plug wires, coil, fuel pump, and so on, pretty much everything. I'm in this for the long haul and want this to be reliable.

Carb: So I get it running, but not great. The carb on it is a reman Holley 1920 from around '91, and I was pretty sure this was the problem. Not having an original carb to rebuild, I figured I'd take a chance with a new reman. (I know, but I wasn't sure which was the lesser of 2 evils, this, or rebuilding a reman). Got an AutoLine from RockAuto, plug it on... NEW CAR! The thing runs great. Get it all set and runs amazing.

For about a week... sure there were a few glitches here and there, but I'm working the carbon out, it has some compression issues, real bad blowby, I'm just trying to free up the rings, valves, etc by working it...

Then trouble: So then after about a week, I'm out driving and out of nowhere it starts sputtering, loses power, and dies. Hard start, but I finally get it going, and make it the mile home, but it's real low on power. To me, it felt like a car that was real out of time, but will barely run.

Trying to fix: First thing I do is I find the soft lines at the fuel pump and sending unit are soft, I assume from ethanol, so I swap those out for injector line. Still runs like crap.

So today, I poke around and find that the choke pull off vacuum came disconnected. How the heck. But, the car runs a bit better now.

I let it run for a bit, and it randomly sputters and dies. Just loses power and goes down, can't keep it running even with foot on gas, then starts real hard, and only by pumping (not holding to floor, but actually pumping while cranking). Waiting a minute helps, but still starts hard.

After awhile of this, I get out the video camera to show you guys and obviously when it's on camera, it runs perfect for 13 minutes. I mean really really perfect. Like a top. Smooth, great throttle response, blasts up and down the driveway like a champ. Just great. So I shut down the video camera.

Wait a bit, start it up, runs great for a few minutes, then sputters/stumbles and dies from idle, randomly. Start again, and sometimes it will die as I'm starting to give it some gas.

Summary: So basically, car runs great, just stumbles and dies randomly, then hard start and starts easier if I pump the pedal a couple times while cranking.

I have my theory on what the issue is, and what I should maybe do, but I don't want to influence anyone since I could be totally off base. Also, a few of the details I gave weren't meant to be leading, just simply trying to give an overview of what I did and how it's acting.

Any thoughts? I'd love to be driving this car again, but need it to not randomly die in the road. Unfortunately, I live in a pretty busy area, the car dying on the road would be more troublesome than if I were out in the country!

Thanks!
 
After it dies pull the air cleaner and look down the carb throat with the engine off. Give the linkage a pull (open the throttle) and watch to see how much fuel squirts into the carb. It sounds like you are running out of fuel to me.

It is very possible that the filter sock in the fuel tank is clogged or that something is floating around in the tank and randomly plugging it up causing your car to starve for fuel.

I heard a story a few years back about a fwd small suv with an intermittant low oil pressure problem. After the engine was replaced the factory tore it down and found a pay stub of one of their engine plant employees floating inside the oil pan. It would occassionally block the pickup tube I imagine he got fired, but the same principle applies to rust, leaves, and random debris. I would flush the tank and install a new filter.
 
Yeah, I was thinking fuel too. When it first happened, I thought timing slipped, because of the way it acted and how sudden it was, but once I got it running again, it seemed more like fuel.

What you're saying makes a lot of sense to me... I will do that. It needs to be done either way. Pulling the tank is one of the few things I didn't do that I should have done immediately.

My other thought was due to same thing, the new carb got plugged with crap and is acting up, which still could also be.

Anyone else with any thoughts? But yeah, I'll check fuel at carb, then clean out tank.

Thanks!
 
Could be many things. Indeed, everything needs to be almost perfect for an engine to run smoothly. You need more diagnostics. To rule out spark, get an in-line spark tester (cheap @ Harbor Freight). Stop and install it when it starts acting up. Maybe easier for catching it in the act, is to run 2 wires from coil+ and BATT- into the cabin and monitor with a multimeter (cheap/free @ HF). If you see it drop <8 V, investigate further. Carry a can of starter fluid and spray it down the carb throat when it is running bad and see if that smooths it. If so, you are running lean. Once the engine warms up, the choke plate should be strongly open.

My 1st suspicion would be a wiring problem, like a poor ground on the ignition module. You wouldn't see that from the coil+ reading. Who converted it to electronic ign? I have seen a lot of Billy-Bob jobs, like wrapped wires w/ scotch tape. For some reason, many think electrical stuff is magic, so doesn't matter if they half-@ss it, as long as they pray to the gods. Post photos.
 
fuel restction, prob filter, kinked hose ..

gas tank could have all kinds of residue, yuk, in it.. and will plug new filter in no time.. take it off and blow thru it,,
 
Bill: I did the EI conversion and I used high quality scotch tape :) j/k, it was the MP kit and I used a butte connector on the only place that needed a connection. I think I did a pretty good job. I'm pretty sure the ignition is solid, but I'll go over it again, and thanks for the tip on wires into the cabin, never thought of that, it could be telling, thank you. I have a good multimeter (and the HF inline spark tester that so far has looked good on all cylinders). As for the ignition module ground, I didn't feel comfortable even with the back to the cleaned off bare metal portion of the inner fender, so I ran a wire from there to ground on firewall also. But... I think I'm going to re-visit that, just to be sure, make it even better. Like you said, everything has to be perfect, which is how I like to make things, I'm pretty retentive which is why it takes me 2-3 times longer than most people to do anything :) I plan to drive this car to CA on 66, so it's got to be right.

Inertia: I think this is my third fuel filter on it (this one is brand new since it started acting up), and there was no crud visible in the last one (last one was clear plastic), which I thought was odd for a car this old, but it could still be crud in the tank causing obstruction.

Thanks all for the great tips and thoughts.

I think my very next step is going to be to run it from a gas can for awhile (after changing filter yet again). It seems to me that would tell me for sure if it's crud in the tank, but I'm going to clean out the tank no matter what anyway.
 
i have had simmilar wierd intermitten problems with the mp ei conversion. sometime ago the orange boxes started be'ing crap. imo. maybee try a napa box? i went back to points myself. sorry for poor spelling. lol
also def clean fuel system again
 
Interesting. I heard about the possible MP orange box quality issue. The one I got with the kit is my spare, and I've been using an older (but new) USA orange box I had. I also have a brand new Echlin (NAPA) box. It only takes seconds to swap it out, so I may as well try that quick just to make sure (since I'm triple-checking the ground on it anyway).

Won't get around to working on the car at all again until next weekend at soonest because our garage/drive is all full of garage sale crap LOL
 
Remove the air cleaner and grab the carburetor and twist it. If you can move it back and forth, that's probably the problem. They are notorious for the gaskets shrinking and the parts of the carburetor works loose. That causes vacuum leaks and internal fuel leaks. I would strongly suspect the carburetor, rebuilt or otherwise.
 
I suspect the carb too, but I have checked (twice) the carb seal. That's how I found the detached choke pulloff vacuum hose. I just hope I haven't gunked up my new reman carb with s*** because I didn't clean out or change the fuel tank first. I'm kicking myself now for not doing that first, oh well.

I just ordered a brand new fuel tank. I can always use this one for another project probably after cleaning it out, but I want a quick, easy and sure swap when I do this. $ well spent I think.
 
Final update. Installed new tank and new sending unit today. Problem appears to be fixed. I couldn't believe how corroded and crappy the old sending unit was. It was partially just gone. I'm surprised it worked at all, I shudder to think what sort of crud it was throwing into my new carb. Doesn't ever die now. I drove it around all afternoon with no problems at all. Last time I don't check this out immediately when getting any car that's been sitting!

Thanks FABO members. Case closed!
 
I think your flooding. sputter and die can be both but a real hard start sounds like too much fuel . If its flooded, you are suppose to be able to just floor it and crank, no pump. If it eventually starts, then it was flooded.


<<<<<<<<< well, wasnt I tardy to the party! >>>>>>>>>>>

glad you figured it out.
 
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