My slant six (72) has been running flawlessly for the past 4 months...until last week happened. Multiple times I've been left stranded because I shut off my car, leave it for what could be either a minute, 30 minutes or once even 5 hours, and then come back to crank, crank, crank, but no fire. But this problem is not every time; it could fire up immediately after or a few minutes after too! Also, if I let it sit for a couple hours or more, I can come back to it, pump the gas and it starts like nothing. While running, the thing runs great! No stumble, good acceleration, and very smooth idle. I'm scratching my head as to what it could possible be. Here's what I've done:

I've recently upgraded to Mopar EI. I know HEI is the way to go but I had it laying around. It ran fantastic for two weeks before this happened. Since then, I've tested my ECU (Napa brand) and it tested good. I've replaced my magnetic pickup in my distributor and gapped it to .006". I've soldered wires to the ballast that were previously just crimped. I've checked resistance values when it would not start. Ballast has 12V on one side, 6V on another. Battery is good. Coil values are good...except when cranking. Showed only 9V instead of 12V. Rotor is turning. Plugs are NGKs, and I pulled to examine. Look pretty normal, maybe a little dark on the ends.

I'm starting to think this is a fuel issue. Last time it failed on me I immediately opened up the hood to see that my plastic fuel filter was completely bone dry of fuel. When I pumped the throttle on my carb (Carter BBD) the fuel was still in bowl and pumped out good. Hissed down the throat of the carb and came up as vapor. Waited a good 45 minutes before cranking it again. The fuel filter filled quickly but it did not start until someone else helped me out. He cranked it once and it fired up; claimed he was pushing on the shifter up that helped it. I got it home, turned it off, then immediately tried to start. Nothing, not even his little "trick". I tried to put my foot to the floor while cranking but that did nothing. A few days before I actually stalled when turning on a corner after a drive, like I turned the key off. My foot was not on the gas, and I have power steering. I thought maybe I was running lean, so I limped it home and richened the mixture. No problem with that now, although the idle does go pretty low (but not stumbling) when I turn without power.

I've had the Super Six setup about a month longer than the EI and the carb does everything that it should right. My rubber fuel line is routed up and over the valve cover, and does not touch the manifolds. I suspect maybe my fuel pump might be going bad? I tried smelling my oil and I smelt maybe a hint of gas, I couldn't be 100%. Does not look diluted. Goodness I posted a lot, but....I'm running out of ideas, and this is my daily driver that can't go anywhere. Any help at all would be awesome, thanks!

Remember, your 40some year old vehicle may have had many owners and changes over the years (like a super 6 for example).

I'm not familiar with 1972 tank venting equipment, but if the gas tank doesn't allow some air in the tank, at some point no more fuel will leave. So check the gas cap if it quits on you.

A faulty fuel pump would account for a dry fuel filter as well. Is that fuel filter clean?

Once or twice I've experienced coils that get hot and quit. When they cool... like magic they work again. Maybe substitute another coil.

Remember to make changes one at a time so you can isolate and identify the problem. Keep posting and this community will find answers.

Funny you should mention that; the car had only 2 owners before me and boy, did they do some strange things. But a lot of it lays on me when I do upgrades, haha.

I'll check the gas cap next time. The one time it started after sitting for a few minutes was actually when I filled it up with gas. It's a aftermarket off the shelf piece.

The fuel filter in-line in between carb and pump is clean. I see no debris.

I forgot to mention; this coil is a NAPA brand coil and it's the points coil. Never replaced it when I converted...should I have gotten an EI specific coil? Is there such thing?


I'll keep everyone updated. I'll try and warm it up in my driveway, but for whatever reason I can never get it to quit at home!

Basics:

Clearly you've got fuel. It might be a little too much or a little too little, but the fact you get an accelerator pump shot means you've got fuel, and the fact that it won't start even in flood-clear mode with your foot on the floor while cranking means looking for fuel problems is probably the wrong tree to bark up.

Check for actual spark when you're cranking and it won't start. I don't think you'll find a spark. Prime suspect is the most recent change, that is your electronic ignition. The ECU could test fine when cold, but fail when hot. So could the ignition coil. Other suspects include the distributor cap and rotor, which can play fun games with you when they change temperature (cold to hot or hot to cold).

By the way, a fuel filter that looks bone-dry is a goose chase in the wrong direction. In the first place, that's normal. In the second place, if you can see through your fuel filter's can, it's an unsafe type; after you find and fix the won't-start problem, install a metal-can fuel filter, preferably in conjunction with the fuel line mod.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

My H.E.I. set up sends 12V to the coil (mid 90's Ford unit). The O.E. Mopar coil from 1972 was designed to see a reduced voltage thru the ballast resistor (except when cranking).

Remember to make one change at a time to help isolate. And knowing that you are running the O.E. coil, I'd start there.

Is there a specific coil for Mopar EI that one would recommend? Right now I've got the basic NAPA coil that comes up under my vehicle.

Original-equipment coil is the same for points and electronic ignition. The NAPA unit will be fine, if it works both cold and hot.

Stop thinking in terms of throwing parts at the problem. Start thinking in terms of diagnosing the problem.

The reason you're only seeing 9v at the coil during cranking is because cranking draws the line voltage down -- just like the lights briefly dim in your house when you start a high-current motor.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Well something must have finally went belly up. Today I couldn't even get the slant to start up. The starter (it's a mini-starter) sounded like it was wearing down a tiny bit, but the battery read 13V (unless I'm doing it wrong). I put in an inline spark tester and cranked it from the key. Nothing at all. Double checked the ECU, made sure it was grounded well with bare metal to the back. Made sure all my connections were secure. Fuel was going, choke was operational. Tomorrow I'll try to test some values on what I can, before swapping out the coil. By the way, my coil is positioned directly across from the spark plug wires and maybe only 5 inches from the block. Is that too close? Or should its location be okay?

The stock coil location has it snuggled right up to the engine behind and underneath the alternator; your location is fine.

Coil faulty? Maybe.
ECU faulty? Maybe.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

hi sages - was up against this conundrum and tried most of the things suggested on my 80 volare wagon with a 1 barrel six . no soap. asked myself what would uncle dan do . asked uncle moe who like dan is amazingly intuitive. he said the smell of gas clue is important. told me to check back the gas line all the way from the pump to the tankwith a light. noticed 2 leaks. the pump had a slight weeping from that little hole at the side of the pump(like the water pump weep hole) and the metal pipe into the pump had a rust crack which allowed air to suck in . replaced the pump, small metal line and the small neoprene hose there. end of problem . parts cost less than 20 in in 09. in tank pump job on 04 merc marquis in dec cost 600. did i go to the cleaners? hope you never do.hope this exciting story helps. bob f

Ran some tests, including replacing the coil just to see if it would be a fix. Nope, still just cranking and cranking. Still getting fuel, choke is operational. Some values:

-BATT to +Coil = 5.5-5.7V

-BAT to -Coil = 1V

-BATT to +BATT = 12V

-BATT to Left side Ballast = 10V

-BATT to Right Side Ballast = 5.8 V

CRANKING:

-BATT to +Coil = 5.5 V (??)

-Batt to -Coil = 1 V

-BATT to Right side Ballast = 5.5 V

-BATT to left side Ballast = 9V

Something is going awry. I have replaced coil to no change. Tried bypassing the key starter with a remote, nope. Tried jump-starting battery, nothing. Tried holding foot down to the floor, nope. Just trying anything that would prevent a full spark. I'm not even getting any hint of a spark here either remote or with key. I have triple checked all my connections, but obviously something isn't going right.

The negative side of the coil is switched to ground by the ignition module. If you see steady voltage on the negative terminal then the module isn't doing any switching. This could mean the module is bad or it's not seeing the distributor signal.

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Joshua

Try Putin key on then disconnect pos battery cable take coil wire out of dist. Check for spark there by just touching battery cable back on and of if there is spark then it is likely the pick up coil in dist. Especially if was looking spark hot only at first

Crank with cap off to make sure rotor is turning too the plastic may have broke and dist. Isn't turning

So I also tested the wiring harness 'prongs' I guess you would say. Key on, NEG at -BATT. The red wire that leads to the ballast tested at 12V, so did the NEG wire to the coil. (Which, if it doesn't get those 12V while cranking, must be the module...?). The other two wires that go to the distributor were none, which I suspect is normal as it would only drive current while cranking/running. So maybe my module went bad? Is it not grounded properly? I have it mounted to the firewall, with it ground down to bare metal and with star lock washers underneath. (I'll try to provide a picture tomorrow) Still wondering why the + terminal at the coil is only a mere 5.5 V when cranking. I'll have to follow that wire up to see if anything wrong is there.

My rotor does turn while cranking, so the gear is not broken. I also just replaced the magnetic pickup. The car did run great after that was installed, so I highly doubt it would have gone bad in 4 days. I would have thought that would have been the problem, but then it stranded me at Wendy's, lol. I think I might be getting closer, at least narrowing in on a problem.