My ECU recently went out, I changed it, (and coil) and the slant ran great for about a week, drove it about 250 miles that week.

On the weekend, I drove 10 miles to go shopping. Came out of the store and it started up, but idling rough and stalling on the way home a few times, hard to keep running without giving some gas above idle. Changed ECU, ballast resistor and voltage regulator (its charging when running). Still has symptoms.

Symptoms: starts up when cold, will idle smoothly, not rough, rev's fine, so it's obviously getting gas and spark, timing seems OK (I'll check though). If I shut it off, whether having run for 30 seconds or 5 minutes, it won't start back up.

Electric chokes are working fine, it's getting fuel, must be spark related, right?

Could it be weak spark, fouled plugs, distributor related? The plug wires are likely older, but the distributor, cap and rotor are relatively new. Pulled a plug to check for spark and (of course) it fired up (on 5). Put the plug back in and it wouldn't start - WTF? The plug wasn't in the best shape, could be fouled plugs? I'll be changing the plugs and wires while I await some advice...

Thanks Everyone!!!

67Dart270

Sounds like the idle circuit is plugged up. How clean is your gas tank?

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Joshua

OK, so I removed the fuel filter, put in a new one and it started right up. But then started doing the same thing again. Could this be a bad fuel pump diaphram (no fuel smell in oil that I can detect). I used a transparent fuel filter, I don't see any particulates in the filter. I can check the fuel pressure I suppose...

I had been pounding on the floor boards previous to my shopping trip, so I had considered crap shaking loose into the fuel line. That's why I had chaned the fuel filter. Assuming it is a bad fuel pump or related, why would it run perfectly and then not start again? If it weren't getting gas, it wouldn't run well in the first place...I'm confused. Could it be running on what was in the float bowl and then running dry? How would the bowls be filled, perhaps with weak pressure slowly....?

Thanks for any help anyone has...

My vote is grounding of your new ECU.......make sure you run an extra grounding wire.......Just getting 12 volts to it is not enough. You need a super good ground to complete the circuit. The lack of ground on a ECU will cause all kinds of symptoms. I usually use the dielectric grease on the bolts too. Be sure and scrape the paint off around the bolt holes.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I did take the extra effort to re-scrape the firewall where the ECU bolts down, but I can make sure the ground is better.

But, Ted, why would it start up and run OK, then not start immediately after? If the ground is bad, it's bad. This to me sounds more like a fouled plug issue or bad wires, spark suppression of some sort.

Could still be a fuel issue. Here's my thoughts. It wouldn't start after the first start. I took off the fuel filter, replaced, then it started right up. I have a low pressure fuel regulator to run the Webers (3-4psi) BUT, I don't have a fuel return line, so perhaps I've damaged my fuel pump (which pushes 6-9 psi). The fuel pump was new about a year ago, so I'm thinking that the stress was too much for the diaphragm. I was thinking I should pop in a new fuel pump and install return line (I should do this anyway).

Most fuel pumps should be fine with a non return regulator,after all, that's what the pump experiences when the float bowl is full and the float valve is shut,at 9 psi I'm guessing its electric? Maybe check with the manufacturer to be sure.check the fuel pressure too, maybe the reg is sticking and the carbs are getting a tad too much pressure and flooding? Those Ecu's don't seem to have a really good rep from what I've read, I personally have never run one, but from apart from install issues like earths etc it may be possible it is faulty, even though you have changed it during trouble shooting, unlikely? yep, but possible! When it heats up something fails until it cools? Maybe check that coil lead as well, maybe it's had it, I think you said the plug leads were old? Even the new coil may be worth swapping for troubleshooting?

So, I changed the plugs, wires, cap and rotor, fuel pump is mechanical, but I put a new one on there anyhow. Changed out the ECU to yet another one, ground is good on it. Installed new ballast resistor and voltage regulator.

Same result. Fired up, runs great, idles smooth, revs up strong, back to idle smoothly. I turn it off, immediately try to start it...won't start. I'm stumped, but it must be electrical.

Seems like the spark is there, and then it's not. I suppose I could try another coil. This one is new (installed two weeks ago), but maybe it went bad or something.

Anybody got any other ideas?

I'll drive my other car this week, like last week....

How about pouring a bit of gas down the carb(s) after you shut it off, then see if it will start back up?

- Mac

Starting a warm engine, even after just shutting it off, you need to open the throttle about 3/4's while cranking. The choke should also be fully open.
Just a thought.

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Mattelderca
78 NYB (gone now), two S series, three old Snow Cruisers and a Doo.

Thanks guys, checked that it's getting gas and the chokes are working perfectly. Pushed gas to at least 3/4 open, and wide open, still won't start. Must be a spark issue.

I'm guessing that new coil I installed two weeks ago is failing for some reason. That's the only thing left that I can think of. Can't be timing, or it wouldn't run so well on the first start.

I'll swap out the coil and check back with everyone. I've seen coils work when cold then not when hot, but not anything like this before....still, can't hurt to try. Everything seems to be made in China these days...have to be careful.

67Dart270
2 deuces

yeah, i bought a chinese made borg-warner off brand, worked when i put it on and then died without the car having ever been driven. absolute garbage.

where i live, it doesn't matter what you say at the parts counter. virtually everything is made in china and your only other choice is online (and pray that you don't get lied to).

Any chance it could be the ignition switch? It turns over, but could that circuit be working but no power to the module/coil?

Yes...! Mine does that from time to time.....
I am too lazy to pull the steering column apart and replace the ignition switch.
I need to rewire the ignition system this weekend by running a hot wire and lighted switch to trigger the relay for direct alternator power to the coil and ECU.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I would get a (adjustable gap) spark tester like Thexton # 404 or 458. When the car won't start then fit the tester to a plug wire (connect the tester ground clip), then check if the ignition can produce a spark that'll jump a 3/8-1/2" gap while cranking (HEI should go 3/4"+). This way you can quantify the coil output & perform repeatable tests- you will KNOW whether spark is the problem & you won't be "guessing" that a part is bad.

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63 Valiant Wagon
225 - 4 bbl

It was the (new) coil.

Must have been vibration and/or just a low quality coil. The little bolt that keeps the coil snug in it's holder was gone and the coil was jostling around in there. Vibration is bad for coils. Switched out with a new one (with a new bolt to hold it snug) and she runs great again. Starts every time.

Thanks so much everyone, this was driving me nuts.

67Dart270