Runs 20 then dies

[Valiantsignet20]

75 Dart sport. 225 auto. New charging and ignition components. Car cranks and runs for 20 min. then cuts off like the switch is off. Power to coil, balist, ecu and dist. When it cools off it fires up and does it all over again. I replaced coil with a good spare and still no spark to the plugs. I am leaning to the distributor.

The back story is. I lost the oil pump drive gear. Replaced the pump all was fine. I left the ignition on overnight. Came back to find a dead battery and dead cell. Replaced batt and all was well again. Drove to work and 20 mins down the road it cut off. Wondering if it zaped the pickup coil in dist.

Also as a side note the belt disconnect is bypassed but it still has the little black boxes that appear to be resistors. I cannot find their purpose on any wiring schematics.

 

[80fbody]

How about tracing the power once it cuts out. May find it's the ballast or ecu getting hot. Just a thought.

 

[67Dart273]

Problems like this can be tough. The coil was a good bet. I'd bet on the ECU before the dist, but try to do some testing to see. Carry a big long clip lead with you. If it quits, run a jumper from coil+ to the starter relay battery stud and see if it starts / you have spark.

Unbolt the ECU, clean it and the firewall, and reinstall with star lock washers. Remove and "in - out" the connector a few times to scrub the terminals clean. "Feel" for how tight it fits. While you are at it, not a bad plan to do this with the regulator connector, as well.

Same with ballast resistor and ESPECIALLY the distributor connector, which has very little current through it. You might get lucky

 

[Valiantsignet20]

80fbody. I done the old tried and true switch the ballast out. I carry a spare in the glove box. Yes the ballast gets hot but the ecu stays cold. Even the coil doesn't get hot. I had good current on both sides of the ballast and coil after it cuts off.

67dart273, I did bypass to the battery terminal to the hot side of coil and used a remote starter switch with the key on also. Still no spark. I will recheck grounds. I replaced the ecu after I tried ballast and replaced battery.

 

[Valiantsignet20]

Thanks for the input fellows. I grounded the dist trigger wire after the car cut off again. It did fire the coil. So, I pulled the distributor. Hooked it up and spun it by hand and it did not fire the coil. I then used a v8 dist I had and it fired the coil. Looks like a dist is in my future.

 

[BillGrissom]

Leaving the ignition on should not have hurt the distributor pickup. It is simply a magnet w/ coil of wire. It produces a small voltage signal, but nothing should flow the other way unless the ECU is really bad. Did you gap the distributor pickup? Should be 0.008" gap, preferably using a brass feeler gage. The smaller gap the better as long as it doesn't hit the teeth as vacuum advance moves it. You can buy new pickups for ~$7 on rockauto.

One thing to check is the double-bullet connector to the distributor. I got a new pickup a year or two ago with the wrong connector. The male pin was too short and made erratic contact. Funny thing is, I bought two pickups at the same time (they were cheap) and one was right. A regular appliance connector doesn't work.

Also, amen 273 on getting a good ground connection for the ECU. Don't rely on a rusty sheet-metal screw like the factory did. That is a common problem.