Power loss

[shrekomo]

Hello guys...new problem today...out cruising in 70 roadrunner...rebuilt 440 with about 400 miles on it..at about 50 mph...car dies. Coasted to side of road. Tried to restart...motor cranks but won't fire at all...pulled the breather and I'm getting fuel when I hand throttle it. Towed back to house and I've not done the spark plug test yet for spark...the only electrical components not replaced at overhaul...are the electronic ignition... the voltage regulator...and that ceramic fuse block...any thoughts?... Thx

 

[Aron Gleason]

Clogged fuel line. Bad fuel pump. Check for kinks in fuel line.

 

[ckessel]

What is the voltage reading at the positive side of the coil? If less than 8, it's not going to light. Had similar on my Challenger many years ago. At every connection on the way to the coil, there was a voltage loss. Not much but it all adds up. Half volt here, quarter there etc. Typical old car wiring. Bad connections, bad grounds, sketchy switches etc. Our cars and many others were also not blessed with enough grounds which really cause problems down the road. My Challenger would light up the opposite side indicator on the dash when I put the signals on. Sign of a bad ground between the socket and the cast housing. My 65 didn't want to start one day after being difficult running for quite awhile. I'm replacing the wiring as one of my many upgrades.

 

[lewtot184]

very simple first test is to replace the ballast resistor. i've had orange ECM's drop dead while driving.

 

[PurpleBeeper]

Yep, check for spark and that ballast resistor having voltage coming out of it into the blue wire. They burn out a lot

 

[shrekomo]

Thx dudes...I had one of them die on me 40 years ago in a 76 dodge pick up...just wasn't driving at the time...I'll pick one up today

 

[GetX'd]

A ballast resister is a must have in the glove box at all times…

 

[shrekomo]

Great idea....I'll buy 2

 

[ckessel]

Hopefully that was a fat finger.

 

[lewtot184]

the msd .8 ohm resistor has worked best for me. never popped one, but popped a lot of parts store resistors; and one in the glove box is as good as having a spare wheel/tire in the trunk.

 

[dadsbee]

If you carry a spare the one on the car will never blow. First thing I'd do is simply jump a wire from side to side on the ballast that's on the car and see if it runs. Won't hurt a thing and it's free...

 

[Master Gunner]

Without more information it's really hard to say, but with that said, break out the multi meter and start tracing power. First turn ignition on and check at the main ignition feed to the ballast resistor (blue wire), should be 12V, if not probably ignition switch probllem.

Next, check the other side of the resistor for power, usually around 8v. (single ballast resistor) Check power at positive side of coil, if you have power here check for spark at a plug-should be nice blue spark. If no spark check ground of ECU. Most parts house ECU's are not that great quality anymore.

Meatball surgury to get you off the side of the road/home, run a jumper from battery to positive side of the coil or the brown wire at the resistor. This will get the car running with a bad ignition switch, or a bad resistor, but is hard on the coil and has to be removed to turn off the engine.

This is a pretty simple system, and fairly easy to find the problem.

Most common failure of these cars is the ballast resistor, so may want to bring a spare with you.

Mark

 

[Sixpactogo]

If you have fuel in the carb as you stated, The problem is most likely electrical. Like it was mentioned, carry a spare ballast resistor. There are however a few more things to check. I would wriggle the firewall plug on the engine harness as that is a likely culprit as well even though there are a lot of other causes for no spark. Could be the plate coil in the distributor, loose coil wire, broken wire in the harness, ignition switch itself, ECU not grounded properly to name a few. You need a good ohm meter and some circuit savvy to figure it out.

 

[Sinitro]

Double-check the bulkhead connectors, these often get oxidized making poor electrical connections. Pull apart, polish the contacts and re-install using dielectric grease..

Just my $0.02...

 

[shrekomo]

Thank you gentlemen...I'll follow up when fixed

 

[shrekomo]

Changed the ballast resistor..no change. Checked and wiggled grounds and checked coil connections. Haven't done all the electrical testing yet cuz all I have is continuity tester lol..I do have a buddy who has all that and is an expert ... question...what I call the electronic ignition is from 2006...could it be culprit?. And since I've been out of the loop so long ...I'm not sure I know what ecu is unless it's the same part...for getting rid of points. Thx

 

[Sixpactogo]

Yes. The ECU (Electronic Control Unit) is what you are calling electronic ignition. It could be the culprit. They have been known to fail without warning. Biggest thing with them is they need to have a good case ground otherwise they get hot and the transistor will open up. Usually when it cools down, it will work again until it gets hot but not always. Did you wiggle the engine wiring plug at the firewall? Unplug it and inspect the connectors. Those connectors get dirty and corroded causing the issues you are having. The plate coil inside the distributor (takes the place of the points) can fail too. If your buddy has knowledge of how these components work, you probably need him.

 

[shrekomo]

I will work on that firewall connector..if that doesn't work...my money is on the ecu cuz it's 16 years old and distributor is new...then I get my buddy on it...thank you for feedback

 

[Sixpactogo]

Good Luck. Persistence will prevail and when you figure it out, it will give you confidence for next time.

 

[Mally69]

Ive had this happen. It was my ignition box going bad.