Car suddenly won't start??? Coil???

04mustang70 · May 6, 2008

I had my 70 Mach 1 completly apart this winter. Got it back together and it ran fine. Took it out a couple of times. Had a radiator leak and I got a new radiator and installed it. Car started just fine. As soon as I put it in gear it started to hesitate and stumble. It then died after moving 20 feet. Would not restart. Just spun like theres no spark. My question is could it be the coil going out? I have a mallory promaster that has been in there for 20 years with no problems. Unilite distributor for the same amount of time with no issues. Theres power going into the coil but with the key on but theres no power going out of the coil that I confirmed with a test light. Should a test light be able to detect power coming out of the coil without the car running? Im testing the wire that goes to the distributor, not the coil wire (spark plug wire) going to the middle of the cap. How can I tell if it's the coil causing these problems Hope I'm being clear on this. Thanks for the help in advance.

68keyblr · May 6, 2008

Disconnect the coil wire from the distributor and lay the end on a good ground so you can see it spark. Have someone crank over the engine and see if you get a good spark while cranking. If you do, the coil probably isn't bad.

I've had a case where a bad starter was causing a very weak spark, so you could see a spark from the end of the coil wire but it was too weak to spark the plugs and ignite the mixture.

Check to make sure you are getting fuel too...

04mustang70 · May 6, 2008

im definitly getting gas I can see it flowing in my clear fuel filter. How can the starter affect the spark of the engine. This electrical stuff drives me crazy

ForceFed70 · May 6, 2008

I agree with the coil test mentioned above... give it a try. You should be able to get a 1/16" arc to ground.

There is no way a bad starter could cause ignition problems. Starter solenoid maybe, but not the starter itself.

woodsnake · May 7, 2008

Give this a read.....

http://www.aa1car.com/library/voltage_drop_testing.htm

67rcks · May 7, 2008

get a $5 spark plug wire tester at harborfreight or pepboys, plug it between distributor and coil, spin the engine with the starter. if you see spark (on the tester) then your ignition should be ok. see your spark plugs if they are clean and not wet. If they are black and wet you have problem with carb (needle does not seal right) or totally clugged air filter; I would say the latter. The dropped voltage is usually the problem in ECU cars (shuts down their computer when too low)

woodsnake · May 7, 2008

I posted the link, as a voltage drop test is one of the best diagnostic tests there are. If you have dirty connections, or a lose bolt, or any other electrical abnomality, that will show you where the problem lies.
It's easy to chase problems as simple as a corroded end for hours, and not find anything conclusive.

I am not a 'whiz' at electrical, and it was a tough subject while I was going to school. However, with this knowledge, many things become way more clear than they may have been before.

Plus, with the link posted it may come up again later for some one trying to learn how to do it. (a voltage drop test, that is...)

68keyblr · May 7, 2008

ForceFed70 said:
There is no way a bad starter could cause ignition problems. Starter solenoid maybe, but not the starter itself.

That's exactly what 5 of us thought when installing the new 331 and firing it for the first time. The engine turned over but fairly slowly but good enough to fire the engine. We all figured a low battery. However the battery was fully charged and fine. The coil spark test showed a very weak orange spark.

Without making a single other change, we swapped out the starter (which was burning hot) and suddenly engine turned over very easily and fired right away with a strong blue spark.

So all of the theories say that bad starter can't cause ignition problems, but my practical experience suggests otherwise.

D.Hearne · May 7, 2008

ForceFed70 said:
There is no way a bad starter could cause ignition problems. Starter solenoid maybe, but not the starter itself.

Oh yea? A bad starter can pull most if not all the amps to it, leaving little or nothing to power the ignition sytem. If you don't believe that, just try cranking with the lights on. Just the fact that they'll go dim while the starter's turning should clue you in.

04mustang70 · May 7, 2008

Thanks for all your help in this thread When I get a chance I will start chasing the problem LOL

ForceFed70 · May 7, 2008

Let me rephrase: A bad starter can cause excessive current draw which could pull the battery voltage too low... but that's not a problem with the ignition system, that'a a supply voltage problem that would effect the entire electrical system.

Regardless, based on his description of the problem and the events leading up to it... this is not what he is experiencing. The vehicle 1st showed signs of problems while the engine was already running.

D.Hearne · May 7, 2008

The starter could have drawn so much juice that the system failed to energize the alternator, and then that could have affected the Unilite. I don't know a lot about the Unilite, but do recall they used to suddenly crap out on many people. Could be thats the case with his 20 year old Unilite. Stranger things have happened with electrical systems.

04mustang70 · May 9, 2008

Found the problem. Talking about jumping to conclusions. I figured I would see if it was getting gas and when I took the air cleaner off the choke was closed. Never really use the choke so when I put the car back together I didn't install the manual choke cable. Must of vibrated closed. Opened it back up and car runs fine. Thanks for the input though DOHHHHH!!!!!!

D.Hearne · May 9, 2008

Better remove it or wire it open. It'll pop closed again when you least expect it. I had the choke on the center carb on my 331 do just that while doing a burnout at the strip. The whole assembly got removed when I got it home.

woodsnake · May 10, 2008

I'm glad it was an easy fix, but that is too funny!

All of us online diagnosticians, and not one of us can see "from here!"

Car suddenly won't start??? Coil???

04mustang70

Member

68keyblr

04mustang70

Member

ForceFed70

That's why they call it "dope"

woodsnake

67rcks

Member

woodsnake

68keyblr

D.Hearne

New Member

04mustang70

Member

ForceFed70

That's why they call it "dope"

D.Hearne

New Member

04mustang70

Member

D.Hearne

New Member

woodsnake

Similar threads

Car suddenly won't start??? Coil???

Member

Member

That's why they call it "dope"

Member

New Member

Member

That's why they call it "dope"

New Member

Member

New Member

Similar threads

Privacy & Transparency

Privacy & Transparency