Very weird no spark (again)

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dartfreak75

dartfreak75

Restore it, Dont part it!
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Aight so its been about 6 days since I started and ran my car because of work and weather. Well today I got up and was mowing this morning I went to move the dart so I could mow around it without blowing grass all over it and it won't start. Im thinking cause its cold and hasn't been ran in a few days (it was like 38 this morning) so I pump the gas and try again nothing, so now im thinking well I flooded it because i can smell gas pretty strong under the hood. So I go on finished mowing went and ate and came back several hours later still nothing. I check and no spark. So I run all the tests that we covered last time and i have the exact same issue as last time. I have like 11.6 volts at both sides of the coil. So bad ecu right? Im looking at the ecu and I have like 12.3 volts at the transistor. I didn't even mean to check it I just accidentally bumped against it. So I check a bunch of other stuff and tighten my connections and check again now I have nothing at the transistor and it fired right off on the first crank. And If check the transistor while it's running it kills the engine. Like a kill switch. Sounds like a bad ground or something to me. Very weird tho never seen that before
 
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Is it possible the box is not actually grounding? MUST be

Loose/ bad connections in the connectors
 
67Dart273 said:
Is it possible the box is not actually grounding? MUST be

Loose/ bad connections in the connectors
Click to expand...
That is what I'm thinking but the weird thing is I didn't change anything as far as the ecu goes. I took off the plug and checked my voltage and checked the ground but I never removed the ecu. If you remember we spoke about it before and determined the ecu was bad so I replaced it and it fired right off haven't had a bit of trouble since. It has to have something with that transducer having voltage. Im gonna unground it and check the transducer again if its got voltage then I will know that is the problem
 
I ran a ground wire to the one bolt hole in the ECU I haven't had any issues. They do go bad though out of nowhere.
 
Dartswinger70 said:
I ran a ground wire to the one bolt hole in the ECU I haven't had any issues. They do go bad though out of nowhere.
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I did the same thing when I installed the new one. I ran a ground from one bolt to the ground on the battery
 
Happened to me years ago. I quit mowing the lawn and never had that issue again
 
AJ/FormS said:
Ok pardon my ignorance but what are you calling a transducer?
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I maybe using the wrong terminology but its the metal part circled.

20210421_180156.jpg
 
Ok got it; that is a transistor and the whole box is called an ECU short for IDK, maybe Electronic Control Unit.

It has just one job not too complicated. It takes the very tiny signal generated by the magnetic pick-up, in response to the reluctor vanes passing by the pole-piece, amplifies it and shapes it, then interrupts the ground between the coil and the case, and from there the electrons have to scurry back to the battery, thru whatever grounds they can find.
So you have five or six parts to this system; namely
1)the ground return path,
2) the power-up path,
3) the signal generator, and spinning reluctor
4) the coil and it's ballast,
5) the ECU,
6) the coil wire and distribution system, including the rotor

The easiest test is the One-Spark Test.
This proves the ECU, the Coil, and all the wiring are working. Simply pull the coil wire out of the cap and near-ground it , then cycle the key to on then off. Every time you turn it to off, the coil should fire One shot.
If it does that then over half your diagnostics are done.
 
Yea transistor sorry I fixed my op! What is the one spark test you speak of?
 
Couple ways to do that test. One is, you "rig" a spark gap with the coil wire, or "rig" it to a plug so you can see it through the hood gap. Repeatedly turn the key on/ off. Each time, you should get a spark

The way I do it is "rig" the coil wire, turn the key to "run" and pull apart the distributor pickup connector. Take the end NOT going to the distributor, and repeatedly ground the bare terminal. Each time, should get one "snap" spark If you do, it's in the connector/ distributor pickup
 
dartfreak75 said:
And If check the transistor while it's running it kills the engine
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If you are checking VOLTAGE with a digital volt meter and touching the transistor with onwme lead and the other (I assume) was on a ground.

Then there is a problem.

Volt meters have super high resistance and should not cause any issues to most electrical systems.

Next time you have things running take a wood or plastic dowel or the like and press on the transistor. If the engine dies then you have a mechanical issue. (Loose /bad ground, connector that has bad pins, a transistor that has bad connections or is internally bad)
 
Dana67Dart said:
If you are checking VOLTAGE with a digital volt meter and touching the transistor with onwme lead and the other (I assume) was on a ground.

Then there is a problem.

Volt meters have super high resistance and should not cause any issues to most electrical systems.

Next time you have things running take a wood or plastic dowel or the like and press on the transistor. If the engine dies then you have a mechanical issue. (Loose /bad ground, connector that has bad pins, a transistor that has bad connections or is internally bad)
Click to expand...
yrs ago, they were having issues with fake ecu's. Fake in that the "transistor" was empty on the back side. It was just for show, hahaha.
 
Dana67Dart said:
If you are checking VOLTAGE with a digital volt meter and touching the transistor with onwme lead and the other (I assume) was on a ground.

Then there is a problem.

Volt meters have super high resistance and should not cause any issues to most electrical systems.

Next time you have things running take a wood or plastic dowel or the like and press on the transistor. If the engine dies then you have a mechanical issue. (Loose /bad ground, connector that has bad pins, a transistor that has bad connections or is internally bad)
Click to expand...

He can just mash on it with his thumb. (shhhhhh). lol
 
RustyRatRod said:
I wanted to maybe shake his day up
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12 volts won't do that, body has too much resistance.

I lost a bet, I thought a tap water wet rag placed between the positive and negitive terminals of a fully charged car battery would heat up and boil off the water.

I was wrong too much restance.

(Ya ya ya salt water might have been different but that was not the bet)
 
Dana67Dart said:
12 volts won't do that, body has too much resistance.

I lost a bet, I thought a tap water wet rag placed between the positive and negitive terminals of a fully charged car battery would heat up and boil off the water.

I was wrong too much restance.

(Ya ya ya salt water might have been different but that was not the bet)
Click to expand...

No, but if that transistor has a short, you WILL know it. Ask me how I know. lol
 
My dart sport started having similar issues. Drove me crazy! My dad and I finally realized that the wiring harness has some break some place. Whenever we wiggle or remove ecu and ballast connectors car fires right up. But if it stays sitting for a few days and try to start just cranks over and will not fire. Everything else checked out good.
 
also when it does start you can drive car anywhere and does great. Most often than not will restart without messing with harness. It's when it sits that no spark rears its ugly head!
 
This really sounds like a "poor connection" problem to me. Connector/ connections. Wiggle test the heck out of stuff. And I will say it again........SUSPECT the dist. connector. If this is an old harness you don't value too much, cut off the dist. connector and replace it with mating insulated "flag" terminals or similar. In any case replace it.
 
probably not your particular problem, but this is indicative of how strange these intermittent wiring gremlins can be: my 74 dustpan 360 had this weird thing where every once in a while, it would not start. This time I was over at my friend's shop, and when I went to leave, it wouldn't start. He came out and found the problem, the lead from the electronic distributor had gotten pinched under the dist. cap and it had just enough pinching to work MOST of the time, but occasionally it would interfere in the signal to the ecu.
 
QuickDart360 said:
My dart sport started having similar issues. Drove me crazy! My dad and I finally realized that the wiring harness has some break some place. Whenever we wiggle or remove ecu and ballast connectors car fires right up. But if it stays sitting for a few days and try to start just cranks over and will not fire. Everything else checked out good.
Click to expand...
I think this maybe the case. Because I did wiggle a bunch of wires and it started working after
 
So I went out this morning to start the dart its been setting about the same amount of time as last time between starts and the same thing. No spark. I checked the transistor with a test light and it lit up like a 12 volt light. So I held it there and very slightly wiggled the plug on the ecu the light went off and it fired right off immediately! Is the plug shorting or a bad connection ?
 
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