74 Dart Sport Spark Issue

[mcp]

He all. New to the forum, great place! I have a 74 Dart sport that I am fimnally getting around to finishing. 340 Auto, nothing fancy just a street beater. Now the new parts are as follows: Coil, ECU, Distrib & pick up, Resistor, Volt Reg, etc. All ohm readings on the parts check out perfect as per specs, I have 12v to the coil, ECU is well grounded, new ground straps in the car, ect. the thing I can't get is the coil to flash ground to fire. Held the coils wire 1/4in away from ground, no arc. tried the standard test for a plug in one wire and looked for spark, nothing. Meter in the coil as you wheel it over, 12v only, no spike. Harness is good and came out of running car. Car ran with old 360 in it years ago, no problem. the motor is brand new so this is the initial fire up. Any thing I am overlooking? I am suspect of the dist plug on the harness side since I can not get a solid ohn reading and when you wiggle it it fails to open line so I an changing that out in the AM. Point is I have power everywhere I need it, ohm readings on all in spec and just can not get the coil to light it off. I have 3 coils and I know they are good (tested in other car) along with all the other components (tested in other car) so any pointers? Thanks in advance for yout time.

 

[mcp]

Here is the status:

With the Key in the ON position.

12v at:
- Alternator Field
- Alternator Main
- Blue Wire on the ballast (2 post ballast / 4 pin ECU)
- Starter Solenoid Main

6v+ at:
- Pos (+) side of coil Brown wire
- Brown wire at ballast

1v at:
- Other field wire on alternator
- Neg (-) side of coil

Battery is 12.93v

Cut the harness open, followed every lead point to point. Cleaned each blade on each bulkhead connector. re-did the 4 into one connection for the blue wire, the 3 into one on the brown wire (re-crimped and re-soddered) and checked continuity on all point to point runs, all good. Ohm reading on the ballast is 1.2 and Distrib is working with .08 clearance (took it out and rotated it slow and whatched it go up and down.

Heading out now to check the readings while I wheel it over.


So what did I miss?

 

[Torrance00]

Hi
OMG so funny I posted almost the exact message in the dodgeforum
in there dart section... I mean our posts look almost word for word
I replaced all the same parts you have, did the same ohm checks
did voltage checks, set the times, 2.5 def btdc...
I get no spark out of secondary wire...
the engine turns over fine. I have had an on going electrical problem
for months, car would start run, then not restart, had to be towed
4 times in the last month,,,more then my whole driving life...
At one point and that time not having a very good electrical diagram
I found 2 red wires from the steering column down to the connector
thought they were something, because if I reconnected them, the
car restarted...but yesterday found out they are the buzzer key ..
Since we both have the same problem, I hope we can work together
to solve it...
You say with the ignition in run you get 6.5v at the +coil, mine was
down to 1.3 -+ so I used a 14g wire and made a bipass, since this
comes off the ballist resistor, it comes right from the ignition switch
and I would think 12v. since the resistor is not in play yet...at least
from my reading. A friend gave me a 73 service manual for
some chysler products...
drop me an email at [email protected]
Best

 

[rumblefish360]

Don't doubt if he did. Many members here also post in other forums, sometimes with different screen names.

Welcome aboard.

 

[moparman9]

Disconnect the connector from the ECU and check to see if any of the contacts are spread and possibly not contacting the ecu pin.

If that looks good, hold the connector so that the pin pattern looks like a pentastar, pin #1 will be on top center, #2 will be the next in a clockwise orientation, #3 under #2, #4 opposite #2, and #5 opposite
With the key in "run" pins #1,2,and 3 should be within 1 volt of battery voltage. If not, find the problem and repair it (possibly the ballast resistor).
Also, pull the connector off the starter relay so the starter does not engage, check for battery voltage at coil + terminal with the key held in "start".

Connect an ohmmeter between pins #4 and #5 with the distributor connector connected, the reading should be 350-550 ohms. If this shows an open, your wiring is broken between the ECU and distributor or you distibutor pickup is faulty.

If this all checks out ok, check for approx. 1 volt AC pulse at the distributor connector when the engine is turned over (disconnect the distributor connector and connect the multimeter directly to it)

If everything checks out ok, check the air gap on the distibutor reluctor, it should be .008". If there is too much gap it may not trigger the ECU.

Another handy way to check spark without spinning the engine over is to pull the distibutor out and reconnect everything to it, then just spin the distributor shaft by hand with the key in "run" and the coil wire near the block, it should spark.

A couple years ago, I got some defective Ecu's from the parts store. I tried three before I just gave up on that brand--every time I put a new one on there was no spark and when I put an old spare I had on, there was spark again.

Good luck on your troubleshooting, hope this helps.

 

[SGGDuster]

I've been having the exact same issue. Car was stubborn starting one morning, then later that day required a jump (kept trying to fire it up until the battery was dead), but after the jump fired right up. Haven't gotten it started since, jump or no jump. I have power where I need it, have cleaned up all my grounds (need to grab a neg battery cable, it's a little shoddy), and the resistances all check out, just not getting a spark out of the coil. I bought a new coil and threw it on, but it has the same readings as the stock coil and still won't send a spark. I'm going to pickup a new ECU tomorrow, but I'm out of ideas. Haaaaaaaaaalp!

edit: reluctor gap and ballast resistor are both fine, as well.

 

[SGGDuster]

An ecu solved my problems. Despite getting the proper voltage and resistance readings and ensuring good grounds, the ECU turned out to be the culprit.