No spark Mopar dizzy and FBO box & coil

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gtsdude

gtsdude

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Like title states, I last drove my dart couple weeks ago, went to pull it out yesterday and no fire. Usually starts right up. I have fuel and no spark. I have done some checking and just need to verify what I have so far. I am leaning toward the ECU, I don't have a spare handy to throw in it yet. I put my spare ballast in right away but did not help. I have 12 volts to #1 pin to ECU, I have 11.5 or so volts to + side of coil and the same on the - side of coil with key in run position. That is what makes me think ECU, shouldn't the - side be lower than the + side with key in run position. Next step is to check voltage while cranking on - and + side of coil when I have a little help. Any thing else to check besides grounds and reluctor gap looked good but need to double check gap. It has ran great for 10 plus years with same set up and all of a sudden no spark?
 
Quick check of the pigtail connector for the distributor just to eliminate that.
Seen more than one loose connection and not fire.
 
See if you have spark while jumpering the start relay, with the key in "run". This will give you an indication of whether the bypass circuit is effected

Make absolutely certain the ECU is grounded. One way to do that is check coil NEG with key in run. Voltage should be quite low, the lower the better, perhaps less than 1 volt. If NEG side of coil is high, near battery, either the ECU is bad, or not grounded

If you have tach or radio condenser on the coil connections, disconnect everything except ECU

Another common trick is to "hot wire" a clip lead 12V right direct to coil PLUS

Don't forget coil could be bad. Coils don't need to be grounded, so you can just "throw one" on the engine and wire it up quickly.

As suggested wiggle the 'eck out of the dist. connector.

You should get some clip leads, will allow you to do so much more.

Clip to your meter and prop it up so you can see it, then you can check cranking voltage.

With a spark checker / gap, you can clip to that and look through the hood gap and see IT while you twist the key.

Put your meter in the dist connector and crank, meter on lo AC volts. Distributor should generate about 1V AC

Inspect the insides of the cap / rotor / reluctor. Look for strike damage to pickkup / reluctor, rust, debri, and moisture / dirt, etc in the cap and rotor. Look for "punch through" on the rotor and UNDER the rotor
 
67Dart273 said:
See if you have spark while jumpering the start relay, with the key in "run". This will give you an indication of whether the bypass circuit is effected

Make absolutely certain the ECU is grounded. One way to do that is check coil NEG with key in run. Voltage should be quite low, the lower the better, perhaps less than 1 volt. If NEG side of coil is high, near battery, either the ECU is bad, or not grounded

If you have tach or radio condenser on the coil connections, disconnect everything except ECU

Another common trick is to "hot wire" a clip lead 12V right direct to coil PLUS

Don't forget coil could be bad. Coils don't need to be grounded, so you can just "throw one" on the engine and wire it up quickly.

As suggested wiggle the 'eck out of the dist. connector.

You should get some clip leads, will allow you to do so much more.

Clip to your meter and prop it up so you can see it, then you can check cranking voltage.

With a spark checker / gap, you can clip to that and look through the hood gap and see IT while you twist the key.

Put your meter in the dist connector and crank, meter on lo AC volts. Distributor should generate about 1V AC

Inspect the insides of the cap / rotor / reluctor. Look for strike damage to pickkup / reluctor, rust, debri, and moisture / dirt, etc in the cap and rotor. Look for "punch through" on the rotor and UNDER the rotor
Click to expand...

I did turn key on and cross the starter relay, still no spark.

I ran jumper from + side of battery to + side of coil, still no spark.

I did have 11.5v or so at + and -sides of coil with key in run position, makes me lean toward ECU, will double check grounds to be sure, but ECU is bolted down on both ends and was cleaned up well when I put it in 10+ years ago.

I disconnected the tach

cap rotor look good

I will run ac volt check on reluctor

thanks for the help
 
gtsdude said:
I did have 11.5v or so at + and -sides of coil with key in run position, makes me lean toward ECU,
Click to expand...

NOTE I could be incorrect on this, here's why.

NORMAL Mopar ECU draws coil current (coil NEG is grounded) with key on / not running)

GM HEI IS NOT. That is coil does not get warm with GM HEI key on / engine stopped

SINCE this is FBO and not "Mopar" I don't know, after some thought, whether they do or do not draw current
 
I am not sure either, but it should be the same, FBO claims if the ECU fails I can buy a parts store ECU to get me home, but any long term use will ruin the coil.

I had another box and coil laying around and ended up using them to convert a lean burn on an aspen I had and sold the car, wish I still had some extra parts to try out.
 
gtsdude said:
I am not sure either, but it should be the same, FBO claims if the ECU fails I can buy a parts store ECU to get me home, but any long term use will ruin the coil.

I had another box and coil laying around and ended up using them to convert a lean burn on an aspen I had and sold the car, wish I still had some extra parts to try out.
Click to expand...

I would not bet on this. There were rumors that FBO is HEI electronics in a Mopar box. I don't know, but don't condemn it just because of this 'til you find out. I would contact them and see if they will divulge this
 
I hear ya, but I have the old system with ballast resistor, I have heard the new system that doesn't require a ballast was possibly made that way, will do some more checking and call FBO if all else fails
 
I ohmed out the pick up and got 288 ohms, checked ac voltage on the pickup also on lowest setting, wich was 200 on my meter, I got .1 for a second and went to 0. Thought I had a bad connection so tried it few times, same every time. I also put meter on - side of coil and cranked it over, no fluctuation, stayed at 11.5 volts. But this has me thinking, does the ECU get it's signal from the pickup to switch the ground side of coil and my pickup is bad so I have 11.5 on - side of coil all the time?
 
I can only speak to OEM parts

On an OEM Mopar box, "just sittiing" with key ON, the box draws coil current, so the coil NEG is at low voltage, IE ground

The pickup signals the box which turns the coil OFF to fire. This is also true of points. The spark is formed when the points open. So an OEM Mopar box works like points sorta

On a GM HEI module (which I run) and the key is on, engine stopped, the coil is shut off.

So the two systems "in a manner" are opposite. However, when the GM one is ROTATING, it still triggers the coil "off" to form the spark.

Once again, I would not bet one way or 't other how the FBO works.

When trying to check the pickup, make SURE your meter is on 'AC' volts not 'DC' volts. The output of the distributor is a positive / negative AC spike

Another check that works on OEM boxes and may or may not work on FBO............I can never remember which (of the two) wire, but on an OEM box, you can disconnect the distributor pickup and ground one or the other of the pickup wires, (harness connector) and it will make one spark each time.
 
Got ya, I was thinking opposite of how you explained it. I am going to try the spark test next to double check the pickup, but I read in few places should be. 400-900 ohms and at least .6 volts ac to run but between 1&2 is ideal
 
I pulled coil wire off cap, had the wife hold key to start and grounded coil wire and have spark, did the same with dizzy connection from ECU, have spark there also. I think a new pickup might be the answer?
 
gtsdude said:
I pulled coil wire off cap, had the wife hold key to start and grounded coil wire and have spark, did the same with dizzy connection from ECU, have spark there also. I think a new pickup might be the answer?
Click to expand...

You are going to have to re-phrase this because what you typed makes it sound like "there is no problem."

Do you mean you replaced the pickup and now have spark?

Do you mean you did this test and have PROPER nice, loud, snappy spark(s) as the engine rotates?

If so "it should run"

Explain exactly what you did and "what you saw."
 
67Dart273 said:
You are going to have to re-phrase this because what you typed makes it sound like "there is no problem."

Do you mean you replaced the pickup and now have spark?

Do you mean you did this test and have PROPER nice, loud, snappy spark(s) as the engine rotates?

If so "it should run"

Explain exactly what you did and "what you saw."
Click to expand...

I pulled coil wire off the dizzy, unplugged yellow wire to starter relay so motor is not turning. Had wife turn key to start, held coil wire to ground and I have spark there. So coil is working. I then unplugged the 2 wire pick up connector off the dizzy, had my wife hold key to start, grounded both sides of the plug and have spark there also. So I have power to the dizzy pick up from the ECU, power from the coil to the dizzy cap through the coil wire, but no spark at plug wires. Sound right? Pickup is bad? The pickup also ohmed low and could not get an ac volt reading while cranking it over.
 
Ok, now I see what you did, LOL. Pickups go bad but seldom. It IS starting 'to sound like'. But first, take a REAL good look for rust, debri, etc between pickup and reluctor.

AND make sure distributor is actually turning.

Have you checked reluctor gap? And checked for bad shaft wear / wobble?
 
Yes I checked under the cap, no debri and reluctor gap is .008. shaft has no noticeable wobble to it.

I was doing some more research, found an old thread on moparts and a guy has the same FBO set up, they trouble shoot just like a Mopar set up. He had same symptoms I am having, including 11.5 volts on both the - and + side of the coil. Taking the male end of the dizzy harness to ground and see if it sparks will tell you pick up or ecu. If no spark its ecu if it sparks its the pick up. I did get a spark when I tried it but I don't remember if it was the male or female end, will have to try it again.
 
Thinking about this, it must be the bare end, but I "ain't" sure LOL

I guess I'm gonna havta go out there and "rig" a Mopar box 'n test it LOL
 
Update, I unplugged the dizzy pick up harness, turned key to run, pulled coil wire off the dizzy cap, everytime I touched the male end of the dizzy harness to ground I got a spark off the coil wire that jumps 1/4 inch. This is supposed to point toward the pick up coil. So I do another test for the pick up coil to make sure, set meter on ohms, ground one end of meter and touch either side of the pick up coil wires coming off the dizzy, if any reading the pick up is bad. My test showed no reading WTF! One test shows one thing another the opposite! So I pulled the 2 wires that run to the pickup coil from the ECU out to inspect them and checked voltage at he coil - and + again, I now had 8volts + side and 1.6volts on - side, I had 11.6 on both sides yesterday? So I thought I will check for spark at the plug wires, I HAVE SPARK! So I try and fire it up, touch the key and it takes off! I am still not sure what happened, I am thinking the pick up wires in the harness from ECU has a bad spot and it. I checked continuity on them while wiggling them around but they were fine? Going to check them out closer tomorrow and check the coil - wire also as it was run with the other 2 wires in question.
 
Measuring from ground to either pickup wire should show infinite, or open. If you get "weird" readings, you are probably touching the probes and "reading" you body resistance

The pick up wires I don't think ?? affect coil voltage. This would be easy to "run down" just re-check coil voltage with and without the pickup plugged in

ARE YOU absolutely, positively certain the ECU was GROUNDED?

Last this could be and intermittent problem IE bad connections at the ECU connector or even a come / go problem in the box.
 
ECU is well grounded, in fact I never messed with while trouble shooting it. It is bolted to the inner fender on top of 1 inch spacers so air can get under the ECU. Think I will take it off and clean up the bare metal just in case. I let it run and wiggled wires trying to get it to quit but no luck. And I agree about the ECU, maybe it's on its way out, I will pick up a cheap parts store ECU in case it does it again. I still have to unwrap the wires and make sure they are all ok also. Thanks for all your help, I am glad it fired up but would like to know why it had no spark to begin with.
 
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