1979 2f Ignition single spark (1 Viewer)

[ratchet]

Hey ladies and gentlemen, I picked up a non running 1974 FJ40 with a 1979 2f in it. As far as I can tell the distributor is the stock 1979 dual vacuum advance dizzy that should be on the motor. For some reason, I can't get a very good spark out of it.

When I first got it, it had a mini truck coil and igniter on it. It seemed to be wired correctly but I could not get any spark from the coil wire. I swapped in a known good igniter for a 1979 FJ40 and now I get no spark while cranking but as soon as you let off the key there is a single spark. I swapped in a known good distributor signal generator (pick up coil) and got the same result.

I have tested the coil by hooking 12v to the positive and then temporarily grounding the negative and this will give me a weak spark so I am pretty sure the coil is not the culprit. Also since I am getting the single spark I think that would mean the coil is definitely good.

I have five wires coming off of the igniter:
black = negative coil post
green = grounded to the igniter body (I also have a ground jumper running from here to the negative post of the battery to make sure I get a good ground)
red = to red wire coming off of distributor signal generator (pick up coil)
white = to white wire coming off of distributor signal generator (pick up coil)

The following power wires coming off of the igniter originally went to a two prong connector together. I didn't have the factory connector for it to plug into so I clipped it and ran two 12v wires to these two wires
tan (goes into the igniter) = 12v when the key is in the run position (pulled from the BY wire coming off the ignition switch)
yellow (goes to the positive side of the coil) = 12v when the key is in the start position (pulled from the starter terminal)

I also tried switching the tan and yellow wires (ie: tan gets 12v from the starter and yellow gets 12v from the ignition but it didn't make a difference)

I know that originally the igniter was supposed to get 12v in the start position (from the starter terminal) and then when the key goes to run, the coil gets voltage through a resistor from the BY wire off the ignition switch. However, during searching the board I read that in many conversions these are both hooked up to full 12v with no ill effects on engine running or component life. Besides, I am still using the mini truck coil which, if I understand correctly, can handle a full 12v all the time.

I tested the voltage at the positive coil post and I get about 12v while the key is in the run position then it drops to about 9v while cranking.

I also hooked a jumper wire directly from the battery positive post to the positive coil post and ignitor's tan power wire but that gave me no spark at all. The ignitor did get hot to the touch (it may have already been warm though so I don't know if it was a result off the jumper wire) so hopefully I didn't mess it up.

An interesting note with this is that as I was hooking up the jumper wire the coil wire was hooked up to the coil on one end with the other end laying on the fender. When there was intermittent contact with the positive battery terminal I got a spark from the coil wire to the fender.

After I tried the jumper directly from the battery, I hooked the power wires back up as I described earlier and got the same result as earlier; no spark while cranking and then a single spark when you let off on the key.

I really thought the known good parts would cure my problems and I am about out of ideas. Any help would be appreciated.

Richard

 

[bsmith123]

ballast resistor

The function of the ballast resistor or a resistor wire with the old points system did cut the voltage in the run pos only and fed 12v for start. The reason for this was to extend the life of the points.

It sounds like you know what's what schematically but I would disconnect the wires from the ignition run and the ignition start positions and run two power wires straight from the battery then try to start it. if this does not work then one of the components is bad

w/o a schematic I am not sure exactly how the spark is triggered but when you switch off power that creates a trigger to give a spark. I would look towards the sensor for that

I think you are right that you should have 2 12 volt wires and the ballast resistor is obsolete on the newer ignition you may be hurting components running them at too low a voltage

"I also hooked a jumper wire directly from the battery positive post to the positive coil post and ignitor's tan power wire but that gave me no spark at all. The ignitor did get hot to the touch (it may have already been warm though so I don't know if it was a result off the jumper wire) so hopefully I didn't mess it up."

Oops I see you did that already--- try this hook up the power wire and then take the neg side of the coil to a clean ground and momentarily touch the ground on and off the metal --if you get weak spark then the coil is bad--if not then it is not being "triggered" as mentioned above

 

[ratchet]

It sounds like you know what's what schematically but I would disconnect the wires from the ignition run and the ignition start positions and run two power wires straight from the battery then try to start it. if this does not work then one of the components is bad

"I also hooked a jumper wire directly from the battery positive post to the positive coil post and ignitor's tan power wire but that gave me no spark at all. The ignitor did get hot to the touch (it may have already been warm though so I don't know if it was a result off the jumper wire) so hopefully I didn't mess it up."

Oops I see you did that already--- try this hook up the power wire and then take the neg side of the coil to a clean ground and momentarily touch the ground on and off the metal --if you get weak spark then the coil is bad--if not then it is not being "triggered" as mentioned above

I tried the coil test once before and got a weak spark. I just went and tried it again twice; once with power directly from the positive post of the battery and once hooked up as described earlier but with the key in the run position.

When powered from the positive post of the battery I still get a weak spark. When powered normally I get what I would call a decent spark. It arcs about 1/4 of an inch from the end of the coil wire to the metal.

My understanding of this test is that it is to isolate the coil. Basically you are taking the pick up coil and igniter out of the equation and doing their job for them (deciding when to create a spark and creating it by grounding out the coil).

You mentioned that "--if you get weak spark then the coil is bad--". Is that a typo? I thought that if you get a spark (any spark really) it confirms that the coil is good.

w/o a schematic I am not sure exactly how the spark is triggered but when you switch off power that creates a trigger to give a spark. I would look towards the sensor for that

I am not sure how the spark is being triggered either. The only thing that I could come up with is that I am powering the coil/igniter with one 12v source in run and then a different one in start. As the key changes from start to run, the voltage source changes and then it may cause it to trigger the spark. However I think that is how the stock wiring was. Anyway that is all conjecture. It could have nothing to do with anything.

I noticed that when I hook 12v to the igniter and coil from the battery it heats up the igniter. Alot and quick. This doesn't seem right.

What I have been doing is running a jumper from the positive battery post to the positive post on the coil and then a jumper from there to the tan wire coming out of the igniter. When I run power directly to one and not the other (positive coil post or tan wire) the igniter doesn't heat up; only when the power is run to both. In addition, if I hook it up normally (with 12v coming from the ignition switch and starter terminal) the igniter doesn't heat up, even if I leave the key in run.

Also when I run power to one, the other, or both I still get no spark when I crank the engine.

Oh yea, I mentioned "known good parts" in the first post. These are used parts I got from Spectre. They guarantee that they are good but maybe they aren't. I really don't want to drop $200-400 to get a brand new igniter. At that point I may as well just go HEI or something of the sort...

Thank you for your suggestions. Got any more?

Richard

 

[3doghouse]

...The only thing that I could come up with is that I am powering the coil/igniter with one 12v source in run and then a different one in start...

This is almost certainly what's going on. Make sure that when you're testing, you disconnect all of the existing wiring to the coil/ignitor, and run right off the battery.

Also, a good ground to the ignitor is essential.

Eliminating all the ignition switch and resistor wiring & let us know if that works.

 

[Pin_Head]

The fact that you get a spark when you turn it off is unremarkable because it always sparks when the primary field collapses. This indicates that the coil was powered up.

If the spark can jump 1/4 inch, it isn't "weak".

Diagnosing problems with electronic ignitions requires either specialized equipment (signal generator and O-scope) or spare parts that you know are good for swapping. You seem to have swapped the distributor pickups and ignitors and still have the problem. You have also hot wired the ignitor directly, which would rule out unusual problems with the power feed. Since you seem to have covered all the bases, I would suspect that one of your swapped parts is also bad, even though this is unlikely.

 

[bsmith123]

isolating

it is a good point to make sure you remove all the other wiring when you run the batt wires to the coil and igniter and short in the original wiring can affect the new wires from the batt as the current will follow the path of least resistance.

If you have a good spark with everything hooked up normally that would make it seem the coil is good

yes a coil can have a weak spark it should be bright, have some blue in it (and snap or ticking noise), a small weak yellow spark is not good

Hows the cap, rotor, and spark plugs?

if it is just not starting then maybe go back over again checking compression, fuel, timing, firing order etc

try some ether in the carb and see if it fires up

 

[ratchet]

it is a good point to make sure you remove all the other wiring when you run the batt wires to the coil and igniter and short in the original wiring can affect the new wires from the batt as the current will follow the path of least resistance.

When I did the tests with the coil/igniter hooked up directly to the battery I made sure to have the other wiring disconnected.

Hows the cap, rotor, and spark plugs?

if it is just not starting then maybe go back over again checking compression, fuel, timing, firing order etc

try some ether in the carb and see if it fires up

I bought the vehicle in non-running order and started my troubleshooting by pulling a plug to see if it was sparking. It was not and so I moved back to the coil wire which I found was not sparking either. That brings me to where I am now. Once I get a spark at the coil wire I will move down the line and make sure there is spark at the spark plugs. If it still won't start with spark at the spark plugs, I will move on to the other things you mentioned.

The cap, rotor and spark plugs are in ok shape but at this point they are not in the equation. I am just trying to get a spark out of the coil wire and am getting nothing.

Also, a good ground to the ignitor is essential.

Eliminating all the ignition switch and resistor wiring & let us know if that works.

I have a jumper running from the igniter body to the negative battery post so I am sure the ignition components are grounded well.

When I did the tests with the coil/igniter hooked up directly to the battery I made sure to have the other wiring disconnected.

The fact that you get a spark when you turn it off is unremarkable because it always sparks when the primary field collapses. This indicates that the coil was powered up.

With all due respect (you really know your stuff), this doesn't make any sense to me. If this were true then it should give me a single spark when powered directly from the battery and when the old igniter was hooked up because I am using the same coil but neither did. If the coil is powering up now it should have been powering up then and giving a single spark when the power is cut.

Diagnosing problems with electronic ignitions requires either specialized equipment (signal generator and O-scope) or spare parts that you know are good for swapping. You seem to have swapped the distributor pickups and ignitors and still have the problem. You have also hot wired the ignitor directly, which would rule out unusual problems with the power feed. Since you seem to have covered all the bases, I would suspect that one of your swapped parts is also bad, even though this is unlikely.

This appears to be the unfortunate truth. I guess I will call Spectre tomorrow and see what they have to say about their used parts. The catalog says no returns on used parts but what if one of them is actually bad? I suppose they will probably say that I may have hooked it up wrong.

Anyway thank you all for your help. If you can think of anything else I can try please let me know. I will post up if I actually get it fixed.

Richard

 

[Pin_Head]

With all due respect (you really know your stuff), this doesn't make any sense to me. If this were true then it should give me a single spark when powered directly from the battery and when the old igniter was hooked up because I am using the same coil but neither did. If the coil is powering up now it should have been powering up then and giving a single spark when the power is cut.

I think you are misinterpreting what I mean by "powered up". It is true that any time that the coil is magnetized, it will generate a high voltage when the power is cut off and the field collapses. In order for it to be powered up, the - side needs to be grounded; either by the ignitor or points or manually in the case where you are testing the coil. Just having 12V at the + side without grounding the - side won't magnetize the coil. Whether the ignitor is grounding the - side of the coil depends on whether it is working and the position of the distributor rotor.

 

[bsmith123]

coil

Do you have a multi meter since you mentioned checking voltage

ohm the coil to the case and the primary windings to the secondary for shorts

Also, I am not familiar with your system but if you have a wire from the starter to the igniter in start and a wire to the coil + side in run how does the coil get power during start?

what year and model mini truck is it off? I could probably help more if I could Google a schematic

It does sound like you have a bad component but I would try to get the schematic for the mini truck and double check the way it supposed to be wired

sounds funny that the igniter is heating up ---like a short maybe? or hooked up wrong? I think that maybe the igniter is wired in wrong have a look at the link for a generic system ---the ignition module is powered off the neg side of the coil and there is the sensor to create a pulse signal to shut the coil on and off by breaking continuity on that ground side---thus inducing the secondary voltage to make the spark. I think both the starter wire and run wire should be going to the + side of your coil --one to power with the key in start and one for with the key in run


have a look at this
http://auto.howstuffworks.com/ignition-system.htm

 

[ratchet]

Sorry guys, I haven't had a chance to post up since last week end. That pesky work thing kind of gets in the way of the important stuff...

I ended up talking to Specter and they said that there was a chance that their parts were bad. They offered to test them if I sent them back which I did.

So now I am waiting to hear from them. I am kind of hoping that they tell me that the igniter was bad so it will be an easy fix. Anyway should get the parts back sometime next week.

Richard

 

[ratchet]

So I got the parts back from Specter. They were very good about working with me on this problem. They said that the signal generator (pick up coil) was bad so they sent me new one. When I got the parts I found that they sent me a different signal generator and a different ignitor which they didn't mention (I was able to tell because one of the plastic connectors was melted a little on the old one and on this one it wasn't).

I put the new (used) parts in and got it to spark like it is supposed to. I then swapped my original ignitor in just to see if it was any good and it sparked like it is supposed to. It appears that what happened is my original signal generator was bad and the one I got from Specter was bad also which is why it wasn't sparking with either ignitor.

It seems unusual to me to get two bad signal generators in a row since they rarely go bad but since I was sent a different ignitor I will never know for sure which component was causing the problem. This is partially my fault because I can't remember whether I tried my original ignitor with Specter's first signal generator.

Anyway, it is working now and I have learned more than I ever wanted to know about FJ40 ignitions. Now I can move on to the other 101 things that are wrong with it.

Thank you all for your help.

Richard