Troubleshooting electronic ignition ('78 FJ40)

[M5driver]

I had hoped to hear the ol' 2F roar back to life this weekend, but no joy!

It appears the problem is with the ignition. Fuel is good - I'm pulling fuel from the tank to the rebuilt carb, via the new pump no problem. Starter is good and strong, battery well charged and putting out 12+ v. But, no spark.

I searched the threads here, but did not find anything that gave me a complete diagnostic or any "where to go from here" suggestions, so I decided to ask.

This is a '78 with the fully electronic ignition. Right now, I'm thinking it might have been nice to have the old points style ignition, because those parts are easy to come by here in Malawi. The electronic parts may be much tougher to source, and I am running out of time to get the mule operational. I'm now due out of here the first week in December

Here's what I have so far on the electrics: No spark from the coil (actually I get an occasional very weak, yellow spark, but I have to practically touch the HT wire to the valve cover or head to get even that.

Starting from that unhappy point, I checked, per the FSM, voltages between the LT terminals on the coil and the spark ignitor body/ground. The FSM states "approximately 12v" to each terminal. I am showing 6.3 +/- to the the positive terminal, and 0.9-0.8v (!) at the negative terminal. Also checked ohms as indicated in the FSM, and the coil (Toyota OEM - ND ) appears to be good in that regard. Since coils can be had here easily, I decided to try swapping in a new (presumed good) coil. The results are the same - 6.3v at the + terminal; 0.9/0.8v at the - terminal, no spark. This made me suspicious of the ignitor, so I decide to check the upstream voltage. I am getting 12v+ from both terminals in the connector from the wire harness that powers the spark ignitor. FWIW, I did not try the third test shown in the FSM - small battery to the ignitor plug, with the caveat to do this very quickly or risk damage to the ignitor. I'm working solo on most of this, although helps anytime I ask, and Chris was able to come by yesterday when I was doing the initial troubleshooting.

SO.... what am I missing? The rotor and cap are good (new shortly before tearing down the Mule), HT wires all check out fine, and I suspect I would have spark to the plugs, if I had spark from the coil. Nothing was changed on the distributor during the teardown/buildup except the base clamp. I verified multiple times that the distro went back in correctly, and there is nothing I can think of that the distro would be adding to the problem, since there is no spark getting to the cap.

Any/all comments, suggestions, help welcomed.

TIA.

 

[Pin_Head]

There isn't much to diagnosing it:
1. hotwire the coil. (wire from battery + to coil +). Try it. if it runs, there is a bad connection in the power feed to the coil/ignitor.
2. If no spark, replace distributor pickup with known good replacement. Does it run?
3. If not, replace ignitor with known good replacement.

If you have a signal generator and oscilliscope, you could test the pickup and distributor.

 

[M5driver]

Thanks for the quick reply. I wish it were that simple. I have the only gasoline version of this vehicle ever imported into Malawi; Chris has the only diesel version. This makes it quite difficult to obtain test items. In the US, I would do everything you mention and probably isolate the problem quickly. Here, it will take longer...

There isn't much to diagnosing it:
1. hotwire the coil. (wire from battery + to coil +). Try it. if it runs, there is a bad connection in the power feed to the coil/ignitor.

I will try this. However, as I noted above, the power from the wire harness is a solid 12+v on each terminal. If there is a bad connection, I suspect it is in the wires that are attached to the ignitor itself, or something internal to the ignitor, which appears to be a sealed box.

2. If no spark, replace distributor pickup with known good replacement. Does it run?

Finding a known good replacement for that pickup will be a real exercise. I'll be checking in with Toyota Malawi in the morning, as well as with a couple of independent shops and a couple of parts houses that carry more than most. If these parts are not on the shelf at Toyota, the small shops can usually find a replacement, although it will almost certainly be Chinese, Vietnamese, Indian, or Nigerian in origin - but it WILL say "genuine Toyota" on it somewhere

3. If not, replace ignitor with known good replacement.

Ditto. Toyota is probably the best bet, but they are not likely to loan me an electrical part for testing. I could be wrong...

If you have a signal generator and oscilliscope, you could test the pickup and distributor.

Ummm... that would be nice, but not even dealership repair shops have such advanced equipment. Most mechanics' tool sets here consist of one or two hammers, one or screwdrivers, a 10mm, 13mm, and 17mm wrench - or one set of slip-joint or lineman's pliers, and a chisel. Electrical repairs are usually made without tools, no soldering, no crimping, just twisting wires together, and wrapping with paper or tape if they have it.

Given those constraints, do you suggest just going for a replacement ignitor? I suspect that will be the easiest piece to find, since the coil appears to be good.

Thanks 'n'
Dan

 

[Coolerman]

I found this information during a search here on MUD:

"The air gap for the reluctor is .008-.016".
Anywhere in that range is fine. The signal generator is a go/ no-go type of thing. It either generates a timing pulse or not. It cannot cause a weak spark, but it could cause an intermittent spark. The igniter will not consistently fire one cylinder, but not another. It will either shut down for good, or misfire erratically. The igniter doesn't know if it is hitting #1 or #4 or whatever. It just makes a spark after it sees the trigger from the dizzy.
The resistance value for the igniter is roughly the same for all 78-87."


"For those of you with >78 full electronic ignition with the magnetic pickup coil, the cheapest spare/replacement NAPA igniter is a TP50, fits dodge/plymouth/chrysler 72-92. It's like 20-30 bucks, and you can get the connector that fits it for a few dollars more. Hookup is as such (clockwise looking in, pointy bit at pin 1 in 3 o'clock
position):

3 - no connection (not even there on some units)
2 - ignition coil -
1 - ignition + from key (black/yellow originally)
4 - pickup coil (polarity is arbitrary)
5 - pickup coil

They seem to last about ten years so don't rely on it (carry a spare)"

All the 78-87 ignitors are interchangeable. Though the coils are slightly different.

The mini-truck ignitor is also supposed to work but I do not know the years that will.

Hope some of that information helps!

 

[bsevans]

I'm sorry you are so far away as I have the complete ignition setup from my '78 which was in great condition when I took it out to put in a DUI HEI.

I certainly enjoy reading your thread and am very impressed by the quality of work and the remote location where the work is being done. When you get back to Southern Arizona shoot me an email and we can trade stories.

 

[M5driver]

"For those of you with >78 full electronic ignition with the magnetic pickup coil, the cheapest spare/replacement NAPA igniter is a TP50, fits dodge/plymouth/chrysler 72-92. It's like 20-30 bucks, and you can get the connector that fits it for a few dollars more. Hookup is as such (clockwise looking in, pointy bit at pin 1 in 3 o'clock
position):

3 - no connection (not even there on some units)
2 - ignition coil -
1 - ignition + from key (black/yellow originally)
4 - pickup coil (polarity is arbitrary)
5 - pickup coil

They seem to last about ten years so don't rely on it (carry a spare)"

All the 78-87 ignitors are interchangeable. Though the coils are slightly different.

The mini-truck ignitor is also supposed to work but I do not know the years that will.

Hope some of that information helps!

Good stuff, Coolerman. I'll keep this info handy when I go to Toyota Malawi tomorrow.

Pin-head's info is also spot on, and if I had a stash of spares, or access to test parts, I would go thru the process he laid out above and find the problem that way.

I have had Toyota (and other brands) ignitors fail before - one in my 86 Camry several years before I sold it, and in the 40 about 3 years ago. That one failed due to all the road junk (salt & chemicals) from the Bulgarian winters. The one there now is Toyota and only a few years old, which is why I am surprised that it may have failed, but electronics, huh? Gremlins.

 

[M5driver]

I'm sorry you are so far away as I have the complete ignition setup from my '78 which was in great condition when I took it out to put in a DUI HEI.

I certainly enjoy reading your thread and am very impressed by the quality of work and the remote location where the work is being done. When you get back to Southern Arizona shoot me an email and we can trade stories.

Wow. Thanks. If things don't work out tomorrow tracking an ignitor down, I'll PM you my US shipping address - it wouldn't take any longer to get stuff from you than from another US source

After getting away from it for awhile this afternoon (went out to take some pix of jacaranda trees) I went back and ran through the FSM troubleshooting procedure again and came up with the same stuff. I really suspect the ignitor is the culprit. Tomorrow evening, I will try Pin-head's method to bypass the ignitor and see if I get a spark from the coil.

We are going to be in Tucson sometime around 10-12 Dec for home leave and will stay thru Christmas. When we get back to AZ, I'll drop ya a note and we can meet. Looking forward to it

BTW, I've been looking at the DUI for a couple of years. How do you like it? Is it reliable? Cold weather starts good?


Dan

 

[Pin_Head]

The fact that it makes a weak spark is encouraging because getting "weak" is not the failure modes of either the pickup or the ignitor. Weak spark is more consistent with a bad, high impedance connection somewhere in the circuit.

The voltages you find at different parts of the ignition circuit depend on whether there is current flowing in the circuit or not. You will always see battery voltage at all points in an open circuit (like when the points are open). Only when there is current flowing will you see a voltage drop across a resistor.

 

[M5driver]

The fact that it makes a weak spark is encouraging because getting "weak" is not the failure modes of either the pickup or the ignitor. Weak spark is more consistent with a bad, high impedance connection somewhere in the circuit.

The voltages you find at different parts of the ignition circuit depend on whether there is current flowing in the circuit or not. You will always see battery voltage at all points in an open circuit (like when the points are open). Only when there is current flowing will you see a voltage drop across a resistor.

That weak spark (almost not visible) is a one-time thing. I don't get a series of weak sparks when cranking - just one very weak yellow spark as if discharging some residual charge, then nothing.

Any ideas why I show low voltages at the coil terminals? The FSM says there should be "approximately 12 volts" on each side. But when I measure, I show +/- 6.3v between the ignitor body/ground and the + terminal; and 0.8-0.9v between the ignitor body and the - terminal on the coil.

Thanks again for the help!

 

[Pin_Head]

Any ideas why I show low voltages at the coil terminals? The FSM says there should be "approximately 12 volts" on each side. But when I measure, I show +/- 6.3v between the ignitor body/ground and the + terminal; and 0.8-0.9v between the ignitor body and the - terminal on the coil.

The reason you get lower voltages is because there is current flowing in the ignition circuit ( the ignitor is grounding the - side of the coil in order for it to make a spark.) and you are seeing the voltage drop across the resistances in the circuit.

This would seem to me to be the normal state of the ignitor with the key on and the distributor stopped. When the magnet in the distributor crosses the pickup coil, the induced voltage triggers the ignitor to interrupt the ground and fire the coil.

 

[M5driver]

The reason you get lower voltages is because there is current flowing in the ignition circuit ( the ignitor is grounding the - side of the coil in order for it to make a spark.) and you are seeing the voltage drop across the resistances in the circuit.

This would seem to me to be the normal state of the ignitor with the key on and the distributor stopped. When the magnet in the distributor crosses the pickup coil, the induced voltage triggers the ignitor to interrupt the ground and fire the coil.

OK That makes sense. I'll have to get back to this tomorrow evening. It's past my bedtime and I need to clean up and get some sleep so I can go to my day job in the morning If this doesn't keep me awake all night, that is

I'm still bothered by the effective complete lack of a spark from the coil - the "weak spark" I noted earlier is like a small static discharge, and I only see it when I switch off the ignition. I can make a better spark scuffing across the carpet and touching the door handle. Or one of the dogs

I changed nothing in the wiring harness - just cleaned dirt off it and wrapped it in corrugated loom, never hacked. Everything I have checked so far in the harness is good, and so far everything in the dizzy seems good. All the HT leads check out fine. Everything worked when I shut the Mule down for teardown - guess that is what really has me wondering what happened. If I come up with anything else, I'll post it up. Right now, I need to sleep on it.

 

[Vicm]

I have had my share of problems like what you are discribing.
I am going to say . Make sure you have good ground to the coil(?) and all your connection must be rechecked. Don't ignore the HT wire from the coil to distributor. When you pull things apart then hook them back together strange things can happen.
It might be a good idea to run a grounding wire straight from batt to coil bracket.
BTW , I was enjoying that tersto in Malawi, nicely done.
Good luck.
Vic

 

[samwise]

I dont know if this helps or not, but when I was Zimbabwe there were a ton of land cruisers, and I am sure there are a lot in the more stable South Africa. Again this may be impossible, you could probably order parts from the states with more reliability, but just a thought. Hopefully you dont need any parts and can trouble shoot it somehow. I wish I could help but I am new to all this.


Jon

 

[Trollhole]

I have had my share of problems like what you are discribing.
I am going to say . Make sure you have good ground to the coil(?) and all your connection must be rechecked. Don't ignore the HT wire from the coil to distributor. When you pull things apart then hook them back together strange things can happen.
It might be a good idea to run a grounding wire straight from batt to coil bracket.
BTW , I was enjoying that tersto in Malawi, nicely done.
Good luck.
Vic

I think you are on to something.

I'm thinking a poor ground to the coil or possibly the engine is not grounded. That being said I don't see how it could turn over with a poor engine ground but it's worth checking with a jumper cable. Just put one clamp on the negative side of the battery and one to the bracket on the coil. Then if that doesn't work try grounding the engine. Worth a try.

 

[Pin_Head]

The coil does not need to be grounded, but the ignitor does and this ground is part of the ignition circuit. Toyota electronic ignitions are quite reliable compared to electrical connections. If you had to get a new ignitor, I would bet that most Toyota ignitors from the same vintage (cars, trucks) would work. At least around here, junk yards are full of them

 

[Vicm]

The coil does not need to be grounded, but the ignitor does and this ground is part of the ignition circuit. Toyota electronic ignitions are quite reliable compared to electrical connections. If you had to get a new ignitor, I would bet that most Toyota ignitors from the same vintage (cars, trucks) would work. At least around here, junk yards are full of them

I agree 100%,
In the last 2 electronic ignitions I wired , I couldn't get the coil to produce any spark till I ran a grounding wire straight from the batt to the coil bracket which grounds the igniter.
Internally the coil can't be grounded , since this will defeat its function.
If the engine is crancking good this does't eleminate bad ground still. Since the starter is on a different grounding circit.
Another issue I had was that after pulling and reinstalling the
HT wire. the connection was damaged ,no firing. So one must test for spark at the HT output on the coil itself.
Visual inspection is a must as a first step. Inspect all connections.
Vic

 

[bsmith123]

ignition checks

I think there is a required air gap on the sensor so check the FSM and make sure that is right

How about the high tension lead itself?

 

[bsevans]

BTW, I've been looking at the DUI for a couple of years. How do you like it? Is it reliable? Cold weather starts good?
Dan

Dan,
I installed it, set the timing and have not touched it for over 5 years. It works as flawlessly as any distributor I have used. Two wires, one for key switched power and one for a tachometer. It could not be much simpler. Good cold & hot weather starting and parts available just about anywhere. I went to the HEI because, in my opinion, the technology is superior to that available in the late '70s and early '80s. If you go that way, buy the version of the HEI from DUI. It has two major advantages. The advance is curved for the 2F and it comes with a Toyota drive gear not a GM one. I run NGK Iridium plugs with an .042 gap.
Barry

 

[M5driver]

It might be a good idea to run a grounding wire straight from batt to coil bracket.
Vic

I think you are on to something.

I'm thinking a poor ground to the coil or possibly the engine is not grounded.

The coil does not need to be grounded, but the ignitor does and this ground is part of the ignition circuit. Toyota electronic ignitions are quite reliable compared to electrical connections.

I agree 100%,
In the last 2 electronic ignitions I wired , I couldn't get the coil to produce any spark till I ran a grounding wire straight from the batt to the coil bracket which grounds the igniter.
Visual inspection is a must as a first step. Inspect all connections.
Vic

Why didn't I think of this? Bad ground is entirely possible. Even though I have religiously cleaned all the threads where this thing bolts together, that is no guarantee of a solid ground. AND, this item grounds through the bracket on the fender, right? AND I have the fender only lightly bolted up with 4 bolts right now, and there is no reason to believe that is providing a proper ground, or any ground actually.

I will try the battery to bracket ground, recheck everything, and finish bolting that fender up tight. With luck, this will fix the problem.

FWIW, in addition to the ground strap from the starter to the frame, I also always run a ground strap on the other side of the engine to the frame to try to insure the engine is well grounded.

Thanks again. Results of testing soon.

 

[M5driver]

I think there is a required air gap on the sensor so check the FSM and make sure that is right

How about the high tension lead itself?

I'm re-testing everything. Right after I do a better job of trying to establish a good ground connection .

TKS for the help!