how do you check dist signal generator? (1 Viewer)

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Joined
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Location
Shippensburg PA
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www.iluvrocks.com
just swapped a used FJ60 distributor into the 40. After a lot of trouble, I got it running good. It idled for an easy 20 minutes while messing with the timing.

After getting everything buttoned down, I took it for a ride. Ran great and all was well. Then at a stoplight it started sputtering and died. Now it won't start.

Timing light shows no firing off the coil wire, but I have spark to the coil wire when held to ground and shorting the 2 pickup wires to the MSD ignition (as per MSD tech line) cap rotor and wires are used, but look to be in good condition and I sanded the rotor and cap points a little to be sure. I re-used my old wires so I know they're good (as well as pretty new)

It seems like the signal generator in the distributor isn't working properly, thus not telling the MSD to fire.

how do I test the signal generator?

My Toyota FJ60 manual doesn't say anything about testing the signal generator. Anyone know? Hopefully something I can do with a meter and not need an ocilloscope? (which I can't remember how to spell right now)
 
how do I test the signal generator?

1. Put an O-scope on it and spin it.
2. Swap in known good parts, like a Toyota ignitor.

Why use an MSD ignitor with a Toyota electronic distributor? Are you sure that they are compatible?
 
darn.....

neither of which do I have :rolleyes:

do the signal generators go bad often? I always hear that FJ60 distributors are pretty bullet proof.

however... when I swapped it in place of the petronics original distributor. I hooked the FJ60 red and white wires up the same as the old distributor. MSD informed me this was wrong because the FJ60 dist is a true magnetic pickup unlike the petronics.
The problem is..... I fed 12v to one side of the signal generator. It was only grounded through the MSD, and they said it *shouldn't* hurt the signal generator.... but now I'm wondering.
 
Oh rats, the sig generator is prolly toast. It is a very low voltage generating device.

It should not have 12V put to it.

It should not have _any_ voltage put to it.

Another test is resistance. Signal gen is a high impedance device, should have 100-200 ohms.
 
Putting 12V on the pickup coil would only sink about 50-100 milliamps if the coil is 100-200 ohms, which doesn't seem like enough to burn it out. However, the voltage could also exceed the input level of the MSD if it is expecting to see a TTL level signal from an optoelectric trigger. Either the pickup or the ignitor or both of them could be fudged. Why not hook up the old distributor and give it a spin to see if it can trigger the MSD? At least this would test whether the ignitor is still OK. You can't just mix and match pickups and ignitors if their signal levels are incompatible.
 
I had a multitude of problems with a MSD blaster hooked up to a small cap Fully Electronic Dizzy.

Some things to keep in mind.

There are no points in the 60 dizzy.. You shoudl nto sand anything down...
The msd will fire with the 60 dizzy.
The pickup just completes a connection. So if you happen to have a multimeter that tests contunity (alarm ones are nice) try it that way.. Spin the dizzy with the multimeter connected to the two wires coming off the dizzy.. It should beep beep beep....
How muchbattery power do you have. MSD's are extemely susceptable to power loss. Anything short of 12 volts and they have a seriously hard time generating the power required to run them. You can spin the motor just fine. But it will not create enough juice to fire the cylinders.

I ended up giving up on the MSD. Too many hassles.
 
thanks for the replies everyone. Some more info:

The MSD has a completely different circuit for a petronix hookup
(OLD DIST: WHITE wire out of MSD goes to BLACK wire of petronix. RED wire of petronix goes to 12+)
(NEW DIST: VIOLET wire out of MSD goes to RED wire on FJ60 distributor. GREEN wire out of MSD goes to WHITE wire on Distributor)
MSD Tech says the box is good since it fires when you bypass the distributor and short the VIOLET / GREEN wires together repeatedly. 1 spark each time.
I didn't feed 12v to the wrong place on the MSD so it should be OK.
MSD tech say Toyota distributors of FJ60 vintage should work fine (if hooked up correctly :D)

Battery strength is 12.3v or so and I have a charger hooked to it as well now that it's home.

didn't sand anything on the distributor. just the cap points and rotor. of course this probably widens the gap and could cause problems, but I'm not thinking this is the issue.

the truck ran well for about 30min before taking a dump. This is the strangest one. It acted just like fuel starvation, but I've got fuel in the carb glass, filter, and I can smell unburnt gas from the exhaust. Also the timing lite isn't firing now. It fired once or twice when I first hooked it up, then nothing at all and still nothing. Could the signal generator have worked for that long THEN fail?

signal generator questions
what does the signal generator show w/ a meter? is it open until the pickup closes it, then it shows 100-200 ohms?so it would show open, closed, open, closed like Mace suggests?
Or does it vary the resistance so it just jumps around between 100ohms to 200 ohms or something like that?
I have my dad's old simpson analog meter in the garage. I'll have to see if it works. It would probably be easier to see the impedance spikes since my current meter doesn't have a tone (as per Mace's suggestion)

Any idea what a new signal generator from C-dan runs? I really want to decide this one is bad first though.
 
BTW, which MSD?

And, does it have a separate power lead?
 
shoot, just realized I didn't specify.

MSD 6 Off Road and an MSD blaster coil. no resistor or anything on the coil. this has not been changed. IE: ignition and coil were working fine on previous distributor.

ignition has 12v and ground directly on battery terminals and a switched hot to tell it to turn on.
 
The pickup just completes a connection. So if you happen to have a multimeter that tests contunity (alarm ones are nice) try it that way.. Spin the dizzy with the multimeter connected to the two wires coming off the dizzy.. It should beep beep beep....
This is not correct. The sig generator is just that, a tiny generator. It does not make a connection. Spinning it will show a small voltage spike on an oscilloscope, but nothing that can be picked up by a conventional DVOM. The only part of it that can realistically fail is the pickup coil, so a resistance test is a pretty good indicator.

When they fail, resistance will be too high, or infinite (open circuit). Never seen one short, but that doesn't mean it couldn't happen.
 
This is not correct. The sig generator is just that, a tiny generator. It does not make a connection. Spinning it will show a small voltage spike on an oscilloscope, but nothing that can be picked up by a conventional DVOM. The only part of it that can realistically fail is the pickup coil, so a resistance test is a pretty good indicator.

When they fail, resistance will be too high, or infinite (open circuit). Never seen one short, but that doesn't mean it couldn't happen.

Jim, go give it a try with a continuity meter. I just did to make sure and it worked fine..

I did use the small cap fully electronic dizzy but the signal generators are basically the same from what I understand...
 
To be truthful it appears that "connected" is the default. Only when the arm gets to the "signal" point is it interrupted..
 
The signal generator for '78-80 is different than the later ones, which are magnetic pickup coils. I'm not familiar with the small cap distributors, so I don't know what the difference is.
 
78 is a semi electronic unit.

79-80 (IIRC) is fully electronic and magnetic small cap..
you can use a FJ60 ignition system on it (or a mini system or a celica system etc...)
 
Jim, go give it a try with a continuity meter. I just did to make sure and it worked fine..

I did use the small cap fully electronic dizzy but the signal generators are basically the same from what I understand...
I did the same test to a 78 fully electronic.
you will get beep,beep,beep when you spin it.
no beep if it is still.
One thing I find is that if the Toyota igniter is not grounded properly , you won't get a spark.
My question is can the internals be changed or do you have to change the whole dizzy? Sorry to highjack.
vic
 
I'm not the electronic gee-whiz guy here, but I've not seen anyone mention that the 1978-newer Distributor produces a sine wave and the Pertronix produces a square wave. This makes me wonder if the MSD was set up only for square wave (hall effect)?????
 
None of the electronic triggers produces a pure sine wave, but it doesn't matter in automotive applications because the speed of switching is so slow compared to digital electronic applications. What does matter is the output level. Hall effect sensors have the smallest voltage and require the most amplification, but the sensors are very reliable. Magnetic coil pickups have an intermediate level signal, while optoelectronic sensors have a TTL level signal (3.3 V, 10 mA) and they require a power input.

I wonder if the 78-80 distributor has some kind magnitic reed switch. None of the electronic signal generators I am familiar with will give you an on-off switching that you can detect with a continuity checker. The signal generator for the 81 and up distributor costs nearly 4 times more than the 78-80, so it is probably really different.
 
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Stop it, y'all are making my head hurt.

The signal generator does not produce a sine wave.

Spin it on the scope and the signal is flat, then a brief spike, very similar to the ignition coil output, but amplitude is appx 600mV, max. It does generate a small voltage, but it is not a sine wave, like would come from an alternator.


It is not a switch.

If the dissy is spun, and a DVOM is connected, there is a beep from the continuity tester. This not continuity.
The tester works by shoving a small voltage against the probes. If the voltage flows, then the beep happens. when the dissy is spun, there is a brief pulse of 600mV against the probes, which the DVOM sees as the voltage that it has been trying to shove between the probes.
As an experiment, turn the distributor very slowly by hand past the trigger point. There is no induced voltage, so no beep. If the dissy is parked anywhere, there is no continuity. The only way to trick the beep tester is by spinning it.

Signal generators are the same for all years. There is only one part number that is actually available, and it fits them all.

HTH.
 
I'm not the electronic gee-whiz guy here, but I've not seen anyone mention that the 1978-newer Distributor produces a sine wave and the Pertronix produces a square wave. This makes me wonder if the MSD was set up only for square wave (hall effect)?????

thus as I explained above, you hook up the two systems to totally different wires and circuits on the MSD.
 

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