1992 mitsubishi expo 1.8 L no spark

snovelvet wrote:
> Hi Ray
>
> I did the battery biasing test from the manual. They said to hook the
> battery +1.5 volts to pin 6 base and -1.5 volts to pin 5 the emitter which
> is grounded when connected to the dist. Then take the ohm meter and connect
> the neg probe to pin 12 the tach(collector) and the pos probe to pin 5 the
> emitter. This was done with both connectors removed from the dist.
>
> It failed because it had continuity with or
> without the battery connected. From the diagrams of the manual I can not
> see any other path to addd to the low resistance reading. Again looking at
> the diagrams with the CONNECTORS OFF I only see the the power transistor in
> series with the primary dist. coil.
>
> I tried the temperary grounding of the tach wire pin 12 (collector)with
> connectors on. This of course is bypassing the transistor totally. I did
> not get any spark from the secondary of the coil. This may be due to the
> low resistance from the collector to emitter. I think it's time to replace
> the dist. I don't know of any other testing I can do.
>
> Thanks
> Mario
>
OK, one last test.

Disconnect pin 5 from the multi position connector. This is the pin
connected to the emitter of the power transistor. It provides the
ground for the coil, when the transistor triggers.

Disconnect pin 6 from the multi position connector. This is the pin
connected to the base of the transistor.

Now momentarily ground the tach lead (pin2 for me, pin 12 for you).
Monitor the secondary output, if all is well you should get a spark.
This bypasses the transistor, and takes it out of the circuit. Remember
that the ignition should be in the "run" position, and just to make
sure, measure the primary coil side for 12 VDC at pin 1 (on my diagram
the lead is called "Ignition switch 1G1"). If the tach side isn't
grounded, you should also see very close to 12VDC.
Here's another way to do the same thing. Disconnect both connectors
from the dist. Apply 12VDC to the primary side of the coil (pin 1, the
one that is common to both the primary and secondary coils). Ground pin
2 (pin 12), the tach lead, momentarily. The secondary should spark
(center point of dist, cap removed).

Here's a rambling thought. If the transistor is indeed gone, you could
attach an external one, by connecting the collector to pin 2 (12), the
base to pin 6, and then grounding the emitter. Of course you'd want to
disconnect pins 5 and 6 from the dist.

Please be aware that semiconductor representations on these service
manuals, are just that, representations of real circuits, and do not
represent actual electronic wiring. That power transistor could be a
Darlington, for example.

Good luck.
Ray

Hi Ray

Today was a great day.. First thanks again so much for helping. I hope I
can return the favor someday..

After doing that test I decided if was time to replace the Dist. So I took
my Simpson, and went to the junk yard and purchased a dist. When I when to
test it before buying it, I end up getting the exact same readings on the
replacement. So now I not sure what to do. The guy said he took it from a
running 93 Expo. Well, for $65.00 I took the chance. I didn't feel very
good about because I didn't think it would work. The screw on the dist cap
was broken. I had to retap to get it secure.

So I came home, took a few hours break, and then I replaced it, and guess
what, I worked.....So here is my conclusion. It wasn't the so called
transistor and it was not the coil. What I think the problem was in the
camshaft or crankshaft sensor. Thats the only part of the dist I didn't
check. The manual is misleading you have resistance from the emitter to
collector pin5 to pin12. This test makes you think the transistor is bad,
but infact it good. They speak of continuity and no continuity. They
should say what the resistance values are.

So to any reading this, I hope it helps you solve your problem. The garage
wanted $350.00 plus labor for a rebuild. I was vey close to doing it but
decided to check this board. And thanks to Ray who took his time to help I
was able to get the fix with out spending hundreds of dollars. I'm
enclosing my e-mail incase I'm not reading this
board. marios2468.TakeThisOut@aol.com please feel free to ask any questions I have the
complete factory manual from Mitsubishi.

Mario