Mitsubishi: 1992 mitsubishi expo 1.8 L no spark

snovelvet wrote: 
Did you check the ECU diagnostic output pin for an error code. All you
need is a jumper wire and an analogue meter.
This vintage ECU is prone to failure, (but is also easy and cheap to fix).
When was your timing belt last changed / checked.

And because you asked, Pin 6 on the dist plug should have an active
ground to fire the coil. Normally there is a pulse train at this point,
supplied by the ECU, if and when other sensors tell the ECU when the
crank position is correct to fire a SP.
When pin 6 is grounded, pin two will swing from 12 volts to ground (if
the transistor is working) and the coil should fire. Note that the
ignition switch needs to be in the "run" position for this to happen.
The manual suggest the following procedure to test the transistor.
1. attach a 1.5 volt battery (negative side) to terminal 5 of the
connector block. Connect the positive to terminal 6 of the connector
block, intermittently, while measuring the resistance between pins 6 of
the 6 pin connector block, and pin 2 of the two pin connector block
(negative meter lead to pin 2).
2. Battery connected, very low resistance
3 Battery disconnected, very high resistance.

Pin 6 should be Green-Yellow
Pin 5 should be Black
Pin 2, on 2 pin connector block, should be White-Black

O BTW, the primary of the coil is across pins 1 and 2 of the two pin
connector, the secondary is across pin one and the rotor.

But first thing I'd do is check the ECU trouble code. If the signal is
constantly high, the ECU is toast. If the signal is constantly low, the
ECU has no power, If the signal is a 50% pulse train, the ECU is working
fine. Any other pulses are actual error codes.

All this is based on a 1992 Mitsubishi 1.8 liter eclipse, but it should
be the same.
If you don't have an analogue meter (that's a meter with a dial), buy
one, a cheap one (under $10.00 CDN) will do just fine for these tests.
All you need is one that can measure a voltage of 20 volts or less and a
resistance up to 20,000 ohms.

Hi
First, I want to thank you, so so much for taking the time to explain and
answer my question. I’m buying a Mitsubishi factory service manual
but, I won’t have it for a week or so. This will give me a good
point to start at.

I’m a little confused on the ECU diagnostic pin. I don’t know
where to find it. I do have a
Simpson 260 meter & O-scope. Is this a point on the ECU where you can
verify the pulse train and determine that the module is working properly?


I have read where replacing both the dist & ECU did not resolve the
problem. I think this was due to the timing belt jumping a tooth.
I’m not sure if this applies to my situation. My belt was replaced
back at about 115,000 mile, so it may be due. Maybe, the best thing is to
do all three. Normally, I won’t waste time on a car with this much
mileage, but it was such a good running car. I miss not having it. Thanks
again for your help

Mario

snovelvet wrote: 
On an eclipse, the diagnostic plug is located on the right side of the
fuse panel, which is against the left wall of the passenger compartment,
under the dash.
It's a 12 pin connector, with nothing attached to it. Usually covered
by a plastic dust cover.
Pin one outputs a pulse (attach the positive of the meter here),
depending on the error code or status of the ECU (vehicle ignition needs
to be in the "run or ON" position).
Pin 12 is a ground point (attach the negative of the meter here).
However, you may not need the ground on pin 12 to enable the ECU output.
Attaching the negative lead from you meter to a good ground should be OK.
Attach the meter with alligator clips, then turn the car to the "run"
position. Watch the needle deflections, that's the code output.
Longer pauses, indicate the space between digits of the error code.
Example; two long pulses, one longer pulse, then three short pulses,
(signals then repeats) is code 23 on an eclipse, which is "number 1
cylinder, top dead center sensor" , output error (on a 1991 Eclipse),
yours may be different. Your service manual will have all the codes.
With your meter and O-scope, you should be able to test every electronic
item in your car, including all the engine management sensors.

If the ECU is toast, let us know, don't replace it. There is a web page
that has all the details on how to repair it, for about $5.00 CDN in parts.

If you have 85,000 miles on the timing belt I would suggest you replace
it now, as well as the balance shaft belt, tension pulleys, and water
pump ( I guess it depends on how long you want to keep the car, hows the
compression on the engine).

Remember, these details apply to an Eclipse, of your vintage, your car
may be slightly different.

Hi Again

Yes,I did see that connector. And now,it all makes sense. Is the fix for
the ECU the replacement of the 3 electrolytic caps? That would be way to
easy.... From what I'm reading, it appears that this Mitsubishi ECU was
one of the most likly to fail.

I was getting unexplained bucking every now and then. I just thought it
was a bad fuel ejector.
Would that be the processor doing a reset because of the caps? I took a
quick look at mine and they all look good, maybe I should replace them.

So,I now think I can test both the Dist & Ecu. Your information has been
very helpful. My bet is now on the ECU and not the Dist. I'll let you
know

Thanks Mario

snovelvet wrote: 
That is the usual fix. I would do the ECU capacitors on spec. But first
check the diagnostic output codes.

Pay close attention to the larger capacitor right in the middle of the
circuit board.
Usually there is some material, like contact cement, used to hold it a
bit better to the PCB.
On two of the ECU's I've worked on, under that material, there has been
a break on the thick trace on the PCB. Almost looked like it was on
purpose, as the gap was about 1/2 mm wide.


Using your scope, you can also check the TDC sensor, pin 4 (Blue wire)
of the 6 pin block
and the crank angle sensor, pin 3 (brown-yellow wire) of the same
connector.
Should see a 5 volt pulse train as the engine cranks.
On my Eclipse, they are both located in the dist.

OBTW, the capacitors are an industry wide problem. I've even replaced
them on a year 2000, IBM Aptiva system board, as well as switch mode
power supplies.

Good luck
Ray

Hi Ray

I need your help once again. On the 12 pin connector, there are only seven
wires connected.
I take it that pin 1 is yellow/red (pulse train) pin 12 grn/blk (Ground).


Second: question, you mention that there is a 1/2mm gap, is that for the
cap spacing ? Or a problem that needs to be addressed.


Third: I noticed on the pc(ECU)board that there are 4 transistor drivers,
are they for the fuel ejectors, and the one transistor driver in the
middle for the Dist driver to excite the coil. That's just an observation
on my part.

My last question. I remember reading in a post, that if the timing belt
jumps the ECU will know and halt the pulse to fire the coil. This may be a
form of protection for the valve and piston clearance.I'm not sure if this
is true for this vintage Mits.

Thanks once again, I can't thank you enough for all your help

Mario

P.S. I'm still waiting for my factory service manual.

snovelvet wrote: 
My eclipse manual (Laser manual) shows pin 1 as yellow, pin 10 as
white,pin 11 as yellow-white, pin 12 as black
The row of pins that includes the "key" (two missing pin positions) is
the low count pins ( 1 to 6) Pin one is on the side that has three pins.
Pin one is closest to the edge.

The 1/2mm gap was in the actual copper, circuit trace. Almost like
somebody cut part way threw the trace, maybe making it a safety blow out
fuse.

Don't know for sure about the transistor drivers. Injectors are wired
to pins 51, 52, 60, and 61 of the ECU pins. Pin 62 controls the purge
control solenoid. Pin 54 is the drive for the power transistor in the dist.

When I installed the timing belt on my sons Laser (Eclipse, sort of) I
was one tooth out. The car ran fine (but gutless), till you got to a
hill then it hardly moved.
Can't answer for sure about your last question, but my guess is it's not
smart enough to know if the belt jumps a few teeth, but it would not
see and pulses for the TIC and crank angle sensor in the dist if the
belt is totally broken.

Ray

Hi Ray

I see there is a difference on the color code. So'I look over the Net and
I see over and over again that the caps seem to be the problem. Since I
can't wait any longer for this service manual, I decided to check the
caps, and guess
what,the 100 uf is shorted. So tomorrow, at work
I will bring it to our electronics lab and desolder all three caps.

I hope I did cause any problems on my dist. I started to remove some of
the parts to check the coil. I need to get a new gasket for the cover.

I hope this will solve the problem, because right now both of my cars are
broken.

I see that you have help quit a few people with
this problem. How did that women make out with her car? Looks like she got
4 ECU at a junk yard and all four were bad, but at 50 cents each I guess
she got a good deal.

Thanks again

Mario