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Old 01-17-2010, 02:19 AM   #1 (permalink)
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Default Did I fry my 1986 Sammy's ECU?

It never ends... I just finished rebuilding the tranny and installing a winch. When I was installing the winch a ground cable from the winch touched the positive terminal of the battery making a small spark. After that was done I started to troubleshoot the heated fan which never worked since we got it. I then went to start the car and there is no spark. I noticed the wring under the dash was pretty ratty with several splices.

The first sign of trouble was that the radio would not turn on and the car turned over, but engine will not turn on. Now I am wondering if:

A- I loosened a ground connection under he dash when I was working on the heater motor.

B- The ground cable touching the battery fried the ECU.

C- The ground cabe touching the battery fried the coil.

What I have done so far is jiggle all the under dash wires and that got the radio going agin.

Checked all fuses under the dash and all looked fine.

Checked voltage at coil and it has power but 1V lower than battery power.

Ideas anyone?

Last edited by SuzukiPilot; 01-17-2010 at 09:46 AM.
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Old 01-17-2010, 03:25 AM   #2 (permalink)
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are you talking about an 86 model samurai ?

I'd look at the fusable links at the battery if you have them, Is the engine fuel injected??? cause in 86 I'd doubt it and if not there won't be an ecu. there will be a Cdi unit which from memory is part of the dizzy, there pretty tough thou. anything above 9 volts at the coil should be ok but! the voltage must drop off for a brief second, 4 times per engine revolution.
best way to check this is stick a spark plug in the end of the coil lead and earth the plug.

your wiring under the dash, is it burnt? is there a burnt smell under the dash?

I can't imagine the quick short would have done major damage.

Also check the earth wire which should go from the fire wall to the dizzy.

Good luck
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Old 01-17-2010, 07:19 AM   #3 (permalink)
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Default eectrical

It is a bit puzzling what you are describing.

If none of the fuses are blown, I would double-check the ground wires that you may have disturbed.

You may have fried a capacitor or two in the ECU, but these are pretty easy to replace if you are pretty good at soldering. Do a search for ecu at Ack's FAQ (see link in signature, below) and select the iZook article. The ECU that is being repaired is not exactly like yours, but the basic procedure is the same.

There are several people that can fix them if you don't wnat to try. Go to the Zuwharrie.com forum (Zuwharrie.Com BBS - Index) and do a post search for ecu or ecm to find someone who can help.

I once had a problem that was similar to yours but it involved the ignition fuse blowing every time power was applied. It turned out to be a shorted-out ignitor inside the distributor. Since your ignition fuse is okay and you have power at the coil, that is not your problem.

I hope that this helps!
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Last edited by ack; 01-17-2010 at 07:23 AM.
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Old 01-17-2010, 09:48 AM   #4 (permalink)
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It is not fuel injected.
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Old 01-17-2010, 10:32 AM   #5 (permalink)
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Looking at the parts manual, the '86 Sammi appears to have an "electronic feedback carburettor" which uses a computer controlled MCS or mixture control solenoid, so even though it is not fuel injected, it still has an ECU, which should be behind the dash on the passenger side.

Having said that - as far as I'm aware - this ECU does not control the ignition and should not be a factor in your not getting a spark.
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Old 01-17-2010, 12:58 PM   #6 (permalink)
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One thing I noticed is that there is a sharp click sound when I connect the battery cable. I never noticed that before. The click comes from the carb area. Then again, that would not explain no spark. The wiring under the dash is ratty with a few splices making it a bit more difficult to rule out problems. Just like the radio had stopped working, and worked again after wiggling the wires, who knows if one of the spliced wires under the dash could be a problem. I also found a small switch under the dash and wonder if that is stock or an aftermarket ignition kill switch. Need more time to dig further through the dash.

Anyone know for sure that the ECU (ECM) in the Sammy does not control the spark? If not, in theory I should be able to unplug it and it should run right? Here is what the manual say about the computer:

COMPUTER CONTROLLED EMISSION CONTROL SYSTEM
[Feed back system]
A prime purpose of this system is to maintain a controlled air fuel ratio, allowing the catalyst to reduce oxides of nitrogen, hydrocarbons, carbon monoxide and to improve fuel economy simultaneously. The electronic control module (ECM) and the oxygen sensor are provided in this system. The oxygen sensor mounted on the exhaust manifold monitors the exhaust gas air fuel ratio and signals to the ECM.

The ECM processes the oxygen sensor signal and controls carburetor air fuel ratio by the operation of the mixture control solenoid in the carburetor.
Thus the signal of the exhaust gas air fuel ratio sensed by the oxygen sensor is fed back to ECM and the carburetor air fuel ratio is controlled.
[Electronic control module (ECM)]

The ECM controls the fuel cut system, idle-up system, bowl vent system, EGR system and secondary throttle valve system, as well as the feed back system. The ECM is located under the glove box of theinstrument main panel. Refer to Fig. 5-l -9.
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Old 01-17-2010, 01:57 PM   #7 (permalink)
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I'm not willing to state as fact that the ECU does not control the spark, simply because I am not that familiar with how it works - I have a friend who has a Sammi with that setup and his ECU was removed by a previous owner - he still has the original carburettor so I know it does work without the ECU, but neither he, nor I, know what changes (if any) were necessary.
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Old 01-17-2010, 02:23 PM   #8 (permalink)
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In Australia A 86 model zook didn't have any ecu's you should be studying that manual. The carburetor will have a fuel cut solenoid in it, it will have one wire will be on the engine side of the carby and yes will click as the ingnition is switched on and off.

can you see the o2 sensor? if so you have some kinda module doing something if no o2 sensor than no ecu.
I can't imagine the spark will be different to oz's models there should be 2 wires going into the dizzy thats simply power 12volts.

that little switch you found? these in my mind could cause a problem, I'd be looking into what it was suppose to do, if it was a kill switch it probably killed the ignition.

I love electrical problems, If only I had my head under your zook.
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Old 01-17-2010, 02:46 PM   #9 (permalink)
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Quote:
Originally Posted by SuzukiPilot View Post
I also found a small switch under the dash and wonder if that is stock or an aftermarket ignition kill switch. Need more time to dig further through the dash.

By any chance did the switch you found look like either of these? The silver switch on mine is aftermarket, you probably don't have it, but it was tied into some kind of alarm system. The little black switch I found under my dash on a 94 and Ack told me it's part of some old school style diagnostics before OBD came about. I just have no idea if your year model had those.
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Old 01-17-2010, 03:23 PM   #10 (permalink)
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Hi Wrenchwoman,
The switch in your photo (small square sliding switch) is the same one in mine. I thought maybe it was a hidden kill switch. Guess not?

Gav,
Yes mine has the O2 sensor. (I live in CA where they put in cars every device known to man to reduce smog. Lately they were trying to ban the sale of black cars in CA because black cars bet warmer inside and therefore you may use your AC more than a person in a light colored car. They are nuts over here.)

I'm going to go through the manual some more to see if there are any other fuses besides the ones near the clutch pedal. It seems like if the ECM does not control spark, it should not be too bad to troubleshoot the problem Might pick up a coil too to quickly rule out the coil having gone bad in the small spark incident.

I have a miserable cold/flu now and despite a strong desire to solve this puzzle, my body just wants to lay in bed.
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