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Discussion Starter · #1 ·
No start issues, maybe ECM?

92, 8 valve, 2 door automatic

I have searched through a bunch of posts & diagrams.

I have constant power to black/red into main relay, key on power to black/white.

Power to fuel pump relay on blue/black, black /white & pink. Relay doesn't click, swapped with main still doesn't click. Connect pink/black to power & pump runs. Pink/black tests as a ground.

No CEL light.

Photo inside ECM, looks like it has had some stuff replaced by the look of some soldering.

Can anyone advise what else to test to confirm if ECM needs changing or not please
 

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1991 Hardtop 3-door Tracker 1.6L 4WD 5-Speed No A/C
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Hello,
Others will chime in with better advise. You have a re-manufactured ECM, but how many miles & years on this ECM? Did it die all at once or were there other problems?
I don't know if there is a way to TEST an ECM on its own. I doubt it.
 

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If the CEL does not light when the ignition is first switched on, with either the ECU or power to the ECU - that is, assuming the the CEL has a good bulb installed, some folks remove the lamp to hide the fact that the ECU has a code set.

The presence of 12V power on the main relay black/red & fuel pump relay blue/black says there is power to the ECU and the ECU is activating the main relay, the ECU will however only activate the fuel pump relay for 3 seconds after switch on, whilst cranking, and whilst the engine is running, so if you are not looking at the correct time you could miss the activation, other than that it sounds like there is an ECU issue.
 

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Discussion Starter · #5 ·
The CEL has been working up to the point where it didn't start, hasn't had any other issues or CELs activated. I'm a bit confused about the fuel pump relay. The three wires other than pink/black have 12v all the while the ignition is on, the relay doesn't click.

We're at 340,000 kms so exchange ECM could have been a long time ago. I'm comfortable testing inside unit but wouldn't tackle soldering.
 

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Font Schematic Parallel Auto part Engineering


You have 12V constant battery power on the black/red wire, and 12V ignition power on the black/white wire.
The ECU holds the blue wire at ground potential, so when ignition power is applied on the black/white wire, the main relay is activated, passing 12V power from the black/red wire to the black/blue wire - we'll call this fuel injection system power, just to give it a name.
The fuel pump relay gets 12V ignition power to the relay coil on the black/white wire, as well as 12V fuel injection system power on the black/blue wire to the relay contacts - the pink wire has 12V power because it's the other side of the relay coil, if the ECU grounds the pink wire it will go to 0V, and activate the fuel pump relay, which will then pass 12V power (fuel injection system power) to the pink/black wire turning the pump on.

Your ECU is not pulling the pink wire low, for whatever reason, the ECU may be defective, there may be a broken wire between the ECU and the relay - the relay doesn't activate.

If that CEL was working, was coming on when the ignition was switched on, but is not doing that now, I would start by making sure the bulb is good - if it is, the probability is you have a bad ECU.
 

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It would appear that you still have the original caps in your ECU, at least from the photo you’ve shown. Look at the large cap in the top of photo - there appears to be damage around it. If your CEL is not working with key on, the car will not start, your ECU has the original caps in it, it would be a good idea to change out those caps. Search for Mouser.com in the forum search function, and it will advise you of the three caps you need to change out, their values and where you can get them. Any computer geek near you can replace them and clean the damage to the board.
 

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Discussion Starter · #8 ·
Thanks very much for the explanation, I will test that pink wire at the ecu connector but it does seem like I'll be looking for a replacement.
 
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