Announcement

Collapse
No announcement yet.

Ecu??

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Ecu??

    Hope I'm posting in the right section.

    Hi everyone. I'm hoping to get some info here. So buckle in adn hold on tight because Im going to take you on a wild roller coaster ride.

    Six years ago I bough thte perfect little 318is. It's a '91 and had 250,000 kms when I picked it up. It isnt a daily driver and is parked during winter so I've only put 45,000kms on it in the time I've owned it. It is a beautiful little car and is in great shape.

    In January, I gave it to my son as a 16th birthday present. You've never seen someone so happy. His anticipation for decent road conditions hasn't wavered in 4 months. A month ago he had a chance to get it on the road. Unfortunately, as soon as he pulled out of the driveway the engine simply stopped. It turned over but just wouldn't fire. The first thing I wanted to check was the presence of spark. So as I removed the cover to access the plugs I noticed the sparkplug chamber was flooded with oil. So, that being a somewhat obvious spark inhibitor, we decided to change the plugs and replace the valve cover gasket. that was a great little project for the boy to sort of christen the car as his own. He learned a lot, especially about the importance of applying torque specs to bolts that thread into aluminum LOL. That little lesson also gave him the opportunity to use helicoils to repair damaged threads. Anyway, after the job was complete, and we ensured there was spark, it still just wouldn't fire. It cranked beautifully though. So thats when I started to refer to the web to diagnose the issue. Electronics has never been my strength but we decided to figure out what the problem was ourselves. The first thing we did was swap the aftermarket chip for the OEM chip that came with the car. Nothing changed but I decided to leave the OEM chip in place for the time being. Next was to clean and test the crankshaft position sensor (crank pulse generator as its referred to by real OEM). With that ruled out as the culprit, my next target was the fuel pump relay. After testing the relay and jumping the realy terminal to send power to the fuel pump, we found the culprit, the fuel pump! I purchased a replacement pump and fit and wired it to the OEM housing. SUCCESS!!! My son was as happy as the day he got the car as a gift.

    Having been down for the past few weeks we let the car heat up to temp slowly to allow the valve cover gasket to seat properly. We took it for a light drive that night (two days ago) and all was right with the world. My son has been saving for insurance money since his birthday so yesterday my wife helped him set up the insurance and today we got it registered.

    Here's the problem, when he tried to start it , it turned for a moment or two but wouldn't fire. Same symptoms we started with. So, I kind of stood there scratching my head. He tried again and it turned over but this time it sounded pretty rough and still wouldn't fire. He tried again and this time it barely turned over. Meanwhile, the fuel pump was audible even with the key out of the ignition. That's when he decided to inform me that he took it upon himself to put the aftermarket chip back. This is where I cringe. First of all, he forgot to disconnect the battery while doing this. Second, he may have put the chip in backwards. We aren't sure. Needless to say, he is bummed right out and so am I frankly.

    I have since returned the OEM chip to its socket within the ECU in the correct orientation and tried to start the car again with the same results mentioned above. Rough cranking and then hardly turning over. And the fuel pump running for 20-30 seconds with the key out of the ignition.

    My question is; are the symptoms I've described likely related to the ECU being ruined? Or could there be something else? Is there a way to test the ECU?

    Thanks in advance

    #2
    Lots of life- lessons seem to come from owning a car, huh?

    cranking and turning over both mean the same thing-
    do you mean it cranks, catches, and barely runs, badly? Or that it cranks
    a few times and then stops cranking? Because weak batteries cause all sorts
    of secondary symptoms, as do loose or corroded high- current connections...

    The fuel pump running isn't a good sign- it's not supposed to run unless it sees
    that the engine's rotating (erk, this is true for the M20 and the M42 in the E36, I'm
    extrapolating for the E30)

    The approved diagnostic procedure for the ECU is to try another one. I'd hit ebay or the
    classifieds and see what you can find. Dig a little- is the early E36 ecu the same as the E30?
    That would widen your candidate pool.
    You could also try basic diagnostis- make sure the ECU's firing the plugs at the
    right time with a timing light, etc...

    From what I remember of 1980's computer technology, the EPROM tself might be damaged,
    but it seems less likely that the EPROM hurt the ECU. But it's been a LONG time.

    t
    just thinking with the keyboard, here.
    now, sometimes I just mess with people. It's more entertaining that way. george graves

    Comment


      #3
      I second trying another DME. I have 3 DMEs now, two of which I bought on ebay for less than $40 shipped (each). It's worth a try.

      Comment


        #4
        Your ECU is probably fine, or at least I doubt anything you did damaged it if it was not already damaged. You can just unplug the big 88 pin connector without disconnecting the battery, and putting the EPROM in backwards is not likely to harm anything.

        The most common culprits are the crank position sensor (cleaning it is probably not necessary since it is a magnetic sensor), a plugged fuel filter and a moisture-damaged ECU. You can usually test the CPS with an Ohmmeter...IIRC it should read ~1.2kOhms between two of the pins (forgetting which). Since you mentioned the fuel pump running with the car off, that does make me think that there could be an ECU problem. To run the pump, both the main relay and the fuel pump relay have to be activated, which the ECU would not do unless the car was running/starting. The ECU will usually momentarily switch the pump on as you enter accessory mode II as a priming step, so if you hear it run for a second or less, then that is normal.

        Transaction Feedback: LINK

        Comment

        Working...
        X