[Gmecm] Crazy 7730 problem - random numbers for TPS& ECMverywarm...

Mon Mar 18 14:48:51 UTC 2013

Thanks. I was using the original 27C512 UV-erase chip. It will verify fine and the code runs fine. I thought that could be the problem (the EPROM) so I put a different code ($A1) on the chip. Same thing happened.

It has to be something in the resistor pack or the knock filter board IMHO. The chip appears to work.

I will eventually be using a SST flash-memory chip. For now I just wanted a program to get the engine running.

  ----- Original Message ----- 
  From: Beau Blankenship 
  To: gmecm at diy-efi.org 
  Sent: Sunday, March 17, 2013 11:46 PM
  Subject: Re: [Gmecm] Crazy 7730 problem - random numbers for TPS& ECMverywarm...

  I had one of the adapters from Moates go bad (it got some moisture on it) but re-flowed solder joints and it worked fine after that. I also had MULTIPLE 7447 Eproms go bad. Not sure what chips you are using, but, it happens.

  Beau 

  From: gmecm-bounces at diy-efi.org [mailto:gmecm-bounces at diy-efi.org] On Behalf Of David Allen
  Sent: Sunday, March 17, 2013 11:18 AM
  To: gmecm at diy-efi.org
  Subject: Re: [Gmecm] Crazy 7730 problem - random numbers for TPS & ECMverywarm...

  And the answer is......

  ...a bad MEMCAL!

  I don't know how it caused this, but changing to another MEMCAL (with the same program in it) cured the problem.

  I erased and re-programmed that MEMCAL and again it did the same thing no matter what program I install in it. 

  That one goes in the trash.

  Later,

  David

    ----- Original Message ----- 

    From: David Allen 

    To: terry ; gmecm at diy-efi.org 

    Sent: Sunday, March 17, 2013 8:46 AM

    Subject: Re: [Gmecm] Crazy 7730 problem - random numbers for TPS & ECMverywarm...

    It's a 1987 car, with a newer model ECM, possibly an early 90's ECM. 

    I'm going to check some things this morning and will see what the grounds look like.

    Thanks!

    David

      ----- Original Message ----- 

      From: terry 

      To: gmecm at diy-efi.org 

      Sent: Saturday, March 16, 2013 10:51 PM

      Subject: Re: [Gmecm] Crazy 7730 problem - random numbers for TPS & ECM verywarm...

      David,

      What year Buick are you working on? I have had issues with ground circuits on that ecm where the terminals become loose 

      cause skewed the data.

      Terry

      From: David Allen <davida1 at hiwaay.net>
      To: GM-ECM <gmecm at diy-efi.org> 
      Sent: Saturday, March 16, 2013 11:35 PM
      Subject: [Gmecm] Crazy 7730 problem - random numbers for TPS & ECM very warm...

      Hello guys, I've got a stumper of a problem.

      Just finished re-pinning a MAF ECM (old 3.8 Buick, has the 2 connectors) for 
      a 7730.

      I powered it up to see the data on the computer, and I get some strange 
      things.
      The fuel pump prime function and Check Engine light function as normal.

      When first powered up, the TPS shows a seemingly normal voltage. The TPS 
      reading will move with the pedal position. Then, gradually, it starts to 
      read a bogus higher and higher voltage, eventually stopping about 3V, with 
      no change when the pedal is moved.  Verifying with a meter, the TPS voltage 
      is stable at 0.5V and does operate normally with the throttle.

      The second thing is, the MAP reading is fixed at approx. 60 kPa. The MAP 
      sensor voltage is correct (measured with meter) and does fluctuate with 
      vacuum.

      Then, the ECM gets warm, after 3 or 4 minutes. This is without starting the 
      engine or activating anything.

      I have disconnected everything from the ECM other than the "A/B" connector, 
      and powered it up. The scan data does the same thing, TPS starts at low, and 
      after a few minutes it climbs.

      The TPS issue will return to normal (for a few moments) if I power off the 
      ECM and power on again. The MAP never reads other than approx 60 at any 
      time.

      The sensor +5V reference and sensor ground are correct and never fluctuate 
      even as the readings drift.

      I thought the ECM was damaged, so I tried another one. It did the same 
      thing. I know both these ECM's have worked correctly before.

      I'm running Code59 V.23 exactly the same as another identical engine which 
      runs fine.

      I've used the same diagram for 2 other conversions, and they both worked 
      fine. I am at a loss.

      Thanks for any insight!
      Sincerely,
      David 

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