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Thread: 89 Turbo Van Bad HEP?

  1. #21
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: 89 Turbo Van Bad HEP?

    I had a code 54 one time which would cause the car to cut out. The root problem ended up being a bad alternator which was on the way out. Low probability, but it did happen to me. I chased it until the alt died.

  2. #22
    turbo addict
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    Re: 89 Turbo Van Bad HEP?

    electronics like proper voltage .. my flakey alternator in my truck keeps turning the ABS light on

  3. #23
    Supporting Member Turbo Mopar Contributor
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    Re: 89 Turbo Van Bad HEP?

    I had a number of codes that appeared with a faulty O2 sensor. Only once did the O2 code pop up.Changed to a new sensors codes when away.
    The point everyone is getting at, is that codes are a guideline for troubleshooting and may not be definitive.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  4. #24
    boostaholic Turbo Mopar Contributor Lee'sdaytona's Avatar
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    Re: 89 Turbo Van Bad HEP?

    Quote Originally Posted by chromguy View Post
    I had a number of codes that appeared with a faulty O2 sensor. Only once did the O2 code pop up.Changed to a new sensors codes when away.
    The point everyone is getting at, is that codes are a guideline for troubleshooting and may not be definitive.
    Hmm.... I never heard of some of these issues. The alternator isn't that old, though that doesn't mean anything. I did leave the map light on for a few hours before this issue started. I do notice the positive terminal of the battery is corroded. Maybe I'll clean the terminal, and read voltage while running to see what happens.

  5. #25
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: 89 Turbo Van Bad HEP?

    Quote Originally Posted by Lee'sdaytona View Post
    Hmm.... I never heard of some of these issues. The alternator isn't that old, though that doesn't mean anything. I did leave the map light on for a few hours before this issue started. I do notice the positive terminal of the battery is corroded. Maybe I'll clean the terminal, and read voltage while running to see what happens.
    If you have access to an oscilloscope, that would be ideal. You can take a reading right off of the alt.

  6. #26
    boostaholic Turbo Mopar Contributor Lee'sdaytona's Avatar
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    Re: 89 Turbo Van Bad HEP?

    What would the oscilloscope do that I can't read with a multi meter? If I put a volt meter on the battery terminals while its running, wouldn't I see a voltage drop if the alternator is acting up?
    -Lee

  7. #27
    Supporting Member Turbo Mopar Contributor jonnymopar's Avatar
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    Re: 89 Turbo Van Bad HEP?

    Quote Originally Posted by Lee'sdaytona View Post
    What would the oscilloscope do that I can't read with a multi meter? If I put a volt meter on the battery terminals while its running, wouldn't I see a voltage drop if the alternator is acting up?
    -Lee
    Maybe. It's the real quick millisecond-range drops that are hard or impossible to see on a multimeter. An oscilloscope will show you a very obvious dip in the graph.
    Jon J.

    1989 Daytona ES 2.4L DOHC
    2003 Neon SXT - gone but never forgotten

    If it ain't broke, fix it 'till it is!

  8. #28
    Supporting Member Turbo Mopar Contributor
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    Re: 89 Turbo Van Bad HEP?

    A oscilloscope can react very quickly to voltages changes and the multimeter is much slower to react. A multimeter is excellent for stable signals but a oscilloscope is specifically designed to analyze changing signals. For example, if the ECU is having issue controlling the alternator, a meter may not see the issue unless it is nearly dead.
    https://en.wikipedia.org/wiki/Oscilloscope
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  9. #29
    Hybrid booster Turbo Mopar Contributor 85lebaront2's Avatar
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    Re: 89 Turbo Van Bad HEP?

    This is a nice handheld one, it is a dual trace unit. I made a pair of HEP test cables that can be used in between the HEP leads and the engine harness. If anyone has a dead HEP and can send me the plugs, I will put them in place of Ford wedgelock pins I used (they are the same OD as the HEP connector pins).
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  10. #30
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    Re: 89 Turbo Van Bad HEP?

    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  11. #31
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: 89 Turbo Van Bad HEP?

    It was suggested to me that my alt might have been failing and a bad diode could have allowed a little AC current out of the alt which temporarily freaked out the computer. I'm not good enough to know, but I did buy a cheap scope after that.

    https://www.seeedstudio.com/DSO-Quad...ope-p-736.html

  12. #32
    Supporting Member Turbo Mopar Contributor
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    Re: 89 Turbo Van Bad HEP?

    Quote Originally Posted by cordes View Post
    It was suggested to me that my alt might have been failing and a bad diode could have allowed a little AC current out of the alt which temporarily freaked out the computer. I'm not good enough to know, but I did buy a cheap scope after that.

    https://www.seeedstudio.com/DSO-Quad...ope-p-736.html
    Yes a faulty diode will do that
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  13. #33
    Hybrid booster Turbo Mopar Contributor 85lebaront2's Avatar
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    Re: 89 Turbo Van Bad HEP?

    Here is an interesting tidbit, AMC when they were still called Rambler, used a Motorola alternator which had a large pair of external diodes as a protection against failed internal diodes drawing the battery down. It also kept a bad internal diode from creating the telltale "whine" in the radio.

    These were probably 60 amp or thereabouts alternators so it wasn't a real high current output.

  14. #34
    boostaholic Turbo Mopar Contributor Lee'sdaytona's Avatar
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    Re: 89 Turbo Van Bad HEP?

    Good evening everyone!
    I am digging this post up again. Apparently I never posted back that I solved my issue by replacing the SMEC with a used one from another turbo van, thanks to a member on this site. Drove the van for several more miles since then. Today, I started having similar issues again. About two weeks ago, I took it to a shop to have a brake line replaced at the front drivers wheel. They discovered the wiring harness, just under the air intake hose coming out of the computer was all chaffed up, and many wires were exposed. They spliced some of the really bad ones, and used liquid insulator to repair the rubbed away insulation. I wonder if this caused something to short out in the computer and ruin this one?
    I removed my MOPAR HEP and swapped in an aftermarket one I have, but the condition got much worse. Put the MOPAR one back in, and the car is at least somewhat drivable.
    I'm thinking I should cut and splice in new wires where the damage was, and solder the connections to make a better repair, then I guess try to replace the computer again? Are aftermarket computers any good?
    I know HEPs were Mopar all the way, but I don't think you can get them anymore.
    Thanks for any help!
    Lee

  15. #35
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: 89 Turbo Van Bad HEP?

    I have never hesitated to go with an aftermarket hep and I haven't had problems because of it.

    I would imagine that if you fix the wiring, the computer will most likely be fine.

    I recommend crimping rather than soldering. If anything, it's better, and there is less chance of it being worse in my opinion. Regardless, once you get those wires taken care of, you can see if it will drive correctly.

  16. #36
    boostaholic Turbo Mopar Contributor Lee'sdaytona's Avatar
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    Re: 89 Turbo Van Bad HEP?

    Quote Originally Posted by cordes View Post
    I have never hesitated to go with an aftermarket hep and I haven't had problems because of it.

    I would imagine that if you fix the wiring, the computer will most likely be fine.

    I recommend crimping rather than soldering. If anything, it's better, and there is less chance of it being worse in my opinion. Regardless, once you get those wires taken care of, you can see if it will drive correctly.
    well crimping is certainly easier. I would have thought soldering would be better because it won't loosen up....but I'll pick up some of the heat shrink crimp connectors and go to town

  17. #37
    boostaholic Turbo Mopar Contributor Lee'sdaytona's Avatar
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    Re: 89 Turbo Van Bad HEP?

    So I cleaned up the wiring harness and repaired the frayed sections. Still misfiring or shutting down.... I tried tapping on the computer with a screwdriver, to see if the shock caused the issue. Did the same to the distributer/HEP, plug wires, and wiring harness. Those tests were inconclusive because it seems to randomly misfire. My gut tells me this ECM went bad too. I realize these are old electronics, but two computers going bad causing the same issue?
    Has anyone successfully fixed their ECM by taking it apart and re-soldering the connections? I can try that, then I guess just order a new ECM?
    Lee

  18. #38
    Garrett booster
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    Re: 89 Turbo Van Bad HEP?

    There are places around that repair ecms. I am sure a internet search would pull some up. I recently used a place called circuit board medics to repair a f350 instrument cluster and trailer brake control module. It wasn't cheap though.

    I remember years ago I went into a place to drop off a instrument cluster for repair. They repaired clusters, ecms etc. It was a giant warehouse type building with a fancy front. They let me in the back and it was full of people sitting at folding tables. Each table had soldering irons, multi meters and trays with various electronic components. Resistors, diodes etc. They would tear the stuff apart and just start testing. They would replace the bad components and give it back to you. They couldn't tell you exactly what functions they repaired, just that they replaced this or that and it functions correctly. It was interesting. It wasn't what I expected to see.

  19. #39
    Supporting Member Turbo Mopar Contributor
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    Re: 89 Turbo Van Bad HEP?

    I have repaired many of our ECUs. My first suggestion is to replace the caps. I have videos in our electrical section.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  20. #40
    boostaholic Turbo Mopar Contributor Lee'sdaytona's Avatar
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    Re: 89 Turbo Van Bad HEP?

    So I have decided to just buy a new computer. On rock auto, there is a long list of computer OEM numbers, despite they all look the same and are meant for the 2.5 Turbo I caravan. My current computer is not original to the van, I replaced it with a used one back in 2020 when I started this thread. So the current SMEC is 5235105, which of course is more expensive than the other ones on Rock Auto. Do these numbers really matter? I always thought as long as its for the 89 TI its good to go?

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