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TBI/TPI Module Problems

Discussion in 'The Garage' started by Hossbaby50, May 29, 2004.

  1. Hossbaby50

    Hossbaby50 3/4 ton status

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    I am having a problem with no starts in my truck. I swapped in TPI and had it since January. Within the last 3 months I have been having problems with my ignition parts.

    First I blew a pickup coil.
    Then I blew out the module.

    Since the first module went out I have been having the problems. The first module was a Delco. The replacements have been Borg Warner parts.

    About once every 3 weeks (or less) my truck won't start. If I change the module it starts up just fine. The wierd part is if I leave the truck alone for a few hours and don't change the module it usually starts. /forums/images/graemlins/dunno.gif WTF?

    Today I tired changing the EST and the ECM before I replaced the module. Niether worked. Thanks

    TBI & TPI use the same modules that is why I posted it in the Subject too.

    Harley (85K5 with 350 TPI. '88 MAF setup with stock ignition and painless wiring harness, MSD 8.5 wires, MSD cap & rotor)
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Have you checked over on thirdgen?

    Have a no-start problem myself, but until I get new plug wires, I can't diagnose it. (got a new battery, suspecting bad one wasn't supplying enough voltage during crank)

    Have you gone through the factory flow chart for a no-start complaint? I can probably scan it if you don't have it, my manual is for '88.

    In any case, I was just searching posts on thirdgen.org looking for "no start" problems, and what the causes/solutions are, and there are quite a few posts. I seem to vaguely recall one or two like yours, no start unless they waited awhile.

    Again IIRC, on the TPI setups, spark under 400RPM's is controlled ENTIRELY by the ignition module. Are you getting spark when it won't start? (mine is) I have a feeling my problem is that the injectors aren't pulsing when it's trying to fire, however I've also got an '87 ECM that is looking for a cold start injector, which in that programming delays the other 8 injectors from firing until the engine has cranked a few times. Non-cold start vehicles pulse the injectors longer and earlier to compensate for lack of the CSI.

    In any case, I'm relating my problem because we are in a similar situation. I'm going to make a test light today so I can see if the injectors are pulsing when it's cranking. Won't have plug wires untiil Tuesday though. /forums/images/graemlins/frown.gif
     
  3. Hossbaby50

    Hossbaby50 3/4 ton status

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    I diagnosed injectors not pulsing in my original install. You can buy a NOID light at Checker, Autozone, etc that plugs into your injector wires. It will pulse the light if the injectors are firing. It is only like $8 or something.

    I also used one of the $3 cheapy test lights as a NOID light. you can use them but it is a PITA trying to hold them in place.

    Do you know how to test for the injector pulse? I had to use a test light connected to a 12v source (battery) pushed into one of the module wires. Every time you remove the 12v source it should fire if I remember right. I don't remember which wire offhand but can find it for you if you like.

    I don't get spark when the module is acting up.

    I do have the flow charts for the TPI. Thanks

    Harley
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    Heck, I got plenty of spare 192 bulbs around, (and more wire than I'll ever need) I'm just gonna solder a wire to each wire lead on one. /forums/images/graemlins/smile.gif

    Since the ECM switches ground to pulse the injectors, and the other injector wire is 12V constant, all you have to do to test the injectors is stuff the test light leads into each cavity into one of the injector connectors.

    I can imagine with actual probes that might be hard, but I've found with the injection stuff, half the time I'm better off with bare wires for leads (instead of the metal probes) if I'm using the multimeter, etc., since you can stick the bare wire into the connector and it will typically stay, especially if you end up testing continuity on things that are too far apart to reach with your hands.

    Don't know which flow charts you have, (the whole manual?) but the one I'm looking at is "cranks but won't run". (Chart a-3)

    Easy test for MAF sensor is unplug it and see if it will run. If it does, something wrong with MAF. Just mentioning that because the flow chart doesn't indicate it.

    Here are the scans for the cranks/no run for anyone that is interested: click the arrow for page two

    Tell you what, I'm REALLY getting my use out of the factory wiring and service manual.
     
  5. Bruiser

    Bruiser 1/2 ton status

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    I think I am going to go this route for computer when I do mine. This you can even change the curve and such and not have to burn a new module etc. Check it out , one of the car mags got 400 hp/420 tq with mistakes (not computers fault theres). Looks great for a DIY like most ck5 members

    http://www.bgsoflex.com/megasquirt.html

    Also if you havn't got chart A-3 yet, I have it and can scan it for you if you need it still.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    I don't like the fact that megasquirt doesn't control spark. At least from what I've seen before, that was the case with it.

    I think it might be a good idea for engines that were never injected, (Buick Olds Pontiac AMC, etc) but a SBC should get a SBC designed injection system IMO.
     
  7. florida4x4

    florida4x4 1/2 ton status

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    yep, go oem if you want spark control. But it's not too hard to curve a distro and megasquirt is mega cheep! /forums/images/graemlins/thumb.gif
     
  8. realsquash

    realsquash 1/2 ton status

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    What distributor are you using? The large cap or small cap? Do you have a stock chip? What did u do for VATS?

    Check for spark when you're cranking. No spark=no injectors will fire, so simply checking the injectors doesn't eliminate the ignition system.

    Andy
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    No curving a distro isn't hard, but OEM doesn't just run fixed timing values either. I think that potentially you can lose a lot of performance from not being able to precisely control spark in all conditions, not to mention the "failsafe" of having a knock sensor to pull out timing if something goes wrong.

    I'm by no means an expert on EFI timing and performance, but if you look at the different calibrations (car, tranny, rear gears, so on) you see a HUGE variety in the timing values, and with the "adaptability" of the computer to change timing, that to me means "fixed" (I know it changes, just changes a given way when the same engine RPM/Vacuum is met) timing has the potential to hold back performance from what it could be.
     
  10. Bruiser

    Bruiser 1/2 ton status

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    But also you have to figure it's a trade off, you can adjust fuel delivery with a laptop on the megasquirt yet you can't without burning a new chip on the OEM. Just to get more accurate timing.

    Plus there are other ways to get your timing controlled by a computer MSD makes timing controls.

    So it is possible to have best of both worlds without buying an expensive all in one system. You can upgrade over time.
     
  11. Hossbaby50

    Hossbaby50 3/4 ton status

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    No I check for spark at the plug wires not the injectors. The injector thing was a little offshoot conversation. I get no spark at the plugs.

    Harley
     

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