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Need TBI help, any guru's got a second?

Discussion in 'The Garage' started by Emmettology 101, Jun 16, 2003.

  1. Emmettology 101

    Emmettology 101 3/4 ton status

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    Need TBI help, any guru\'s got a second?

    Man o'man.. What a weekend(and wed-fri of last week).

    Ok heres the situation.. Ii have an 89 GMC heavy half 4x4.. My buddy owned it before me and had a 383 built for it. After a while with pissing with the TBI, he yanked it in favor of a carb(due to the high price of chip burning and such)... So Wed. a friend and I started putting the TBI back on. The wiring harness was elft in the truck as well as the comp. We put a new fuel pump in and hooked up all the wiring.. And we're using all the stuff my friend took off...
    There is one plug that I know if that is unhooked, it is redish ornage and somewhat round. It is behind the disty. My buddy said it should be the oil pressure sensor connector. He removed the stock sensor in favor of a mechanical guage...
    So everything is hooked up. We left the fuel line unhooked and turn it on and got fuel.. After this we pulling a plug wire and gorunded it to the header and got spark. But no firing. Hell I even tried putting a little fuel down in the TBI just wondering if it wasn't getting it somehow and it still didn't fire. I am baffled. We also tried messing with the timing, thinking it maybe 180* out, but no go....

    Anyone have any ideas? (if you want more info, just ask) /forums/images/graemlins/smile.gif
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: Need TBI help, any guru\'s got a second?

    Did you try replacing the oil pressure sensor with a stock one and hooking that plug back up?

    Rene
     
  3. DaveCowley

    DaveCowley 1/2 ton status

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    Re: Need TBI help, any guru\'s got a second?

    Were the injectors firing? I had a similar problem to that since my OP Sending unit is not hooked up. My problem ended up being a massive vaccuum leak.
     
  4. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: Need TBI help, any guru\'s got a second?

    No, haven't gotten a sensor yet.
     
  5. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: Need TBI help, any guru\'s got a second?

    Not sure on the injectors. My buddy who is a GM tech is coming over this week to take a gander. I did dump fuel into the TBI and still no fire.
    I ran all new vacuum lines but will double check them...
     
  6. bushmaster

    bushmaster 1/2 ton status

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    Re: Need TBI help, any guru\'s got a second?

    emmettology, im building an 88 blazer im taking stuff from my 1 ton pick up and inst in blazer i have a built 383 that i want to inject ,whats in your engine ie cam heads comp ect thanksi heard that stock tbi may be to small
     
  7. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: Need TBI help, any guru\'s got a second?

    Well.. Hhmm... Good questions! Just make sure whoever you take it to is a good builder. Here's my situation.. My friend wanted a big and bad motor. They went too high on the comp, but the builder said it would be fine. ALso, the cam is too large for the injection.. Supposedly it is a middle of the road or towards the upper range for a carb which menas its about the largest, if not too large, cam for a TBI... Right now I have the stock TB on it, but have a 670cfm Holley sitting in the garage that will go on when I can wire up a new connector...

    Right now, we dont know what style of pistons are in it, nor do we know the exact cam profile.... All I know is that with about 1/2 tank Turbo Blue and half tank 93 octane, I get pinging with the timing retarded! The comp ratio is very high.. We are thinking its around 11.5:1+.. THe heads are Trick FLow Twisted Wedge's and they were milled down .008".. They had a 64cc chamber ot start with.
    I just wanted to get the EFI on it to make it a little more road friendly and help with winter starts.. I wasn't going ot worry about it, but a friend fealt it would be an easy swap and I wanted ot hit the truck pulls Saturday(didn't get to go)..

    I say as long as you keep the comp ratio within normal range and get a good EFI cam, you should be fine. You will also need to get a chip burnt.. DOnt go to Hypertech or Jet, find a smaller place that does it cheaper!

    Here are some specs(that I know of) on my engine:
    stock 89 block bored 30 over
    Trick Flow ALum. Twisted Wedge Heads - milled .008"(supposedly)
    Scat 383 crank
    Manley 6.0" rods
    KB Hyperu pistons(not sure on style)
    COmp Cam(not sure which one)


    When my friend first had it built and had the EFI on it, it had a 3" body lift and 38's on it at the time. He said he had no problems breaking the tires loose on any surface. BUt it wasn't running 100% and needed a chip. For some reason he went ot a carb instead... Not sure why, I think he felt it would be easier to deal with.
     
  8. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: Need TBI help, any guru\'s got a second?

    Ok,so we did some wrenchin tonight and here is what we came up with......

    The Oil Pressure sensor cuts off the fuel pump if disconnected.. SO we jumped it. Right now, we're getting no fuel out of the injectors and no spark.....

    So where next.. Hmmm... No clue.. But I will keep everyone informed. Anyone have any ideas?
     
  9. bassmannh

    bassmannh Registered Member

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    Re: Need TBI help, any guru\'s got a second?

    I know this sounds simple but did you check the ecm fuses and run a self diagnostic on the ecm by jumping the aldl terminals A+B to see if you get code 12 3 times
     
  10. K5 NUTT

    K5 NUTT 1/2 ton status

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    Re: Need TBI help, any guru\'s got a second?

    That is the oil psi connector....which is inline with the fuel pump relay...its part of a fail safe design...if the realy fails to work the ecm will see oil psi and forward power to the pump through the tan/white wire...and on some models the was a HOT fuel handling cicuit also...

    DW
     
  11. DesertDueler

    DesertDueler 1/2 ton status

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    Re: Need TBI help, any guru\'s got a second?

    On our trucks if you fround the oil ppressure wire it will show 0 psi, or at least on all three I have owned, so leave that wire open. BTW I dont think the TBI is going to work with your setup. I built a 350 with 9.0 comp. ported heads, 2.02/1.60 valves and a lunati bracket master cam with 220 duration at .050" and it didnt idle worth crap(Meant for a carb), but ran great after 1500 rpms. TBI motors do not adapt well to a cam change since they are speed density, not MAF. I would reccomend an aftermarket EFI setup with that kind of motor.

    Dan
     
  12. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: Need TBI help, any guru\'s got a second?

    All fuses are good as well as the relays.. Pump runs and pumps fuel, but the injectors aren't supplying the engine with fuel..

    I'll try the terminal jump tonight. Also, my friend who is the GM Tech shoul dbe ocming back over so hopefully he'll spot somethign again...

    Thanks!
     
  13. HarryH3

    HarryH3 1 ton status Author

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    Re: Need TBI help, any guru\'s got a second?

    GM's EFI system will not fire the injectors unless the distributor is working properly. The signal for when to fire the injectors goes from the ignition module to the ECM, then the ECM fires the injectors for a calculated length of time, based on the programming and engine parameters at that particular moment. So you'll have to find out the reason for not having any spark first. Once you have the ingnition system working, then you should see fuel spraying from the injectors as you crank the engine. /forums/images/graemlins/cool.gif
     
  14. Mudzer

    Mudzer 1/2 ton status Author

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    Re: Need TBI help, any guru\'s got a second?

    There are two different oil sensors. One is a pressure sender - not needed for TBI operation. The second is an Oil Pressure Switch - which is needed for the TBI operation. It may think the engine doesnt have oil pressure and will not fire the plugs. Ive seen these go bad and cause a non firing situation.
     
  15. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: Need TBI help, any guru\'s got a second?

    Thanks Harry. Hopefully we can track down the problem tonight!
     
  16. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: Need TBI help, any guru\'s got a second?

    Yes, I am missing the upper sensor. However we jumped it last night and got the pump running, but still no fire. I am having a hard time finding the right sensor. My friendd who is the GM Tech is supposed to look at work today if he has time. I need a senso with the small threaded hole going into the block and a oval/round plug end with 2 prongs and a notch in one corner.. /forums/images/graemlins/smile.gif Confused? /forums/images/graemlins/smile.gif MY plug is a tan(kinda ornage maybe) with a pink and a Ornage wire goign into it. /forums/images/graemlins/smile.gif
     
  17. K5 NUTT

    K5 NUTT 1/2 ton status

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    Re: Need TBI help, any guru\'s got a second?

    87 to 89 R/V series motors have two different sensors....the one behind the distributor is for the ecm's realy by pass circuit...the one on the drivers side of the block is for the gauge...90/91 R/V series used a 3 terminal oil psi gauge by the dist...both functions were incorperated into the single sensor...

    But yes...got to have the spark...most often the dist module takes a dive...on rarer occasions it is the pick up coil...

    DW
     
  18. fortcollinsram

    fortcollinsram 1/2 ton status

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    Re: Need TBI help, any guru\'s got a second?

    where is this sensor...it kinda sounds like the oil pressure switch

    Chris
     
  19. fortcollinsram

    fortcollinsram 1/2 ton status

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    Re: Need TBI help, any guru\'s got a second?

    yep, the oil pressure switch...You gotta have that thing... /forums/images/graemlins/thumb.gif
     
  20. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: Need TBI help, any guru\'s got a second?

    [ QUOTE ]
    87 to 89 R/V series motors have two different sensors....the one behind the distributor is for the ecm's realy by pass circuit...the one on the drivers side of the block is for the gauge...90/91 R/V series used a 3 terminal oil psi gauge by the dist...both functions were incorperated into the single sensor...

    But yes...got to have the spark...most often the dist module takes a dive...on rarer occasions it is the pick up coil...

    DW

    [/ QUOTE ]

    Well the other night we jumped the oil pressure switch for the pump and had the pump sending fuel to the TBI.. We still didn't have spark at the plugs or the coil. We tried a different coil also with no luck.
    Last night we didn't get to work on it because of rain and it wont fit in my garage... I am wondering now if the control module in the disty is bad... We have another one I will swap in and try....
     

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