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TBI swap nightmare

Discussion in 'The Garage' started by deadguy, Mar 5, 2005.

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  1. deadguy

    deadguy Registered Member

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    I have an 86 blazer that came from the factor with a carb'd 305 I swapped in a 92 tbi 350 and I can't get it to run.I am using a fuel pump from jegs that is suppose to work for the tbi they said it runs 15 psi I turn the key and themotor turns over without starting I have checked the timing so many times I'm sick, then my friend sais the pupm I had was rated at 20 psi so I went to the local parts store and bought a pump rated at 7-10 psi (info I read in a mag) after instal the blazer started and ran for about 10 minutes (the engine surged a couple of times) now it will start and run for about 15-20 seconds. My guess it was fuel starved since I had just put another 2 gal of gas in I was sure the pump did not have enough pressure I went back to the manual read fuel pressure should be between 9-13 psi so a pump with 15 psi should be in the range right, I thought to rebuild the fuel pressure regulator reinstalled the 15 psi jegs pump the blazer will still not start and after sevral attempts fuel was coming out of the headers indicating that fuel is still getting to the engine. Any ideas?
     
  2. dirtwarrior17

    dirtwarrior17 Banned

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    sounds EXACTLY like what my motor was doing... I had a couple vacuum leaks along with some vacuum lines that didn't get hooked up right. It would start up everytime but then would die in 30 seconds if i just let it idle. Is there raw fuel leaking from in between the tbi and manifold? those tbi gaskets are only made to be takin off once and if you take em off and put em on over and over they will leak. Its not the pump because i am running a 45 psi pump with no problems.

    sounds like a vacuum problem to me.

    also check for spark.... make sure all the plug wires are on tight and especially the coil wire.
     
  3. R72K5

    R72K5 Banned

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    im just curious why anyone would want ot swap to tbi, fuel injection is such a pita, never know what its gonna do wrong next,.


    so you swapped everything from a donor ? harness, ecm, sensors, whole nine yards ? oil pressure switch, extra temp sensor, etc,

    thats alot of trouble, will never ever catch me ever trying to swap to soem electronic injection crap, i work on enough of them all the time to knwo ill never own one, troublesome junk,

    good luck :D
     
  4. Fierospeeder

    Fierospeeder Banned

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    no you had bad battery cables :p:


    theres a fuel regulator in the tbi so a fuel pump isn't a real concern.


    Pull the plugs out and clean them up because they are prob fouled already. Try cranking it over again and see if anything happens.

    Check to see if all your plugs are getting spark with a timing light and verify your timing with it too.

    Hook up a vac gauge to see if your getting some vac during crank.

    is your egr valve stuck?

    get a multimeter and just see if your HEI is within specs.


    Worst case scenerio, you have a bad ECM.


    Carb all the way. Especially the one that only needed one vacuum line to run.
     
  5. gravdigr

    gravdigr 1/2 ton status

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    Take your carb up a vertical rock face once and see how superior it is :grin:
     
  6. dirtwarrior17

    dirtwarrior17 Banned

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    I meant before i burned a hole in my starter/battery cable... had a lot of minor problems with getting her running but now she runs like a champ.
     
  7. Thunder

    Thunder 3/4 ton status

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    Well........ have fun living in the stone age...... kid

    Deadguy:..........
    Is your oil pressure sender hooked up? If the ECM sees no oil pressure the engine will run about 20 seconds then the ECM shuts off the fuel.
     
  8. hi pinion

    hi pinion 3/4 ton status

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    Because the 85 non fuel injection type trucks,,, in my opinion that system SUCKS!!!!!!!! Computer contolled carberated junk. I treid everything from rebuilding the carb , etc etc, and my truck still runs like a POS. Same old song and dance here. :)
     
  9. firefighter184

    firefighter184 1/2 ton status

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    Carbs are great. For the street or maybe mud. Try climbing rocks at 10,000 feet. I traded a strong GM Performance 350 H.O. for a TBI 350 with a leaky head gasket, just so I could have TBI. That carb f**ked me on a hill one too many times.
     
  10. dirtwarrior17

    dirtwarrior17 Banned

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    thats why my hunt for a blazer was strictly 87-91...

    Its easy to modify for more power as long as you have the $$$
     
  11. RustBuket

    RustBuket 1/2 ton status

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    Carbs have their place but FI is definately superior in a wide range of conditions.
     
  12. Fierospeeder

    Fierospeeder Banned

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    to diagnose a carb, you only need 200 dollars worth of tools and with fuel injection you start getting into thousands. Plus the knowledge of what is new in the field. Instead of one sensor doing the work, there will be two additional sensors to check up on the one sensor.

    If you want to "hot rod" your motor, then you need to deal with someone that can supply a new chip and at a certain point an aftermarket ECM is required. Add extra for larger injectors and a fuel pump. etc...


    There are carbs available that allow drivability on slopes. Or you can always change the setting on the float.


    There are pros and cons between the two, but carbs are easier to fix and cheaper.

    Fuel injection is great for new vehicles or a new engine, but it starts getting to be a pain on older vehicles or when you choose to hot rod the motor and make major changes. It is great for turbo cars because of the knock sensor and its ability to compensate to changes.

    I will always be running carb on a majority of my vehicles. :cool1:
     
  13. TJS

    TJS 1/2 ton status

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    Sounds like you are guessing on the fuel pressure. Get yourself a fuel pressure gauge set up for TBI and then start diagnosing it. Stop swaping parts. Get a noid lite and a FP gauge.

    T.J.
     
  14. 7blazer5

    7blazer5 Registered Member

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    my friend had the same problem on his K5 and it was the Coil on the HEI
     
  15. bluejeep

    bluejeep 1/2 ton status

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    I'd second that testing fuel pressure is a very important thing. Too high of a pump normally isn't a problem because of the pressure regulator, but too low is. I had a pump on my Jeep that wouldn't push enough gas through it to feed the motor at much above idle. That was very frustrating. If you ran it, your timing must not be too far off so pull the plugs and make sure they're clean and dry. Check for spark at the plugs. If that looks good and the fuel pressure is @15psi for the feed line and 0psi for the return, it should run.
     
  16. beater_k20

    beater_k20 Banned

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    someone without experience right there.... DVOM, a test light, maybe a set of injector noids, and some chip burning hardware, you're in like $500 tops. so much for thousands. :rolleyes:
     
  17. Fierospeeder

    Fierospeeder Banned

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    labscope more then 1000 bucks You cant diagnose a majority of sensors with a multimeter
    scan tool, a real scan tool, more then a 1000 bucks
    EVAP tool 900 dollars
    four/five gas emissions analyzer 1000 bucks
    fuel pressure tester 200 dollars or more
    break out box 300 dollars
    temperature reader 100

    looks like it is more then 500 dollars, and i even didn't include noid lights.

    noid lights are great way to tell me what the pulse width of the injectors are while a misfire occurs. :rolleyes:

    You cant use a multimeter with an 02 sensor properly, tps sensor, injectors etc...


    What backyard repairshop are you working out of?
     
  18. dyeager535

    dyeager535 1 ton status Premium Member

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    Get off your high horse. You have no clue. Wait, let me rephrase that. You have a clue, but thats it. Anyone that says they will run a carb on their vehicles by personal preference has little basis to comment on fuel injection, because obviously they aren't interested or endeared to it. If it weren't for your condescending attitude, correcting you wouldn't be such a big deal, as long as eventually you start posting correct info.

    Anyone here can download winALDL, and get ALL the data that the GM scanner gets. Oh yeah, it's FREE. Make a $10 cable, a laptop or long cord for desktop PC, done. -$990

    Most don't care to see how the sensor operates, just whether it works right or not. winALDL -$1000

    Umm, carb setups use evap. -$900

    Uh, can't you use an exhaust gas analyzer on a carb setup? $-1000

    I've never looked one up, I guarantee a fuel pressure tester doesn't run $200, and I'm so sure, I'm not even going to bother wasting my time to prove you wrong. Heck, you can even get an inline adapter for TBI AND a tester for less than that. Let's say -$100

    Ok, from what I can see, it's a multimeter that checks a variety of plugs, or something along those lines that my GM service manual doesn't call for to diagnose EFI problems? In any case, a multimeter easily checks wires for continuity, and winALDL tells you what the sensor readings are. -$300

    How many do you want?? The vehicle already has two independent temp sensors, and winALDL lets you see what the CTS says engine temp is. Of course, this is academic, because last I checked, carbureted liquid cooled vehicles use coolant that heats up as well. -$100.

    I'm by no means an electrical expert, but I pay attention. Lets see. We can do a leakdown test of the fuel rail to see if an injector is leaking, with your fuel pressure tester. We can also pull the fuel rail (or injector pod, etc) and prime the engine and see if it leaks. You can ohm the injectors. winALDL I believe shows the injector pulse width as well, although for accuracy, you would need something on the injector itself as the engine was running. I can replace all 8 of my injectors for $220, if it fails either test above, it/they will get replaced. If it's present at idle, unplugging the injector will also help prove where the fault lies. I'm not sure what you'd ACTUALLY use to authoritatively test an injector on a bench if you wanted to go that far.

    winALDL. And again, you are incorrect. TPS can be measured with a multimeter, it's a voltage reading to the ECM, and it's just a rheostat. :confused: Most multimeters (mine does, and its cheap) have an ohm setting that will work on the injectors. :confused:

    So what was the grand total? $110 in diagnosis equipment over a carb. Nah, let me change that. I might want to see what my carbed fuel pump PSI is, -$100 for the fuel pressure checker.

    Theres one thing you forgot which is really indicative of you so far. A service manual set. Bought mine off of ebay for about $25. Let's say $50 because I'm generous, even if a service manual set covers carb issues and it can be used for everything else on the vehicle. So we end up with $60 more in diagnosis costs over a carb.

    Nowhere in the original posters question did I see him ask whether he should go carb or not. *You* felt the need to bring that into the mix, (or agree with others that did) apparently so that you could make a bunch of incorrect statements. The guy is running TBI, get over it. If you want to help, help. If you want to slide in anti-efi comments wherever possible, think twice about posting to EFI threads. :rolleyes:
     
  19. TJS

    TJS 1/2 ton status

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    Wow well said dyeager535. Could'nt have said it better myself. I am too converting to TBI. Got wire harness on e-bay for 40.00 and it even came w/ecm. I got dist. for 20.00. had a late model coil laying around. Got a 350 TBI set up on e-bay for 25.00. Downloaded the wire diagram I posted a while ago here. For all I have spent I think it evens out to a deamon carb. I am not running yet though..hehehe. I need to get some sensors and stuff, but my parts collection is coming along. Just think when you get your TBI running and running right (which you will) of the fuel savings you will incur. My holley is killing me..or maybe it is my right foot.:grin: And yes Fierospeeder I can diagonse this stuff without the wiz-bang tools you mentioned. A multimeter, paper clip (to read codes) and a home made fuel pressure tester for 20 bucks and most importantly a manual or TBI diagram.


    T.J.
     
  20. loafer

    loafer 1/2 ton status

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    fuel system basics...

    Pumps produce a flow rate at a given pressure, the fuel pressure regulator controls the pressure. What you need is a high flow efi pump. These pumps are usually rated for use up to 60-psi and are usually rated at X gallons per hour at free flow (zero outlet pressure). The higher the pressure is set at the regulator, the lower the flowrate from the pump

    As an example, I run a Walbro high flow pump that is rated for up to 60 psi however, my fuel pressure holds a constant 20-psi because that is what I have adjusted it for.

    How did you plumb your fuel supply and return lines? Don't use the stock 1/4" ID return line, it's too small. Your return line needs to be have at least a 5/16" ID. I use 3/8" on mine.

    Check your fuel pressure on the up stream side of the regulator AND the down stream side. Up stream fuel pressure should be 9-13 psi, downstream should be less than 2-psi. If it's much hogher than 2-psi you have a restriction in the return line or the fuel lines are too small.

     
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