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TBI Wiring HELP PLEASE

Discussion in 'The Garage' started by NorCalKid, May 1, 2006.

  1. NorCalKid

    NorCalKid 1/2 ton status Premium Member

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    Soooo... I am in the middle of swaping out my carb for a TBI setup from a 89 burb into my 73 k5. I got all the parts on but know I am realizing that it is a pain in the ass to wire. Soooo I got some questions.

    How does the in tank fuel pump hook up to the fuel pump relay?

    I have a sm465 and the burb that I pulled the ecm out of had a automatic. do I need a diffeerent chip?

    What wires from the fuel injection harnes to I have to hook up to my k5?

    Please help I want to go wheeling!!!
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Fuel tank wire is just a single one from the relay to the pump.

    Yes, you should get a chip that is correct. (same size engine I hope?) It will run your truck, but it won't be right, and you will likely notice this right off the bat. One of the advantages of injection is driveability. :)

    To go along with driveability, GM didn't throw any wires in there that weren't necessary. It just so happens that EVAP an AIR aren't necessary for your application. Trying to cut things out of the harness/simplifying it, really aren't in your best interest. Plenty of wiring diagrams in posts here, it won't take much for you to find them, and use those to understand what you are dealing with. Factory manuals (both service and electrical) are extremely handy to have, but in a pinch the wiring diagrams can get you by.

    The only wires off the top of my head that you WON'T need are the AIR and EVAP ones. You can leave those unplugged and not throw a check engine light. EGR left unplugged should throw a check engine light, but if you don't have it, you can have that "turned off" if you have someone burn you a chip.

    If your engine is stock, you may get away with just getting a *stock* manual PROM with EGR turned off (and AIR and EVAP to be thorough) which should be pretty cheap. $40 maybe?

    If the engine isn't stock, you may want to look at some different options. Getting it wired up first should be priority, then see how it runs and take it from there.
     
  3. NorCalKid

    NorCalKid 1/2 ton status Premium Member

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    the fuel pump relay has a wire the same color as the pump but it comes out of the relay and splits into four wires. can I get rid of these wires and just conect the one from the pump to the one from the relay or are the other 3 necessary? Do I have to hook the relay up to the ignition switch or does the ecm give it power?

    thanks for the help
     
  4. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Here is a diagram I just drew up that shows you exactly how the factory hooked up the fuel pump. The orange wire between the relay and the stock oil pressure switch also runs to two different pins on the ECM, then off to it's own fusible link. Just not enough room to draw as much into the diagram :)

    I personally used a Bosch cube relay instead of the big junky thing the factory uses, eliminated the oil pressure switch, and eliminated the inline fuse.

    I instead put the 30A fuse before the relay on my stock fuse block, and went from the relay directly to the ECM and the fuel pump.

    I have my relay mounted directly to my ECM, using one of the screws that holds the casing together. This protects it from the elements, and reduces a lot of excess wiring.

    Just be sure you keep another relay or two handy if you decide to get rid of the oil pressure switch. If that relay ever quits, and you don't have a spare, you're dead in the water.

    tbi.jpg
     
  5. theperfectgarage

    theperfectgarage 1/2 ton status

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    I too have eliminated a few fuses and oil pressure switches in my day but it's never good advice, the lack of the oil pressure switch can potentionaly turn a minor accident into a fatal accident or at best a burnt down truck. I just had to add that.
     
  6. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Actually, in this case, it isn't a safety system. The oil pressure switch does NOT cut off the fuel pump in the case of a loss of oil pressure, which is the common misconception. You could technically wire it to act that way, but from the factory, it isn't wired up that way.

    All that the oil pressure switch is used for it to act as a backup to the fuel pump relay. So, if your relay quits working, your truck will still start once sufficient oil pressure is achieved (3 PSI in the factory pressure gauge's case)

    And, as far as the fuse goes, I just moved it from behind the relay, to infront of the relay :) I've got a seperate circuit for the ECM power feeds, rather than combining them with the fuel pump feed.
     
  7. theperfectgarage

    theperfectgarage 1/2 ton status

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    My mistake, I thought you were refering to the oil pressure switch which kills the fuel pump when there's no oil pressure. Thank's for taking my words as intended and not as a attack.:waytogo:
     
  8. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    No problem!

    Like mentioned, its a commom misconception :) If it were a safety system, then I'd agree 100% that it'd be foolish to disable it just to save some time wiring!

    And no, I definitely didn't take it as an attack! I'd prefer someone call me on a mistake than have someone do something unsafe / wrong by far!
     
  9. daleearnhardt01

    daleearnhardt01 1/2 ton status

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  10. NorCalKid

    NorCalKid 1/2 ton status Premium Member

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    thanks for all of your help I am going to work on it tonight and we'll see what happens.
     

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