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TBI Fuel Pressure and Guage Questions.

Discussion in 'The Garage' started by nvrenuf, Apr 26, 2004.

  1. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    I've asked this before but never saw a definitive answer.

    Does anybody make a fitting for tapping into a TBI fuel line to install a pressure guage? I'm wanting to put one on my 91 crew cab but I can't find anything. I would prefer not to cut the factory line, if possible.

    Doesn't the OE pump run about 15psi?
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Only way I can think of running a fuel pressure gauge is to get some of the AN fittings, some adapters from Earl's or the like (for the Saginaw fittings) and have the sender in between.

    Only thing I've ever seen for those Saginaw fittings are sections at Napa that have a fitting on one end, and nothing on the other. The adapters for the Saginaw fittings are like $8/each. Not bad when doing just two I guess.
     
  3. y5mgisi

    y5mgisi 1 ton status

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    [​IMG] I think this is what your looking for. There's moer info about it here. CFM-tech /forums/images/graemlins/thinking.gif
     
  4. Thunder

    Thunder 3/4 ton status

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  5. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Sorry guys but I failed to give you an important piece of info, I want to run an in-cab guage (with an isolator). /forums/images/graemlins/doah.gif

    The Saginaw fittings that Dorian mentioned are the o-ring type, right? *I think* this is what's on my truck although
    I have not verified it.

    Also, what is the average pressure? More or less than 15 psi?
     
  6. burbBoy

    burbBoy 1/2 ton status

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    less then 15 PSI. Did you make yours adjustable yet? The 3 i've seen had the pressure set to the lowest from the factory.

    *you should be able to buy the adapter w/o the gauge and tap the sender into one of the 1/8" NPT ports on the above adapter*
     
  7. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    I haven't done anything to it yet. I've been thinking about getting the adjustable regulator and the spacers for it, my old tired motor could use all the help it can get. /forums/images/graemlins/rotfl.gif

    My main reason for the guage is for diagnosis. I had a cranking problem with it today and having a guage would have quickly narrowed the problem down.
     
  8. fortcollinsram

    fortcollinsram 1/2 ton status

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    You can get a fuel line adapter that is intended for FI cleaning from NAPA. It plugs in the feed line of the TBI and have an 1/8" NPT port. That is what I am running with 3' of SS line and an AutoMeter 2-1/16" mech gauge on my hood...
    Chris
     
  9. 1-ton

    1-ton 1/2 ton status Premium Member

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  10. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Thanks for all of the suggestions! Hopefully, soon I'll be hooking a guage up and I'll post a list of part numbers for everything I use.

    [ QUOTE ]
    A mechanical fuel pressure gauge inside of the cab of a truck sounds pretty risky. /forums/images/graemlins/yikes.gif

    [/ QUOTE ]

    Autometer offers an isolator which is a diaphram that mounts in the engine compartment with non-flammable fluid running to the gauge inside. /forums/images/graemlins/thumb.gif
     
  11. chevyjeff

    chevyjeff 1/2 ton status

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    I am going to tap into the hot wire of the 02 sensor and using a volt meter read the voltage from it. The specific voltage for a perfect lean/rich mixture can be found here web page this way you can see what your fuel pressure is doing from inside the cab and is a lot cheaper than all the gauges and accesories
     
  12. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Now that's an interesting twist on the idea. Very cool. /forums/images/graemlins/thinking.gif
     
  13. 4xcrazy

    4xcrazy 3/4 ton status

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    I dunno, but when i had my tbi unit removed, i remember the hard lines being alittle tough to move around due to the fact they were specifically designed to fit right up to the tbi input, there was absolutely no room for an adapter that large, i have used the fuel pressure check gauge before, and that was a pain to install. Would probably need something similar to that setup for it to work ok.
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    O2 voltages

    IMO those voltage ranges are WAY too narrow to do much effective tuning except making sure an engine is either running 14.7:1 or not going lean at WOT.

    I know you can do a lot with an O2 sensor, but with that kind of curve, a miniscule A/F ratio change will change the voltage reading immensely.
     
  15. chevyjeff

    chevyjeff 1/2 ton status

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    What would the ideal #'s be if your using the o2 sensor voltage to tune. The only way to change the mixture is to either adjust the reguator and or do mods to the t.b. or burn a custom chip correct?
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    In actuality it doesn't appear 14.7:1 is ideal. There really is no "ideal" anyways, just as in everything else, all variables have to be added together.

    Guys running Fuel Injection have leaned their cars out quite a bit past 15:1 and not had problems with cruise, but thats cruise. WOT again is dependent on many factors, but it's less than 14.7

    The problem with "standard" (narrow band I guess) O2 sensors is that the voltage readings, as shown in that diagram I posted, are pretty much worthless once outside of 14.7:1. For the "average" tuner getting 14.7:1 at cruise is probably fine, and making sure the engine doesn't go lean under WOT is also good.

    Like you say though, the only way to CHANGE this stuff is to make hardware and software changes.

    I think about the best place to go for information on this kind of stuff is www.thirdgen.org, in the forums you'll see the ECM related ones. Much more info than I can regurgitate, or even remember.
     
  17. fortcollinsram

    fortcollinsram 1/2 ton status

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    yeah, that is similar to what I have but mine has a male fitting on one end and a female fitting on the other. Pretty simple and effective and makes a tap possible and easy on the funky GM TBI fuel lines

    Chris
     
  18. fortcollinsram

    fortcollinsram 1/2 ton status

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    Fuel line adapter with 1/8"
    NPT port for FP gauge
    [​IMG]



    FP gauge on hood
    [​IMG]



    My vacuum referenced fuel pressure regulator all plumbed in. Lets the engine idle with about 12psi of FP and when you romp on it it goes to about 18psi
    [​IMG]


    stainless steel line to FP gauge on hood...
    [​IMG]


    Chris
     
  19. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Fortcollinsram, that is exactly what I'm wanting to do! Are your fuel lines flared or o-ring (Saginaw) style? When you got the fitting from NAPA was it something in a generic pressure testing kit or was it application specific?

    Looks like I'm going to NAPA tomorrow. /forums/images/graemlins/woot.gif /forums/images/graemlins/woot.gif

    Thanks to everyone for all your help!! /forums/images/graemlins/thumb.gif /forums/images/graemlins/peace.gif /forums/images/graemlins/peace.gif /forums/images/graemlins/thumb.gif
     
  20. fortcollinsram

    fortcollinsram 1/2 ton status

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    [ QUOTE ]
    Fortcollinsram, that is exactly what I'm wanting to do! Are your fuel lines flared or o-ring (Saginaw) style? When you got the fitting from NAPA was it something in a generic pressure testing kit or was it application specific?

    [/ QUOTE ]

    I have the o-ring style lines, they are kinda a bitch to work aroundb/c they are so unique. Go to NAPA and ask them to look in the Echlin or Carb illustrated buyers guide...It is a CRB (carb) line code...I wish I had the P/N but lost it and don't work at NAPA again until Sat. It is part like 1-7xxx. It was like one of TWO fuel injection cleaning adapters for TBI systems that was listed in the book...The only draw back is that it moves the feed line back about 2". ON my BBC it wasn't an issue but it may be on an SBC.

    Keep in mind that this adapter was intended for "Fuel System Cleaning" not pressure testing and it is listed as such in the book, Then I just threw a 1/8"NPT --> -04AN male fitting on it and my SS line threaded right up /forums/images/graemlins/waytogo.gif
     

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