89 350 TBI problem

Discussion in 'Troubleshooting & Diagnosis' started by Chuck78, Jan 6, 2007.

  1. Knuckle Dragger

    Knuckle Dragger Moderator Staff Member Lifetime Gold Member

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    Nov 2, 2002
    Waddell AZ
    I can't remeber, do those have the presure regulator in the fuel lines. The regulator could also be the issue. 5psi is too low.
     
  2. Chuck78

    Chuck78 Veteran Member

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    Oct 22, 2000
    Columbus, OH, USA
    regulator is in the throttle body I believe. Definitely not in the line anywhere. We were already questioning wether or not we should change the 2 month old fuel filter. I think I may pick one up today. There is nothing in the line but the line itself, and the fuel filter, between the pump and the gauge.
    I also have a slight hesitation about trusting the gauge's reading as accurate.
    I broke loose the line after the filter where there is a flexible stainless line up to the engine block, and inserted the tee fitting there.

    I'm gonna look into how to test the MAP sensor and the TPS.

    EDIT:
    I didn't understand how the regulator worked in TBI's, as I was thinking in my occupational terms of HVAC/natural gas regulator that reduces pressure on the outlet side only. Apparently the regulator works on a back pressure basis, and increasing the line pressure means restricting flow of fuel through the return line to create more pressure between the pump and throttle body outlet (regulator). NOW THIS ALL MAKES MORE SENSE! Wish I would have known more about this before! It had a replacement carter pump in it already and non-stock hose clamps like the pump had definitely been replaced once! Live and learn...
     
    Last edited: Feb 4, 2007
  3. GoldenOne7710

    GoldenOne7710 Veteran Member Lifetime Gold Member

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    Jun 23, 2004
    Athens, GA
    You'll need to remove the injector pod to access the fuel pressure regulator. The problem with the stock unit, is that the spring inside is too weak and breaks VERY easily. A lot of people drive TBI equipped vehicles for a very long time with malfunctioning fuel pressure regulators without problems. Others however have harsh symptoms like yours, but never suspect the regulator. An after market (adjustable) regulator can be bought for about $60 or less. Also visit http://tbichips.com and check out ALL sorts of mods, upgrades, and troubleshooting on TBI equipped vehicles. Another good thing to do would be to remove the vacuum hose on the front of the throttle body where it pulls off the PCV valve and see how much vacuum you have there. While this probably has nothing to do with your problems, it'll give you a good idea of all the other crudd that is stopping up various ports inside your throttle body. I'll bet that port is completely clogged.
     
  4. Chuck78

    Chuck78 Veteran Member

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    Oct 22, 2000
    Columbus, OH, USA
    As far as vacuum goes...
    I tested the PVC by putting my finger over the end of the valve, and it was sucking a good bit. The vacuum is not steady at all, as the engine revs up and down so much that it goes from 9 or 10 in. up to 18, back and forth every few seconds. Tried to check timing, but due to this and it kicking up on fast idle a lot sometimes (sometimes it stops loping and kicks up on fast idle when we are messing with vacuum lines), we weren't able to get good readings on either.
     
  5. Chuck78

    Chuck78 Veteran Member

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    Oct 22, 2000
    Columbus, OH, USA
    http://www.partsamerica.com (Advanced Auto/Checker) has a regulator kit for $30, this is what it looks like:
    [​IMG]

    I think I'll be buying one of those asap! Searching their site, it also shows a TBI filter as well.
     
  6. GoldenOne7710

    GoldenOne7710 Veteran Member Lifetime Gold Member

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    Athens, GA
    That's amazing. 90% of all TBI's I've ever messed with had a clogged PVC port. That rebuild kit is a decent piece. For $30 more dollars, you could get the entire unit that is adjustable. You can crank up the pressure a tad more than stock and FEEL a noticable difference in power.
     
  7. Chuck78

    Chuck78 Veteran Member

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    Oct 22, 2000
    Columbus, OH, USA
    This thing weighs 5300 lbs with me in it, and is my daily driver... With TBI and an overdrive 700R4, used to knock down 21mpg highway. Although it would be nice to have more power out of it, I'll stick with the stock setup for gas mileage!

    I have contemplated when I get rid of this beast once my Camaro is done, and I build a 60-63 GMC Panel Truck or Suburban (might do a 60-66, or 67-72? and might do a Chevy with the dual GMC headlights/grille), that I might do a real mild vortec 400 with a Quadrajet, but have considered putting a throttle body unit like this in it. If I junk my daily driver after it becomes too much of a rustbucket, I'm defuinitely yanking the engine and trans, and the entire computer and harness necessary to do the swap. I'm still in the computer/TBI learning curve right now though! Maybe if I do that swap, then I would scrap the stock regulator and put in an adjustable regulator like you mention! Then I could tune it for power when I was towing or had the extra budget money for gas guzzlin'.
    [​IMG]
    [​IMG]
     
  8. Chuck78

    Chuck78 Veteran Member

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    Oct 22, 2000
    Columbus, OH, USA
    Diaphragm solved it all!!! Now that I checked out everything else tune-up and sensor related, the entire truck runs and drives like brand new! Not bad for 240,000 miles! Now if it were that easy to make the body not look like a rustbucket!

    The new diaphragm kit came with a shorter, weaker spring, so I used the old one. It wasa good 1-1/4" taller than the replacement. I figured more fuel pressure would make it run stronger, and that I didn't really want to go weaker than stock and lower on fuel pressure (for a 5200 lb truck, no way).
    The thing runs really really strong now at all rpm's, best performance I've gotten out of it since I got it 4 years ago. Great running truck, once again, and first major engine issue ever. 3rd transmission though, love those 700R4's... the OD is great however.

    The spring was not silver soldered in like someone said, and it was a large coil spring, but there was a part of the regulator housing that did have a stud or bolt with the head of it silver soldered over as to not ever be tampered with.
    The TBI is incredibly simple, no real tuning at all. Just put the thing together and go! Set the timing, and that's it! The learning curve was a little frustrating for me, but looking back on it, I understand it really well other than all the mathematics involved in the computer's calculations. It does what it needs to, love how this truck runs. Might yank the engine and entire wiring harness when the body rusts out totally, to save at least the TBI fora 60-66 'burb or panel truck.
     
  9. K5JMP

    K5JMP Veteran Member Lifetime Gold Member

    That is what makes TBI so great. It's simple... get the right amount of fuel there and it will run great. A highly underrated system... Glad you got it together.
     
  10. danbrennan

    danbrennan Veteran Member Lifetime Gold Member

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    Mar 13, 1999
    Brighton, MI
    I'll have to remember that one for the future. Now if only the fact that my Blazer burns a quart of engine oil every 250 miles could be solved by something so simple - unfortunately, I think I have a problem with the rings in the #1 cylinder.

    One thing about the 700R4 trans that one of the guys around here told me(probably applies to any trans with a lockup converter) - when I started to feel some slip at light throttle, 40-55 MPH, I unplugged the lockup clutch wire, just to see if the problem would go away. It did, so I just left it unplugged, figuring the fuel economy loss wouldn't be that much. When I told one of the trans guys about this, he said I probably saved the transmission - the debris from the disintegrating lockup clutch gets carried into the bands/clutches/valves, and can ruin them.
     

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