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Tbi Problems


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#1 eddinger

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Posted 12 June 2010 - 02:02 PM

Hello everyone,


I am so glad I found this site, I need help finding my problem. Quick background about my skill, I have none, but I'm learning. I recently bought a 1993 Suburban 2500 off an old man for a great price. Bought it to pull a camper that I traded my motorcycle for. The Burb has a 454 in it, 2 wheel drive. Thanks to help from my freinds and a lot of reading I have started to tune it up myself. So far I have replaced- plugs, wires, fuel filter, air & oil filters, PCV, serpintine belt & tensioner. I am about to change the brakes tonight.

Now, here's my problem, when I give it a lot of gas/ throttle, it sounds like it wants to go but it won't. I just cleaned the top of the throttle body with carb cleaner and put it Seafoam to hopefully clear any carbon build up. If that doesn't work I was wondering what it might be? I have been told the fuel pump is bad, injectors on one side might be clogged, need to take apart the TBI and give it a good cleaning. Has anyone had a similar problem? I am more than willing to go through the TBI, just don't know what, if any, parts I should replace when I do. I hope it's not the fuel pump but I fear it might be. I just thoght that they either worked or they didn't, can they start to fail but still send enoughv gas for me to drive it with slow pick up?

I also converted the R12 to R134a and it is working great, saved a lot of money doing that myself, I proud of that little accomplishment.
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1993 GMC C2500 Suburban. 2002 Trailblazer LTZ. 1992 Accord

#2 Rod R

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Posted 13 June 2010 - 04:30 PM

I have no experience with a big block TBI, but if you suspect the fuel pump then get the fuel pressure tested ... my Haynes manual says that a tbi 454 (7.4L) the fuel pressure should be 26 to 32 psi

... and yes, fuel pumps can fail slowly/progressively ... as the delivered fuel pressure continues to drop below the minimum spec you may get problems starting the engine or with acceleration performance... (if you are buying a new fuel pump get ACDelco or Delphi brand ... these are far more reliable than the other brands of fuel pumps)

if the fuel pump checks out OK ... then try also to replace the distributor cap and rotor (get ACDelco ignition parts... they just work better in a GM engine)

... by the way, when you get this thing running fine, you will have a very good vehicle for pulling a camper trailer

Edited by Rod R, 13 June 2010 - 04:40 PM.

Rod Ramage, Saskatoon, Saskatchewan CANADA
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#3 Mike G

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Posted 14 June 2010 - 10:03 AM

The TBI units are very easy to work with and have few parts. I am about to replace the injectors on my 92, since I feel they have seen better days. There are only two in the 220 TBI. Here is a page of some info and replacement parts, there is plenty more out there.

http://xtremefi.com/

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#4 eddinger

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Posted 15 June 2010 - 12:20 PM

I scheduled my feul pump replacement for Monday. I also noticed that one of my injectors is not working properly, can I just replace the one, or sould it be both?
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1993 GMC C2500 Suburban. 2002 Trailblazer LTZ. 1992 Accord

#5 Mike G

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    What do you mean you can buy colors????

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Posted 15 June 2010 - 03:03 PM

I usually see the injectors offered up as a paired set..
06 2500HD Crew Shorty 4x with the 6.6 LBZ turbo diesel beast and 6 Speed Ally
02 Avalanche (wife's driver)--Front leveled and 285s look sweet!
92 GMC K1500 Z71--Refreshed warmed 5.7L at 190K (sold 5/5/11 to an excited neighbor)
(02 F350 Crew Dually 7.3L PS Diesel - the #1 sons)

Dirt Bike-Street Bike-Two classic vehicles-5.7l Boat-32 Ft 5th wheel-Too much other stuff to fit in my sig

White truck club member? - I own it....

#6 eddinger

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Posted 15 June 2010 - 09:11 PM

after I get the injectors you guys still think I will have to replace the fuel pump??
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Butch "stogias" Eddinger
1993 GMC C2500 Suburban. 2002 Trailblazer LTZ. 1992 Accord

#7 88k5

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Posted 16 June 2010 - 08:29 AM

after I get the injectors you guys still think I will have to replace the fuel pump??



I would replace the injectors 1st. Then see how it runs.
You said at WOT it sounds like it wants to go but doesn't. Does this statement mean the engine is screaming but the truck isn't moving?
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#8 Cliff883

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Posted 16 June 2010 - 09:28 AM

You can buy just one injector, but I would replace both so that you know they are both flowing the same.

#9 eddinger

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Posted 16 June 2010 - 12:45 PM

ordered 2 delphi's today, hope they're here by Sat.
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#10 eddinger

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Posted 22 June 2010 - 02:48 PM

Well, I just put in the new injectors( Delphi ) and it now sounds worse than before. I don't know what size injectors were in there but I am pretty sure that the ones I put in run 90lbs/hr. So, I am taking it in this Monday to have the fuel pump replaced. I hope that's it and not something wrong with the injectors. I will remove them and reinstall again tonight when I get home just to make sure I didn't do something wrong the first time.
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1993 GMC C2500 Suburban. 2002 Trailblazer LTZ. 1992 Accord

#11 darkfox1

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Posted 28 June 2010 - 12:27 PM

You may already k now this, but if you take off the air filter and then the trim ring around your tb you can start the truck an watch the injectors. Have someone rev the engine and you can watch the fuel squirting into it.

that way you can at least test that they're installed correctly..

if I were you I would have just completely rebuilt the throttle body when you changed injectors. (in fact, that's exactly what I did to mine and now it runs quite well.. BUT I have a new fuel pump and fuel filter as well..)

#12 eddinger

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Posted 03 July 2010 - 09:04 AM

well, here's how it all panned out. I got the fuel pump replaced. Thank goodness I had a garage do it, they ran into a couple problems. First, when they removed the old pump it had blue silicone in and around it. He had to remove it from inside the gas tank and fuel line. Once that was done when they tried to test drive it the idle was jumping all around. Come to find out that the new injectors that I got off ebay were incorrect. They were in the right box, but the injectors were not. So we put the old ones back in and now everything is running great. Drove it down to the Outer Banks of North Carolina without a single problem. As a matter of fact I'm here right now posting this message waiting for my family to wake up so we can ride out to the Hatteras Lighthouse. Thank you all for all your help with my problem. I hope I can do the same for some one down the road.

Oh, and the best part, the mechanic didn't charge me any extra for the extra days work he put into it trying to get it right. He even cleaned out the carbon build up in the intake free of charge.
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Butch "stogias" Eddinger
1993 GMC C2500 Suburban. 2002 Trailblazer LTZ. 1992 Accord




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