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desertjoe 
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Location: New mexico
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 Topic: Throttle Body Injection change over,,,,?
Posted: 06 Jul 2024 at 9:31pm |
I decided to go ahead and sell the 1988 GMC ONE TON. Got too dang many projects and I want to concentrate on getting the Lambo 55 finished up instead,,,! The One Ton has a very good 454, altho the dang Throttle Body Injection has started to give me fits!! I've never worked on one of these, bet feel I can handle the repairs,,,if I could just find an overhaul kit!! It is stamped on side of body as Rochester 17087021 but that number has yet to produce any results from Oreillys or Autozone or Amazon,,,!!
After setting, it will start easy but misses badly by constantly backfiring thru the exhaust, which may indicate an over-rich fuel condition,,,,?? After warm up it settles down somewhat but still backfires thru the exhaust,,,but does rev up very smoothly,, and sometimes engine will die while at idle. I notice that both injectors are always shooting fuel spray at a pretty good clip even at idle,,,? The fuel spray does not look too be very atomized,,,,?? I'm thinking,,I would like to locate a 4 barrel aluminum manifold for the 454 and remove all that extra TBI stuff,,,?? Any thoughts,,,??
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Dirt Farmer
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Joined: 15 Sep 2020
Location: Illinois
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Posted: 07 Jul 2024 at 12:13am |
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Joe, don't go backwards, you will spend as much for a carb and intake, gaskets, antifreeze and the list goes on as you would to get the truck running top notch with injection. Did this just start or been happening for a while. Check the timing, while doing that look for a vacuum leak like a hose pulled off or weathered away, spray carb cleaner around injector body to see if there is a leak there, notorious for the base gasket to start leaking. If that fails go to parts store and have them put a scanner on it and see if there are any codes. Probably gonna be a simple fix. Worst case bad ecm and they can be had online for a couple hundred bucks. Don't give up, if selling, the next person isn't gonna want a carburator. Just my thoughts. Is that a square body truck, that is about the time they were changing over, if so they are in demand and 4x4 would be a plus. Good luck and keep us posted
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DMiller
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Location: Hermann, Mo
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Posted: 07 Jul 2024 at 5:59am |
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The electronics of the later engines varied timing across a 40 degree spread, would have to mod nearly every aspect on the engine to get it to run effectively. Buy a Reman TBI Unit, Do NOT buy just Injectors and try to clean the TBI Body with Carb Cleaner as that will remove the 'Coating' that was used when produced to Seal it to prevent Vacuum Leaks.
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Codger
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Posted: 07 Jul 2024 at 7:18am |
Usually a pretty easy system and the first step above a carburetor. Biggest trouble with them was vacuum leakage, and low fuel supply pressure. Reman units were the way to go back in the 90's, but the technology was current and parts were readily available.
I've not worked on one in years but cannot see why they would not still be available.
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A career built on repairing and improving engineering design deficiencies, shortcomings, and failures over 50 years now.
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Thad in AR.
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Posted: 07 Jul 2024 at 7:31am |
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Joe if I were to go the carb route, I’d find a stock cast iron intake and a quadrajet.
Then I’d really want the capability of a mechanical fuel pump.
Not sure on the big blocks if some had fuel pump amenities and some not?
As far as the TBI unit, vacuum leaks can be problematic.
I had one on a 383 stroker that I never could get to run.
I went the carb route and never looked back.
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jaybmiller
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Posted: 07 Jul 2024 at 8:39am |
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3 D-14s,A-C forklift, B-112
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DrAllis
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Posted: 07 Jul 2024 at 9:21am |
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Start with an honest compression test of the engine before doing ANYTHING ELSE. Know that you have a healthy engine to work with !!!
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DMiller
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Posted: 07 Jul 2024 at 10:00am |
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Better response and fuel economy of a TBI, Quadrajunks are history as unable to find midbodies in decent enough shape to rebuild. Biggest problem gas leakage past the Swedged in Plugs from Corrosion under the metering rod wells. Are a few late model Aftermarket Four Barrels but as I stated, will NOT EVER match the available flows from a functional TBI. Late model blocks have NO provisions for Mechanical pumps even as casting still had the plated holes.
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desertjoe
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Location: New mexico
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Posted: 07 Jul 2024 at 2:19pm |
[QUOTE=jaybmiller] this....
what you got ???
JAY MILLER,,,I'm gonna nominate you for "King For A Day",,,,!!!!  I had looked at several places for a rebuild kit for the TBI unit that is on this One Ton Truck,,,,and,,,,and,,,you went and fount what I needed,,,!!! You a whole lot like ole Steve,,,he has so many sources for what a guy needs,,,, You guys are a treasure,,,,!! Many Thanks,,,you guys done Many Wonderfuls,, Hey Thad, I checked and this block does not have the provision for a mechanical fuel pump,,,,CHIT,,!
DMiller, I hear what you are saying,,and I did find a reman TBI for $685 and since I'm gonna sell the trk ,,,I ain't wanting to turn loose any more geetus that I have to. I done what ole Dirt Farmer suggested and sprayed some carb cleaner all around the btm of TBI unit and all 18 of the vacuum hoses and NO change in the idle,,!!! Engine was running rougher than a 3 season cob,,,!!! THEN,, I took a small ball pien and tapped around on both injector bodies and Lo And Behold,,the engine settled down quite nicely and the stream of fuel got considerably finer and Best Of All,,,the engine stopped backfiring out the frigging tail pipes,,,???
SO, there appears be an issue within the injectors,,,,? I'ma gonna call them folks that ole Jay sent me that link to,, tamarrow to see about a kit for this TBI. Wish me luck,,, Thanks again,,Jay,,!!
Edited by desertjoe - 07 Jul 2024 at 2:45pm
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desertjoe
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Posted: 07 Jul 2024 at 3:04pm |
 DrAllis wrote:
Start with an honest compression test of the engine before doing ANYTHING ELSE. Know that you have a healthy engine to work with !!! |
Hey Dr. Allis,,that right there was first thing I done when I bought the trk was to run a compression test.,,,  The readings were very even across from 150 to 155. I always check the exhaust pipe for further proof of engine passing any oil and exhaust was nice and dry with a slight gray powder feel.. The trk was bought new and the guy added a welding bed and was used all it's life in oil fields of Oklahoma and I bought it with only 68,000 miles on the clock . Thanks for the interest.
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Thad in AR.
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Posted: 07 Jul 2024 at 4:12pm |
DMiller wrote:
Better response and fuel economy of a TBI, Quadrajunks are history as unable to find midbodies in decent enough shape to rebuild. Biggest problem gas leakage past the Swedged in Plugs from Corrosion under the metering rod wells. Are a few late model Aftermarket Four Barrels but as I stated, will NOT EVER match the available flows from a functional TBI. Late model blocks have NO provisions for Mechanical pumps even as casting still had the plated holes. |
Better response??? Not hardly. Many newer than this had a fuel pump block off plate and bored for the pump rod. Many did not.
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DMiller
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Posted: 07 Jul 2024 at 5:30pm |
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Thad, seen actual Dyno tests TBI can deliver well atomized higher pressure gas near to 1100 cfm and Two barrel, QJ worked up to 850/900 depending on metering system. Crate engines will come bored for but lack Mechanical pump push rod. Engines newer than 04 have no bore for the pushrod and no cam lobe. Engine electronics can vary timing out to 65 degrees, cannot get close to that all
Mechanical.
Fixing to FAFO if go there so do not be angry.
Edited by DMiller - 07 Jul 2024 at 5:31pm
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DMiller
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Posted: 07 Jul 2024 at 5:34pm |
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Tapping on TBI could also have had a stuck Idle Air Control(IAC), very typical for these, several sensor inputs to tell it how far or little to adjust.
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desertjoe
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Posted: 08 Jul 2024 at 11:08pm |
Well,,,I finally got the cobwebs outa my brain and remembered I DID have a spare manifold with a perfectly good TBI that was operating good when manifold was removed from it's 454. I had "saved" it for no reason, just did not want to throw it away,,, This intake with TBI came off a 454 I had bought to put in the the Black Square Body after the camshaft went flat right after I bought the truck,,anyone remember that story about 2 years ago,,,? I installed an aluminum intake on that 454 with a 750 Holly, then sold the trk at a very good profit,,,,,!!! Anyway, I dug thru my stash in boat shed and LO,,,there it still was and just waiting on ole Joe,,,,  TBI unit did not need any cleaning but during removal of the old TBI, I find 3 vacuum hoses that were most likely leaking,,PLUS, a weird happening,,,the btm gasket between a "Cooling water adapter" and BTM of TBI unit appeared to be leaking fuel while engine was shut down,,,,?? WTH,,,?? I HAD sprayed this area liberally with carb cleaner with engine running and did not notice any change in rpms,,,??? HMMMmm Decided to remove that adapter to also replace the gasket UNDER this "adapter" and find yet another Oh-Oh. There is a 5/8" metal pipe at back of TBI that takes cooling water from under TBI to the truck heater,,it had also been leaking but leak was not visible until TBI is removed,,it has a really weird connecting fitting at the manifold,,,SHEEEESH,,,!! It has 1" NPT with a kind of slip fit of pipe into the NPT fitting,,,???
Can't wait to see how the engine will run with all these Oh, Oh's are fixed,,,,
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Dakota Dave
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Posted: 09 Jul 2024 at 9:14am |
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Mt 454 suburban also ran poorly the previous owner had fiddled with every thing disconnected the sensors and controls. I put new iac map and AC solitude replaced the TBI gaskets and all the vacuum lines. Runs great now I ve got about 100 dollars into it.you can't put an old 4 barrel manifold on the vortec the bolts are vertical instead of angled in.
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desertjoe
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Posted: 09 Jul 2024 at 10:49pm |
Hey Dakota,,,I don't have an idee when the vortec engines came into existence,, altho,, I think Thad and I were discussing early 7.4 engines,,, I don't remember which BBC 454 I used on the Black Beauty Square Body,,,just remember the cylinder heads were of the large round port design and the aluminum intake I used bolted right up on them heads.
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DaveKamp
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Posted: 10 Jul 2024 at 12:21am |
The throttle body is Rochester TB220. It was provisioned with several different injector sizes to suit everything from the 4.3L V6 up to the 454 V8. The GM ECM used on the '88 model year is frequently referred to as the '7747, as that's the last four of it's formal model number. It is by far the most common, and most popular controller that DIY injection guys used for their hot-rods before aftermarket manufacturers grew into viable options.
The elements that change from the 4.3 up to 454, are ignition module (it has integral electronic timing), and injector size (flow rate). One can also adjust the fuel pressure, but the TBI-220 'likes' a constant pressure.
I'm running a TBI-220 with 46 lb-hr injectors on the GM 250ci inline six in my 1970 Sea Ray 17' runabout. Works great, especially in the face of some pretty extreme mods.
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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