4.3 TBI to Carb.... Possible?

I was thinking of converting my 4.3 Throttle Body Injected Engine to a Carb sysem. The TBI system has given me so many problems. Gas Mileage is horrible, Running so rich it shoots black smoke.... 4 miles to the gallon it is running so rich. Rough idle and rough start. My truck is a 1986 with a 1989 Chevy Blazer engine. So far I have ripped apart the internal fuel meter/Pressure Regulator.... Everything seemed to be fine and the gasket kit is not that old..... Motor is in time... Inectors seem to be shooting so much fuel... I have a high pressure pump but stilll?


I was thinking about riding all of my headaches and putting on a 4 bbl carb style setup and eliminating things like the MAP, O2 Sensor, IAT, IAC, and all the sensors not needed...

You think any of this would be possible while keeping the 4.3 Computer? Just to run things like my Heat and stuff?

Let me know on opinions and suggestions...

Also Can I use that current fuel pump with say a regulator and a fuel return line?

What about the intake manifold, will I need a new one, OR so they sell a kit?


Any help, tips, comments, suggestions would be appreciated.

Thanks -peter

possible, yes, practical no,... so have you checked the cat lately?? black smoke, do you have blow by? How much oil, if any, are you going through, try a product ill sware by, you will run like shit for a half a tank or longer, but its worth it, its called sea foam, its a mirical drug, put a full can in your gas tank right as you top off, also put some in your air intake when you get home and some in your crank case, it will clean the internals of the fuel lines and injectors from the gas tank, it will clean out the air intake system from the throttle body, and it will losen up any sticking in lifters in the crank case, its realy great stuff.... switchin to a carb would suck, and you wouldnt get the greatist of gas mileage, remember your runing an obdI in an 89 moter, its not the newest thing on four wheels

what size engine did you start with? i love the tbi. what is your fuel pressure? it should be 9 to 14 psi.
that is alot of fuel youre burning. what all have you changed out or done to try to fix the problem? i think it will be less of a headache to figure this out than to try to switch to carb. so many ?s to ack but dont know where to start.

Haven't checked fuel pressure yet.

I checked the diaphram in the internal fuel meter. All the gaskets and the diaphram are fine.

Injectors spraying fine although it seems like way too much fuel....

It has a high pressure fuel pump, could be my problem?

Haven't checked o2 sensor.

My friend had a 92 4.3 he would let me use his TB, but is it the same?






what size engine did you start with? i love the tbi. what is your fuel pressure? it should be 9 to 14 psi.
that is alot of fuel youre burning. what all have you changed out or done to try to fix the problem? i think it will be less of a headache to figure this out than to try to switch to carb. so many ?s to ack but dont know where to start.

are you not running a stck intank fuel pmp? tb should be the same just have to look to make sure. youll be able to tell at first glance if it is the same or not,but it should be. yeah a tbi only requires 9 to 14 psi. the newer cpi
is much higher its like 51 to 60 or something. i do know that type pump is to much for the tbi, so what ever youre using might be too. check it and see. make sure you check it with key on engine off.

Just don't do this swap.

All a TBI is is a electronic carb and is so much better than any carb on the market.

Just don't do this swap.

All a TBI is is a electronic carb and is so much better than any carb on the market.

Well I talked to the kid who I bought the truck off today, and he said It is a high pressure or high flow fuel pump.. which is mounted under the drivers side seat.

He also said everytime it would belch black smoke they would change the MAP sensor and it would quit for about 6 months. He said they would have to replace it every 6 months.

I also saw a friends 92 TBI Injectors spray today, Man they are putting out way less fuel.

Last night I took the Throttle Body off, brought it in and cleaned it up, checked passageways for clogs, took the injectors off...Rubbed some ATF on the o-rings. I am missing the steel retainer ring for the injector cavitys.

They also put one injector in backwards and the set pin was smashed, I fixed this though.

Going to get all new vacum lines for my TBI.

Also, I noticed my Vacum Canister (ball looking thingy) is round like a ball and his was like a coffee can.

The line from the TBI to that can is terminated due to no fitting on the ball for it.

Any help, Tips, Places to find a fuel pump, Clues, Suggestions, Or any comments would be appreciated. Thanks again -Peter

Fuel Pump is aftermarket, but shouldn't the internal Fuel pressure regulator be taking care of the excess PSI?

I'm going to run a fuel pressure test tomorrow.

My injectors are def. spray way too much fuel.

Should I look into changing the computer?

Timing? Still a good idea to check?

Fuel Pump is aftermarket, but shouldn't the internal Fuel pressure regulator be taking care of the excess PSI?

I'm going to run a fuel pressure test tomorrow.

My injectors are def. spray way too much fuel.

Should I look into changing the computer?

Timing? Still a good idea to check?

EGR, does anyone know of a 2 prong plug egr? with a 4 prong MAP?

Let me know... Thanks... Peter

pressure regulator is suppose to keep a 9 to 14 psi at all times, if the pressure is greater from the pump to the throttle body, the excess fuel is sent back to the tank
were you able to repace all the missing and damaged parts to your throttlebody?
maybe your regulater is bad.
what i would and did was to go to the junk yard[ my
favorite place] and buy a complete tb. clean it and get a seal kit and put it on. only cost me $50, to do that. while youre there get a canaster.

dmbrisket 51 (http://www.automotiveforums.com/vbulletin/member.php?u=240041) said "Possible, yes, practical no,"... Not to mention that it is illegal. I don't know if PA requires you to have your vehicle's emissions checked on a schedule of some type, but if so, you will never pass if your vehicle's factory emissions system is not in place.

Pressure regulator probably not designed to handle inlet fuel pressure being fed to it by the pump. Best bet is to install factory FI fuel pump and replace the regulator, then continue diagnosing this problem.

Also, you should at this point replace your O2 sensor if it hasn't been replaced in the last 30k miles or if you are unsure. It is probably giving the computer an incorrect reading, causing the computer to think the engine is not getting enough fuel. Also, after running that rich, it's probably no good anyway. They only cost about $15. Use a breaker bar and do it when the manifold is warm (but not so hot that you can't get near it) and it should come out pretty easily.

Pick up a Chilton's or Haynes guide - they both have instructions on how to run the ECM's self-diagnostic routine, which may give you other places to look to troubleshoot the problem. (All you need is a paperclip to jumper the A and B terminals on the diagnostic connector under your dash.) You can also get instructions on this procedure and code meanings by doing a search on Google.

its alwase illegal to take a vehical back to older technology, speaking with emissions of corse

Hey, I would definately not put a carb on - if I remember correctly, there are about 20 hoses that need to be connected, along with lots of other junk. I had a carb in an 84 astro van with the same engine. It got 22-26 miles per gallon, highway. With a catalytic convertor, and good oil in the engine, it did pass emissions, in WI. However, you should contact your state to see what they would do in such a situation. Many states have waivers, or will test emissions without connecting to the computer. It may take some work. Don't try this in california!

Are your injectors spraying a constant mist, a funnel, or a stream?

Here are some things to check:

1. One wire of each injector connects to your car computer. The "common" wire between the two goes to a fuse. Sometimes, this fuse blows because of electrical malfunctions, or because the injector wires get caught between the air filter cover and the metal pieces. The fuse may blow, and may cause a condition by which both injectors are on constantly, at max. This will result in a constant flow of fuel at almost max speed. The computer will then adjust the Idle Air Control valve to lower the "idle" speed, which will cause the engine to run rich, blow smoke, etc, and really "stink".

To test for this condition, with the engine running, unplug the connector of one of the injectors. The engine should run rough, but check to see if the other injector is on. If it is NOT and the engine dies, you have a bad FUSE!

2. Check your throttle position sensor. Unplug the sensor, and start the engine. Does it spray less gas and does it ldle less? If you cannot tell, remove the TPS, connect it, and manually move the lever. Do you notice a change in engine speed? If not, the sensor is bad, or your computer is not responding to it.

3. Do you hear or feel a clicking or buzzing sound from your injectors? IF yes, they are probably working, but the gas may be bypassing them. You may want to "rebuild" the TBI, meaning replace the seals, o-rings and gaskets. They make a kit for this.

carberator...why? lol jus fix the tbi its cheaper easier n more practical

my 1988 was spraying WAY too much till i bought new injectors

hey logikal what did you ever do? kinda curios.

pressure regulator is suppose to keep a 9 to 14 psi at all times, if the pressure is greater from the pump to the throttle body, the excess fuel is sent back to the tank
were you able to repace all the missing and damaged parts to your throttlebody?
maybe your regulater is bad.
what i would and did was to go to the junk yard[ my
favorite place] and buy a complete tb. clean it and get a seal kit and put it on. only cost me $50, to do that. while youre there get a canaster.

I know this thread is a few weeks old, but I wanted to comment on this. The regulator doesn't know how much fuel pressure you have, it only restricts the the flow depending on engine speed. The regulator will drop the pressure 3 - 10 psi depending on the amount of vacuum applied. If he has a 60psi pump the most the regulator would reduce it to would be 50psi.