95 4.3 tbi, will excessive fuel pressure, 40 , cause a tbi not to work? If so, please explain why. Also what is a good way to regulate the pressure?
Thanks

 

Yes, high fuel pressure will cause the injectors to be shut down. The ecm is trying to shorten the pulse widths to the injector, something it just can do when the pressure is high.
Is this a custom engine swap or stock setup in a truck? The stock tbi unit should have a fuel pressure regulator in it. If it has an adjustable one (aftermarket) it could be maxxed out. It also needs a return line (to the tank) that needs to be 100% unrestricted.

 

This is a swap from a blazer into a jeep. we used the 4.3, 4L60E, and t-case and we are trying to use the fuel pump on the jeep. the jeep had a 2.5 mpi 4 cyl and we thought that we could use jeep pump. but we are all stock just ignorant about some things. so, we need to regulate the fp pressure and provide ample fuel return. does the return line need to be same size as the main feed line? What is a good way to lower the fp pressure? could we constrict the main feed line and lower the pressure. The local parts stores dont have a fuel regulator that will lower 40 # to 14 #. all help is greatly appreciated, Thanks

 

On F body TBI setups the return is slightly smaller than the feed. I don't know the exact sizes off hand, but they are different. Can't go wrong if you make the return the same diameter as the feed. For fuel pressure you can modify the GM TBI unit to be adjustable. The pressure range you can adjust with that is somewhat limited though and so you may want to consider getting a nice external regulator with AN fittings. The local parts guys are probably not going to be much help here. Best bet is to do your research and then order parts online.

 

thanks pound, i see that the spring in the tbi reg is very strong, and there is a small bolt in the bottom of the reg, but it is soldered in or welded. It seems to me that the tension on the spring is already high enough, but only guessing. I can pull the 4 wire plug from the dist and touch the ppl/wht wire with a voltage wire and the injectors will work. i hooked a light to the injector wires and when cranking the light flashes, showing that the ecm is pulsing the inj, but not spraying, so the high pressure is probably keeping the inj from actually opening. could i be right on that point? Thanks for your help

 

I believe there are some TBI applications that actually run at 40 PSI stock. You need to find out what you have. There are part numbers stamped or etched on the tops of the injectors. You may have to remove them from the pod to get a good look. Also I would think that if you haven't messed with the stock TBI regulator then it should provide the correct pressure for the injectors.

 

this tbi came from a 94 astro 4.3, so it is probably set right. will do some mods on fuel press and return and see what happens . thanks pound

 

Me again Lord i got a problem that i cant solve. The injectors are now instead of spraying gas is dripping from injectors. so, i now have injectors soaking in some berryman. If cleaning does not help will replace. will too much fuel press cause the dripping instead of spraying? thanks

 

The # on my tbi is 17091033. dont see any #s on the injects. they have the orange coating on the terms.
can you tell what year and which injects this is.

thanks

 

I have a 96 Blazer with the 4.3. It needs 60+ PSI to start.

 

i believe you have tpi and in that case you would need 60. Is there a way that I can lower the fuel press just long enough and safely to see if that indeed is the problem. At this time we dont have the money for a regulator, online they are over $100. I thought about restricting the main fuel line but would that harm the fp, because of the back press on the fp? Thanks guys, I'm sorry to be so much trouble but i sure need help. Getting old and tired and will be glad when this project is finished. Amen

 

Mine looks like this.

*edit*
Okay looked online and in 96 they changed. I have the injectors inside the intake manifold and a spider fuel injector system. I assume you have the traditional TBI with injectors and all, incorporated with the throttle body.

I think you're going to have to get the OEM Blazer pump or the AFPR.

 

if the 02 is disconnected will that keep the engine from starting or cause the tbi not to spray?

 

I believe oil pressure is also required. So that is communicated to ECU.

 

tbi gets its signal from the distributor. and ecm. it will start with the 02 sensor unplugged.

 

on the fp press would a fp for 6cyl jeep tbi have the right press or should i adapt a fp for the gm 4.3 tbi into the tank of the jeep, i know im crazy, but time i seem to have more of than good sense. thanks guys for all your help, this is a great site.