TBI help (1 Viewer)

[fyresq]

I have an 89 chevy with a 350 SBC chevy motor in it that I aquired to use for my FJ40. The motor has less than 8000 miles on it (GM crate motor). I have had the truck sitting for about 8 months now and it ran fine when I first got it but now I can't start it. It will fire with ether and I can sometimes get it to fire with gas but it won't stay running. The fuel pump seems to be working ok and the fuel filter isn't clogged and I'm get fuel all the way to the throttle body. I have 3/4 tank and added 5 gallons just to be sure. I replaced the plugs and I know it will fire with ether so it has ignition. I don't have a code reader and the truck's tranny is blown so I can't trouble code it. What am I missing here? I thought about bad fuel. Will try to eliminate this today. Any other thoughts?

 

[bkfj40]

do you have a fuel pressure gauge to see what kind of pressure you are getting?

bk

 

[inkpot]

Howdy! Yea, fuel supply versus actual fuel pressure are two different subjects. Check the pressure at the throttle body, for sure. I have had to change the fuel pump on two similar setups due to the little filter element on the pump fell apart and sucked up into the pump. What a pain. One was an 89 Suburban, and the other was a 91 Camero. John

 

[fyresq]

What's the best way to test for pressure? The only way I can tell if I have pressure is to uncouple the gas line and turn the key. These year chevy's have that 2 second pressurization and from that I get a steady stream of gas, but nothing crazy. Would making a temp electric fuel pump from a gas can into the throttle body work or would that mess with the computer?

 

[Downey]

One or both of your injector bulbs could be bad. If yours has the oil pressure sensor, it could be bad or unplugged. I don't know that I agree with the bad fuel pressure idea because I think you said it would run for a short time?????

 

[inkpot]

Howdy! Use a fuel pressure gauge to check on the fuel pump. There should be a jumper wire for the pump on the passenger side of the throttle body. Check the shop manual for the right pressure. The screens/tips of the injector eggs could be varnished over and plugging up the fuel supply, if the pressure is OK. I would not pull them out without a rebuild kit. They have little itty bitty O rings inside the housing that can be a pain. John

 

[Gumby]

Are the injectors pulsing? If you have fuel under pressure at the back of the TBI unit, it's likely that you have enough pressure at the injectors to get them to at least dribble if they are pulsing.

Power to the injectors? You should have constant power to one wire at the injector. The other wire is grounded through the ECM. Don't test for ground there. It's not good for the quad drivers. If no power then you probably blew the injector fuse.

Do you have power to the purple crank signal wire coming from the starter solenoid to the ECM?

If it runs for a short time on the fuel from the injectors (your comment about firing on gas is confusing. Is it firing on gas you pour down the TB or on it's own?) then jumper the test wire on the fuel pump relay. If it runs then, try checking for power from the ECM to the relay.

 

[mmcinnis]

TBI

make sure the injectors are spitting and also check and make sure you have a good ground. I had a similiar prob. and it was a module not grounded properly.

 

[fyresq]

Think it was a bad ground - got it fired up today and it sounds good. I'm super happy to be able to get this running before I swap it! Thanks for the help guys. All of these troubleshooting suggestions you guys have given me makes me a little nervous about running the TBI. It would have sucked to be figuring this out broken down in BFE. There's a lot to be said for simplicity of a carb, but I also don't want the flooding issues that I used to have with my quadrajet

 

[FJBen]

Think it was a bad ground - got it fired up today and it sounds good. I'm super happy to be able to get this running before I swap it! Thanks for the help guys. All of these troubleshooting suggestions you guys have given me makes me a little nervous about running the TBI. It would have sucked to be figuring this out broken down in BFE. There's a lot to be said for simplicity of a carb, but I also don't want the flooding issues that I used to have with my quadrajet

double and triple check all wires/grounds. I had a few stumbling blocks but they were mostly the wiring, missing a ground, forgot to connect a wire...

good luck!