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TBI stopped working any experts?

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nsxxtreme

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I may have hooked a wire up wrong. When I first fired it up they were squirting correctly. Then they started dribling and then stopped all together. There is this red wire that I assumed went to the alternator that I'm not sure of. If I disconnect it the injectors dont work at all. If I connect it they start dribling again.

They are new injectors and I have fuel pressure.

IMG_0073.jpg
 
not sure about your red wire but I believe the injectors have power all the time and the ecm controls the ground to fire them. Maybe see if you have voltage at the injectors.
 
So I figured out the Redwire is some kind of ignition wire when I disconnected it the dome lights go out so im positive that that wire does go where it's at.
 
So the thought is I probably broke the hose going from the pump to the sending unit when the pump tried to pump up to 22psi. It was just the stock pump and I figured what the heck lets see if it runs. Truck started but didn't last long.

I had bough a new pump in anticipation of the new motor. But now I have to drop the tank and of course the tank is full of gas. Just cant catch a break with this thing.
 
Before dropping the tank, do some investigating to prove that the hose popped before assuming so and doing a bunch of work for no good reason.

Hook up a fuel pressure gauge and see what you have for fuel pressure. Should be around 10 - 15 PSI for TBI. Also, hook up a noid light (12V LED bulbs work great!) and check to see if the injectors are pulsing or not to confirm your wiring.
 
Russell said:
Before dropping the tank, do some investigating to prove that the hose popped before assuming so and doing a bunch of work for no good reason.

Hook up a fuel pressure gauge and see what you have for fuel pressure. Should be around 10 - 15 PSI for TBI. Also, hook up a noid light (12V LED bulbs work great!) and check to see if the injectors are pulsing or not to confirm your wiring.
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I need to replace the fuel pump anyway the stock one won't flow enough gas. I drained the tank already just need to drop it now.
 
So killed two birds with one stone. My blazer fuel gauge always read 1/2 full once you got past 1/2 a tank. I never knew why until I removed the fuel pump. There is a little slosh tray inside there that came loose from the posts that hold it in place. So I put that back in place and secured it back down and installed the new pump.

I didn't see anything wrong with the old pump but I didn't look to hard. I need to run to the gas station get some gas and try it out. At least my fuel gauge should read correctly now.
 
nsxxtreme said:
So killed two birds with one stone. My blazer fuel gauge always read 1/2 full once you got past 1/2 a tank. I never knew why until I removed the fuel pump. There is a little slosh tray inside there that came loose from the posts that hold it in place. So I put that back in place and secured it back down and installed the new pump.

I didn't see anything wrong with the old pump but I didn't look to hard. I need to run to the gas station get some gas and try it out. At least my fuel gauge should read correctly now.
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You shopuld have used an Ohm gauge and checked the empty and full resistance, it is a 0-90 Ohm sender. I can't remember which way would read 0 or 90 but i'll bet the rheostat is bad.
 
4X4HIGH said:
You shopuld have used an Ohm gauge and checked the empty and full resistance, it is a 0-90 Ohm sender. I can't remember which way would read 0 or 90 but i'll bet the rheostat is bad.
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I'm pretty sure the float was getting hung up on that slosh box in there, the box was twisted completely the wrong direction. I put gas in it and the gauge seems to be working now but the injectors still wont spray gas.

I Measured the positive side of the injector with the key "on" and that reads +12V. So I assume the problem is something is preventing the negative side from firing. I would measure that with my DMM but I assume it pulses rather quickly and I probably wouldn't "see" the pulse on my DMM anyway. I have an oscilliscope but its raining out and I dont want to take the chance of that getting wet.
 
No one has any ideas? I have fuel pressure, I checked the grounds they appear ok. I loosed and retightened them. If I have an OBD1 reader does that help?
 
Brian at TBI chips figured it out. Yes I had spark and the truck would run if I poured gas in the intake.

There are two plugs on the back of the distributor. One of those plugs the ecm uses to detect the rpm and then squirt the injectors. One of those plugs popped off. Plugged it in and it fired right up. Now I'm still waiting on the slow boat from china to deliver me my UV eprom eraser so I can get the new tune programmed in. I ran it for a little bit and gave it a few rpms but the header started to turn red so I shut it down. I assume that means I'm getting way to much gas.

Thanks to all those who commented!
 
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