Need TBI help

[Mavis79]

Hi all, I have an 84 extended cab with a TBI swapped in. We (Son’s first truck) bought it not running. Was told the fuel tank selector switch went bad and then other electrical issues started.

So far, I have gotten spark but no injector pulse (checking with a Noid light). Pulled the distributor and it looked a little rough so we ordered a new one (thought it might be the pickup coil). No change, unplugged the TPS to ensure that the computer wasn’t in “flood” mode. I confirmed I am getting 12 volts to the injectors. As this was swapped when we got it wiring is a little bit of a challenge. I haven’t found a fuse in the wiring (unless they hid it somewhere under the dash). Any thoughts on what to check next?

I did notice that the fuel pump continually runs with the key on, and the brake warning light is always illuminated (even with the key off). I am getting fuel to the TBI (I don’t know what the pressure is).

Would insufficient fuel pressure cause the injectors to not pulse?

I’m starting to think the wiring is bad enough that I might pull all of the electronics and start from scratch.

http://67-72chevytrucks.com/vboard/s...d.php?t=808381

[Palf70Step]

Since you have a dash warning light on all the time, one think that comes to mind ois the ignition switch near the base of the column is not adjusted correctly. If that is off you may not be getting the correct during the start to the coil/dist.

Here is a link to the manuals for the TBI years, maybe one of the service manuals can help ya out some..
http://67-72chevytrucks.com/vboard/s...d.php?t=700011

Is it getting spark to the plugs when you crank?

Also I do know that if fuel pressure is wrong/low, the injectors don't work/pulse right. I just don't know how to test all that stuff very well. I mostly just fumble around till I get lucky or mad enuff to take it some where (or go back to a carb)

This link have some help info that may get you thru your isssue also

http://67-72chevytrucks.com/vboard/s...d.php?t=445487

[Kudzupatch]

I knew I had this link somewhere and I finally found it. Might help you with the troubleshooting.

http://www.73-87chevytrucks.com/tech...TBISystems.pdf

[Mavis79]

Yes, I have spark at the plugs. Checked fuel pressure before the filter and I get only about 8psi and the pump continuously runs. It also doesn’t hold pressure once the key is off.

I’m hoping that the low pressure is the reason for no fuel injector pulse. Either way it’s a problem the needs to be addressed...