TBI issues

[team39763]

 I wanted to get a tune for my 94 Dually, but most people that I talked to told me there would be tons of problems trying to get it right with the mail-order tunes + it was a hassle to change the chip over and over.  I had looked into the FlashMemory thing, but I didn't feel like it was worth it unless I had I really nice motor that just happened to be TBI.
  The TBI system on my 94 S10 has gone crazy and I'm tired of trying to figure out what it wants.  All that TBI stuff is being ripped out right now and going in the garbage.  I couldn't figure it out for nothin' and nobody seemed to know anything about TBI systems around here.  I know they're supposed to be super simple, but it's just not working out that way for me.  I haven't met one person who could figure out these TBI systems...atleast not in my area.  I agree with a bunch of others "TBI is the Devil".

[VileZambonie]

Why didn't you ask on here for help? TBI isn't the devil.

[team39763]

I posted up in a few S10 forums, but none of the advice seemed to help.  It was all good advice, but for some reason the system just won't work.  Myself and several people agreed what should be the problem, but the truck still wouldn't start.  We want the truck running ASAP, but we don't want to spend tons of money on stuff just to end up being wrong(atleast not at this time).  Ok, maybe TBI isn't the devil, but it sure does make me say a lot of 4-letter words.

[VileZambonie]

Care to elaborate on the problem?

[team39763]

The injectors won't fire.  I got fuel pressure, I got spark, the distributor and wires are new. All wires going to the computer seem fine.  At first the truck would just randomly stall with no warning and no indication of what was wrong.  We would just start it back up and go on.  Then it started stalling more frequently and developed a random misfire and the check engine light would flash.  Then the misfire became a lot more frequent so I told my brother to stop driving it.  The last times we tried to start it(didn't start though), the injectors were firing, we had spark at the two wires we tested.  My neighbor told me to change the fuel filter first because it's an old truck - 217,000 miles.  I did that and the injectors stopped spraying.  That was the only thing I touched at that point.  I swapped out the injectors for some known good ones and a new regulator, I swapped the coil, I inspected the module and rotor.  All seemed fine and clean.  We tried to manually fire the injectors, but that didn't work(I must have been doing that wrong).
  I can get the truck to run by pouring gas down the throttlebody, but that's about it.  I asked a few mechanics in my town and the next town and all say put a scanner on it.  That doesn't work because the diagnostic port is unresponsive.  Other than that, they say throw parts at it(dizzy,coil,injectors,pump,regulator,computer,new TBI,IAC,CTS,MAP) or swap it out for CPI.  The guys online mostly said the pick-up coil or the module.

[VileZambonie]

Disconnect the injector connectors. Key on, engine off take a test light to ground to the injector connector. Verify B+ at one terminal of each injector connector.

[Marc]

Scanner doesn't work?  I might be suspicious that the computer may be at fault.  A junkyard computer would probably be fine.  If you have spark but no injector pulses either the "trigger" signal isn't getting to the computer or the computer itself is at fault.  If you could get a schematic of the computer and check for power / proper signals at a few points it may get you started.  I believe the ignition system is a more or less seperate entity from the computer.  Do you have a 5V reference power on the coolant temperature sensor, or TPS?  Does the check engine light light up when you turn the key on?

[team39763]

The check engine light doesn't come on anymore when I turn the key on and it won't flash with the scanner.  I'll see what I can find as far as schematics...I had a haynes manual, but I don't know if that'll have it.  I don't have any way to check for 5v power, all I have is a test light.  Vile I'll give that a try, I just need to put back a few parts that I removed over the last few days.
  Thanks for starting this thread for me.  I appreciate the help.

[VileZambonie]

Let us know what happens

[team39763]

We have B+ at one side of the connector.

I'm gonna try to figure out what's wrong with the data port.  From what I've been reading, it's usually the cigarette lighter fuse that kills the data port.

[dumbucket1]

It does have good fuel pressure for sure? I have come across a few that the rubber hose between the fuel pump and sending unit has a split in it causing low fuel pressure.

[team39763]

I'll check the fuel pressure again.  We had checked it before the truck completely stopped running.

[VileZambonie]

OK now go to the other terminal that didn't have B+ with your test light connected to B+, habe an assistant crank the engine. The test light should flash.

[team39763]

While I was gone I had my friend to run the test you suggested Vile.  He said it didn't flash.  So when I got back I changed the ignition module like some others told me to do.  Now it won't start at all even with gas poured down the throttlebody.  I'm sure I put everything back the way I found it.
  I'm in a bit of a slump right now.  I don't have anymore money for repairs and 2 of my 3 trucks are broke down.  With the way my wife is, our 3rd truck will be broke down soon also.  If it comes to it, I'll let her drive my race truck to work, but that won't be pretty since the seat is too small/narrow for her.  I do have a 4th truck, but I don't have a title for it and it needs another starter which I'll probably get from my dually when my wife breaks it.  I'm gonna go play with my race truck and try to cheer myself up.  Thanks for all the help guys.

[VileZambonie]

Verify the test yourself. B+ on one side, B- on the other side while cranking.