TBI issues

[team39763]

Ok, I'll give it another shot.  It would really make my wife happy if I got this truck running.  I'll post up what I find.

[team39763]

I verified B+ on one side and other side was unresponsive.  I also had a problem seating the distributor in the motor.  Like the gears didn't want to seat except in one position, anything other than that and it would sit about 1/4" out of the hole.  So I just stuck it in there.  I'm no longer getting spark after swapping in the new ignition module.  I triple checked to make sure I put everything back where I found it and I can't see anything I did wrong.  I may try putting the old module back in there.

[VileZambonie]

OK, install the distributor correctly and on time. You need to engage the oil pump driveshaft and the distributor should essentially drop right in. You may need to bump the engine a little bit to get them to engage. Once you verify it make sure the rotor is turning when you crank it.

[team39763]

Vile, I got the distributor in correctly, but it still won't fire the injectors.  I also found out one of the sparkplugs was partially out.  I checked the injector plug/harness again and verified it was getting B+, but the other side was not getting B-.  I tried to manually fire the injectors, but they didn't do it.  I'm guessing my fuel pressure is too low for them to fire?  I lost my fuel pressure fittings, so I can't check the pressure right now.
  My wife offered to get a loan to buy some parts, but we have to for sure take care of the problem.  It'll really suck to spend $300 and still not be able to drive the truck.  Here's what I plan to buy: new distributor, new coil, new fuel pump, new computer, new injectors, new regulator.  Should that cover anything that might be keeping it from running?

[VileZambonie]

It's not fuel pressure...  ok now that you've verified B+ to the injectors but they are not commanding on, disconnect the 4 way connector at the distributor. Key on engine off- take your test light to B+ (touch B-to verify your light) and tickle the purple/white wire (cavity C) at the distributor harness. This should energize the injectors. -Report

[Marc]

I typed this while vile replied - here is some other stuff to maybe help I hope, since it is so close to Christmas...

So you have spark but it's still not firing the injectors?  I wouldn't go throwing parts at it.  Perhaps a good place to start would be an alldata subscription that you give you some good schematics to locate splices and common grounds, and some diagnostic stuff.

You could hook up a test light to the injector connectors or even buy a set of noid lights to see if the computer is firing them.  Where the check engine light is not coming on and you aren't getting codes by jumping the aldl, I'd verify the bulb in the dash is OK, the connectors on the computer is OK, and all grounds are good.  The schematics would tell you which wire to check for on the computer connector to see if you are getting the ignition pulse that tells the computer the rpm.

If you pull the line off the throttle body and put it in a can or something similar, do you get gas for a second or two?  If you crank it for 15 seconds or more will you get gas?  The computer will prime the pump for around two seconds and stop when you turn the key to on to pressurise the system, and I know some other GM products will start the fuel pump after cranking for a number of seconds (as far as I can tell there was a oil pressure switch that would put power to the pump once it closed.  could your supply and return lines be reversed, or the wires on the pump be reversed?

Hope this helps.

[team39763]

It's not fuel pressure...  ok now that you've verified B+ to the injectors but they are not commanding on, disconnect the 4 way connector at the distributor. Key on engine off- take your test light to B+ (touch B-to verify your light) and tickle the purple/white wire (cavity C) at the distributor harness. This should energize the injectors. -Report

We checked that purple wire and the rest of them with B+ and none of them did anything.  We did finally get B+ and B- on the injectors, but they still didn't fire.

Marc, I connected 12v to the pump to make it turn on.  They key doesn't do anything for the pump.  Right now I'm working on getting the distributor set correctly.  I think we had it 180* off, but we're not sure...can't get a finger in the hole to check for tdc.

[VileZambonie]

That doesn't make any sense. You tickled the terminal with B+ connected to your test light to cavity C and got no injector pulse? But now you have injector pulse but the injectors are not firing? So what are you saying? They are comanding on but no fuel is spraying out of them?

[team39763]

No, they aren't getting commanding on.  The purple wire just doesn't do anything when B+ is added to it.  There's no B- at the injector connector still.  We grounded one side of the injector and added B+ to the other side and it lit up the light but didn't fire.  It didn't light up before.  We got the distributor in correctly and have turned the truck on with carb cleaner.  The injectors just won't fire.  I noticed that these injectors can't be manually fired.  I tried the ones on my neighbors running TBI truck and we couldn't make his fire either.
  What should I look at next?

[VileZambonie]

If you do not have a noid light, disconnect one injector connector. Take a test light and install it across one injector connector so the probe end touches one terminal and the alligator clip end makes contact with the other end. Key on engine off take another test light connected to B+ (touch ground to verify your light) and tickle cavity c of the 4 way harness connector with the test light. this should make the test light installed in series blink. If it does not blink Trace the wire from Cavity C back to the pcm for an open or short. -Report

[team39763]

We did that test and nothing showed up.  We found the wire at the pcm, but it was too hard to access the wire behind the motor(the local mechanic suggested removing the motor was the easiest way to get to it).  I also checked to see if the pcm was grounded and it was.  What should I do next?  Can I just splice in some new wire for that purple/white one and connect it to the correct pin on the PCM?

[VileZambonie]

Nothing showed up as in what? Infinite resistance?

[team39763]

Whoops, forgot to turn the key on.  I'll try it again.

[team39763]

Vile, thanks for your help man.  I really appreciate it, but this is just not working out for me.  I did the test that you said and I'm guessing the wire is broken somewhere, but there's no way to find it.  There's about 4 different wires of the same color and they are all tied into the same clump of wires tucked behind the motor aswell as being tied under the truck under the truck and routed all crazy.  We attempted to trace the wires, but it requires removal of the motor just to get see them.  I started taking it apart, but I'm just tired of it.  We removed the TBI system and were thinking of converting the motor to carburetor, but There's so many wires going in so many directions that the truck may not even be functional anymore.
  I don't understand why GM didn't just make things simpler.  Why 4 purple wires with white stripes, 2 solid purple, 3 pink with black stripes, 4 white, 3 black? It was just frustrating along with the fact that most of them could barely be touched without removing the motor and front fenders/hood.  And there's so many wires...I don't know what to do with this truck now.  As it sits, it's probably only good as a parts truck.

[VileZambonie]

You're giving up too easily. All you had to do next was a pinout test from the connector back to the ECM.