Hello wise folks,

I am having some trouble (I think) with the throttle body on my TBI electro injection 89 KA24(?). Mine has a single injector that feeds both sides of the carb, I think it is leaking fuel resulting in too rich especially at idle. And, I can see fuel "puddling" on top of the throttle plate on one side. I have not yet looked for any codes, but not sure I want to replace the ECU if it is bad.

I know as the truck ages getting all the components controlled by the ECU may get more difficult due to parts avail, etc.

And, I would be happy using a manual choke and hand throttle for idle control, etc. So wondering about a weber carb, and deleting/removing the ECU altogether. Or perhaps leaving it in place but not really let it do anything?

Biggest issue might be power to the distributor and advance?

I apologize for not really doing that much research yet, but thought I would ask the crew about this, I cannot seem to find any threads on the subject.

So appreciate any wisdom. Would be nice to have a "totally non-electronic" engine.

Well, for what it's worth I like the idea. I am no help on this subject though. Good Luck!

Oh, BTW, can you get the injector rebuilt?

Yes, it appears so, there is a outfit in CA that offers to try, they will not sell direct but you can go through Rock Auto.

For what's it's worth, I'd keep it going with the parts you can get for as long as you can. That way you have more time to research, buy parts, and get ready to swap over.

I've thought a lot about taking a newer car, and doing somewhat the same. Just leave the ECM to talk with the BCM and such, and bypass all the engine stuff. Probably need to get a separate transmission controller too (the old days of a Transgo kit with springs and plates and such are not so prevalent anymore!

I have experience with older rides though. Points and condensors on distributors, plug changes often, etc.

Please keep us in the loop on this. I am very much pulling for you on ths!

Hello,

Thank you all for your help.

My conclusions were (may not be spot on, YMMV (FYI this truck has a 5 speed (that even when new had trouble pulling top hole due to lack of snoose))):

1. This truck came out during the still early days of mfg's trying to comply with emerging EPA rqmts, was still a work in progress. Not a good transition time maybe, I know they started years earlier but is what it is. This truck has a few critical points of failure due to it's age and lack of parts avail. A few might be TBI injector, carb fuel pressure regulator, distributor/ECU function, distributor/Coil transistor function, there are more.
2. As I understand it the ECU on this truck is pretty busy, it monitors many ancillary (could be bypassed), and some vital things things such as crank angle (from the dist sensor), O2 level, Exhaust Gas temp, throttle body position, engine temp, and it modulates both the amount and timing of fuel squirts and directly sends a firing signal to the Transistors on the coils. The distributor appears to make zero decisions on it's own, it seems to only distribute the high voltage and send crank angle to the ECU. BTW interesting aside, I was always amazed with this engine as it had two spark plugs per cylinder (like a airplane!)! Where in a airplane it is done for redundancy (safety, fired by mags not distrib) in this case the second plug appears to fire only when the engine is cold!?? Blows my mind to think they added a second plug for pollution reasons, but appears they did. Now THAT was not cheap! Also makes it hard to find a replacement distributor although I would be happy to give up one bank of plugs (I believe the exhaust bank are the ones in "normal" use). Amazing to me.
3. I think it is fairly easy to convert this motor to a Weber carbureted motor (replace factory in tank pump with inline 720 low pressure pump rather than new pressure reg, maybe use a aftermarket adapter to turn the carb 90deg, install manual choke and hand throttle if desired, much more). Lot of info out there on this, I think it would be a solid swap.
4. The remaining issue for me then becomes the ignition. When you swap out the carb the ECU will lose some inputs. This part I am not sure of and would depend on the computer algorithm it runs (not knowable I think), but looking at it seems likely the ECU may throw a code and go into some sort of failed state that will put it into some sort of limp mode where among other thing ignition timing advance may not work. I guess I could test that theory but not will to spend time on it. If you want to try just unplug everything from the TBI and see what/if it throws any codes. Although I can find several reports on the inet about this carb swap I cannot really find one that details how the truck then runs over all, but is scary stuff for me. And, I cannot seem to find a replacement distributor with centrifugal advance that will fire the plugs independently, haven't really looked at pre-ECU units, etc. Hard to believe Weber sold all those kits and diminished all those trucks???

As a aside, I have ridden a old Indian MC where you had to set ignition advance manually via a lever on the handlebar, not fun unless you are on the highway. And DO NOT forget to retard the timing before you kick it.

Rock solid truck that I will miss but time to part ways at least for me... and oh, there is that pesky body rust!!!

Again, thank you all.

Cummins 4BT might be an interesting swap. Nothing electrical needed except a starter.

Yes, but not optimal what with the rear tires up in the air and all.

So, what's the verdict on this?