'55 R-122 rehab

Busy day. Some success and some failures. No time for pics or videos today. Maybe tomorrow.

I essentially installed the entire system today aside from the wiring that was already laying in place. After the missing wiring was added I snugged up the fuel fittings and put about 6gal of gas in the new tank. I ran the fuel pump for a few min to purge any air from the system and check for leaks- all was well. My system has the GM oil pressure sensor installed. I cranked the motor so long while trying to check/adjust the base timing (with the fuel pump fuse removed) that the engine built enough oil pressure to run the fuel pump... Imagine my surprise when it started to cough and stumble to life.

After I felt the base timing was close I warmed the engine and re-adjusted it. The idle was all over the place and mostly slow rolling but hunting none the less. I went for the IAC adjustment. Even after stroking and disconnecting the IAC the TBI unit was drawing air past the IAC. I removed the IAC, cleaned the pintle and seat. Not knowing what would happen I cycled the IAC while it was removed from the the TB. The pintle and spring shot out of the unit. I managed to find them and reinstall them. The unit actually seems to work better now. Between the cleaning and fiddling with the throttle stop I was able to get a reading around 40-45 for the IAC (sometimes...). While I did seem to get the IAC to respond properly I am tempted to replace it since the pintle popped out and they really aren't that expensive. The motor hesitates off idle unless you're very smooth with the butterfly rotation. Quick snaps make the engine almost die before it figures out what's going on. I have more research/testing/adjusting to do as soon as I can get back to the garage. I saw the TPS was reading .72v when I had to stop working for the day. The idle seemed to smooth out some as well as the afternoon wore on.

I am disappointed in the throttle cable assembly that I created. The cable itself is binding off idle. It's impossible to feather the throttle. You're applying a pile of force to the pedal then all the sudden the cable gives way and you bury the pedal... Not gonna fly on the streets so I didn't even consider goin g for a drive today. Tomorrow (If my wife is put on call) I will rework the design to get that smoothed out.

All in all I'm pleased that the truck runs on EFI. Now to get the kinks hammered out so it can be useful again. It's gotta be driveable on Sat. morning...With possibly only 2 half days on Thurs/Fri to work on it I really hope that I don't have to swap back in the carb/dist/etc. Looking forward to getting some seat time later this week for data logging.

I remember those IAC motors (stepper motor) being a PIA when TBI came out. They would stick and not close or open. At one time I made a device to cycle them in place, don't know what I did with it.
The problem with the throttle linkage may be in part that when the throttle plates are closed, it take more force to open them a 1/4" or so than it take to move a partial open throttle another 1/4" With the large circle plate you made, you can play with the geometry so you get more mech advantage at the beginning, and less as it rotates so the force at the foot pedal remains more consistent.

The problem with the throttle linkage may be in part that when the throttle plates are closed, it take more force to open them a 1/4" or so than it take to move a partial open throttle another 1/4" With the large circle plate you made, you can play with the geometry so you get more mech advantage at the beginning, and less as it rotates so the force at the foot pedal remains more consistent.

I agree. If the cable was in a groove around the edge of the circular plate, the throttle response would be more linear.

Dean

The problem with the throttle linkage may be in part that when the throttle plates are closed, it take more force to open them a 1/4" or so than it take to move a partial open throttle another 1/4" With the large circle plate you made, you can play with the geometry so you get more mech advantage at the beginning, and less as it rotates so the force at the foot pedal remains more consistent.

I agree. If the cable was in a groove around the edge of the circular plate, the throttle response would be more linear.

Dean

I came to a similar conclusion while I was taking our kid and dog for a walk this morning. I had a few minutes to tinker with the truck while my son napped earlier and discovered that the cable seems to be binding internally. After blowing some powdered graphite through the sleeve the action became much smoother. Only problem was that it didn’t last very long. I’m thinking that I may be better off working with a genuine throttle cable not a bicycle brake cable.

I agree with CB. you're trying to use a linear means to perform a curvilinear function. That increases the effort required to start the motion, and the tendancy to "over-center" one direction or the other [or both].

I'll be heading to the JY tomorrow to grab a trans for one of my BMW projects. While I'm there I will find a cable (just in case) and some diff sized throttle cable cams. I'm also going to look for a firewall mounted throttle pedal. Getting away from the block mounted bell crank could also save some hassle/effort.

A quick pic was really all I had time for yesterday.

Too late/dark to get any good pictures but a proper throttle cable (happened to be from a Dodge Dakota) was the solution to my sticky/hard pedal. I fitted a Cam cable guide to the TB a few days ago. It made no appreciable difference. Along with the cable I also made a custom mount for the throttle pedal from the same truck. It made sense that extra leverage of the new pedal would also help to smooth the operation of the throttle.

I found the issue with my IAC adjustment. For anyone else that may take this path (GM TBI) in order to set the base idle you are supposed to bridge the “A” and “B” pins of the ALDL diag connector turn th key to the run position, wait 30 sec and as I had read it in several places “turn off the key and unplug the IAC connector. Well, if You turn off the key before disconnecting the IAC plug the IAC will retract... took me 3-4 tries and a nights sleep to discover that I needed to disconnect the plug first, then turn off the key. The base idle is now set to about 700rpm. This gives me an ECM controller idle of about 625-675 rpm- a happy idle for my truck.

Looking forward to final adjustments to the throttle system and data logging/final tuning. Even in a “raw” state the EFI has completely transformed the truck. I suspect it will be well worth the effort at the end of the day.

Recontoured the throttle pedal arm to get the pedal resting closer to the floor. Yesterday the resting position was almost on the same plane as the brake and clutch pedals. I also got a few minutes to start the install of the Jags That Run 2 pulse VSS. It will allow the ECM to cut/trim fuel based on vehicle speed and TPS position. It’ll also be useful if I were to ever install a factory cruise control system.

Well I wrecked the engine while I was trying to collect "highway" data for the chip programmer. I've got it mostly pulled apart and so far I've seen 4 wasted wrist pin bushings, all 6 bores are scuffed and the #6 piston is utter garbage. The metal on the skirt is re-arranged. This was a 30k mi rebuild. To say that I am gutted is a mild understatement. I have no idea what I'm going to do now...

Sorry to hear that, do you know what caused it? It is a shame.