I had a small coolant leak under the UIM at AutoX on Sunday, so I tore into the TB/UIM for the first time Tue night. I put it back together this morning, and now it won't start... cranks fine, won't run though. I've been searching, and I've got a few ideas to go look at, but what I want to do is compile a list of ALL connections to the UIM & TB, and the effects of having them unplugged. Hopefully this will make a handy reference for future UIM/TB newbies like myself.

Electrical:
1 - ISC (Idle Speed Control)
2 - AWS (Accel Warmup Solenoid)
3 - IAT (Intake Air Temp)
4 - TPS (Throttle Position Sensor)

Vacuum:
1 - Break booster line (pass side)
2 - Double Throttle Actuator (rear)
3 - MAP sensor (rear)
4 - ???? (rear) (with check valve to hard pipe - Maybe "Switching" solenoid)
5 - PCV (front)
6 - Purge Control (front)
7 - Double Throttle control solenoid (front)
8 - ???? (front) (to hard pipe in front of rats nest)

Coolant:
1 - into TB (from lower hard pipe)
2 - from TB to top of engine near firewall

Throttle Cable

I think thats a complete list.

So first question is where do vac lines 4 & 8 go to??? I tried tracing through the hose diagram, but got lost in the rats nest.

Next question.... What missing (or incorrect) connections could cause the car to not start??? I think all of the electrical connections are uniquely keyed, but is it possible to plug them into the wrong sensor/solenoid?

Can any of the vacuum connections missing cause the car not to start?? (I can see maybe a rough idle, but not starting?)

After searching, looking at parts lists, and the service manual, I've got a few ideas to go chase..... verify all electrical connections (I don't remember hooking up ISC, so I hope thats it)... double check vacuum lines (doubt any of those would cause it not to start)... check plugs/de-flood.

I also did the TB coolant removal mod while I was in there (to reduce the number of hoses that could fail) And I adjusted the screw for the warmup plunger all the way in to keep the warm-up cam out of the way.

--Lee
PS... pics from Sunday's AutoX:
http://lee.jeepaholics.com/AX04/Legends-4Apr/Apr4.htm
I'm 73 SM2 (no pics though), a buddy was codriving as 7 SM2, and 93 SM2 is another local FD owner.

 

Get a few of the easy answers out of the way:

Throttle Cable - car should start, but obviously won't rev if its not connected.

TB Coolant lines - okay to remove: http://www.rx7turboturbo.com/robrobi...dy_coolant.htm

5 - PCV - vacuum leak if this line is missing and not capped, but should run.... possible rough idle from the leak?

6 - Purge Control - small vac leak if this one is missing. Possible smell of gas fumes when purge solenoid opens.

I'll leave the rest to the guru's....
--Lee

 

I missed one vac line connection: Off the passenger side, there is one line going down to the blow off valve.

I checked all of the connections, and everything was in place... so much for the IAC problem I was hoping for... it was plugged in fine.

Anyone have any ideas on what to check next?
--Lee

 

Check vacuum lines to FPR and PRC solenoid. Even though they are not part of the UIM cluster, they are near it.

Also check that MAP sensor is plugged into a nipple and not into that little metal dowel near the TB.

 

Well ... I tore everything back apart, and couldn't find anything that was connected wrong, or missing. Finally put it all back together and still had the same problem. DOH!

I then started checking the spark plugs to see if they were fouled, and found one leading spark plug wire that was loose. I have no earthly idea how that got knocked off... I wasn't working in that area at all... didn't remove the coil packs or anything. But it was loose. Plugged that back on and it started right up (with a couple extra coughs.... probably a little rich).

Its idling a little rough now... probably a partially fouled plug, so I'll probably put new plugs in this week.

Just curious.... does anyone know what the failure mode is if any of the 4 electrical connections is missing/failed? (ie will the car start? run rich? etc?) I could see problems with the ISC & TPS, but it seems like AWS & IAT might be fairly un-noticeable.

--Lee

 

they will through codes if open.. not sure if they are shorted. a important thing when a car wont start is to establish spark, fuel ( in ours that it is not flooded) and the car WILL start with a bad/dissconnected map sensor