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Unread 12-20-2013, 09:17 AM   #1
Incondite__
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1991 YJ 2.5L No Start

Hey guys and gals. New to the forum, although I've been browsing for over a week now. I was hoping to gain some help by joining. Awesome forum btw

I acquired my Father-in-laws 1991 Wrangler 2.5L 5-Speed about a month back. It's been sitting in his backyard for just over 2 years. He parked it because he couldn't figure out why it was stalling and not restarting.
Now the Jeep is mine, and I'm left with the task of repairing it. I'll try to keep it short(er)....

I've replaced the TPS (had a code for it), the Pick-up coil (cam sensor), Plugs, Wires, Distributor Cap, Rotor, Ignition Coil, CPS, and replaced the Capacitors inside the ECM. Most of this stuff needed replacing just from sitting. I have perfect fuel pressure at the rail, Injector Pulse, and spark from the Ign coil and at the plugs. This thing purrs like a kitten when it's first started. The problem is when I shut it off after it warms up. It WILL NOT restart for about 20-30 minutes. Everything I've checked for above, I've checked during this no start concern. I've cleaned all the grounds, cleaned every single connector (including relays and fuses) and added dielectric grease, and wiggled every single wire harness....no problems found.

That being said, I have one code left. Code 22 (Coolant Temp Sensor). The gauge itself works fine, so I assume it's the sensor that sends the signal to the ECM that's bad. In discussion with my fellow technicians (I work at a GM dealer), it came up that possibly the CTS might be skewed enough to cause the engine to flood or get starved for fuel once I shut it off. I'm not familiar with the setup in this Jeep. Any comments or possible fixes would be GREATLY appreciated. Thanks in advance!

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Unread 12-20-2013, 09:38 AM   #2
Luuca
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Quote:
Originally Posted by Incondite__ View Post
Hey guys and gals. New to the forum, although I've been browsing for over a week now. I was hoping to gain some help by joining. Awesome forum btw

I acquired my Father-in-laws 1991 Wrangler 2.5L 5-Speed about a month back. It's been sitting in his backyard for just over 2 years. He parked it because he couldn't figure out why it was stalling and not restarting.
Now the Jeep is mine, and I'm left with the task of repairing it. I'll try to keep it short(er)....

I've replaced the TPS (had a code for it), the Pick-up coil (cam sensor), Plugs, Wires, Distributor Cap, Rotor, Ignition Coil, CPS, and replaced the Capacitors inside the ECM. Most of this stuff needed replacing just from sitting. I have perfect fuel pressure at the rail, Injector Pulse, and spark from the Ign coil and at the plugs. This thing purrs like a kitten when it's first started. The problem is when I shut it off after it warms up. It WILL NOT restart for about 20-30 minutes. Everything I've checked for above, I've checked during this no start concern. I've cleaned all the grounds, cleaned every single connector (including relays and fuses) and added dielectric grease, and wiggled every single wire harness....no problems found.

That being said, I have one code left. Code 22 (Coolant Temp Sensor). The gauge itself works fine, so I assume it's the sensor that sends the signal to the ECM that's bad. In discussion with my fellow technicians (I work at a GM dealer), it came up that possibly the CTS might be skewed enough to cause the engine to flood or get starved for fuel once I shut it off. I'm not familiar with the setup in this Jeep. Any comments or possible fixes would be GREATLY appreciated. Thanks in advance!
The CTS could be feeding the ECU bad info and causing issues once the vehicle warms up enough to come out of the closed cycle. Replacing the CTS would mean an investment of between $24-$40 at NAPA, depending upon the quality/version of the CTS you choose.

If you have a Service Repair Manual, I'm sure you can find the tolerances and methods for testing a CTS. If you lack a manual, here is a link to an online FSM:

http://www.jeep4x4center.com/knowled...ex.htm#service

Get out your Multimeter and make sure you are out of spec on the CTS before you spend the money. Or if $40 isn't going to kill you, you could just replace the part.

Congrats on the new-to-you YJ. Welcome to the /f12. Hope this helps.
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Unread 12-20-2013, 09:40 AM   #3
Jeepsr4me
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Did you pull the fuel tank and clean it out?
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Unread 12-20-2013, 09:42 AM   #4
Luuca
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Almost forgot: A quick search for "Test CTS" on the YJ forums brought up about 8 threads dealing with this part. In them, QUE posted this chart for the IAT/CTS specs:
coolantandairtempchart.jpg

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Unread 12-20-2013, 09:44 AM   #5
Luuca
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Quote:
Originally Posted by Jeepsr4me View Post
Did you pull the fuel tank and clean it out?
Good point; however, he did state that he has good fuel pressure at the rail and it runs fine for about 20 minutes. This tells me the fuel delivery is probably OK, but it's falling down once it starts running off of the sensors. Thus: CODE 22 means check the CTS.
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Unread 12-20-2013, 10:16 AM   #6
Incondite__
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Originally Posted by Jeepsr4me View Post
Did you pull the fuel tank and clean it out?
The Fuel Pressure never drops, ever. So, I've rules out anything fuel delivery wise. It ramps up about 10psi when you stomp the throttle, and never drops below ~32psi, even after it stops running. I can cycle the key and it primes up to ~45psi. That's one of the first things I checked. I actually just removed my Fuel Pressure Gauge last night and brought it back to work...

Luuca, Thank you. I'll take my meter home tonight and have a look. I'm sure I'm going to pick up a new CTS anyway, but for my own amusement I want to see what it's actually reading.

I'm over-anxious to get this thing on the road. I've always wanted a Jeep, AND my Intercooler setup for my "other" car showed up yesterday. So, getting a 3rd reliable vehicle is imperative at this point so I can start with that project. Did I mention I've always wanted a Jeep?

It's ugly, but it has a new rag top and roll bar padding, new clutch/slave cylinder, and all new brake/fuel lines. He took care of it when it ran....now it's just rusty and dirty from sitting.
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Unread 12-20-2013, 10:36 AM   #7
Jeepsr4me
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Old fuel makes for diagnostic problems. Thats all I was getting at with point that out. I bought a many jeeps and the sock was just so deteriorated that it just broke at the slightest touch.
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Unread 12-20-2013, 11:20 AM   #8
Peety
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I had a similar issue a year or so ago, for some reason the O2 sensor was back feeding into the ECU making the engine run like crap and stall with no resatart. By sheer luck I unplugged it to to check the heater circuit, then forgot to plug it back in before I tried to restart. Problem solved.
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Unread 12-20-2013, 11:40 AM   #9
Mark05059
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Quote:
Originally Posted by Peety View Post
I had a similar issue a year or so ago, for some reason the O2 sensor was back feeding into the ECU making the engine run like crap and stall with no resatart. By sheer luck I unplugged it to to check the heater circuit, then forgot to plug it back in before I tried to restart. Problem solved.
that would put it back into open loop... so obviously problem solved
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Unread 12-20-2013, 12:01 PM   #10
Incondite__
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Quote:
Originally Posted by Peety View Post
I had a similar issue a year or so ago, for some reason the O2 sensor was back feeding into the ECU making the engine run like crap and stall with no resatart. By sheer luck I unplugged it to to check the heater circuit, then forgot to plug it back in before I tried to restart. Problem solved.
It looks like I have a couple of things to try out when I get home tonight.

Thanks guys!

I'll definitely post what I (hopefully) find.
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Unread 12-21-2013, 08:41 AM   #11
Incondite__
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Well, I got home and started the Jeep to let it warm up. I fixed the driver door switch while it was running. I now have interior lights and a buzzer, yay. The thing ran the whole time, until I shut it off....no restart (not surprising).

I unplugged the CTS and stuck my meter on it. It was OL for about 30 seconds, then it started reading 7.6 M Ohms, and dropped steadily with the temp drop. That sensor is obviously bad. I'll replace it this weekend. I tried to start the Jeep with the CTS unplugged, no go. Then I climbed underneath and unplugged the O2 sensor, still no start. I then gave up, like I have night after night. Thoughts?
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Unread 12-21-2013, 10:27 AM   #12
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Quote:
Originally Posted by Incondite__ View Post
Well, I got home and started the Jeep to let it warm up. I fixed the driver door switch while it was running. I now have interior lights and a buzzer, yay. The thing ran the whole time, until I shut it off....no restart (not surprising).

I unplugged the CTS and stuck my meter on it. It was OL for about 30 seconds, then it started reading 7.6 M Ohms, and dropped steadily with the temp drop. That sensor is obviously bad. I'll replace it this weekend. I tried to start the Jeep with the CTS unplugged, no go. Then I climbed underneath and unplugged the O2 sensor, still no start. I then gave up, like I have night after night. Thoughts?
It's important to change one thing at a time. You need a "control" set. WHat often hapens on here is the OP presents an issue and gets about 20 different ideas as to what it could be, They then try to tackle all of them at once, muddying the waters as to what helped and what didn't.

IMO: You now know the CTS is bad, Change that but TEST the new unit immediately to ensure you didn't get a bad on out of the box. If that doesn't solve the issue, we move on from there. Best of luck.

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Unread 12-21-2013, 10:32 AM   #13
pete1991YJ
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It doesn't surprise me that it won't start when warm. Basically its flooding out because the computer is going into open loop "limp home" mode with *either* a bad CTS *or* a bad O2 sensor. This open loop mode is a very rich running condition , on top of a motor thats already warm. The computer does not read the O2 sensor until it gets up to 185 deg. You may be able to "fake it out" by sticking a 180-ohm resistor into the CTS leads for the time being - just a trick to know if you are ever in an emergency.

Bring your own toilet paper however.

I highly recommend the dealer for the CTS since it seems that none of the aftermarket ones are correct enough.
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Unread 12-21-2013, 01:31 PM   #14
Mark05059
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the sensor for the gage is known to be incorrect.. didn't know about the cts sensor as well
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Unread 12-22-2013, 06:08 AM   #15
Que89YJ
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When you have the no start disconnect the battery for 10sec. Reconnect and try and start it.
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