Starting Problem: B+ Latch relay not the culprit.

[tordan]

My 1990 Jeep Cherokee Laredo is having problems staying running.
Its a strange situation.
When the car is cold, I turn the ignition, the engine turns over and engages. No problem.

When the car has been parked for a short time (somewhere under 3 hrs approx.) after having been driven for at least 15 minutes; I turn the ignition, the engine turns over, engine engages, I release the ignition and the engine dies immediatly. I can rev up the engine when engaging the ignition but as soon as the key is released: sudden rpm drop and the vehicle dies.

I replaced the B+ Latch Relay after someone in another forum recommended it. No change in behavior.

Maybe the ignition switch?
I don't know enough about the ignition system to guess, though.

[AlohaBra]

Could be the ignition switch. Test the switch with a voltmeter.

Fig. 31 has the ignition switch in the upper left corner:

*Dark Blue wire is the power feed....

http://www.autozone.com/servlet/UiBr...3d80153e8f.jsp

EDIt: looks like some fuses are in the wiring diagram also....those are probably worth checking...

Best regards..

[89ltd]

also check starter relay,

[tordan]

Thanks for the tips.
I'll swap out the starter relay first because it is a lot easier to get at.
Wish me luck.

[jeeper186]

This is the same kind of trouble Im having. I have found so far that it is not the ignition switch. I have changed it out already. The B+ latch relay is not getting power to liven up the fuel pump etc. But there is spark. I am still trying to find the right orange wire with a black stripe "There is a ton of them" that is feeding it. I have connected a hot wire to the starter relay on the F plug to keep it going. I tried holding the key in the start position and having someone unplug the starter wire from the solonoid it still runs until you put it into gear, then it will again die. It sounds like you have the same issues here.

[mightymouse466]

My girlfriend's '99 Cherokee has the opposite problem. Runs fine hot but won't cold when you release key from start. It will run fine if you sit in the vehicle and hold the gas until the engine has warmed up to operating temp. There is some kind of module directly behind the battery on the passenger side along the fender that has a cable going to the throttle body, some vacume lines, and a wiring harness connected. What is this?? And could this be the culprit? I have concidered that maybe there is moisture in this that freezes or could be bad.

[AlohaBra]

mouse..

I don't have the answer to your problem...yet...
But it is not the thing you describe which is probably the cruise control activator device...which is what make the cruise control work...by pulling the accelerator cable.


tip: You might start a different thread....because your problem is not related to the B+ thing that they are talking about here on this post...

[tordan]

I have installed a new starter relay and am now having trouble re-wiring it. I somehow confused the color of a wire and threw the diagram I drew for the re-wire out the window. Now I cant find a diagram in the Chiltons chasis diagram that has the same configuration of wires on the relay. The picture of a starter relay they show is missing a wire mount from what was in the car and the one I ordered. Any one know where I could find the right diagram?
The relay in the diagram is missing the "F" connector. Proccess of elimination could work but I don't want to screw anything up.

[jeeper186]

The F connector is the one that I am having the trouble with getting power to the relay. It is what looks to be an Orange Fusable link that is about 6 inches long and then turns into Orange with a Black stripe. I hope this helps you out. Let me know if you need more info.

[tordan]

Okay, I got the Starter Relay all wired up and in place but there has been no change in behavior. Same starting issue. I don't have the tools to check the wiring for shorts or problems, but it sounds like that may be the issue. Is there anything else I could do before taking it into the shop?

[jeeper186]

Thats what I have been trying to figure out. I have access to AllData. but I still cannot figure out what tells the computer to not send the negative connection to the B+ relay. I have a bad feeling that it just might be the computer itself that is the problem. If you do take it to the shop to be fixed please post the answer to the problem. I did hook a switch to the "F" connector on mine to make the Jeep run but I would rather have it run the way it should.

[Tim4wd]

I've been dealing with what might be the same but different problem on my 96 Cherokee. It appears that the Jeeps have a not so good design in it's PowerTrain Control design. I'm reading too many posts in many different forums and everyone is having a problem trouble shooting this and including mechanics and the dealership it self. Each posting being somewhat different symptoms, but I'm begining to think that most are related to the same issue. My problem started 7 months ago with following accumalated symptoms in order:

Stumbles while driving (regardless of speed or temp conditions)
Looses power (sometimes will recover by it self and sometimes not)
Stalls (at any speed and mostly at stops)
Hard to start (Occurs after stall outs, re-start after running and a couple times cold)
Backfired once


No codes showing until yesterday when I took it to a dealer on recall to reflash the PCM due to it not giving codes when the CAT goes, I then received the codes P0351 (which is misfire, coil related but coil is not bad) I also now have a code for my blown CAT (my second CAT due to this problem) Changing components is not going to fix this as many have already replaced things to a point that it would have been better to scrap the vehicle. It all over the board with some replacing: CAT, Fuel Pump, CPS, TPS, Dist Pickup Sensor (it's not a Cam sensor), battery, alternator,Ign Coil and on and on....... To no avail

OK now, what I learning about all of this is it has something to do with Coil vs PCM which is causing a injector shut down I know this by the fact that during a hard start I had my spark checker plugged on and had spark so I then sprayed start fluid into the throttlebody - and NO Start was achieved. This has to be a circuit shut down of the injectors caused by who knows what but will cause the coil to not function correct via the PCM. No your PCM nor Coil is bad, it's a bad signal.

What to do. By chance I ran across a couple guys that had a 1994 Cherokee that was having the same problem and they had simply done a MSD Ignition Module to the existing coil that affectively bypasses this problem. It is a standard kit with install instructions and done commonly to increase power and gas mileage. I will be installing one today. However, I found other posts which another guy having the problem said the dealer gave up trying to fix his stalling/starting problem and ran a wire from coil to PCM that fixed it. I don't the particulars but he said he thought it was a ground wire from the coil hmmmm

I hope that this helps others and provokes some mutual investigation into the common problem to feed back any information that you may find on this. So please let's keep a healthy thread going.....

So, do not change CAT until you the problem resolve the CAT is a casualty of the real problem that raw fuel is being dumped into it and burning them. Also, anyone that has not done the recall to re-flash the PCM you will not get a code on the CAT going bad. In fact I didn't get the misfire code until the flash also.

Well this is as far as I have gotten so far and hope this will spur more investigation and thought by all of you to investigate further and feed back ideas knowledge and answers so that we can keep our Jeeps so please take the ball and run with it I look forward to some feed back, thanks

1996 Jeep Grand Cherokee Loredo
4.0L, Automatic, 4WD, 3" Lift

[jeeper186]

This is very good info, but at the same time this does not seem to be our problem. We are not getting the ground signal from the computer to activate the B+ Latch relay "AKA Shutdown Relay". I am trying to find out what component tells the computer to sent the ground signal. The Jeep will run just fine when you turn the key in the start position. When you let go of the key to let it run, it will shut down. I have found that the fuel is then shut off. There is still spark. I will be looking into the relay power etc tomorrow since I will be off work.

[Tim4wd]

I have just been messing the electrical and found bad connections on all my fuses and relays due to oxidation, go figure I live in California, anyway, I had forgotten that I have been having a problem with interior lights not coming on all the time when door is open and dash lights fading in and out. I found the fuse for this to be shorting in and out due to the oxidation and simply touching it made it go crazy. This would have something to do with security entry and fuel injection shut down thereof. I ran fine all day after cleaning up some connections on fused (pencil eraser) but I think the fuse panel is shitty design and some McGyver will need to be performed.

When not starting check spark, spray starter juice into throttle body and see what happens. If not start then injectors have shut down and probably due to the security circuit which will shut down the coil signal and or injectors.. Oddly, yesterday visiting a friend that owns a muffler shop had a 94 Cherokee that wouldn't stay running because a combination of bad battery neg contact and not using the remote door open transmitter, start but no running unless key is held on.

Come on folks lets add to possible answers here. Oh, tomorrow I will be installing a work around to these problems given to me by a couple of youngins with a Cherokee. I'm installing a MSD 6AL Ignition pak that will run the Coil direct and is actually more efficient for gas and power. However, we still need to find the original problems with these vehicles so that we can bring Chrysler Dealerships up to speed....

Originally Posted by jeeper186

This is very good info, but at the same time this does not seem to be our problem. We are not getting the ground signal from the computer to activate the B+ Latch relay "AKA Shutdown Relay". I am trying to find out what component tells the computer to sent the ground signal. The Jeep will run just fine when you turn the key in the start position. When you let go of the key to let it run, it will shut down. I have found that the fuel is then shut off. There is still spark. I will be looking into the relay power etc tomorrow since I will be off work.

[tordan]

A friend and auto-electical fiend has suggested I check the ballast resister running from, I beleive he said, solenoid. Any ideas about that?