sensor,sensor,sensor

First of all let me introduce myself by saying I am new to Jeepin, just bought my first 92 XJ I6 HO , have had it to the body shop for some clean up of her black exterior, new exhaust, flowmaster, serpentine belt, valve cover gaskets, battery, tires, she is a super clean honey, have had all the fluids drained and filled , but now she wants to kick up her heals.. It started last week we I went to pick her up at the body shop in -6degree weather , she moaned and groaned but wouldn't start.. Battery finally died.. On Sunday of last week just prior to calling AAA to have her towed I tried Eather, pulled plugs , checked spark at coil and found no spark .. But aaaaaaaaaaaaaaaaaaahhhhhhhh I remembered some info about saftey switches about moving the shifter from park to neutral and back again and wallha she started , I then proceded to purchase a new battery because I was sure I killed that on and it appeared to have lived a good life .. Well she ran fine for two days so I pampered her and praised her and had her detailed on my day off.. The next day when I really needed her a storm was comming and knew it would happen before I would get home I dashed to my honey to find she moaned and groaned but wouldn't start even after not beating her steering wheel , but again shifting her from park to neutral at which point she gave up and showed me what a jeep was about , a dead battery..
She left me no choice to to take my 94 camero to work with no snows and was 1/2 hour late for work .. Well the weather man was right the snow commith and it took me 5 hrs to get home a normal 45 min ride ..
I have done everthing I could to make her happy but now I read about saftey switches, and crank senors ..
I do understand neutral saftey switch , but don't get why a vehicle with a distributor would have a crank sensor .. ?????? :bawl:
I am sure the triple A man will commith to tow her away and at this point I will replace everything I can to get her running ...
Any help out there would be appreciated where to start first ...
Geepers (Bob)

geepers, Welcome to . Do a search for NSS in this forum. A thread for the last couple of days had a link on cleaning the NSS. HTH Jim.

geepers said:

p
I do understand neutral saftey switch , but don't get why a vehicle with a distributor would have a crank sensor .. ?????? :bawl:

Geepers (Bob)

Click to expand...

The computer system on XJ's controls both the injection and the ignition, including the timing (which you cannot set yourself). In order to get timing right it has to know the absolute crank position (not just the distributor position). When you first start, the computer won't let the ignition fire at all until it has read the crank position. 91-up XJ's are a little better at this. The early ones required 4 full engine revolutions before they would fire, even with a fresh CPS, and very long crank times are a common complaint.

The neutral safety switch will not allow you to crank at all if it is bad, so if you were getting crank but not fire, look elsewhere. Before getting too deep, you should go through the entire engine compartment and unplug and replug every connector you can find. Look especially for the one that leads to the crank position sensor, which is located on the bell housing at about 1 o'clock as you stand at the front looking back. If unplugging and replugging the CPS seems to help, you should probably schedule a new one soon.

If even with a new battery it's moaning and cranking poorly it might be a good idea to check out the starter and the battery cables, too.

The XJ is an oddity - the distributor is there to route spark, but timing signals for fuel injection and ignition come from the crank sensor mentioned previously.

As also mentioned, a no-crank/no-start would likely be caused by either:
1) Failed or failing NSS (rebuildable part)
2) Start relay (ChryCo usually used them, but I'm not sure where they are on the HO offhand)
3) Failed or failing battery cables.

Excessive battery drain could be:
1) Failed or failing battery cables
2) Abrasion on a power cable somewhere leading to a short to chassis
3) Failed or failing switch for a light somewhere that is not turning off.
These can all be checked for with a decent ammeter (10A DC or less - you'll be checking drain with everything off.)

Crank/No-Start is usually the CPS, but there are a couple other potential causes. I'd have to refer to the manuals for more info here, since I'm used to the 1987-1990 (Renix) XJ systems than the ChryCo HO.

Recommendations -
Check and clean CPS connector. Should be at rear of inlet manifold. Also run the cable and make sure you have not melted/worn thru the jacket, and therefore losing the signal by shorting to ground. I've had this happen.

Replace the battery cables. If they're original, they're 12 years old and should be replaced anyhow. Go to a larger gage - I get my battery cables at the welding shop (2/0 gage) and make them myself. Also, I find that using marine-grade brass battery terminals is a significant improvement over the OEMR lead, and they are easier to keep clean. While you're making cables, make one to go from the back of the alternator (I believe the hole there is threaded M8 or M10) and tie the case to the chassis for more effective charging. I also make sure to have good solid grounds from battery - to the engine block (at the right rear near the distributor, there is a machined boss) to the chassis (pick a location) and get rid of the braided ground between the cylinder head and firewall and replace it with a cable. This will improve things greatly.

You will want to look up the NSS thread for future reference anyhow - it's good knowledge to have. A replacement switch can be had for about $300 (OEMR only!) while you can rebuild it yourself for significantly less. A point to ponder...

Once you've checked all that, please post again and let us know what's going on. I have a feeling that will be enough, but give us more information if not and we'll go at it some more!

5-90

:read: http://www.e-toolbox.com/ads/rq.cfm I find that this site is very informational with a little (which you seem to have)mechanical expirience. Check it out!

Thanks all for you input , went out today to play or kill her and again shifted from park to neutral and back to park several times and just before a hammer was ready to pierce the engine block she started ... Hummm
Thanks all again
geepers