Itinerant Fred

I'll start by saying Hi all and thanks in advance for any advice. Here goes.
I have a 1993 Cherokee Ltd. It runs on petrol as well as auto gas, LPG. At times she starts up 1st crank and runs like a dream, whether on petrol or gas. I arrive wherever i'm going come back to the Jeep and it's a none starter. Doesn't matter whether i'm starting on either fuel, it just wont go. Sometimes it fires and starts but then the revs just die and she cuts out again. Sometimes it just wont start at all. Twice i've had it recovered and by the time its back on my drive and off the recovery truck she starts first time again.
I've had the coil tested ok, new disributor cap and rotor arm and HT leads. Plugs are fine, spark is fine and according to the nice recovery man, fuel is getting there fine.
I'm at the end of my tether with it, any suggestions or advice gratefully received. I love my Jeep and am lost without it at the mo as she's my only form of transport.
Help Please.
Thanx Muchly.

tjwalker

The "crankshaft position sensor" could be flaky. Without that critical input signal coming to the computer, you will not have spark and you will not have fuel going to the injectors.

JeepingDan

Those cps can be intermitent little bastards. Heres a testing procedure.

https://www.cherokeeforum.com/f51/testing-cps-5563/

Itinerant Fred

Thanx for that info. I have done the diagnostic and get the codes 12 and 55. I have had the battery off to re-charge so expected code 12, i understand that code 55 means the end of the check. This indicates crank sensor is ok i presume.
I tried to start the Jeep on petrol again to no avail but she started on LPG (autogas) first turn of the key. I let her temp rise and sprayed some carb cleaner in, this stopped the engine. I tried to start her again and after a couple of cranks she started ok. I let her idle for about ten mins and turned her off. I then tried to start her again and now i have nothing. All the dash lights come on indicating power but no turnover, not even a click. Then all the indicator lights go out. Any ideas on this anyone please. Everythings there just no cranking it's like there isn't a battery connected.
Sorry to be a pain but once again any help appreciated.
Take care all.

tjwalker

If the engine doesn't even turn over, then the crank sensor has nothing to do with this problem, but it is still in play for your ORIGINAL problem.

You very well may have two things going on here.

The #1 thing to do is to FRESHEN all battery connections and engine grounds. Remove battery terminals and clean them and the battery posts until they are shiny with a commercial battery cleaner (parts store) or sandpaper, emery cloth, something abrasive.

Don't forget engine grounds! They should be disassembled, cleaned, reassembled.

And if that checks out and the engine still doesn't turn over, you have an electrical "control" problem, like a neutral safety switch that prevents the engine from starting in gear. When they go bad, they can prevent the engine from turning over at all.