Hey Guys. My 1992 W1500 runs beautiful, just touch the key and its purring. That said I'm told the truck has a history of just shutting off and that has happened to me once so far while sitting at a light. Its like the spark just shuts down yet it did start right back up. Sometimes when I go out for the first start-up of the day it turns over beautifully but again acts like no spark and does not start. This morning it did this and I noticed something that may be a clue to what is causing the intermittent issue. When I power up the key normally three lights come on in the warning panel- brake - maintenance - anti-lock and quickly go out and she starts instantly.
Today I noticed the 'maintenance' light did not come on with the others.. truck wouldn't start. Sat and played with the switch - on and off, cranked it a couple time and no spark. Then on one of the key ups I see all three lights come on.. tap the starter and shes purring. The original owner had had the computer, coil and fuel pump replaced trying to figure this issue out.
So it seems whatever the reason for the 'maintenance' light not coming on correlates with no spark = no start.

I am currently working 'slow' on a full drive-line service and tune up and also plan to replace parts one by one until this problem is resolved. Have searched this issue immensely and hoping some of you Mopar experts could give me your thoughts on what to replace first given the warning lamp symptoms. Thanks in advance.

 

if you are getting fuel but no spark then it is most likely the crank position sensor on the transmission.

 

I would second this being the crank sensor.
I had to replace mine in my 96 when i pinched the wires redoing the trans.
I bought a Napa sensor.
Afterwards the truck would start fine and within 6 to 8 minutes it would die.
Then as long as you didnt let it cool completly down you could shut it off, start go any where and no issues, unless i let it cool completly down.
Oh of course no codes for six monthes until it did it twice within 1/4 mile of driving then i got a loss of crank signal.
Replaced the Napa sensor with OEM and no issues for the last 3 years.
The moral of the story use ONLY OEM sensors!!
There are threads all over the 2nd gen forum and other forums on the web that cover the issues with aftermarket sensors.

Dave

 

sometimes OEM sensors are better than aftermarket but then other times aftermarket are just as good as OEM at a fraction of the cost. you really just have to do some research before you buy stuff sometimes.

 

Thanks guys, the threads I've read about trucks with these symptoms also seem to lean towards the crank position sensor and what a tough job it is to change out, if it is a real difficult job maybe it would indeed be smart to use the oem part. I picked up a Hall Effect Sensor and will install it with a new cap, rotor plugs and wires here in a day or two and see what happens. Next part after that will be the CPS. Many of the threads on trucks with these symptoms were incomplete and this seems like a pretty common issue so I will continue to update here and hopefully nail down the fault for others to read.
I still feel that 'maintenance' warning lamp not coming on only when the truck wont start is clue but have no idea as to what controls that circuit.

 

Just to update- I noticed not only the 'maintenance' light doesn't briefly come on when the truck wont start but also the 'check engine' light also doesn't light. Keying up the switch several times will eventually turn these lamps on with the others.. when they do light there is additional noise under the hood that I am amusing is the fuel pump relay and the truck starts right up. I replaced the pickup sensor in the distributor and no change to the condition.

I can not read any codes because the key trick doesn't work and may be because of check engine light - no start issue. A mechanic friend wants me to replace the ignition switch first as he feels they are a common problem so I may do that first and if it doesn't cure the problem next will be the crank position sensor. The truck stalled in traffic three times the other day so I don't really dare drive it much now for safety reasons.

 

Installed new ignition switch, it did need one as the original was very loose and worn compared to the new one. Everything seemed good and thought I had it fixed but tonight driving with my wife on a busy road it just died again, same issue.. the two dash warning lights wouldn't come on for a couple of minutes of working the key.. when they did come on the truck started right up and we drove home. Next part going on is the CPS, will order it from the dealer tomorrow and try to get it installed this next week and see what happens.

 

Sounds more like a wiring or ground problem if at times the lights come on and other times they don't...

Have you checked all the grounds and connections at the computer etc?

 

Not yet, but I agree it sounds like a wire grounding out. Crank sensor from the dealer is about $140 just for the part so I really need to check it out before throwing more money and parts at it. The original owner said first time the truck ever died out it was some wires melted on the exhaust manifold. I didn't see any that looked repaired. Think it would help put me in he right direction if I knew what circuit the 'check engine' and 'maintenance' lights were on. Going to be up over 100 degrees here for the next few days but I am going to try and look it over as much as I can. I really appreciate any and all input.

 

I don't know how much the locations of the grounds changed between the magnums and non but on my 1988 the grounds that caused the most headache were at the back of the passenger side cylinder head and back corner of the intake...also the cluster of grounds behind the battery near where the SMEC computer is.

Unplug the computer and check to see if the conneciton is clean and dry and reconnect and make certain no wires are loose etc.

Also check the wiring and connectors at the relays on the drivers fender as well.