new won't start issue

[TajMan]

At first my truck was just unreliable- sometimes it wouldn't start. Always had to stop trying and then the next time I would try later it would always run fine. 1 time it died when it was running then wouldn't start till I tried later.

 

Now it just won't start from the last time I parked it. Tried multiple times over a few days. I just checked, spark plug isn't getting sent spark.

 

I know this is most of the time the crankshaft position sensor.

The thing is my sensor is new, and the engine wiring harness between sensor and ECU was even swapped out once!

 

Is the only thing to do, test the wires for voltage fluctuation while cranking (at the ECU plug end) and/or re-wire the CPS directly to the ECU and see if that fixes?

 

Any links, walk-throughs, ECU pinout diagrams etc would be helpful.

[Pete M]

Your truck has the C101 connector. I would check that. Corrosion can creep in and cause havoc. Although it's less likely if you live in a dry area.

It connects the engine harness to the interior harness and is located in the engine compartment on the fire wall above the booster (or somewhere around there).

[TajMan]

My harness was changed with a Cherokee harness, I don't have the C101 connector.

 

I've driven the car over 3,000 miles this way, then this problem creeps back now.

[TajMan]

Yep, crankshaft position sensor.

 

Wasn't even a short in the harness between sensor and ECU, its the CPS connector(3-prong, only 2 are used) itself that plugs into the harness near the engine.

 

I ran new wires, soldered them directly between the ECU connector and the CPS (no connections between, continuous wire). Starts fine now.

[TajMan]

I did my fix the other day and thought It was good ever since...

 

Then yesterday morning, it had just snowed and truck was out in the cold, it wouldn't start again!!

 

I remembered that some of the times it hadn't started in the past HAD been on very cold days then it worked later when I tried and warmer.

 

1 thought crossed my mind. That CPS is a new unit I got from NAPA I believe. Is it possible a faulty or weak new sensor could work intermittently or not work sometimes if its too cold/ice somewhere/etc?

Its not powered and the sensor only picks up a .5V magnetic fluctuation doesn't it?

to me makes since that it would be easy to mess up not getting ECU a good signal

 

advice?

[TajMan]

After last post, wouldn't work for a long time then 1 day it just started and ran fine.

 

Last night I was driving it.

This morning, another COLD morning, it won't start again.

 

HELP!

 

I need to find and fix this so it doesn't break on me when I go somewhere.

Its like an electrical issue that causes no spark.

 

Is it possible a CPS from NAPA is a malfunctioning unit that doesn't work when its too cold?

[maddzz1]

Is it possible your NSS is sticking somtimes? Did you check/clean it?

[TajMan]

Pretty sure its not the NSS, I found that problem and cleaned/fixed that when I got truck running for the first time originally.

 

Unless its possible for a cleaning to be just enough to get running.. but barely good enough to last just 3,000 miles before problem crops up again etc..

[TajMan]

Its my birthday, I wish my vehicle would drive. :(

 

Once again Sat. it worked, pulled into garage and worked on front fender flares, pulled out of garage and parked. Sun. it won't start again, still not now.

 

I also tried taking NSS thing off again, got it kind of loose and wiggling around but couldn't get off. Knocked on it a bit and bolted it all back together. Still no-go of course.

 

I guess I just have to know what I HAVE to do/test to go from here. :roll:

[Car RamRod]

When my CPS went, it was an intermittent no start, but after I got stranded at work I figured I'd go for it and change it. Well the new one didn't work at all. So I returned it for a different one, and that one is working fine (knock on wood!).

 

Matt

[Eagle]

Is it possible a CPS from NAPA is a malfunctioning unit that doesn't work when its too cold?

My guess would be "yes." I only buy CPSs from the dealer. It's too critical to take chances on saving a couple of bucks on a part that should last over 100,000 miles, but can leave you thoroughly up the creek without a paddle when it decides to not work.

[TajMan]

Is it possible a CPS from NAPA is a malfunctioning unit that doesn't work when its too cold?

My guess would be "yes." I only buy CPSs from the dealer. It's too critical to take chances on saving a couple of bucks on a part that should last over 100,000 miles, but can leave you thoroughly up the creek without a paddle when it decides to not work.

 

Talked with Jeep dealer, their sensor for $43 was better than Autozone's $44 anyway. Ordering from Denver dealer.

 

Thing is they said the '87 is its own unique unit, unique part number.

 

I know NAPA and other stores had more than 1 option, more than 1 pic, but no REAL way do discern which one was correct besides black or grey connector. I guess its possible I had the wrong one on there anyway. Worked sometimes hmm.

 

My wirings already hacked now right to the 2 ECU pins. I'll get new sensor and solder wires up directly, see if it fixes my issues.

 

Truck outside in the snow to work under, yay.

 

:roll:

[TajMan]

We're gonna call this one a NAPA bad!

New part, started working intermittently then failed completely within a couple thousand miles.

 

New Jeep part fixed :chillin:

 

Also bad on NAPA's computer system, couldn't look me up and replace under warranty from my phone number (like say Autozone's system), I would have had to have original CPS receipt from them.

 

Just means $43, a lot of stress, and a big F U to NAPA... but hopefully she'll be reliable for awhile on me now.