Intermittent "crank won't start" until it sits a few hours.

[Lftrn97]

1989 4.0...Trans shop replaced flex plate about a month ago and this week it had a couple of "crank no start" episodes. The first time it sat for 3-4 hours before I went back to call for a tow. I tried it first and it fired right up. Started a bunch over the next four days then did it again and I had it towed to a shop. After sitting overnight I just went to the shop and it fired right up twice.  Seems like its the CPS or maybe NSS but I have two questions:

 

1.  Is there any significance to the fact that it fires after sitting, like something resets; and,

2. Could the flex plate work have done something to either the CPS or NSS (they had to drop the trans)?

[Eagle]

If it was neutral safety switch it wouldn't crank.

 

I think you need a CPS.

[Lftrn97]

i agree...thanks. 

[HOrnbrod]

If they pulled the tranny, they unplugged the CPS. Check to see if the connector is plugged in tight, and that the pins are clean and making good contact.

[Lftrn97]

good idea. will do in the morning.

[Minuit]

A "crank no start" situation that fixes itself after a few hours (usually when the sensor cools off) is a common failure mode of the CPS.

[cruiser54]

Check this out. It is easily tested.

 

http://cruiser54.com/?p=50

[IronManche87]

When I first got my truck it was doing this as well. It would start right away and would run for maybe 5 mins and would sputter out and wouldn't fire up for a few hrs. After some research on here, I tested the cps and low and behold my cps was deader than a door nail! Swapped it out she ran like a champ for well over an hr straight right afterwards!!