XJ Cherokee - no spark condition

[tazwegion]

After almost 3 years of sitting idle I brought the Jeep out of mothballs, drove fine for 3 days but suddenly wouldn't start after being parked overnight, the engine would happily crank but not fire up.

Confirmed engine bay fuses all correct and detected no spark was present so I replaced the coil (it was old and had a cracked casing) but still no go, confirmed there was power to the coil but no pulse signal.

Fuel pump spools up

MAP sensor throws code 13 & 14 but tests fine (voltage variation with vacuum)

Cam angle sensor has 5v source, confirmed ground but output signal does not alter as engine cranked (replacement on order).

Crank angle sensor replaced prior to vehicle being taken off the road.

Anything else I should consider/check whilst awaiting new CAS?

[LuluBelle]

all the main earths are located on the engine block at the bottom of the dipstick they might be crusty after sitting refresh the connections on the pcm but the crank could be bad from sitting

[tazwegion]

CAS arrived early, I bit the bullet and placed a new MAP sensor on order as well, back on the road again but the distributor button looks to be getting pretty worn and had left some dust/residue inside the cap as well... all cleaned up and new part added starts great 👍

Back probing with a sewing pin and multimeter paid off in the end, ordered a decent set of wire piercing probes for the next fault to rear it's ugly head.

Thanks for the response.

[alexbrown64]

Great that you run some tests and got it sorted.
Generally, best bet is to do a Rockauto order every few years.
Get plugs, rotor button, cap, airfilter, coil etc.. all in one hit. So cheap and your XJ will love it.
Ive found that the new Crank sensors are junk. The magnets are so weak on them. I found a New Old Stock Mopar Made in USA one on Ebay. The quality was 100 times better.
Cheers,

[Sobek]

Originally Posted by alexbrown64

Great that you run some tests and got it sorted.
Generally, best bet is to do a Rockauto order every few years.
Get plugs, rotor button, cap, airfilter, coil etc.. all in one hit. So cheap and your XJ will love it.
Ive found that the new Crank sensors are junk. The magnets are so weak on them. I found a New Old Stock Mopar Made in USA one on Ebay. The quality was 100 times better.
Cheers,

I think this is solid advice. Rotor buttons and distributor caps always oxidize badly inside of a year if not driven, that's usually the go-to for dodgy starts after long sits (besides rat chewn wiring!).

FYI, you can still buy the proper Mopar crank sensors off Rockauto as I worked out recently... they just don't show them in the list of sensors when you bring up your year / model etc, I really don't know why that is. For pre-update XJ's, the Mopar crank sensor link is here;

https://www.rockauto.com/en/moreinfo.php?pk=5102934

If you have an update XJ, find the Mopar part number and put it into Rockauto, I'm pretty sure they have the Mopar sensors for updates too. And like Alex said, there's no comparison between the strength of the magnets used on the Mopar units vs everything else... The Mopar sensors will pick up a heavy ratchet, the non-Mopar units, will not
Also be extremely diligent when installing the crank sensor, it's so easy to route the wiring a tiny bit wrong and let it get too close to (or touch) the block or the exhaust. If that happens, you're going to get stranded somewhere. Ask me how I know

I have a good MAP sensor and once in a blue moon it will throw a code 14 too... no idea why. Everything works perfectly though