So I got this '96 Jeep Cherokee XJ that cranks but doesn't start. It's got around 180k on her but I keep everything in good shape. Batt seemed strong.

I used to drive it everyday but this past year I've driven it only about twice a week. It's been just slightly slower to start in the last couple of months, but just barely slower. Was guessing it had something to do with aging plugs or something.

Drove it yesterday and everything was normal like always, sat overnight and today it cranked but didn't catch.

Any ideas on where to start?

 

Your guess could be on the money, and the only way to know is to check those plugs or if you are going to go through the trouble to remove them. just verify the gap on the new ones and install them. Not knowing the maintenance history of the vehicle . you have to start somewhere and good plugs are never out of season !

 

Thanks hanky. Actually I changed gears on ya. This question is about my 96 Cherokee that I've had for about 12 years now so I'm sure the all the maintenance has been done on time for a while now. Lucky I've been able to keep it in good shape. I'll have to look at my records but I think the plugs are still within their recommended mileage but they could be getting close to the end. I should probably go ahead and do a complete tune up anyway because it couldn't hurt. If it was just the plugs though I would have thought it would have come on more gradually. Not ruling anything out yet.

 

Without naming names, some plug manufacturers hold up better than others. Having learned the hard way we stay away from certain brands.

When we are confronted with a no start condition, we try to determine if we have at least 2 things for the engine to start and they are fuel and spark. If we have those and it still won't start, now we go after possible fuel contamination, timing of the spark, sufficient air available, and no blockage of the exhaust.and also engine condition , a compression check. You have plenty to check out , so let us know what you find, thanks.

 

Appreciate all the good information there. In all the years I've been working on my own cars I've only faced one no start situation that turned out to be the NSS, so I'm sort of glad to be learning these procedures for tracing what could be wrong.

So far I've been able to run two tests..

I hooked up a fuel pressure gauge and first key turn got it up to only 20psi. Second turn got it up to 45. And third and subsequent turns got it up to 48. It only fell to 43 after 2 minutes so I think that means the fuel pressure is good.

Hooked up a spark tester between a plug and wire and it didn't light at all when cranked so I'm guessing I've got a spark problem. I'll start by doing a tune up with new rotor, cap, wires and plugs then see what happens.