yorkite

Mainly what causes it, how to prevent it, how to fix it. Don't expect anyone to give an essay...just curious because i see people talk about it alot on here.

Another reason for asking, Jeep's been not wanting to start back up lately after running for a while. Cranks and cranks, then after about 5-10 minutes will fire back up. Cold start - fine. Does this once in a while, but getting more frequent lately.

superj

usually, what causes it is the temps near a fuel line reaching over hte boiling point of hte fuel. when the fuel turns to vapor, the pump cannot push it through the lines so you get vapor lock. if your jeep is doing it, i would insulate the fuel lines in the engine bay as that is the hottest point in their journey but as much as i hate to say it, it is very hard to vapor lock a fuel injected vehicle because of hte pressure that the fuel is kept at. vapor lock is from the old days of carburation and was especially prevalent in air cooled volkswagens.

what makes you think you are having vapor lock issues? just hte hard start deal? i would change the temp sensor that feeds the ecu before i started worrying about vapor lock

yorkite

Ok, doesn't sound like that's the problem then....I really just had no idea what it was, and was explaining my problem with a friend, and that was the first thing he mentioned. Where's that sensor at? It's not the one that's in the back of engine that sends to the temp gauge is it?

Did a tune-up about 10k miles ago, new plugs, wires, cap. Runs great. Just weird to me how it only does it sometimes. Maybe try a new coil too? I don't know, just guessing, and hate to replace a bunch of parts for nothing.

2Evil4U

First thing I'd do the next time it does it is see if you have both fuel and spark if possible. That will narrow down the search a bit.

superj

yours is the same year as mine so i think ours is on the front on the cover for the thermostat. since i have not had to work on it though, i am not 100 percent sure. i know the one in the back is hte one for the gauge though as i changed to a different cluster and had to change that one

yorkite

i do know it's got fuel pressure at the rail. and yeah, ours didn't have that sensor on the thermostat housing. What's the easiest way to check for spark when you're stranded at the gas station?

superj

get your buddy to hold the wire while you turn the key

as far as that sensor, no idea then if its not on the thermostat housing. my jeep has been terribly reliable so i've had to only minimally open the hood

yorkite

okay, i have some friends that i could convice to do that!
going to play around, triple check electrical connections, and pull a couple plugs, cap and stuff this weekend too. not much else i know what to look for.

superj

its probably that temp sensor since it does it only when warm. either that or fuel pressure because the pump is wearing out and is losing pressure as it gets hotter but i would go with the sensor.

someone will come on and tell you were it is for sure though.

yorkite

hey hey, what are the chances? another similar no-start thread going on currently!!!
thanks for the input superj

superj

no problem man. hopefully someone comes on soon as i am about to sign off for the weekend. if no one helps, pm me and i'll pop the hood and find the sensor for you. any messages go straight to my phone so i get htem quickly

GRABLE

I think U R right about vapor lock. In the last 2 weeks I have been pulling an 5500# RV with my 2001 XJ, outside temp in the high 90's. It would hardly run after a 15 minute stop. I finally found out that if I open the hood while I am at a restaurant or other stops and it starts and runs perfect. I am amazed at the torque that little 6 cylinder has. I am still looking for a front and rear differential that will bolt right in,,,,4:10 ratio.

sandaddik2

hydro/vapor lock- when you suck water in the filter and the engine will not crank over like it is siezed up. just take the plugs out and crank the motor over til the water quits shooting out the cylinders then change all of your fluids start it up and drive it again... iv had it happen before

Rock Toy

Sandaddik, They are talking about hard to start engines that are hot. ( maybe vapor locked as in hot fuel, not hydro locked as in water ingestion. ) And it is possible to vapor lock an injected engine. Some guys have put fuel pumps on the frame rails instead of in the fuel tank, and had them vapor lock, because they aren't being cooled by the gas in the tank.

sandaddik2

i didnt read the entire thread before posting but thats interesting, iv never had that problem knock on wood, but i guess you learn something new everyday