Jasel

my 99 grand cherokee won't start or stay running unless i constantly give it gas. i just got it back from the mechanic today and he said that cylinder 6 hardly has any compression. he tested the cylinder next to that one and he said it was testing at around 125...he checked the fuel injectors and that they all flashed light through them....i still think its a fuel injector for some reason, cause it don't want to stay running unless u give it gas.
how this happened was:
i pulled in my driveway and hopped out and ran inside for like 5 minutes. then i came back out and got in jeep and it didn't start when i first turned the key. i thought the battery was dead battery..i started to give it gas and had to keep giving it gas to get it to start..if u let your foot off the gas it dies....constantly have to give it gas for it to run...i knew then something was wrong and called mechanic and drove to his shop 2 miles from house and left it their..
i've searched for other threads and i will try the things they suggest tomorrow, as i'm getting ready for bed now..
the mechanic said it could be a valve spring or a hole in the piston....
it happened so fast that i wouldnt think it's a hole in the piston...
checked the oil and it's fine....so when i get up i will try some things i searched...i just had to ask cause it came up with only cylinder 6 losing compression.. thanks for any help
this is long question

dave1123

Bring #1 to top dead center compression, then go one complete revolution more bringing #6 to top. Put air pressure in the spark plug hole and see where it leaks from. Oil filler cap shows broken or bad rings, throttle body shows an intake valve, and exhaust pipe shows an exhaust valve.

Jasel

thank u for the help, i will be doing that this weekend
appreciate your reply

IStoleIt

*MIND BLOWN*


You never cease to amaze me Dave.




I was just telling my wife, that your UNLIMITED knowledge has you always the first to answer, then an incredibly detailed extension of someone else's post, and the last post of the thread, "Glad I could Help."


Dave your a Cherokee Angel!


lol

dave1123

Actually, I'm a GRAND Cherokee nut. I've owned a 97 ZJ and now own a 00 WJ. I learned the hard way, but I have worked on cars and trucks for over 50 years. Glad to help.

I like to be there to welcome new people to the forum and help get their post started. A lot of this comes from the way I was treated when I was a newbie. Just keep in mind this is an OPINION site so all responses may not be factual but based on their personal experiences. Having said that, there are a bunch of guys here you can trust to lead you right. I won't mention any names because their heads might explode! LOL! If I have an opinion, I'll tell you. If I don't, I'll give you my best guess, but tell you that's what it is, a guess.

Besides that, I'm retired and bored out of my mind!!!

Bustedback

I can't wait until I can retire...23 years from now. That will give me 30 years at my current job and put me at the right age for social security if there's anything left.

dave1123

I retired in self defense, so to speak. My wife died, my boss cut me no slack and I had it out with him. He fired me for insubordination, no unemployment. Being partially disabled, I couldn't find another job so filed for SS Disability and got it. Quit looking for another job since there ain't no manufacturing in Syracuse anymore. Doing pretty good on SS and a part time newspaper delivery job. Enjoying the rest of my life.

What were we talking about?...Oh, yeah! A 99 WJ! LOL! That air pressure test works the cat's! I've used it many times. The hardest part is making sure each cylinder is really at TDC or it will flip over when you clip on the air. I use a spark plug base with a air snap-chuck fitting on it. One tapered seat and one gasket seat.

Jasel

i finally got it figured out...i've been battling a sinus infection, so i may be a little slow.
it was a rocker arm that fell off on cylinder 6...
i have a 99 grand cherokee 4.7 4x4......what is my next step from here.
do i have to get heads completely done, or i've been reading on internet that and watching on youtube on being able to put them back on without a special tool..
good idea or bad ?....new lifers?
thank for help and any suggestions

IStoleIt

I cant tell you for sure, but i dont know how well a repair could be and it should be rebuilt.

Think about your RPM's. A rocker arm band aid, doesnt sound very good @ 4k rpm.

dave1123

I'll tell you about rpm's. When I built my 392 Hemi, I grooved the main bearings on the crank for better oil flow to the rods. After getting the grooves cut in a lathe, I turned it up as fast as it would go to polish the journals. 750 was the fastest the lathe would turn, which is an idle, and I could barely see the crankpins as it spun! I wasn't getting near that thing with crocus cloth! Imagine what it's like at 6000!! How do the pistons take it? I can't figure out the piston velocity easily, but from zero to max to zero in 4 inches has to be incredible!

Jasel

great, thank u all for the replies!

dave1123

Wait......Don't go away just yet!! I've done a little research and it seems rockers flying off is a common problem with this engine. It is attributed to sticking valve lash adjusters. You can take them out and clean them or replace them and save yourself a head job.

Jasel

dave1123, i'm glad to hear that, cause i haven't done anything with it.....
hopefully tonight or tomorrow sometime i should get around to doing that.
thank u very much for letting me know

97grand4.0

I'm not up on this 4.7 engine, but curiosity got to me. There seem to be a lot of Utube videos that show various ways to fix the rocker falling off. Here is one, the first one, (never go with just the first one).

Jasel

thank u, i appreciate that