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Chris, ASE Certified Technician
Category: Car
Satisfied Customers: 294
Experience:  I am a Master Certified ASE technician. ASE Certs A1-A9 & L1. I have been a general auto repair tech for over 18 years.
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wrangler: 2008 wrangler. only get fuel to right fuel rail

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2008 wrangler. only get fuel to right fuel rail

Hello and welcome to Just Answer, I will try to help you solve your problem. I may need to jump out but someone should step in if I do.


Have you checked for any codes? Do you have a scanner?


With the ignition key on unplug the injectors on the bad side and check to see if you have battery voltage on one side of every injector connector.

Customer: replied 3 years ago.

sorry for late reply I had to take the tow truck and go get the jeep. I just got back and scanned it. (all I have is a code reader)

I have p0300, p0157 and p0430

I was on my way home from work. I think all these codes are a result of the problem. Have you had a chance to check the power on the injector wires yet?
Customer: replied 3 years ago.

wasn't sure how to. it looks like the top half of the plenum needs to come off just to get to the injectors


Oh they are the buried type. I hate when they build them like that. Any chance that you have a stethoscope or a piece of hose? You can put the hose down on the injector and other end to your ear with it running and you should be able to hear it clicking.
I am seeing a lot of problems with the coil packs. How did you check the spark? Was it a nice bright blue and jump at least 1/2-1 inch?
Customer: replied 3 years ago.

I thought it looked a lil weak but not enough to cause these symptoms. im sparking at the plug I pulled plugs and checked each one. and I could only check front two injectors rest are buried. they re clicking away just fine

OK I think that the injectors are ok if you got one from each side. Did the spark look the same on all the plugs? Do you have anything to check the engine compression?
Customer: replied 3 years ago.

.spark looks good all the way around.yes I can check compression. but it'll have to wait til morning.

i'll catchya tomorrow

OK not a problem.
Customer: replied 3 years ago.

I did a compression check. im running about 150 on all but cylinders 2 and 4 are running about 70. im guessing a blown head gasket. and its gotta be blown between cylinders cuz theres no water in the oil. don't worry about answering tonight. im done for the day. gonna pull head off tomorrow



Yes that sounds like a good assumption.
Customer: replied 3 years ago.

I just thought of something. I had a jeep liberty a couple of years ago that had a v 6 in it. I believe it was an 04. anyway. when I went to have the heads machined (shaved and vacuum tested) my machinist said he didn't mess with those heads because they were nothing but trouble. and he's one of the best in town. is this the same engine in the 08 as it is in the 04

I will be out for most of the day. I will check on that for you as soon as I get home.
Customer: replied 3 years ago.

im pretty sure that's what it is so im just gonna leave your feedback. i'll let ya know how it goes when im done. . unless you can think of something else to check before I start rippin heads off. im not startin it til Tuesday morning

In 2004 they used the 3.7L engine so it is a different engine.


The only other thing I can think to check would be with a vacuum gauge. If you have all the spark plugs back in. It can be running or just cranking. with a vacuum gauge hooked up to manifold vacuum the needle should be steady (no mechanical problems) if it fluctuates or flutters then there is mechanical problems. Did this problem happen driving down the road or at start-up? If the 2 cylinders are low then it has to be from a leaking valve, head gasket or piston rings. Like you said since they are side by side a head gasket seems to be the place.


You could also do a leak down test. Basically you are putting compressed air into the one cylinder when the valves are closed and see where it leaks out. This is the best way to check a low compression cylinder. If you pump air into the one and it comes out the other then you know it is bad. (you must make sure that the valves are closed. To much air pressure can push the piston down and open the valves)

Customer: replied 3 years ago.

I just bought a leak down kit today. gonna do a leak down test tomorrow and then pull heads off (assuming they need it) i'll let ya know



Sounds good.
Customer: replied 3 years ago.

I hooked up the leak down tester and ive never used one before so im not sure if I was doing it right. but with middle cylinder on left (drivers) side at TDC compression stroke. I hooked up the air hose and turned the knob until I heard air flowing threw it. then I kept turning it until the first gauge got up to about 10 and the second gauge reached the SET mark in the yellow field all the way to the right. with a length of hose I used like a stethoscope I code hear air coming thru the front cylinder spark plug hole and I could hear more air through the dip stick tube

sorry about the delay in response. To use the tester hook shop air to it (disconnected from the engine) and adjust the knob till it is in the "set" area. Then you attach it to the hose in the cylinder. Take the reading and if it is low listen for the leak. Here are some directions.


If you put it in the front cylinder do you hear it in the middle one? You will get some from the dipstick. Air will push past the rings. Also make sure that the crank did not turn off of top dead center for that cylinder. You might even have to hold it.

Customer: replied 3 years ago.

yes I can hear air in the other cylinder.

Well if the crank did not turn then it sounds like a head gasket problem to me. Time to tear it on down.
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Customer: replied 3 years ago.

I kinda figured. but before doin a major job like this its always good to get a another professional opinion. i'll let ya know what I find out whne I pull the head off. just out of curiosity. what is your opinion on do just ONE head. the other side has great compression and no leak down problems. ive always done both when doing a job like this but kinda curious what a veteran like you thinks

I will have to say it is best to do both. You have a problem with this side so how long till the other side has a problem? That is the question... The other side could last 50 years or 50 days. Your call on that one.
Customer: replied 3 years ago.

ive never not done both so im not gonna start now. just curious what you thought.



I'll let ya know what happens

Customer: replied 3 years ago.

well I pulled the heads off. im dropping them off at machinist this morning. but I didn't find anything VISIBLY wrong with the heads valves or gasket????will know more in a few hours. curious,, is there a way to pressure or vacuum test the cylinders with the heads off? do the make any kind of tool for that?

The machine shop should be able to do that.
Customer: replied 3 years ago.

the machine shop can check the heads. but I was wondering about the cylinders. the machine shop is 20 miles away and I don't wanna tow the jeep there and back

Sorry I miss understood you. Not really that I know of. How did the head gasket look? Is it one of the layered metal or lead type gasket?
Customer: replied 3 years ago.

layered material. and I really couldn't find any indication of a leak. im hoping the machinist will find something. cuz if its in the cylinder,,, im going to hate to have to tell the owner they need a new engine. im running to machinist now so i'll let yua know what they say in a few hours

OK let me know. The layered gaskets are very hard to tell because they can leak between the layers. Make sure they check that the head is flat mainly around the cylinders you were having trouble with.
Customer: replied 3 years ago.

I always have the machinist mill the heads anyway for safety sake.

would just be nice to know if that is where the problem might be.
Customer: replied 3 years ago.

machinist says all is good. he did a vacuum test on all intake, and exhaust ports as well as the cylinders area. he milled nice and clean and said they weren't warped at all. basically no problems with the head. he also said that if im only pushing 40 lbs of pressure on those cylinders that there would have to be a noticeable issue. the heads are ruled out. and he says if it was rings only holding 40 lbs then it would be smoking like a chimney and it wasn't smoking at all. so I need to look at lifters or cam. whatta you think?

My only thought with that is that the lifter and cam would not make the pressure go into the other cylinder. It could cause low compression and a misfire though. Did you ever check it with a vacuum gauge when it was together?
Customer: replied 3 years ago.

no but I have a vacuum unit I modified so I think I can check the cylinder with the heads off. what should the pressure be?

It would be to check engine vacuum while cranking to see if it is steady. This is a push rod engine right? Not over head cams?
OK I got home and see that it is a push rod engine. We know that the heads are good and we thing the rings are good. How about you put the head back on only. Leave the push rods out so that the valves stay closed. Do a leak down test again per the directions I added earlier. If that looks good then install the push rods and rocker arms then do another compression test to see if it is back up where it belongs. If that is good then you should be good to go.
Customer: replied 3 years ago.

will do. I let ya know how it goes. most likely be tomorrow

ok sounds good


Customer: replied 3 years ago.

I was able to vacuum test the cylinders with heads off. I have 25 pounds on all cylinders but the two in question I only have 10. so its rings. just thought youd like to know. looks like im rebuilding an engine

cheers thom

ps. did I already rate your help?

it doesn't show on my end

Well at least you fond the problem. I think you did rate it. Kinda hard for me to tell also. Hope the rest goes well for you. Have a great day.
Customer: replied 3 years ago.

I ended up replaceing the engine with a new one from (don't laugh) autozone. got it all together and fired it up. it ran good for about 5 minutes then died. wont start now. I did a compression test and had 40 to 60 lbs on cylinders 2,4 and 6. I didn't even try 1,3 and 5 . anyway I called the company that makes the engine and they told me to try squirting some oil in the cylinders to bring the compression up. ive herad of this before but never tried it. just wanted your opinion

Well Thats no good. You are having no luck with this thing. When you have low compression you usually squirt a little oil in the cylinder to see if it is the rings. If compression comes up then the rings are the problem. If not then it is a valve or something. Just don't put to much.
Customer: replied 3 years ago.

well i ended up rebuildiing original engine. i just got everything back from the machinist, if nt too much trouble, could i get some torque specs from you? i need rod cap bolts, main cap bolts and head bolts. i have everything else. im more than happy to rate again and leave another tip



Man this has been a real project for you. Here are all the engine specs.



Customer: replied 3 years ago.

yeah tell me about it. the new engine had no compression on 2 cylinders. it took me a week of fighting to get them to refund my money. I ended up just rebuilding the orginal engine. it turned out the the rings for some reason, were frozen to piston and would not expand to cylinder walls. that's were I lost my compression

I hope this works out better for you.
Customer: replied 3 years ago.

seems like I got a few more follow up questions. I will rate your answers and leave another tip, so I hope you don't, but I got everything back together and engine seems sluggish. not much power. I don't have any check engine light but the change oil light keeps flashing. I did install new oil pump and I primed it with Vaseline. I did not, however, change the oil pressure relief valve. I couldn't figure out how to remove plug. would oil pressure relief valve cause engine to loose power?

The "change oil" light is flashing? If the relief valve was bad it would either cause to much or to little oil pressure. That should not effect power unless it is starving for oil. That should show by not pumping up the lifters and having a tapping sound to start then it will start wiping out bearings. I will see if I can find something on the oil light flashing.
If it is the "change oil" turn the key on with engine off and press the gas peddle to the floor 3 time (should all be done within about 5 seconds). That should reset the oil light.
Customer: replied 3 years ago.

well that did the trick but i still have no power. and i reuilt this engine myself. i know everything is right. gonna do compression test now

ok let me know.


Customer: replied 3 years ago.

S%#T D#&MN PI$$ HELL F%#K i have the same two cylinders with no pressure. i took the block in and had it bored. i got new pistons, new rings , new bearings everything, i did the assembly myself and vacuum tested the cylinders before i put the heads on, had the crank turned, had the heads re built, . (even the new engine had the same 2 cylinders) i dont get. im a damn good mechanic and cant figure it out. i wanna bump the starter to get the cylinders at TDC but when you turn the key the engine just keeps turn ing over till it starts, even when you let go of the key. is there a way around this?

Well that is crazy.... You can run a jumper wire from the starter small terminal and tap it on the battery to run the starter. I could think of things like the camshaft but that changed with the new engine. Anything blocking up the intake or exhaust on those 2 cylinders? This is going to take some thinking here.
Customer: replied 3 years ago.

well while your mulling it over, im gonna see if I cant find another professional who might have experienced this before. (no offense to you, you've been great. but you seemed to as baffled as I am)

i'll let ya know if I find anything out. oh by the waY. I just did a leak down test and on cylinder 2 and four I can hear the air very clearly through the dip stick tube.

That's not a problem. If it is doing it with original, remand and rebuilt engine than it has to be outside of the main block Like something blocking the air from the intake or exhaust.

You will push some air past the rings. As long as all the ring gaps are not lined up that should be OK. I just can not imagine the same internal problem with all 3...that is just to odd.
Customer: replied 3 years ago.

if its not in the block. then it would have to be the head? because of time frame I had heads done a different machinist than the block. ive never used that machinist before

but the rebuilt engine cam with heads correct?
Customer: replied 3 years ago.

yes it did. so that only leaves intake. but I cant see were the intake would cause compression problem. it would have to leak past heads first. right?

Are you sure that all the ports are clear. Shop rag maybe... If something is blocking air from getting into the cylinder or the exhaust from getting out can cause low compression. Other then that I am out of ideas other than original and 2 rebuilds having the same problem and that would be VERY RARE!!! I would rather look at other possibilities first.




Where you going to start a new question or would you like me to opt out of this one?

Customer: replied 3 years ago.

what about the intake throttle assembly. its all electronic. would anything there cause it?. I don't have any check engine light on. but when it starts and I try to rev the engine it has a very hollow boggy kinda sound

That would effect all cylinders. I was thinking more down in the individual ports to those cylinders.


Try disconnecting the exhaust down pipe. That sounds like possible clogged exhaust and it is trying to come back trough the intake.


You said it was cyl. 2 and 4? What is cyl 6 compression like?