96XJSport4x4
NAXJA Forum User
- Location
- Florida
Basics: 96 XJ, 4.0, AX-15, 181k miles, bone stock.
I APOLOGIZE IN ADVANCE FOR LENGTH OF POST! But I did want to be thorough and include test results…I have searched and done my testing! ALSO, to anyone who can help, thanks in advance and I PROMISE to follow up with what resolves the problem!
Hard starting issue - only during heat-soak period of maybe 5-45 minutes AFTER hot shutdown. An IMMEDIATE restart is not an issue. Only when the engine has had time to "soak" after a nice hot drive do I have the issue. On cold starts, the engine cranks right over. It seems to me I am having vapor-lock type issues. When I have the hard start condition, the fuel coming out of the fuel rail test port is bubbling and under high pressure. I have thoroughly checked the area around each injector and have found no fuel leaks whatsoever, even when wiggling each injector and running the engine at 3k+ rpms.
It seems this issue has slowly gotten worse. I don’t recall having this issue last summer. I was having funny fuel delivery problems several months ago which appeared to be vapor-lock. I tracked down a hot run condition (temp would easily climb to 220-230 in a lot of idling or wheeling) to the fan clutch, which was shot! Now it roars, literally, and I thought my fuel delivery issues were solved.
Brand new fuel cap. Nearly new fuel filter, within 1k miles. (OLD WAS NASTY!!) Air filter fine. No CEL or codes.
Engine runs very strong and climbs smoothly. Never really idled like a Lexus, but not much different than any older domestic. With 181k miles, I don’t expect a brand new car.
As far as symptoms, sometimes it is a long start with a roughness for a couple of seconds after finally starting. One good push of the throttle clears it right up and it runs normally...Cool fuel now flowing??
Sometimes, it won't start at all on its own. Then I need to shoot some starter fluid in the intake, open the throttle, and crank. It will eventually turn over with the roughness then clear right up. Cool fuel now flowing??
It does start with a bit of richness out of the exhaust when I experience the longer starts, even without starter fluid.
Fuel pressure gauge shows rapid fluctuation during all running conditions (idle, part, or full throttle) of 48-52 consistently at any temperature. Now, I have read many different things about the proper numbers. 48-52 with a rapid flopping of the needle sounds normal. I have heard different things about the leak-down pressure. HERE I read lower than 30 psi within 5 minutes and HERE I read 24 in 5. I tend to believe the 24, since it specifically states my 96 model year and the 30 seems to be people referring to the 97-01s. QUESTION: Does the leak-test have to be performed immediately after turning off the motor OR can the leak-test be done at anytime, as long as you place the key in the run position and begin the 5 minute countdown?
I performed the test several times. Each time, immediately after shutdown, I have 47 psi. Over the 5 minutes, it never drops below 44, and sometimes climbs back up to 47 or 48. Even though I just shut down a motor that was running at 195-205 (dash gauge, no IR, sorry!), the fuel rail wasn’t too hot.
Here’s where the problem is: I allow the engine to heat soak and check the pressure between 5-45 minutes after shut down. I turn the key on and pressure always comes right up to 44-46 psi. I start the clock watch. The pressure drops VERY fast!!
Approx 10-15 minutes after nice hot shut down…Hood was left open too!
TIME (minutes)- PSI
START- 44-46
.30- 42
1:00- 39
1:30- 36
2:00- 33.5
2:30- 30
3:00- 27
3:30- 23
4:00- 22
4:30- 19
5:00- 19
Approx 20-25 minutes after hot shut down…left hood closed…
TIME (minutes)- PSI
START- 44-46
.30- 36
1:00- 29
1:30- 25
2:00- 22
2:30- 21
3:00- 20
3:30- 18.5
4:00- 17
4:30- 15
5:00- 11
So, assuming I am testing it properly (okay to test even if engine wasn’t just running) I am WAY below both the 30 psi and the 24 psi. I think the fuel in the rail is still nice and cool immediately after shutdown, hence the nice strong pressure the first 5 minutes after shut down.
Out of the possibilities available, I think I can rule out a lot. New fuel cap – tried 2 different brands just to be sure! Don't think it's an air issue...I have tried opening the throttle up for 10 seconds before starting to let air fill before cranking...doesn't help. Fuel pump seems to be very consistent and putting out adequate pressure. Check valve/pressure regulator assembly is in the tank, correct? If so, that rules that out as the problem is directly related to heat soak. Not sure if any of the sensors could cause something like this...IAC, TPS, MAP, O2, etc., but from my little knowledge on those sensors, I'm thinking no. So, because of the leak down, the only thing this leaves me with is a leaky injector, right? I have read stories of an injector leaking into a cylinder and flooding a cylinder, causing a leak down condition. Could this only happen when hot? Maybe a seal inside of the injector? This could also explain rich exhaust…
Maybe my period of "overheating" further rotted aging injectors or their seals?
Love to hear what you guys think….If you made it this far, thanks again for reading it all!
I APOLOGIZE IN ADVANCE FOR LENGTH OF POST! But I did want to be thorough and include test results…I have searched and done my testing! ALSO, to anyone who can help, thanks in advance and I PROMISE to follow up with what resolves the problem!
Hard starting issue - only during heat-soak period of maybe 5-45 minutes AFTER hot shutdown. An IMMEDIATE restart is not an issue. Only when the engine has had time to "soak" after a nice hot drive do I have the issue. On cold starts, the engine cranks right over. It seems to me I am having vapor-lock type issues. When I have the hard start condition, the fuel coming out of the fuel rail test port is bubbling and under high pressure. I have thoroughly checked the area around each injector and have found no fuel leaks whatsoever, even when wiggling each injector and running the engine at 3k+ rpms.
It seems this issue has slowly gotten worse. I don’t recall having this issue last summer. I was having funny fuel delivery problems several months ago which appeared to be vapor-lock. I tracked down a hot run condition (temp would easily climb to 220-230 in a lot of idling or wheeling) to the fan clutch, which was shot! Now it roars, literally, and I thought my fuel delivery issues were solved.
Brand new fuel cap. Nearly new fuel filter, within 1k miles. (OLD WAS NASTY!!) Air filter fine. No CEL or codes.
Engine runs very strong and climbs smoothly. Never really idled like a Lexus, but not much different than any older domestic. With 181k miles, I don’t expect a brand new car.
As far as symptoms, sometimes it is a long start with a roughness for a couple of seconds after finally starting. One good push of the throttle clears it right up and it runs normally...Cool fuel now flowing??
Sometimes, it won't start at all on its own. Then I need to shoot some starter fluid in the intake, open the throttle, and crank. It will eventually turn over with the roughness then clear right up. Cool fuel now flowing??
It does start with a bit of richness out of the exhaust when I experience the longer starts, even without starter fluid.
Fuel pressure gauge shows rapid fluctuation during all running conditions (idle, part, or full throttle) of 48-52 consistently at any temperature. Now, I have read many different things about the proper numbers. 48-52 with a rapid flopping of the needle sounds normal. I have heard different things about the leak-down pressure. HERE I read lower than 30 psi within 5 minutes and HERE I read 24 in 5. I tend to believe the 24, since it specifically states my 96 model year and the 30 seems to be people referring to the 97-01s. QUESTION: Does the leak-test have to be performed immediately after turning off the motor OR can the leak-test be done at anytime, as long as you place the key in the run position and begin the 5 minute countdown?
I performed the test several times. Each time, immediately after shutdown, I have 47 psi. Over the 5 minutes, it never drops below 44, and sometimes climbs back up to 47 or 48. Even though I just shut down a motor that was running at 195-205 (dash gauge, no IR, sorry!), the fuel rail wasn’t too hot.
Here’s where the problem is: I allow the engine to heat soak and check the pressure between 5-45 minutes after shut down. I turn the key on and pressure always comes right up to 44-46 psi. I start the clock watch. The pressure drops VERY fast!!
Approx 10-15 minutes after nice hot shut down…Hood was left open too!
TIME (minutes)- PSI
START- 44-46
.30- 42
1:00- 39
1:30- 36
2:00- 33.5
2:30- 30
3:00- 27
3:30- 23
4:00- 22
4:30- 19
5:00- 19
Approx 20-25 minutes after hot shut down…left hood closed…
TIME (minutes)- PSI
START- 44-46
.30- 36
1:00- 29
1:30- 25
2:00- 22
2:30- 21
3:00- 20
3:30- 18.5
4:00- 17
4:30- 15
5:00- 11
So, assuming I am testing it properly (okay to test even if engine wasn’t just running) I am WAY below both the 30 psi and the 24 psi. I think the fuel in the rail is still nice and cool immediately after shutdown, hence the nice strong pressure the first 5 minutes after shut down.
Out of the possibilities available, I think I can rule out a lot. New fuel cap – tried 2 different brands just to be sure! Don't think it's an air issue...I have tried opening the throttle up for 10 seconds before starting to let air fill before cranking...doesn't help. Fuel pump seems to be very consistent and putting out adequate pressure. Check valve/pressure regulator assembly is in the tank, correct? If so, that rules that out as the problem is directly related to heat soak. Not sure if any of the sensors could cause something like this...IAC, TPS, MAP, O2, etc., but from my little knowledge on those sensors, I'm thinking no. So, because of the leak down, the only thing this leaves me with is a leaky injector, right? I have read stories of an injector leaking into a cylinder and flooding a cylinder, causing a leak down condition. Could this only happen when hot? Maybe a seal inside of the injector? This could also explain rich exhaust…
Maybe my period of "overheating" further rotted aging injectors or their seals?
Love to hear what you guys think….If you made it this far, thanks again for reading it all!