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Heat Soak Issue

Quailman

NAXJA Forum User
Location
Hunt Valley, MD
Hello I'm a new user here, just bought a white 1996 XJ with around 130k miles a couple days ago. First XJ!
I am however having a heat soak issue (I think).

I've been scouring the threads and a lot of people with this problem seem to have a rough idle or sputtering. Mine is a bit different. It has only happened twice so far, but it will basically just shut off when pulling into a parking spot (I guess I've just been lucky that it hasn't happened at a stop light).

It doesn't really "stall," just shuts off. No crazy noises or anything like that. Then, it won't start for about 1.5-2hrs when it fully cools down.
My current plan is to wrap the fuel injectors and surrounding area with heat shield tape to see if that helps.

Basically just looking for advice. FYI I do have CE codes for a downstream 02 sensor as well as P1899 which apparently is "manufacturer control; transmission," but I don't believe the P1899 to be related to this heat soak issue (although I could definitely be wrong).
 
Welcome to the forum. Is this really your first post since you joined in February? What your describing does not really sound like heat soak. What operating temperature is your jeep at when she dies? Does it idle down and then die? Are you getting fuel to the rail after it dies with the key "on"? When it restarts does it stumble back to life or does it start up clean? It could be a number of things ranging from electrical gremlins to fuel pressure. I think we will need more information.
 
yeah it's my first post. Created the account in February for the hell of it but I just bought the xj on Wednesday.
The gauge is at around 210 when it dies, nothing out of the ordinary. Since it dies while pulling into a parking spot I'd say that it's already at idle when it dies. It starts up clean as long as I wait long enough for it to cool down.
Appreciate the quick response.
 
It is a good place to start. Temp it fine. Im thinking you have an electrical issue. We can drive and crawl these things everywhere, at any speed, and never experience heat soak. Have you checked if your fuel pump is priming after she dies? Only happened twice before tells me the fuel pump could be on its way out, or a fuel pump relay is toast. You need to verify fuel pressure. Ok once it dies again- crack the fuel bleeder valve on the fuel rail and let the pressure out (use damp rags and soak up the fuel- and be careful) then crank her over again and see if she fires. This will take out the hot fuel in the line if it is indeed heat soak. This will also tell you if you have fuel pressure at the rail after she dies. Also listen to the fuel pump to be sure that it primes again upon attempted start up.
 
It is a good place to start. Temp it fine. Im thinking you have an electrical issue. We can drive and crawl these things everywhere, at any speed, and never experience heat soak. Have you checked if your fuel pump is priming after she dies? Only happened twice before tells me the fuel pump could be on its way out, or a fuel pump relay is toast. You need to verify fuel pressure. Ok once it dies again- crack the fuel bleeder valve on the fuel rail and let the pressure out (use damp rags and soak up the fuel- and be careful) then crank her over again and see if she fires. This will take out the hot fuel in the line if it is indeed heat soak. This will also tell you if you have fuel pressure at the rail after she dies. Also listen to the fuel pump to be sure that it primes again upon attempted start up.

All good suggestions. Thanks again everyone. Luckily I have a long weekend due to the holiday to do some trouble shooting.
I'll let you know how it goes.
 
It is a good place to start. Temp it fine. Im thinking you have an electrical issue. We can drive and crawl these things everywhere, at any speed, and never experience heat soak. Have you checked if your fuel pump is priming after she dies? Only happened twice before tells me the fuel pump could be on its way out, or a fuel pump relay is toast. You need to verify fuel pressure. Ok once it dies again- crack the fuel bleeder valve on the fuel rail and let the pressure out (use damp rags and soak up the fuel- and be careful) then crank her over again and see if she fires. This will take out the hot fuel in the line if it is indeed heat soak. This will also tell you if you have fuel pressure at the rail after she dies. Also listen to the fuel pump to be sure that it primes again upon attempted start up.

I think I'll just borrow a fuel pressure gauge from AutoZone to check the fuel pressure. Just to confirm, fuel pressure with regulator plugged in should be around 30psi and with regulator unplugged should be around 40 (in order to check both the pump and the regulator)?
 
I think I'll just borrow a fuel pressure gauge from AutoZone to check the fuel pressure. Just to confirm, fuel pressure with regulator plugged in should be around 30psi and with regulator unplugged should be around 40 (in order to check both the pump and the regulator)?

1996 is in tank regulator and fuel pressure should be 45 to 50 psi.

Could very well be the CPS starting to die but usually when they go out it just happens. In my case usually in an intersection.

People runs these thing pretty hard in Death Valley where it regularly gets to 115+ with out heat soak issues.
 
1996 is in tank regulator and fuel pressure should be 45 to 50 psi.

Could very well be the CPS starting to die but usually when they go out it just happens. In my case usually in an intersection.

People runs these thing pretty hard in Death Valley where it regularly gets to 115+ with out heat soak issues.

I'll keep that in mind. At least if it is the CPS it's a cheap fix (although a PITA) lol.
 
1996 is in tank regulator and fuel pressure should be 45 to 50 psi.

Could very well be the CPS starting to die but usually when they go out it just happens. In my case usually in an intersection.

People runs these thing pretty hard in Death Valley where it regularly gets to 115+ with out heat soak issues.


:thumbup: This...
 
:thumbup: This...

UPDATE: I got her home perfectly fine, tried to start back up and won't start again.
I cleared all CE codes to see if the "misfire" would throw a code which it did not.

I bled the fuel valve on the rail until the gas coming out was around ambient temp (seemed to be adequate pressure), then tried to start it and still won't start but cranks just fine.

I guarantee if I try again in 1-2 hours, it will start.
FYI it is 92 degrees here right now.
 
Do you have spark? Maybe your coil is "heat soaked"... So you KNOW the pump is making pressure.

Fuel, ignition source (spark) and oxygen. You just ruled out two of them.
 
Do you have spark? Maybe your coil is "heat soaked"... So you KNOW the pump is making pressure.

Fuel, ignition source (spark) and oxygen. You just ruled out two of them.

So you're saying it's most likely that it's either my ignition coil or my CPS? How can I test to see if that is the cause?
 
You have to verify if you DO or DO NOT have spark when the symptoms occur. And yes, it can be either of those. I would replace the CPS first because likely it has not been done before- they seem to go between 65k-100k miles. Then look into ignition coil.

Btw: Have you done a tune up yet? Replace the distributor cap, rotor, wires, plugs, fuel filter, air filter, etc...
 
You have to verify if you DO or DO NOT have spark when the symptoms occur. And yes, it can be either of those. I would replace the CPS first because likely it has not been done before- they seem to go between 65k-100k miles. Then look into ignition coil.

Btw: Have you done a tune up yet? Replace the distributor cap, rotor, wires, plugs, fuel filter, air filter, etc...

I have not yet. I've only had it for 3 days so far Haha but it's a good idea to do soon.
How do I test if I have spark or not? Multimeter? If so, where do I put the leads?

Sorry I'm new to all this.
Thanks
 
Its okay to be new to all this. We were all new at some point. I remember my first xj 15 years ago- I knew nothing about them at that point.

You can pull the coil wire and ground it to check for spark, but it would be better to pull a plug wire from the first cylinder, put a spare plug in the wire socket, lay it on a good ground on the engine and crank her over. Look for a nice bright spark between the electrode and the housing.
 
Its okay to be new to all this. We were all new at some point. I remember my first xj 15 years ago- I knew nothing about them at that point.

You can pull the coil wire and ground it to check for spark, but it would be better to pull a plug wire from the first cylinder, put a spare plug in the wire socket, lay it on a good ground on the engine and crank her over. Look for a nice bright spark between the electrode and the housing.

Okay I'll do that then. I'm gonna use my buddy's driveway as a workshop on Sunday lol. My plan is to do a full tune up, and also bring a CPS and ignition coil and return whichever one I don't need.
I'll let you know how it goes.

BTW.. I saw somewhere that only a little bit of fuel should come out when bleeding the rail but mine bled quite a bit of fuel. Does that point to high fuel pressure coming off the regulator or the pump? My guess is no since it still didn't fire up after bleeding but just want to make sure.
 
It will slowly bleed back the pressure to the tank over 30 min. Also If your not hard up for cash- I would replace both for good measure.

You can also switch around the fuel pump relay with another to rule that out as a problem. I have seem them get hot and then open the circuit.
 
Okay I'll do that then. I'm gonna use my buddy's driveway as a workshop on Sunday lol. My plan is to do a full tune up, and also bring a CPS and ignition coil and return whichever one I don't need.

I'll let you know how it goes.



BTW.. I saw somewhere that only a little bit of fuel should come out when bleeding the rail but mine bled quite a bit of fuel. Does that point to high fuel pressure coming off the regulator or the pump? My guess is no since it still didn't fire up after bleeding but just want to make sure.



It's proportionate to how long you held the bleeder open. It's good it came out with force. I had a CPS fail in a stupid way once. Middle of a busy intersection, dies. Won't start. So I push it through the intersection. Get in and it fires right up. WTF? I limp it home popping and backfiring and lots of pinging. Not good. I finally get around to the CPS. Look at it and the harness leading into it was breaking a wire off and causing loss of contact. The sensor it self was perfect just the wiring. I was in need of a running vehicle so I bought a sensor. All I could get was the Chinese one. Been through 2 in a year but this one seems to be holding up better


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