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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
I wasn't saying it would help hold pressure. If the fuel rail was leaking off pressure a higher octane gas could withstand a higher temp before it vaporized.
It's not an issue of no or low pressure at startup. One turn of the key will build enough pressure as long as the fuel pump is functioning properly. It's when the Jeep is shut off. If the pressure leakes out of the rail the fuel will vaporize at a lower temp add the extra heat of the old clogged CA emission cats.
Mine always gives the multiple cylinder misfire cel.
You had heat soak issues and a cracked head. Not applicable to every 00-01 XJ.
If my head has been cracked for 3 years my motor is definitely a trooper.
I think the octane is a non issue at this point. The low fuel pressure when trying to start is. but its not because the fuel is vaporizing, its because the fuel is leaking... either back into the fuel tank through a faulty fuel pump check valve or out of a leaky injector. if it is leaking through the injector and into the manifold then you would actually want the gas to evaporate as quick as possible in the intake manifold so that it doesn't cause a temporary over rich condition. in that case per your octane theory you would actually want a lower octane so that it vaporizes faster.
If your jeep starts right up with one turn of the key chances are you dont have a bad enough leak to justify a problem.
On my old jeep the pressure drop off was so bad that if it sat overnight it required a poor mans prime, but i was ok doing that instead of dealing with my rotted out fuel pump retaining ring.
The reason i mentioned the faults is because the OP stated in his first post that he had a cylinder 3 and a cylinder 4 faults not a random miss. The fact that he mentioned those two specific cylinders and combined with knowing that is where the heads like to crack, is why i jumped, perhaps prematurely, onto my head gasket bandwagon so fast.
I'm not refuting that heat-soak is an issue. which is why i repeatedly said that the proper diagnosis should be followed. My heatsoak i experienced was not the same that most people experience. it wasn't an electrical issue causing a hard start it was mechanical. it would start after an ever so slightly extended crank then would run with a steady misfire for about 20 seconds progressively getting better. if i reved it up and cleared the cylinder of coolant and after the spark plug dried off enough it ran normally. this has been a non issue since replacing the head.
I did search on the heat soak issue before posting, but apparently I didn't read deeply enough as I thought most people mitigated the issue with the fixes mentioned in the TSB.
I got the information I needed - thanks all! If a mod can/wants to close this thread, that is fine with me.
I did search on the heat soak issue before posting, but apparently I didn't read deeply enough as I thought most people mitigated the issue with the fixes mentioned in the TSB.
I got the information I needed - thanks all! If a mod can/wants to close this thread, that is fine with me.
Someone once said the heat soak is caused by the ethanol in the gas vaporizing in the fuel rail while the vehicle is off. The vehicle temperature will rise for for x amount of minutes after you shut it down. Without the constant flow of gas and the rise in temperatures, the excess heat causes the ethanol to vaporize. I always wanted to test the theory and run straight gasoline all the time, but I do not have a gas station that sells it close enough. I opted to put a timer on my electric fan and it has helped.....edit--just found a gas station close by. I will start running straight gas in mine and see if it helps.
Someone once said the heat soak is caused by the ethanol in the gas vaporizing in the fuel rail while the vehicle is off. The vehicle temperature will rise for for x amount of minutes after you shut it down. Without the constant flow of gas and the rise in temperatures, the excess heat causes the ethanol to vaporize. I always wanted to test the theory and run straight gasoline all the time, but I do not have a gas station that sells it close enough. I opted to put a timer on my electric fan and it has helped.....edit--just found a gas station close by. I will start running straight gas in mine and see if it helps.
A higher octane gas will not help the fuel rail hold pressure, only slow the combustion slightly. I suggested the poor mans prime to help diagnosis this issue. By turning the key on and waiting 5 seconds and repeating before starting you are priming the fuel rail and building pressure, if the cause of your hard start was because of low fuel pressure this would eliminate the hard start.
The reason i'm not sold on the heat soak is because the computer isolated two particular cylinders as misfiring, not a random cylinder misfire which I think would be more likely under the traditional heat-soak theory. Mine is still a heat-soak theory, just not the one people are familiar with.
My jeep was only symptomatic in the summer or when allowed to sit for a week or more. when it finally came to the point where the cooling system was building full pressure within a matter of a minute and the heat began to suffer because air was being pumped into the heater core.i began to order parts for the head job. I suspect the reason my particular head blew was that a previous owner had overheated the jeep due to low coolant caused by a faulty freeze plug replacement ( they used a rubber replacement on the rearward most plug.) as well as a rotted out second to rear plug.
After cylinder head dissasembly. Note the Number 4 Piston
if you can pull the plugs on 3 and 4 and the pistons are exceptionally cleaner than othersthen that verifies it.
but again i'm completely advocating crossing all the other bridges first. I went and did the full ignition tune up as well as i upgraded the injectors and fuel filter. Now those repairs I did were more because of the wanting to replace worn and tired components as well as a hope for fixing that particular starting issue.
Oh Crap... I too am currently having this hot start up issue and when I replaced the spark plugs today, that #4 plug was colored just the same as that #4 piston in this picture... Great!
My hot start up problem happens with the hood open or closed. And it does have the slow mystery coolant disappearance thing, has since I bought it even after a whole new cooling system replace. The hot start up problem has only started with in the last three months tho and is getting worse and the coolant bottle leaks down faster.
Thanx for the picture and description XJRed96= I'll be checkin out your other thread next.
03-23-2017, 06:15 AM
