Difficulty starting '01 XJ...please help!

[Bullitt4113]

Ive owned my '01 XJ for about 6 months now, and since I bought it I always had a hard time with it starting. Let me preface this by saying, the LONGER I let it sit, the easier it is to start. I'm talking days, not hours though.

Every morning when I start it, normally it will start almost right away, maybe a few cranks. From then on all throughout the day it takes 2 key turns to make it fire. Turn, crank crank crank crank crank, let it go, turn, crank crank crank FIRE. Once it fires up it runs a little rough for a few seconds, then smooths out. Once it has smoothed out, I have good oil pressure and the truck runs awesome. I did however get a po303 "CYL 3 misfire" code the other day.

Anyhow, I've already checked the fuel pressure at the rail to see if it looses pressure, which it does not. Makes sense since it will fire perfectly if I don't touch it for a day or so. I have checked the IAC valve which looks like it had been replaced, and I cleaned that up. I wrapped the fuel rail and injectors in 2000 deg heat wrap because I thought it might be a vapor lock issue. That didn't work. I have also changed the plugs and that didn't do anything. Yesterday I changed the crank position sensor, and it didn't do anything either. It seems to maybe run a bit smoother, but no change in the way it cranks.

At this point I don't know where to go. I hate to bring the truck to the dealer to have them diagnose it, I really don't have the extra cash for that and I hate other people working on my vehicles. I'd really like to fix it, I just need some suggestions as to where to look next.

Anyone here have any experience with SCAP Jeep in Fairfield, just in case it comes down to that?

[customcreationsllc]

The garage I work at is not too far away Imported Automotive at 8 Brock St. Trumbull 203-445-0277, don't mistake by the name we work on everything but have all the special scanners for the foreign cars.
We can check all the sensors before replacing them.


If I had to totally guess. I would start by looking at the temp sensor readings.
Not the one on the dash but the one the computer reads just plug in a scanner and see what it says.

Crank/cam sensors make no sense, plus I can read the signals very easy.
Fuel would have been one to check but you said you did that.
If it idles fine after starting no way it could be an IAC.

If it is doing it all the time makes it that much easier to know when you fixed the problem.

~Justin

[ct67_72]

The garage I work at is not too far away Imported Automotive at 8 Brock St. Trumbull 203-445-0277, don't mistake by the name we work on everything but have all the special scanners for the foreign cars.
We can check all the sensors before replacing them.


If I had to totally guess. I would start by looking at the temp sensor readings.
Not the one on the dash but the one the computer reads just plug in a scanner and see what it says.

Crank/cam sensors make no sense, plus I can read the signals very easy.
Fuel would have been one to check but you said you did that.
If it idles fine after starting no way it could be an IAC.

If it is doing it all the time makes it that much easier to know when you fixed the problem.

~Justin

This. You really need a scanner to monitor data, but it does sound like a coolant temp sensor.

[Bullitt4113]

Thanks for the info guys. I'm going to double check my fuel pressure to see if I heave a leaky injector as I've done a lot more reading and this seems like a possibility. It looks like the coolant temp sensor had been changed before I got the truck. I guess I don't understand exactly how that would contribute to the cranking issue, though. Can someone explain this please?

[ct67_72]

The ecm determines the amount of fuel needed to start based on the engine temp. Think of it like not having a choke on a carb on a cold day. You can't get the extra fuel and it doesn't want to start. Your ecm is essentially doing the same thing.

[customcreationsllc]

Just like Dan said.
If the computer in your case thinks the engine is always cold it will be too rich to start when it is hot like starting with the choke on. But start perfect when the engine is cold.
The temp sensor is just a variable resistor and I think it is a two stage sensor has 1 range for cold then jumps to a second range for hot.
If you look up the temp specs you can use an Ohm meeter to measure the resistance then look at the table to see what that means in temp.
If you plug just about any scanner it should tell you the engine temp just look to see if it make sense, it might be in C°

Seen it plenty of times.
One time I tried adding a resistor to make the engine think it was hotter than it was so it would turn on the fans sooner, but then started like crap on clod days because it thought it was already hot.

If you just turn the key on for a few seconds before cranking to let the fuel pump run. Does it start right away? Then it would sound like a fuel pump issue.
Fuel pumps have check valves to hold pressure in the fuel line, or it could be an injector leaking less common.

I would trust new parts to be good.
Even brand new parts, we get plenty of brand new bad parts.

I usually work Mon and Wed nights if you want to stop by only take a second to plug in the scanner. If I'm not there I'm sure the other guys will help you out.
Or stop by my house one friday night just not this week.
I also have a Snap-on Vantage a oscilloscope (graphing multimeter) you can watch the signals from all the sensors in real time. Makes it easy for diagnosing sensors.

~Justin

[Bullitt4113]

Just like Dan said.
If the computer in your case thinks the engine is always cold it will be too rich to start when it is hot like starting with the choke on. But start perfect when the engine is cold.
The temp sensor is just a variable resistor and I think it is a two stage sensor has 1 range for cold then jumps to a second range for hot.
If you look up the temp specs you can use an Ohm meeter to measure the resistance then look at the table to see what that means in temp.
If you plug just about any scanner it should tell you the engine temp just look to see if it make sense, it might be in C°

Seen it plenty of times.
One time I tried adding a resistor to make the engine think it was hotter than it was so it would turn on the fans sooner, but then started like crap on clod days because it thought it was already hot.

If you just turn the key on for a few seconds before cranking to let the fuel pump run. Does it start right away? Then it would sound like a fuel pump issue.
Fuel pumps have check valves to hold pressure in the fuel line, or it could be an injector leaking less common.

I would trust new parts to be good.
Even brand new parts, we get plenty of brand new bad parts.

I usually work Mon and Wed nights if you want to stop by only take a second to plug in the scanner. If I'm not there I'm sure the other guys will help you out.
Or stop by my house one friday night just not this week.
I also have a Snap-on Vantage a oscilloscope (graphing multimeter) you can watch the signals from all the sensors in real time. Makes it easy for diagnosing sensors.

~Justin

Justin, thanks for the info, makes perfect sense. I'll be out of town this weekend and next weekend, but maybe one night I'll stop by the shop or we'll pick a Friday I can come up after work and maybe we can troubleshoot, I would really appreciate it.

I'm fairly new to the Jeep world, I'm really a Mustang guy at heart so some of this is Chinese to me haha. I'd love to learn as much as I can because after owning this truck for only 6 months, I can't see myself ever not owning one!

[hippie metal]

Leaky injector cause the same issue on my brothers 01' TJ

[Bullitt4113]

Leaky injector cause the same issue on my brothers 01' TJ

Yea, I'm thinking its probably either the coolant temp sensor or a leaky injector.

[customcreationsllc]

didn't you say the fuel pressure doesn't drop. Then it wouldn't be a leaky injector.

[Bullitt4113]

didn't you say the fuel pressure doesn't drop. Then it wouldn't be a leaky injector.

That's what I thought too...might have to be double checked, can never be too careful.

I sent you a PM