Hello all. My 99 XJ Sport has been sitting for about 10 days as I rebuilt the front diff. When I started it to test drive I got a P1494 code. If I read the description of this code right it has to do with the fuel system pressurizing at start up and staying pressurized till engine shut down. I noticed the last time I fueled up that the gas cap didn't do it's click thing upon tightening, it just got harder to turn. would replacing the gas cap be a plausible fix or am I going to need to look deeper into the fuel system?

Thanks in advance.

 

Maybe. Bad gas cap will throw emissions codes. Before replacing it I would check rubber evap hoses/connections. Especially the three barbs coming off the intake manifold and connections around the evap purge solenoid. If you do replace the cap, get a mopar one ($15?). I had two crappy aftermarket ones that nearly caused me to replace my charcoal canister (~$115) unnecessarily.

 

Sounds like you have a leak Detection Pump (LDP) issue, not a gas cap.


Here's some data from the diagnostics manual:


P1494-LEAK DETECTION PUMP SW OR MECHANICAL FAULT

When Monitored: Immediately after a cold start, with battery/ambient temperature
between 40 deg. F and 90 deg. F and coolant temperature within 10 deg. F of battery/
ambient.

Set Condition: The state of the switch does not change when the solenoid is energized.




Possible Causes




WIRING HARNESS INTERMITTENT


LDP SWITCH SENSE CIRCUIT SHORTED TO GROUND


LDP VACUUM SUPPLY


LEAK DETECTION PUMP


LDP SWITCH SENSE CIRCUIT OPEN


POWERTRAIN CONTROL MODULE








TEST ACT

 

Verify vacuum hoses are connected to the LDP.


Verify the electrical connector is free from corrosion and secure. Verify the electrical wiring is not chafed or broken.


Below is a diagram of the LDP. The electrical connector goes to the switch (which may be defective).

 

Upon inspection when I got home this evening I noticed that a vacuum line from the intake manifold was off. If the picture comes thru the line is circled. It was the one closest to the front of the engine. I slid it back on the nipple and will see if it stays on.

 

That's the vacuum supply to the LDP. That should fix it.