Was just reading thru the threads in hopes of finding a solution to a fuel pump issue with my 2003 XG350 L.

I dont know if there is any connection, but a few weeks after having the PCV hose & a/c compressor replaced due to it seizing from the inside, my car stalled out while driving. I brought it to my mechanic who ran a computer diagnosis on it detecting no problems. After he cleaned the fuel injector and throttle he brought it back "running fine", that is till I tried starting it an hour later ~ no go. Back to the shop... another computer diagnosis. Again, no codes. They put it up on the lift, took a rubber mallet to fuel pump and it starts up. Fuel Pump replaced. Problem solved? Not quite.

Car still wasnt running normal afterwards. Not starting on first turn and while idling at a red light, or in park, felt almost as there was air running thru the fuel line and rough vibrations in the steering wheel. While driving at times car would feel like it was going to stall. Back to my mechanic... still no codes after computer diagnosis. Fuel Pump replaced once again. Better than before, but still not quite right.

Thinking it could have something to do with the timing belt, I took it in to the dealer a week later to have it replaced at 82,500 (I know - long over due ). While there, they too hooked it up for a computer diagnostic check, with "no problems". Yet there are.

Its still not running as it did prior to the first fuel pump replacement. MPG is lower than normal. Wont start up on first try after sitting for a few hours. If gas tank reads just below a 1/4, previous problems reoccur, as well as stalling out if driving on an incline, or curve. Definitely not good when going on to or getting off a hwy ramp. (Which happened to me yesterday).

Any thoughts or suggestions that I may pass on to my mechanic to correct this problem, would be greatly appreciated.

 

You have all the classic symptoms of the "gunked tank" problem. Over time, especially in cold, damp climates, gunk forms on the walls of the gas tank. It can break loose and clog the fuel pump pre-screen, or clog the fuel filter itself.

The solution is to find the fuel filter of your XG and change it (sometimes it's outside the tank like hmaservice.com tells you, other times is in the tank as part of the fuel filter like everyone else says), clean the fuel pump screen, and clean the fuel tank.

You can check the problem by removing the fuel pump/filter out of the tank, look in the tank, look at the fuel screen, and replace the fuel filter all at the same time.

Remove the filter/pump by removing the back seat. Here's a really good instructions page for and Elantra XD, it's almost the same thing: http://www.elantraxd.com/DIY/fuel.php

 

Thanks for the suggestion but after speaking with my mechanic, he said he had already checked my tank, as well as replaing the filter when the new fuel pumps were put in & said they were both clean. No gunk build up what so ever.

Any other thoughts or suggestions would be greatly appreciated.

 

Ok, well problems like you describe indicate a fuel problem. The key symptoms are:

Rubber mallet test.

Absence of trouble codes.

Trouble below 1/4 tank, going around turns, etc.

I suggest you have a fuel pressure test done. It requires a special pressure gauge to be hooked up to your fuel system under the hood. You might need to take it to the dealer for this. If the pressure test checks out ok, then you have definitively ruled out that problem.

 

Our 2002 XG350L runs fine generally but now and then just dies, sometimes at a very inopportune time -- it's a serious safety issue. Stopping and turning off the ignition for as little as 20 seconds allows a normal restart and continued operation.

I first though it was a clogged fuel tank vent, since the symptoms were fuel starvation-like, but quickly opening the fuel cap didn't produce the tell-tale whoosh of incoming air. After a couple of years of mechanics' bafflement, I installed a OBDC recorder to see what was going on. The only clue is that all 4 O2 sensors go to zero as the failure occurs, indicating a lean mixture.

Our working theory is that the fuel pump is overheating and turning itself off (as designed). Since it's immersed in fuel, it cools rapidly, the thermal sensor resets, and you can restart and go. This is theory only at this point -- if anyone has any ideas, I'd love to hear them.

I see there are many, many "compatible" pumps offered by online vendors -- any advice pro or con any particular vendor's pump?

 

The big puzzlement is the fact that when we experience the failure, we can coast to a stop, turn off the ignition, immediately restart, and we're good to go. The question is -- what sort of failure is cured by turning the ignition off or on?

Anyway, our mechanic says there's a Hyundai service bulletin (I haven't found it yet) pointing to the throttle body (a $1200 part). I really hope that's not it.