My fuel rail is losing pressure after the engine is off for more than an hour. I assume this means a bad fuel pump or a bad fuel pressure regulator. Since the regulator is the easier thing to get at, I bought the replacement part and I'm going to try to replace it myself. Has anybody replaced this item? I'm just wondering if this is a risky replacement in terms of giving myself a fuel leak. I'm worried about having ill-fitting hoses after I put the new unit in place. The attachment shows the new unit that I will be installing.

This is a 1999 Sonata GLS V6, 2.5 DOHC engine with 78,000 miles.

Should be pretty easy to do. I wouldn't worry too much about spilled gasoline, just avoid open flames or sparks from the battery. Disconnect the negative battery cable.

Shouldn't take to long, if it's plastic take care not to over tighten and crack it. Before you start if you still have fuel pressure you might try removing the fuse to the fuel pump then start the car let it run until it dies. On the fuel pump, I'll check one this morning, but I think you can gain access to it by removing the back seat. I'll post a few pictures if you can. Good luck and as always be EXTRA careful when dealing with gas you don't get a second chance!

This post has been edited by Elvis: Nov 17 2009, 07:47 AM

Thanks for the encouragement. I'll give it a try tomorrow night and see if it helps. Regarding the fuel pump I saw that, indeed, it is accessed under the rear seat. I saw a description of the procedure somewhere online. The drawings on hmaservice.com are pretty hard to understand. I would certainly appreciate any information about that procedure.

Here's a DIY for and Elantra XD series. I'm sure it's similar:

http://www.elantraxd.com/DIY/fuel.php

Success!!
With a minimal amount of swearing, I was able to access and replace the regulator. And the first start this morning was instantaneous, instead of requiring a few seconds of cranking.

To make things even better, I noticed a definite improvement in smoothness when accelerating from a dead stop. There used to be a hesitation after pressing the accelerator pedal, but now it responds instantly. That was a bonus that I wasn't expecting.

However, something worrisome has resulted: there is now a rough shift when going from 2nd to 3rd gear. It seemed to go away after driving for several minutes last night, but it was intermittently occurring this morning. Does the transmission have some adaptive sequence that "learns" the best shift point? I seem to recall hearing that sometime in the past.

Thanks for the support!

Yes, the transmission does an adaptive learning thing. You reset it by disconnecting the negative battery cable for 10 minutes. That will reset all the electronics. Then you just drive it normally for a week or two.