: Fuel Pressure Regulator and hot start problems

09-10-05, 08:37 PM
I'm posting this because I think I've fixed my hot start problem and wanted to share an extra insight. This summer my 96 SLS has been hard to start hot, even after leaving it outside all day without running, it would be hard to start if the temperature was above about 85. We typically associate these problems with a leaking fuel pressure regulator, and that was the cause of my problem, but the diagnosis wasn't as easy as I thought it would be.

Usually, we would say to disconnect the vacuum line from the fuel pressure regulator and turn the ignition on to run the fuel pump. If fuel leaks from the vacuum nipple, the FPR is bad. In my case, I checked that %&(@# thing probably 10 times, and it never once leaked a single drop from the nipple. Our friend Ranger suggested to me that I try putting a vacuum gauge on it to see if it holds a vacuum. Guess what? Even though the thing didn't leak a drop of fuel with the vacuum line disconnected, when I applied a vacuum to it, it leaked like a sieve. I just replaced it with a new one, and the new one does hold a vacuum.

So, word to the wise, if you're having hot start problems and the FPR doesn't visibly leak, try using a handheld vacuum pump. If it won't hold a vacuum, it's bad and needs to be replaced. It might also work if you remove the FPR and hold it upside down. If fuel has seeped past the internal diaphragm and is sitting on top of it, fuel will come out the nipple when you turn it upside down. If you get any fuel out of the nipple, replace the FPR. For my 96 SLS, a new FPR was about $45 delivered from www.rockauto.com. That should solve the hot start issue, and it will save you mechanic labor costs and high parts markup at a reputable shop or <shudder> a stealership.

Good luck, and my thanks again to Ranger for his good advice...

09-10-05, 08:42 PM
Glad to hear you got it figured out Mike. I love a happy ending.