How long should fuel pressure hold?

Bob Avellar

May 25, 2001
Mine will stay at 38 psi without moving at all for 10 minutes. Then it proceeds to drop of at a rate of about 1 psi/minute. (After the fiirst 10 minutes are up it drops off by 18 lbs iover the next 14 minutes). I don't understand why it can hold rock solid for the first 10 minutes and then decide to drop off? The motor was only run for about a minute before shutoff so I don't think the heat from the motor would be enough to heat the fuel in the rail and cause the pressure to rise and offset any bleed down. I know when I used to shut the car off when it was hot I would normally see the pressure actually go up for a while before it began to decrease. Don't think heat was a factor when watching it today. The reason I was asking is because I have been having a rough and rich idle (sometimes) at startup recently like an injector was bleeding down and flooding a cylinder. After a few seconds it would clear and then run fine. Doesn't always do it though. Usually a cold startup caused the problem. I have a new T+ and extender chip along with a LT1 MAF. Runs ok after the initial smokey, rough idle. Again, doesn't always do it. I did put some injector cleaner in the tank and startup today (before the FP test) was fine. Can't actually drive the car yet since not all the body parts are on it yet so I can only drive it a few hundred feet in 1st and second gear so I know the chip can't learn in real good yet. I don't think the T+ is the problem though. Who knows, maybe it will be fine now. Just curious how long your FP hols under similar conditions.
mine holds for about 30 to 45 minutes. should be fine. when i did have a fuel probem it dropped immediately after i shut the car off.
Thanks. Sorry guys. I should have just done a search like I usually do. There are a ton of posts on this thread. I usually read just about every post on most of the forums but didn't remember so much discussion on this topic. Use that search engine!!