Hello,I have a 1998 Bonneville with 145k miles. It runs great but sometimes when warm it cranks alot and if you just lightly touch the gas it will fire right up. It cranks fast enough just wont catch. I ran Chevron Techron thru a tank full and replaced the Idle Air Control Valve and cleaned the MAF sensor. It never throws a trouble code and it will fire and run fine when cold even below zero ! First thing in the morning it fires right uo no problem ever when cold. Also sometimes even when hot it starts right up it seems to be more after its been driven and shut off for about 20 mins that it cranks too much and again if you just open the throttle it will fire and run fine. Goes down the road and runs like a champ,gas mileage is the same its always been about 28 mpg,any others run into this ? any ideas or better places to post ?Thanks a bunch ! Wires,plugs etc are all in god shape and fairly new. Again this car runs down the road like it has 10k miles on it and its in mint shape !

My brother has a 1995 Lesabre and it too does the same thing,hs has 180k Miles and he'* just gonna live with it.

Sounds like it could be the Fuel Pressure Regulator.

I'll 2nd that, the 20 min 'cool' down is dropping fuel pressure. Hot or cold starts and the fuel pressure is fine.
Cold the pressure would have dropped off enough to cause the pump to turn back on and pressurize the fuel system.

Isn't there a test he can do, like pinching the vacuum line or something like that?


-justin

You need a pressure gauge to test the regulator......its called a leak down test and a quick search will get the info needed.

tell me where it is ? I looked on the fuel rails both front and rear and I only see one small valve sticking out with a vaccuum line on it but it looks like part of the fuel rail > anyone got a pic ? Thank you

No pic handy, but as you stand in front of the car, it will be on the right hand side of the front fuel rail.


EDIT > Lookit what I found...



http://www.autozone.com/servlet/UiBr...3d80178fbc.jsp

and no fuel came out but I broke the hard plastic vaccuum line,I fixed the line but not sure if you test it while running or shut off. Shut off nothing come out but if you pull it off while running after about 15 seconds a few spits of gas come out of the nipple on the regulator,is this normal ?? Its a real small regulator with a snap ring that holds it together,kinda a cheesy looking thing. PLEASE only respond if you are sure if this is normal or not and thanks a bunch !

When shut off, you should get fuel coming out. The whole point of this thing is to make sure you have the right amount of pressure.

When I get home, I can break out my Factory Service Manuals and give you the factory test instructions.