GM 3800 series II low mpg and now will not start

  • 1998 OLDSMOBILE 88
  • 6 CYL
  • FWD
  • 110,000 MILES
1998 Oldsmobile 88 98 Low MPG can smell gas but not see it.

1998 Oldsmobile 88LS 3.8L series II. I am getting only 19 MPG. The car normally got 22-26. I have replaced the gas tank filler neck, cap & vent (With one out of a 92) and 3 sections of fuel line coming from the tank with rubber fuel lines (quick connect crap) last summer.
I can smell a little gas but cannot see any obvious leaks. Even put the front wheels on ramps to get gas in the filler neck hose and still can see nothing leaking. Tires are not flat either.
Car runs fine and I have no trouble codes.

Update: The car failed to start today. It starts momentarily and immediately stalls out. The fuel pump seams to run longer then normal when the key it turned and I can hear gas in engine when pump is on followed but what sounds like a suction noise when pump turns off. Acts and sounds like a leak in the main feed fuel line. Still no visible gas anywhere under the car and no codes.

Pressed the fuel regulator valve and got gas to shot to the opposite side of the hood when pump is on. Appears to be getting fuel. Took return fuel line off regulator. Gas comes out of regulator but can be stopped by placing my thumb over end of tube. Not sure if its 50 psi. Took a spark plug off and turned car over. Plenty of spark. Small blue spark when turning over and large bright spark as the engine sputters.

I bypassed security (key resistor pellet) system about a year ago with resistor and installed a remote starter last month.

Still no codes.
Do you
have the same problem?
Saturday, January 8th, 2011 AT 10:29 PM

1 Reply

First, you need to check the fuel pressure to make sure it is strong enough. You will need a pressure gauge, but most parts stores will lend one to you. Check that. Also, was there any fuel in the vacuum hose? One last thing. Make sure the injectors are getting power.

As far as the fuel leak, you need to check above the fuel tank and check around the injectors to make sure the o-rings aren't leaking. Also, if you replaced steel fuel line with rubber, check them.
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Sunday, January 9th, 2011 AT 6:58 AM

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