Fuel pressure drops on Chevy minivan after warmup

  • Article by: PAUL BRAND
  • Updated: February 8, 2013 - 11:02 PM

Q: Our ’93 Lumina minivan has the 3800 V6 engine. Fuel pressure is good when the key is turned on and while it warms up. As soon as it warms up, and I’m assuming goes into “closed loop” operation for fuel-air mixture calculations, the fuel pressure smoothly drops to zero over about 3 seconds. I’m assuming the computer is turning the fuel pump off. The factory manual doesn’t describe what inputs to the computer would cause it to shut down the in-tank fuel pump. My suspicions would point toward either the fuel pressure regulator or the oxygen sensor. Can you enlighten me?

A: There’s one more scenario that could shut the fuel pump off with the engine running — low oil pressure. The fuel pump is controlled two ways. The ECM — electronic control module — grounds the fuel pump relay when the key is turned on for 2 seconds to bring fuel pressure up quickly for startup. When the ECM sees a “start” signal indicating the engine is cranking, it grounds the fuel pump relay to allow the engine to start. Once running, the relay is continuously grounded by the oil pressure sender — as long as oil pressure is adequate. If oil pressure drops below a safe level, the oil pressure sender will open the ground to the relay to stop the pump and protect the engine from mechanical damage. Low oil pressure or a faulty oil pressure sender could conceivably be the problem. It is possible to bypass the sender to operate the relay out of circuit as a test.

Another possibility is a clogged sock filter on the fuel pickup in the tank. As the fuel pump picks up fuel to pump forward to the engine, debris in the tank may be progressively restricting fuel flow through this fine-screen filter until fuel pressure falls to the point of stalling the engine.

The oxygen sensor would not be a factor in the total loss of fuel pressure and it would seem unlikely that a failed diaphragm in the fuel pressure regulator could bleed fuel pressure down to zero. But, if the vacuum line to the regulator shows evidence of liquid fuel, the diaphragm has failed and the regulator should be replaced.

 

Q: My 2005 Nissan Altima 2.5-liter automatic with 72,000 miles has a shift shock when shifting from first to second gear and from second gear to third gear. We have already done transmission oil flushing but no change. An OBDII scan by our local dealer showed no codes. The auto transmission light and service engine light are not on. What could be the solution to this?

 

A: That’s a tough one but here are some possibilities. Harsh shifts are often related to high hydraulic line pressure in the transmission, sometimes related to high operating temperatures. Other potential issues include solenoids or accumulators that buffer pressure during shifts or a problem with the control valve assembly. But don’t overlook the possibility of a misadjusted throttle position sensor, inaccurate speed sensor or transmission fluid temperature sensor.

 

Q: Just recently, for no apparent reason, the air bag light on my 2001 Mercury Villager started flashing. The local repair shop couldn’t get its computer to communicate with the car’s computer, so is there a way to reset the light or is there a sensor problem?

 

A: Believe it or not, it is possible to manually display air bag fault codes in this vehicle. Press and release the LH front door courtesy lamp switch five or more times within 7 seconds of switching on the ignition. If there is a current air bag fault, the code will be displayed as a sequence of flashes — one through nine — of the air bag warning light. Have your local shop read the procedure in its ALLDATA database, or take your vehicle to a Lincoln dealer.

  • get related content delivered to your inbox

  • manage my email subscriptions

ADVERTISEMENT

Kansas City - WP: J. Guthrie 3 FINAL
San Francisco - LP: T. Hudson 2
Detroit 10/26/14 8:30 AM
Atlanta
Buffalo 10/26/14 12:00 PM
NY Jets
St. Louis 10/26/14 12:00 PM
Kansas City
Houston 10/26/14 12:00 PM
Tennessee
Minnesota 10/26/14 12:00 PM
Tampa Bay
Seattle 10/26/14 12:00 PM
Carolina
Baltimore 10/26/14 12:00 PM
Cincinnati
Miami 10/26/14 12:00 PM
Jacksonville
Chicago 10/26/14 12:00 PM
New England
Philadelphia 10/26/14 3:05 PM
Arizona
Oakland 10/26/14 3:25 PM
Cleveland
Indianapolis 10/26/14 3:25 PM
Pittsburgh
Green Bay 10/26/14 7:30 PM
New Orleans
Washington 10/27/14 7:30 PM
Dallas
New Orleans 10/30/14 7:25 PM
Carolina
Dallas 117 FINAL
Orlando 92
New York 80 FINAL
Toronto 83
San Antonio 87 FINAL
Houston 96
Miami 104 FINAL
Memphis 98
Minnesota 113 FINAL
Chicago 112
Phoenix 105 FINAL
Utah 100
Sacramento 93 FINAL
LA Lakers 92
Denver 112 FINAL
Golden State 119
Portland 99 FINAL
LA Clippers 89
Dallas 3 FINAL(SO)
New Jersey 2
Tampa Bay 4 FINAL
Winnipeg 2
Vancouver 3 FINAL
Colorado 7
Carolina 3 FINAL
Edmonton 6
Columbus 1 FINAL
Anaheim 4
Connecticut 21 FINAL
(18) East Carolina 31
Miami-Florida 30 FINAL
Virginia Tech 6
So Florida 17 FINAL
Cincinnati 34
Troy 13 FINAL
South Alabama 27
BYU 30 FINAL
Boise State 55
(6) Oregon 59 4th Qtr 8:12
California 35
North Texas 10/25/14 11:00 AM
Rice
UAB 10/25/14 11:00 AM
Arkansas
Rutgers 10/25/14 11:00 AM
(16) Nebraska
Maryland 10/25/14 11:00 AM
Wisconsin
Texas 10/25/14 11:00 AM
(11) Kansas State
Minnesota 10/25/14 11:00 AM
Illinois
Memphis 10/25/14 11:00 AM
SMU
North Carolina 10/25/14 11:30 AM
Virginia
San Jose St 10/25/14 12:00 PM
Navy
Northern Ill 10/25/14 12:00 PM
Eastern Mich
(25) UCLA 10/25/14 1:00 PM
Colorado
Akron 10/25/14 1:00 PM
Ball State
Massachusetts 10/25/14 1:00 PM
Toledo
Ohio U 10/25/14 1:00 PM
Western Mich
Ga Southern 10/25/14 1:00 PM
Georgia State
Kent State 10/25/14 1:30 PM
Miami-Ohio
Oregon State 10/25/14 2:30 PM
Stanford
Fla Atlantic 10/25/14 2:30 PM
(23) Marshall
Louisiana Tech 10/25/14 2:30 PM
Southern Miss
(1) Miss State 10/25/14 2:30 PM
Kentucky
Georgia Tech 10/25/14 2:30 PM
Pittsburgh
(22) West Virginia 10/25/14 2:30 PM
Oklahoma State
Texas Tech 10/25/14 2:30 PM
(10) TCU
Michigan 10/25/14 2:30 PM
(8) Michigan State
Boston College 10/25/14 2:30 PM
Wake Forest
Central Mich 10/25/14 2:30 PM
Buffalo
Vanderbilt 10/25/14 3:00 PM
Missouri
Old Dominion 10/25/14 3:00 PM
Western Ky
UNLV 10/25/14 3:00 PM
Utah State
Temple 10/25/14 4:00 PM
UCF
(15) Arizona 10/25/14 5:00 PM
Washington St
Texas-El Paso 10/25/14 6:00 PM
TX-San Antonio
Wyoming 10/25/14 6:00 PM
Colorado State
Syracuse 10/25/14 6:00 PM
(21) Clemson
Texas State 10/25/14 6:00 PM
ULM
(3) Ole Miss 10/25/14 6:15 PM
(24) LSU
(4) Alabama 10/25/14 6:30 PM
Tennessee
So Carolina 10/25/14 6:30 PM
(5) Auburn
(13) Ohio State 10/25/14 7:00 PM
Penn State
(20) USC 10/25/14 9:00 PM
(19) Utah
(14) Arizona State 10/25/14 9:45 PM
Washington
Nevada 10/25/14 10:59 PM
Hawaii
(2) Florida State 10/30/14 6:30 PM
Louisville
Troy 10/30/14 6:30 PM
Ga Southern
Cincinnati 10/31/14 7:00 PM
Tulane
Tulsa 10/31/14 7:00 PM
Memphis
Purdue 11/1/14 2:00 AM
(16) Nebraska
(17) Oklahoma 11/1/14 2:00 AM
Iowa State
Oklahoma State 11/1/14 2:00 AM
(11) Kansas State
(10) TCU 11/1/14 2:00 AM
(22) West Virginia
Texas 11/1/14 2:00 AM
Texas Tech
Northwestern 11/1/14 2:00 AM
Iowa
Maryland 11/1/14 2:00 AM
Penn State
Houston 1 FINAL
Chicago 2
Montreal 23 FINAL
Ottawa 17
Saskatchewan 27 FINAL
Calgary 40
Hamilton 10/25/14 3:00 PM
Toronto
Brt Columbia 10/25/14 6:00 PM
Winnipeg
Hamilton 10/31/14 6:30 PM
Ottawa
Winnipeg 11/1/14 3:00 PM
Calgary
Brt Columbia 11/1/14 6:00 PM
Edmonton
Toronto 11/2/14 11:00 AM
Montreal
Connect with twitterConnect with facebookConnect with Google+Connect with PinterestConnect with PinterestConnect with RssfeedConnect with email newsletters

ADVERTISEMENT

ADVERTISEMENT

ADVERTISEMENT

 
Close