Bad Mechancial Pump?
Thread Starter
Junior Member
Joined: Sep 2002
Posts: 53
Likes: 0
From: Pottstown, PA
Car: 1983 z/28 t-top
Engine: 305 Carb LG4
Transmission: 5 speed
Bad Mechancial Pump?
Quick question...
Do the mechanical fuel pumps fail SLOWLY, or do they stop working...I mean is it possible to have a fuel pump that should normaly pump 5-7 psi, only do 2-3? Or will it just stop working?
Jim
Do the mechanical fuel pumps fail SLOWLY, or do they stop working...I mean is it possible to have a fuel pump that should normaly pump 5-7 psi, only do 2-3? Or will it just stop working?
Jim
Senior Member
Joined: Jul 1999
Posts: 997
Likes: 0
From: Katy, TX
Car: 1985 IROC Z-28
Engine: 355
Transmission: TH-350
Axle/Gears: 3:73
It's entirely possible. One way to tell is if there's gas in the oil. Then the diaphram has cratered and it's pumping gas into the oil. Check that first! It could still be pumping low pressure and NOT pumping gas into the oil, though.
Thread Starter
Junior Member
Joined: Sep 2002
Posts: 53
Likes: 0
From: Pottstown, PA
Car: 1983 z/28 t-top
Engine: 305 Carb LG4
Transmission: 5 speed
No gas in the oil...I had that on my 442 last winter though...really messed up my bottom end before I relized it...
Sounds like tomie to pull the old sprirter...
Thanks again!
Jim
Sounds like tomie to pull the old sprirter...
Thanks again!
Jim
Member
Joined: May 2003
Posts: 264
Likes: 1
From: SillyCon Valley, CA
Car: 83 Z-28 (Original owner)
Engine: 305 CC-carb
Transmission: Richmond 6-speed, Rear:3.73
YES, I had a bad "pump" that was not putting out enough pressure at idle.
The stock fuel pumps have a built-in pressure regulator (it's on the bottom of the pump), that's why there are TWO gas lines coming "from" the tank. The smaller line is a return.
When the regulator spring gets weak, it "returns" too much fuel, causing the supply pressure to drop.
My carb was acting like it had a weak Accel Pump. Replacing the pump/regulator fixed the "carb" problem.
Best $40 I've ever spent on the car.
The stock fuel pumps have a built-in pressure regulator (it's on the bottom of the pump), that's why there are TWO gas lines coming "from" the tank. The smaller line is a return.
When the regulator spring gets weak, it "returns" too much fuel, causing the supply pressure to drop.
My carb was acting like it had a weak Accel Pump. Replacing the pump/regulator fixed the "carb" problem.
Best $40 I've ever spent on the car.
Last edited by 83_1/2 L69; Mar 5, 2004 at 10:08 PM.
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