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Registered
Join Date: Apr 2003
Location: Carnation, WA
Posts: 623
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Fuel pump swap rear for front?
I have been troubleshooting a fuel starvation problem. I can't maintain fuel pressure. The car will idle and pressure is around 48psi, but as soon as I put my foot on the gas the pressure drops to 35, and I am sure it is worse when under load. The car runs really lean.
I thought it was the rear fuel pump because it seemed very noisy compared to the front pump. So I just replaced it and the problem is still there. So I just spent a few hundred dollars replacing the wrong pump. I now think the rear is noisy because the front pump is not supplying the rear with enough fuel. The front is a slightly different part number. Does anyone know if I can use my old rear pump in the front, and are the fittings the same?
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David |
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07-20-2007, 11:46 AM
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Join Date: Mar 2006
Location: Elk Grove, CA
Posts: 513
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I just had the same problem....noise from the rear and the indy told me that he thought the front pump was going...so I bought a new front pump but haven't installed it yet. I don't believe they are interchangeable.
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1987 factory Slantnosed 930 Cabriolet/Guard's red 2002 Midnight Blue 996TT X50 1999 Iris Blue 996 (Dash fire burned and totalled 9/07) |
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07-20-2007, 09:25 PM
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Join Date: Apr 2003
Location: Carnation, WA
Posts: 623
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I just figured out my problem and it was not the fuel delivery or pumps after all. Turns out an entire bank of coils was firing intermitently and sometimes not at all, and this was giving a lean reading on the wideband, lack of power etc. Last time I had the engine out I didn't put the rubber boot back properly on the connection to this bank of coils and it had moisture in it. Its really surprising how well the engine idles on only 3 cylinders!
Costly error, but I got the beast running again and I have a perfectly good spare pump. I now understand the pressure drop off idle too and will be making a few adjustments to my fuel pressure regulator.
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David |
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07-22-2007, 03:01 PM
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Join Date: May 2005
Location: Loxahatchee, florida
Posts: 2,894
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make sure you put oil in the pump it will rust and seize up they are shipped with oil in them and if you bench test it you have to put oil right back in or it will be seized up a few days later. ask me why I had to replace BOTH pumps when all I really needed to do was have the WUR rebuilt and flushed. I pulled both pumps out and ran them then put them back in. they never ran again. the reason they were not running in the first place was a problem with the engine harness plug by the time that was sorted out it was a few days later and both pumps were seized up from being exposed to air.
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88 turbo Guards red Targa slant nose, and yes I am a horsepower junkie, 3.4liter,7.5 to 1 JE pistons, Adjustable WUR, Imagine fuel head, 1 bar waste gate headers,allthe cis toys. Now apart to become the next EFI monster. fabbing my own intake, headers Individual throttle bodies, MS-3, pauter rods, Xtreme twin plugged heads, gt-2 evo cams cop's. 2019 Silverado 6.2L |
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07-25-2007, 12:06 AM
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,249
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Did you peel the aluminum housing apart and find that they rusted inside?
I doubt it... You said you took them out of the car and ran them? Running them one second without fuel or oil in them to lubricate the pump rollers could have damaged them and the housing they spin in enough causing them to seize or sound nasty if you get them to run again. Try some WD 40 in the pump and see if you can get it running by tapping on it and jerking it in a rotational motion while hooked up to 12 volts to see if you can get the pump motor to spin up. |
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07-25-2007, 12:35 PM
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