 Is fuel filter unidirectional? |
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| andreic |
 May 25 2018, 12:51 PM
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#1
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Member  Group: Members Posts: 172 Joined: 21-December 15 From: Madison, WI Member No.: 19,479 Region Association: Upper MidWest  |
I just replaced the fuel pump and all the fuel hoses on my 1972 Porsche 914 1.7L. Now I don't get any fuel pressure when running the pump.
The pump (3 port) was refurbished by one of the members here, and looks very good. But I did not test it outside of the car. When I apply power to it it certainly runs. All the plumbing was redone to respect the original plumbing. So far I have checked that there are no kinks in the lines, and I have attached a fuel line to the fuel pressure port (on the driver's side injection rail) and put the other end of it in a portable gas can. Nothing comes out of it when running the pump. The one thing that I wonder is if the fuel filter could be the issue. I bought a cheap one from amazon, which looked exactly like the original one (like a cube) but turned out to have one port 1/2", the other 5/16". As it is plumbed now, the fuel line from the tank goes to the 1/2" port, and the 5/16" port is hooked up to the intake of the pump (port farthest away from the check valve on the pump). Could it be that the fuel filter is completely choking the flow, if it was installed backwards? Another thought I had was that maybe when the pump was rebuilt, maybe the wires at the electrical connector may have been switched, and the pump now runs in reverse. Is there any way to check that? (When I run the pump, I can sometimes hear gurgling in the tank, as if air was being pumped in, but as I said there is no fuel pressure.) Thanks for any suggestions, Andrei. |
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| andreic |
May 25 2018, 12:55 PM
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Member Group: Members Posts: 172 Joined: 21-December 15 From: Madison, WI Member No.: 19,479 Region Association: Upper MidWest |
I should say that when I tested the pump with an external 12 volt source, I applied the positive terminal to the spade on the pump which is the first one when going clockwise from the little dot on the circumference of the connector. On my old pump that spade is labeled "13". Is that where the "+" should go?
Thanks. |
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| Mark Henry |
May 25 2018, 01:03 PM
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#3
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
A very long time ago I installed a filter (or was it a pump? long time ago) and had no pressure.
After a full day of head scratching I found it had little internal dust caps...doh! (IMG:style_emoticons/default/wacko.gif) |
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| jcd914 |
May 25 2018, 06:38 PM
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#4
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Advanced Member Group: Members Posts: 2,081 Joined: 7-February 08 From: Sacramento, CA Member No.: 8,684 Region Association: Northern California |
Typically filters are designed for flow in one direction and have some sort of indication of the flow direction.
However I have not seen a fuel filter the only allowed flow in one direction. I would closely rechecked the fuel hose connections most of the problems people have had with no fuel after replacing the pump has been the pressure outlet plumbed to the return line. So the pump was trying to pump fuel backwards through the fuel line loop in the engine compartment. Fuel can't go past the fuel pressure regulator. Jim |
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| JeffBowlsby |
May 25 2018, 07:34 PM
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#5
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914 Wiring Harnesses Group: Members Posts: 8,522 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None 
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Test the pump! Remove the output hose and see if you get fuel flow out of the pump when the key is turned or add a constant +12V source. The filter will have a flow directional arrow on it if it is directional.
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| rhodyguy |
May 26 2018, 10:26 AM
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#6
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,082 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
The intank filter sock/screen may be fouled. They can get sucked flat by the pump. Have you pulled fuel tank yet?
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| Dave_Darling |
May 27 2018, 12:37 AM
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#7
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914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
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At least some of the filters have arrows on them that indicate the direction that fuel is supposed to flow through them.
Can you hear the pump run when it is supposed to? Make sure you didn't hook the pump up backwards, either the hoses or the electrical connections!! --DD |
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| McMark |
May 27 2018, 07:17 AM
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#8
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
The original 3-port pump has markings on it you should familiarize yourself with to double check your work.
The fuel ports have the following markings: Attached image(s) 
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