Clear Fuel Filter Almost Empty - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 07-21-2008, 12:00 PM
Member
 
Last photo:
Join Date: Jun 2004
Location: TN
Posts: 416
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Clear Fuel Filter Almost Empty

I just finished addressing a fuel starvation problem which turned out to be sender unit gasket sealer dripping down into the gas tank and ending up in the clear filter between a pressure gauge and QJet inlet. I rinsed the tank out with water, dried it, blew down the steel fuel line from mechanical pump suction back to tank, then reinstalled sender with new rubber gasket and reinstalled tank. Left mechanical fuel pump untouched. And replaced fuel filter with clean one.

First two times out the car has run fine but when I shut it down and check under the hood, the clear filter is almost empty and the pressure gauge (just two inches upstream of the filter) shows about 4 psi. Gradually the pressure bleeds off over a couple of hours but the filter does not fill.

Starting the car and idling or short pulses of throttle show fuel slowly trickling into filter and pressure at steady 5-5.5 psi.

I don't understand why the filter doesn't fill solid. And how can there be 4 psi of pressure on the gauge and very little fuel in the filter? I disassembled the filter once to check for clogged inlet but it was clean. And there was nothing in the 3/8 inch rubber hose connecting the gauge to filter inlet.

Shouldn't the clear filter fill almost solid with fuel? Any theories? Can it just be air pressurized in the line?

Fuel pump is new with 6K miles on it.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 07-21-2008, 12:55 PM
Registered User
 
Join Date: Aug 2007
Location: Oswego, IL
Posts: 14
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I had the same problem with my 69 Mustang... turned out to be vapor lock. I re-routed the fuel line about a half-dozen times until I found a route it "liked".
Good Luck!
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 07-21-2008, 04:36 PM
Member
 
Last photo:
Join Date: Jun 2004
Location: TN
Posts: 416
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
If it was vapor lock, seems like it should fill solid when the car is first started cold, but it doesn't.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 07-21-2008, 05:12 PM
Mertz's Avatar
Member
 
Join Date: Jun 2002
Location: Reardan, WA
Posts: 655
Wiki Edits: 0

Thanks: 1
Thanked 2 Times in 2 Posts
Mine has been that way for years and I haven't had any problems with how the car runs. Mine is about half full or less all the time. I haven't tried to bleed it because it hasn't caused a problem. It might be worth a try to disconnect the line from the outlet side of the filter and fill it and see if it stays that way after driving for awhile.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 07-21-2008, 05:29 PM
Registered User
 
Join Date: Aug 2007
Location: Oswego, IL
Posts: 14
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Mine stayed empty most of the time cold or not... there was always a lot of pressure when I disconnected the line.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 07-21-2008, 08:10 PM
Member
 
Last photo:
Join Date: Jun 2004
Location: TN
Posts: 416
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Maybe you are right. The element stayed empty (10% full) from 1 p.m. till about 6 p.m. this evening, last time I looked. Then I just looked at it again, 10 p.m., and it is now 90% full of gas, and the pressure gauge reads zero.

If it does it again tomorrow, I will loosen the hose clamp on the inlet to the filter and see if I get any vapor or air released and fuel flow into the filter.

Thanks,

John
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 07-26-2008, 12:56 AM
swcash's Avatar
Squido
 
Last wiki edit: How to get specific belt sizes for custom applicat...
Join Date: May 2008
Location: Anaheim, California
Age: 66
Posts: 13
Wiki Edits: 3

Thanks: 0
Thanked 0 Times in 0 Posts
You have an air pocket trapped in the filter housing. This won't hurt anything until the filter starts clogging up and you need the part of the filter that the air pocket is occupying.
The fuel is not moving fast enough to force the air out. Try disconnecting the fuel line from the carburetor and put the end in a 2 liter bottle and start the engine. The free flow of the fuel may force the air out. Once the air is displaced with fuel you should be ok unless there is a leak in the fuel line and you are picking up air.
If you run out of fuel or run the tank too low the air will probably be back.
Squido
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 07-26-2008, 05:49 AM
Member
 
Last photo:
Join Date: Nov 2004
Location: Lakeland FL
Age: 65
Posts: 4,110
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
John,
it won't/can't stay full constantly because the check valve in the fuel pump will leak down as the motor cools and gravity is moving the gas to be more level with the the much lower gas tank supply.....that's totally normal....
(LOL, mount your gas tank on the roof and it will stay full)

compared to alot of pumps sold today your's is working excellent!!! (my check valve holds pressure for maybe 30 minutes)

all that a mech pump is.... is the rubber diaphram pushes/pulses a bit of gas past that one way check valve and spring combo and if the carb bowl is full so that the needle and seat are closed the line will build pressure...the check valve spring that limits/bypasses the gas at only 5.5psi isn't strong enough to hold the pressure forever....

Last edited by red65mustang; 07-26-2008 at 05:58 AM.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
fuel filter in pvc line on sbc hottrodz Engine 5 05-23-2008 05:40 PM
Fuel Filter Mount 37FordLS6 Hotrodding Basics 2 01-27-2008 09:53 PM
E85 compatible fuel filter, with fuel injection ripple Engine 5 05-10-2007 06:48 AM
Fuel Filter Location leejoy Engine 7 05-04-2006 08:50 AM
350 Chev - fuel filter / gallons per hour? Limey Simon Engine 5 10-24-2003 07:33 AM


All times are GMT -6. The time now is 05:40 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.