Fuel pressure drops from 7# to 3# in 5 minutes of driving

Fuel pressure drops from 7# to 2# in 5 minutes of driving.
Checked fuel tank cap for proper venting, checks ok.
I replaced electric fuel pump with a new one, same condition but went down to 3# due to a new fuel pump.
Tomorrow i will check hose from sender to fuel lines for collapsing.
The next thing i will do is blow 20# of air pressure into fuel lines & then fuel tank sender.
I wonder if after 15 years of ethanol fuel has caused the sock to block fuel flow??
Has anyone had problems with the sock in the fuel tank?
I do not use a mechanical pump only electric for over the last 5 years.

I hate to suggest the obvious, but you might be dealing with clogged fuel filter(s) as a result of sediment being sucked from the tank into the filter(s) and, at some point, it builds up to the extent that it eventually restricts flow. Once draw into the filter is cut off, the sediment may then be back-flowing into the tank - only to later repeat the process.

At least, that is my well-intended suggestion.

If i didn't half a half tank of fuel i would pull the sender.
But air pressure will either clear it or blow it off.
I will find out very soon.

I had a problem where the car would die after driving for about 5 mins from the sock getting mucked up. Changed the sending unit since it was old as heck and I've never had an issue since

Bill,

Any chance you’re experiencing vapor lock, since it’s so hot this time of year?

Thanks
Bob

Bob, the engine never shuts off. It does not seem to be vapor related.
I can leave the engine with the hood open & the pressure still drops.
Hope to get under it to see if its a collapsed fuel hose.
If not i will have to drain the tank or pull it out.
All hoses are fine, looks like a clogged sock.
It would happen with a 1/2 tank of gas.

wsa111":31g7lfqb said:

Bob, the engine never shuts off. It does not seem to be vapor related.
I can leave the engine with the hood open & the pressure still drops.
Hope to get under it to see if its a collapsed fuel hose.
If not i will have to drain the tank or pull it out.
All hoses are fine, looks like a clogged sock.
It would happen with a 1/2 tank of gas.

Click to expand...

If your tank is anything like the Ranchero tank, if you park it on a steep enough grade, you can get away with changing it with a quarter tank. Thats how I did it. My mothers driveway was steep enough for me to try. I believe the sending unit setup is still all the same. I'd try that.

It may well have no sock - mine didn't when I dropped the tank (Im positive I was the first one to do so). Maybe mine rotted off, but there was just the fuel tube.

Drained fuel tank, removed the sender & due to ethanol fuel the sock was black instead of white.
Had 50% blockage.
Installed new sock & hose from sender to fuel line & pressure jumped right to 7#.
During a 15 minute cruise fuel pressure stayed in the 6-6 1/2# area.
Will monitor it & will warranty the fuel pump if pressure drops below the above.

Kou-well !