I have a 1956 Crown Vic with 292 eng. Have installed 2 new fuel pumps. Has good pressure cold(4 1/2#)  but gets hot, pressure drops to 1 1/2 #.
I installed an electric 5# pump.  Problem is without ele.pump on feels like running out of fuel  but can turn ele on and it picks up and runs ok.
Any suggestions as to the problem???     Thannks,  Jim

If it is a gauge that is permanently installed very close to the engine, then it is common for them to indicate very low pressure when hot.  In this case, it will be best to confirm with a remote mounted gauge to compare against the permanent one.

SInce turning on the electric pump does seem to fix an issue with performance, ensure that the electric pump itself is not a restriction to the mechanical pump.  Also ensure that any rubber hoses are in good condition


Lawrenceville, GA

Thanks for the info.. It is a line gauge at the intake. Has new hoses from hard line to electric pump .from there to fuel pump. From fuel pump to carb line.  The pump is mounted on the front fender well. It was doing this before electric pump was installed.

Electric Pumps are really designed to "push" rather than "pull"  Fuel and should be mounted close to the Tank and lower than the outlet from the Tank. The  existing standard Pump can also be check for Volume pumped as well as pressure.It would be very unusual to have tried 2 Pumps and still having same problem. Are they new Pumps as opposed to rebuilt Exchange Units?

  

"Have installed 2 new fuel pumps. Has good pressure cold(4 1/2#)  but gets hot, pressure drops to 1 1/2 #.

I installed an electric 5# pump.  Problem is without ele.pump on feels like running out of fuel  but can turn ele on and it picks up and runs ok."

Fuel line heat soak - resultant fuel blend separation (boiling point) - resultant vapor lock.

The electric pump cured it. That is your indication.

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Is the Line from Fuel Pump to Carb all Rubber Hose or Steel?  Personally I do not like Neoprene Fuel Line as its difficult to space it away from the Engine Block and is also more of Fire Hazard due to a Leak if You also use an inline Filter clamped in the Hose. I have done 3 installs using all rigid Line from Pump to Carb as was originally used from the Factory when Cars were new. I use the Inline Filter and support Bracket originally used on the T-Birds. Brackets are available now as Repros. NPD sells both the Filter and Bracket under their "55-57 T-Bird" Parts.  Line is spaced away from the Block cutting down on the Fuel getting overheated. I have had Zero Problems with any of the 3 Vehicles having Vapour Lock Trouble..