Re: 37 115C fuel system woes

Posted by DavidPackard On 2022/6/11 17:48:56

tsherry

I’m with OD, it’s axiomatic that for every gallon of fuel removed from the tank that a gallon of air must be allowed to enter. Even the modern cars, with a submerged fuel pump, will accomplish this, albeit via the carbon canister. Normally older cars have the vent the fuel cap, while the cap for a modern car does not have a vent . . . it’s sealed to allow the carbon canister to work. Assuming your car is now has an essentially unmodified fuel system the ‘filler’ cap should be vented.

Next subject: There are two types of electric fuel pumps that most of us use. One is a rotary vane pump (Carter for one), while the other is a solenoid ‘plunger’ type (Airtex for one). The ‘plunger’ type does NOT need to be powered all of the time. The rotary vane pump needs to be powered all of the time . . . or, every once and awhile the car will stall. Ask me, I’m the guy that owned a vane pump, and didn’t understand the ‘rules’! My ’48 would run normally for days and days, and then just decide to stall. After stalling just about every time at the same location I concluded that making a tight turn had something to do with it. And after I disassembled the pump it was clear that the fuel circuit can, and will be blocked by one of the vanes, but for a while the offending vane can allow fuel to pass. Taking a turn ‘pushed’ the vane into the offending position . . . every time
.
‘Junk’ in the tank or lines is also one of the usual suspects, but if you tripled checked that when you swapped the tank that is likely not the culprit
.
dp