Combo Fuel / Vacuum Pump

Sarah Young

Recently had the following question asked of me and I thought I'd post it for others who've had this problem to hear some troubleshooting. This is in regards to a 53 Super Jet that's in the final stages of a 2 plus year restoration that had been acquired already dismantled to some extent... "The combo fuel/vacuum pump had the one vac hose from the top rear going to the wiper motor. A short hose/copper tube with compression fitting came off of the top front side of vac but went nowhere. Do you know where that line is supposed to go and what it was connected to? Also, the gas is siphoning back every night. Is this a sign of a faulty fuel pump, the fact that the gas line does not remain pressured up?"

[Deleted User]

Sarah Young wrote:

Recently had the following question asked of me and I thought I'd post it for others who've had this problem to hear some troubleshooting. This is in regards to a 53 Super Jet that's in the final stages of a 2 plus year restoration that had been acquired already dismantled to some extent... "The combo fuel/vacuum pump had the one vac hose from the top rear going to the wiper motor. A short hose/copper tube with compression fitting came off of the top front side of vac but went nowhere. Do you know where that line is supposed to go and what it was connected to? Also, the gas is siphoning back every night. Is this a sign of a faulty fuel pump, the fact that the gas line does not remain pressured up?"

It has to connect to the intake manifold. then to the wiper motor. Today's gas dries out and that is the reason I tell all to install an electric fuel pump on your car. When it sets just turn the pump on and start. All new cars have sealed fuel systems and if there is a leak the check engine light will come on. Our carburetors and tanks have to stay opened or you will suck the tank together. Walt.

SuperDave

Sarah,

Determine which port of the vacuum pump is the suction one. While the engine is running put your finger over the two choices to do this. That port goes to the wiper motor, the other port goes to the intake manifold. so the engine is pulling vacuum through the pump.

Most likely, you have a fuel pump valve leaking back. The line shouldn't be empty overnight. You won't keep pressure in the line as you would with a fuel injection system, but the line should have residual fuel in it as well as the pump. If it drains all the way back leaving air in the pump, you have a small vapor lock situation that takes a lot of cranking to overcome. It only takes a very small piece of debris to hold those very small,valves off their seat. Also check to see if the float bowl(s)?Twin H ?are not leaking all the fuel out overnight. That will also cause hard starting.

Hitting the road soon?

Sarah Young

The question originated from another Jet Owner. I answered as best I could, but thought it would be good to post it so I could hear other feedback (not realizing there was a similar thread going). I've actually already got an auxillary electric pump on mine. I don't have a good pic of that readily available, but here's something. The extra pump is covered by the purple shop rag, wet when it was thrown on while repairs were being made to the rocker panels. You can see a new muffler also.