Is it needed for FI guys to let the fuel pump prime before start Options

[carcus]

Just wondering. I have Bosch FI at Colorado altitude. My car will not start up right away unless I turn the key and wait about 10 seconds for the fuel pump to prime. All plugs and wires new, new fuel pump, and fuel filter. Moroso electronic conversion. New battery. I try to drive the car once a week. Just looking for advice. Car is a 1976 2.0 with 1973 2.0 engine. OEM fuel injection.

[Dave_Darling]

I don't think that valve in the photo is a check-valve to maintain pressure in the system. It is in the return line, not in the supply line. Remember that the high-pressure part of the fuel loop goes from the fuel pump to the fuel pressure regulator, then dumps back into the tank with essentially no further restriction. The return port on the pump is Y'd into the return line, but there should not be much pressure in that line regardless, so the valve shown is not relevant.

The rotor and pucks of the pump body serve as a check for fuel trying to flow back through the pressure line to the tank. The fuel pressure regulator serves as the check valve on the other end. Either could allow fuel to bleed past; I am thinking that it is more likely to happen on the pressure regulator side than the pump side, but that really is a guess.


BTW, the "key on and off a few times" does not work on an L-jet car. The L-jet pump, as stated, only runs when the starter is cranking or the engine is running.

--DD

[brant]

yes and no

I have taken a few 3 port pumps apart
the rubber nipple (not shown in the photo) gets sealed shut by the spring pressure
when the rubber fails (40 years old, and has failed on mine) the valve is no longer sealed...... then it becomes an internal leak that allows the pressure to bleed off

so in a way it is a dual purpose valve
1) to be a blow off for return
2) to also function as a check valve to allow the system to hold pressure when not running.


I repaired my rubber nipple with one from a core pump (also a used piece of rubber)
the car then started perfectly as it used to on the first crank....

that lasted about 3 months and then the used rubber failed also. Now I am currently priming my system by turning the key 3 times after the car has sat overnight

I intend to install a 2 port pump at this point and eliminate this failure
brant

I don't think that valve in the photo is a check-valve to maintain pressure in the system. It is in the return line, not in the supply line. Remember that the high-pressure part of the fuel loop goes from the fuel pump to the fuel pressure regulator, then dumps back into the tank with essentially no further restriction. The return port on the pump is Y'd into the return line, but there should not be much pressure in that line regardless, so the valve shown is not relevant.

The rotor and pucks of the pump body serve as a check for fuel trying to flow back through the pressure line to the tank. The fuel pressure regulator serves as the check valve on the other end. Either could allow fuel to bleed past; I am thinking that it is more likely to happen on the pressure regulator side than the pump side, but that really is a guess.


BTW, the "key on and off a few times" does not work on an L-jet car. The L-jet pump, as stated, only runs when the starter is cranking or the engine is running.

--DD

[BeatNavy]

that lasted about 3 months and then the used rubber failed also. Now I am currently priming my system by turning the key 3 times after the car has sat overnight

I intend to install a 2 port pump at this point and eliminate this failure
brant

Brant (and all) - just reviving this thread. I finally installed the 2 port Bosch pump and ditched the 3-port. It was good to simplify fuel line routing. More importantly, the car fires up within a second or two of cranking without repeated "priming" the pump. It also doesn't die without the initial feathering I had to do immediately after start up previously. I think that old 3-port was starting to get sketchy during normal operation, too.

Don't be afraid to dump the 3-port.