sschefer
09-18-2009, 02:12 PM
Here's a problem that needs a solution:
Merc and Mariner made a inline 4, 2+2 engine. There are two enrichening injectors fed by an accellerator pump that opens with the throttle. These injectors are mechanical and should not open until they get about 5 lbs of fuel pressure. If they do, the cylinders will flood with fuel. Normally, the injectors start working and the cylinders begin to fire at around 1800 rpms. Up until then the carbs give enough fuel for lubrication but not combustion.
Problem -
Today's fuel additives demand that we use a fuel/water separator but these little pulse fuel pumps don't have the umpf to pull adequate volume through a 10 micron filter and the carb bowls go dry at around 3/4 throttle after around 3-5 minutes. It's usually the #4 (last in line) that goes dry.
Placing an electric fuel pump in line as a puller or pusher overpowers the injectors at the first throttle crack (starting) and floods the cylinders.
Placing a fuel pressure regulator also reduces volume and puts your right back where you started.
A couple of ideas I've had include running a second voltage regulator and giving the pump it's power from that. This would make it so the engine has to be running for the fuel pump to work.
The other idea I had was to use a surge tank with a 1 lb pressure relief valve that returned to the main tank. The electric pump would fill the tank after the filter but never allow pressure to exceed 1 lb letting the pulse pump produce the required pressure as designed.
If I could calibrate the electric to produce pressure and volume on a curve it wouldnt need anything more but that would be a pretty expensive proposition for an old but trusty engine. Unless, someone knows of an ECU type system that would adapt?
Thoughts ? I bet there's more than one of us that's run into this problem.
Merc and Mariner made a inline 4, 2+2 engine. There are two enrichening injectors fed by an accellerator pump that opens with the throttle. These injectors are mechanical and should not open until they get about 5 lbs of fuel pressure. If they do, the cylinders will flood with fuel. Normally, the injectors start working and the cylinders begin to fire at around 1800 rpms. Up until then the carbs give enough fuel for lubrication but not combustion.
Problem -
Today's fuel additives demand that we use a fuel/water separator but these little pulse fuel pumps don't have the umpf to pull adequate volume through a 10 micron filter and the carb bowls go dry at around 3/4 throttle after around 3-5 minutes. It's usually the #4 (last in line) that goes dry.
Placing an electric fuel pump in line as a puller or pusher overpowers the injectors at the first throttle crack (starting) and floods the cylinders.
Placing a fuel pressure regulator also reduces volume and puts your right back where you started.
A couple of ideas I've had include running a second voltage regulator and giving the pump it's power from that. This would make it so the engine has to be running for the fuel pump to work.
The other idea I had was to use a surge tank with a 1 lb pressure relief valve that returned to the main tank. The electric pump would fill the tank after the filter but never allow pressure to exceed 1 lb letting the pulse pump produce the required pressure as designed.
If I could calibrate the electric to produce pressure and volume on a curve it wouldnt need anything more but that would be a pretty expensive proposition for an old but trusty engine. Unless, someone knows of an ECU type system that would adapt?
Thoughts ? I bet there's more than one of us that's run into this problem.