Changing the engine driven fuel pump - advice?
 

Hello all,

My engine driven pump is not hacking it at full throttle/full rich settings, often plummeting to 0-1 psi with increasing EGTs as it goes below 1PSI (carberauted). So I?m going to try swapping out the engine driven pump with a new one. Hopefully this fixes the problem.

I?ve never messed with the pump, is there any difficulties swapping these out or is it just plug and play? What are the procedures? Anything specific with gaskets, gears, etc?

Thanks all!!
Wingnut

I can tell you that at least on the IO-540, it can be interesting to change the pump. You have to hold the pushrod up then install the pump before it drops too low. Took us a while but we also had the shroud with blast tube.

-Marc

Its pretty easy. I had to install mine. There is just a gear with a lobe on it that presses the plunger down to push the lever on the fuel pump. That's how the system works.

If the plunger wont go up it's because the cam lobe on the gear is in just the right spot to push the lever down. If this happens, rotate the crank shaft one turn and that should be enough to move the gear out of the way. Its a pretty east job. As long as you don't force anything I don't see how you can screw it up.

Tie a long length of string, dental floss, fishing line, or similar into a big loop. Rotate the crank until the pump plunger is as high as it will go in the accessory case pump cavity. Loop the string around the plunger. Drape the other end of the loop over a handy motor mount tube and hang a big weight on it. Push the plunger up and the side force should make it stay. If not, add more weight.

Insert the pump, install the two screws, and run 'em in until there is just a small gap between the pump and the accessory case. Cut the string loop, pull it out, finish tightening the pump screws. Done.

The above method is good advice, but see if the plunger will stay in place all by itself long enough to get the pump in place. Mine did when I changed it this winter. There are lots of scary threads on how hard this swap can be, I thought it was pretty straightforward, even for a feeble minded old legacy driver. :D

Search on ? replacing engine driven fuel pump?
 

There are some warnings -
Fatal crash due to improper install, with plunger not properly aligned.....


And tips/ reminder
- position prop so that plunger is at top,position...... remember safety with prop
- use lace cord to hold plunger up
- use a wobble (some call ball) hex drive


Read through post started by Alex Peterson...2/11/2007...... and I?m sure there are others with good info

seems you could trouble shoot the problem by turning on the electric fuel pump when the problem occurs. at times we end up chassing problems before diagnossing the problem. :confused:

dan, that is some good diagram work there.

Yes, I do this every time the PSIs drop. The electric pump keeps the PSIs nominal >4PSI.

Thanks!
 

Dan,

Thanks! What torque on the screws? Also, any alignment to be done or is that all there is to it? Ref. - "Fatal crash due to improper install, with plunger not properly aligned....." would like to avoid that haha.

Do these pumps come with new gaskets? What do I seal the gaskets with?

Thank you!
Wingnut

Be sure the pump is your problem. I had an RV4 with a o-320 that 0n two occasions I had the engine fuel pump pressure drop below 1 psi at take off power. Both times it was due to trash in the in line fuel filter. Cleaned the filter and the pressure returned to normal.