Fuel delivery issue?/Low engine power

[jdedea01]

I am hoping one of you guys can give me some insight into what my next step should be. I have been working on my bosses 1980 MF 365. It sat for 10 years so as you can imagine every part of the fuel system was in rough shape. I cleaned out the tank, replaced the fuel lift pump, replaced the fuel filter then bled all the air out of the system. It starts and runs great by some miracle but then things get weird. It will run perfectly for approximately 3 minutes then it starts to drop RPMS until it dies. I can start it again immediately and it will run perfectly again for around 20 to 30 seconds before it bogs down and dies again. If I let it sit for a while it will run for 3 minutes or so before the RPM loss begins again.

 

[MF#1]

Could be the Injection Pump has some sticking parts? OR the fuel line from the tank to the lift pump has some crud in it OR the fuel tap at the bottom of the tank has crud in it. Cleaning out the fuel tank doesn't mean that tap is fully clear, you have to remove it and clean it TOTALLY with carb or brake cleaner then check that the flow is Constant and Continual from that fuel line to the lift pump. I've had to rod out that line before with a stiff wire to get one going. IF you are SURE that the tap and line are clear then I would focus on the Injection Pump, you "may" be due for an overhaul of the pump.

 

[Jim.ME]

Welcome to the forums.

What did you install for a replacement filter? if it was a WIX or Napa type make sure the top seal ring was installed in the groove of the housing head, not in the steped down area around the top rim of the element. The seal ring down in that area blocks the slots the fuel needs to flow through.

If you broke open any lines sealed with rubber "olives", did you replace the olives and make sure they are over the tube, not the tube pushed into the hole and the olive partially blocking the end of the tube?

 

[jdedea01]

I did use a Wix filter, and on the second try I actually managed to do it correctly. The tank was cleaned very well and the petcock filter and valve also. I have excellent fuel flow all the way through. However I did not do the “olive” thing correctly. Is that what I need to tell them I need? My new lift pump came with nothing, no rubbers no gasket. I took the rubber seals out of the old one and put in the new one. They are sitting in the bottom not wrapped around the flare of the fuel line. I will address that this weekend, hopefully that’s what the old girl needs and we don’t have to play the injection pump game lol. Thank you both, I really appreciate your time and advice.

 

[Jim.ME]

You should get new olives and make sure they are on the tube, beyond the flare, when being installed, not the tube butted up against them. If butted up the tube can be partially blocked by the olive.

 

[jdedea01]

Will do. I will seek them out today and give you an update on Sunday when I install them. Thanks again.

 

[jdedea01]

Between the olives, cleaning out some trash in the fuel line between the tank and the lift pump, and a new air filter this old girl is back running 100 percent. Thank you for all your advice.