L2550 looses power and sputters after warm up.

[Captjohn]

Did a search and saw another similar problem but he had gelling in 0 degree weather. I'm on the MS gulf coast and 75 degrees. Till now its run flawlessly for years. 1600 hrs on it. I'm an old school 70's 80's auto mechanic with 4 years of schooling.
1st- I ran it till the fuel filter stopped up and it quit. I know, I know.......any way, cleaned the bowl and changed the filter. Had issues getting all the air out at first. Runs perfect for about 15-20 min then starts to sputter and looses a good bit of power. If it cools for an hour or next day it runs fine again until heats up, 15-20 min. Engine Temp is normal and fuel is fresh and clean. Replaced the lift pump today but no change. Good solid fuel flow from filter to lift pump (1 qt very quickly). Good flow from lift pump to injector pump with the line pulled off. I've bled the lines at the inj pump but not at the injectors. I have a bleeder valve at the entrance to the inj pump and have had it open a lot. Runs bad when open like it should. No signs of water at all.
I'm scratching my head. If I still had air would it run perfect when cold?
TIA
Capt. John

 

[North Idaho Wolfman]

Before you do anything else I would crack all lines to the injectors with it idling and bled out any possibility of air in those lines.

Then run it, if it starts doing the rough running again open the fuel cap and see if it starts running good again.

 

[Captjohn]

Just finished bleeding lines at the injectors.....twice. Still the same thing. Had the cap off several times but will try while running. And may bleed again.

 

[North Idaho Wolfman]

You don't need the cap off for bleeding it.
If taking the cap off when it's running bad straightens it out then it has a blocked vent.

If you've plugged up the system with any junk and it got past the filter you could have gotten something into the input to the injection pump or even into the lines or injectors.

 

[1970cs]

When it sputters and losses power, try cracking each injector line to see which cylinder is dropping out.

I had one cassette style injection pump do the same thing. It had a crack in the housing and would only show or run poorly when the unit heated up.

Pat

 

[Captjohn]

Thanks guys. I've decided that I may be getting air from the filter o ring or line. I messed with the filter before this all started. I keep seeing air at the new lift pump just like the old one (that's why I changed it). It may be taking that long to build up enough air and not the heating up. I'm getting fine air bubbles at the bleeder before the inj pump. Not sure the regular parts houses will have the o ring and NAPA won't open till Monday. I'll update my progress.

 

[D2Cat]

Might have a local hardware store with a good selection of "O" rings, and find a metric one that will work for fuel!

 

[Captjohn]

Well.......replaced the O Ring and fuel lines. I thought it was a long shot but cheap. Still runs perfectly for 20 minutes then starts acting up. Had no air at the bleeder when cold and had air bubbles when warm. Filter bowl is perfectly clear with no bubbles.
Have to jump the clutch safety switch tomorrow so I can crank it from the right side. Going to pull the line off between the lift pump and the injector pump to see if air is there or backing up from injector pump (if that's possible).
Don't think it's any trash because it consistently runs great cool and like crap warm.
The saga continues.......

 

[Captjohn]

I'm also gonna rig a temparary tank straight to the lift pump to bypass the main tank and filter and see what that does.

 

[1970cs]

I was going to mention that also, about rigging up a clean fuel source.

Pat

 

[North Idaho Wolfman]

I'm also gonna rig a temparary tank straight to the lift pump to bypass the main tank and filter and see what that does.

Feed it straight to the Injection pump, and make double or triple sure it's clean fuel, container, and line.

 

[CapnDean]

Is the lift pump running when the engine looses power?

 

[Captjohn]

I think I got it today although not sure the exact cause. I ran it till it acted up and switched the line from the tank/filter to a jug/line I rigged up to the inlet to the lift pump. Opened the bleeder for a minute and ran fine.
I drained the tank, pulled the filter housing and fuel line to the tank. Cleaned everything up. The fuel line seemed fine. It held vacuum I put on it and so did the filter assembly. I put a new line from tank to filter and reinstalled the housing and now all lines are new. Put new fuel in it and runs fine for now. Worked it about 40 minutes.
Don't know if it was a line, filter or fuel but I hope it stays good! I've put over 1000 hrs on it and will watch the filter closer now!
Thanks guys!