Diesel tractor, not car. This Spring I was tootling along on my tractor, mowing my fields, when it started to lose power. Going slower and s l o w e r, like it wasn’t getting fuel. My step-father bled the fuel lines for me, and it worked okay. For a few hours. THen it started doing the same thing. I changed the fuel filter, bled the lines again, and was mowing last night. Again, after about an hour, it did the same thing, losing RPMs.
I rolled this tractor two summers ago. Could I have cracked a fuel line? You’d think once there was enough of a vacuum to pull the fuel for an hour, it would keep going. Maybe it’s not a fuel thing at all? It sure feels like it’s not getting diesel.
Is there a chance in hell that the fuel lines themselves are compromised in some way? Either a tear or leak or somewhat? This is a long shot, but I had brake lines compromised by bad brake fluid, and they eventually just seized up, stopped working, and required replacement of all the lines. Not sure if bad fuel could mess them up, but…? Just a shot in the dark.
Maybe you have too much water in the tank. Any is too much. Can you drain the tank and use that old fuel on something else or filter it to get the water out. The filter and separator you have on the tractor may not handle the volume of water present.
You could test this theory by running off a small alternate tank with new fuel.
distributor or inline injection pump? I had an old diesel F-250 which acted like that. initially it would be OK for a bit, then start idling like crap and lose power. after being off for a while, it would be OK then screw up again. Needed a new injection pump. distributor-style pumps are entirely fuel-lubricated and don’t last as long as inlines.
This is one of those things that’s REALLY hard to diagnose over the 'net.
I assume when you say it’s getting slower and slower that you mean the engine starts getting slower, losing speed.
Check your aircleaner. Make sure the filter is good, and make sure there’s nothing plugging up BEFORE the airfilter (bird nest, mud dauber nest, bent intake pipe)
Take off or loosen your fuel cap (try this while it’s slowing down if you can). If the vent in the cap or tank is plugged up, as you run the engine for a while, the tank gets a vacuum that won’t let fuel flow.
When the engine starts slowing down, does it recover if you stop moving and shut off the mower?
Deereman - By slower, I mean the RPMs decrease, no matter how high the throttle is, until it finally dies. I’ve taken the air filter out and checked it, but I haven’t gone deeper into it than that. I’ll try starting it tonight and will see if it starts, and if so, does it go better with the air filter or fuel cap off.
J-P L - How can a vapour lock be vapourized? It doesn’t seem to be overheating - no steam coming out of the radiator. There’s an overflow tank for that, though. Usually I can smell overheating.
Thanks again, everyone for your input. Keep it coming!
diesel fuel is far less volatile than gasoline, and AFAIK vapor lock is rare to non-existent on diesels.
I wonder if the governor is messed up and reducing engine speed unnecessarily. air in the lines or fuel starvation IME tend to cause stumbling and misfires, not a gradual reduction in engine speed.
and $350 for an injection pump is nothing, you’re lucky it’s only a 2-cylinder. Some of the bigger inline pumps are multiple thousands of dollars.