Buying Advice Fuel System Cleaning Advice Needed

Paddy · Feb 8, 2005

Thanks Chip/Greg.

Sound great. Once again, good dealers look out for you.

My Kubota has a fine screen at the tank fill location. Amazing all the crud you can prefilter.

Patrick

greg_g · Feb 8, 2005

(
My Kubota has a fine screen at the tank fill location. )
I used mine initially, just to see if it there actually was anything to filter out. Guess we have cleaner fuel around here than you, no crud. Since the mesh was so fine as to really slow down the fill process, I take mine out. Six gallon cans get really really heavy, while waiting for the fuel to seep through that fine mesh. Once the tank's full, I put the screen back in. For this purpose, the fine mesh works in my favor - as it prevents a sloshing full tank from dribblihg fuel from around the lousy filler cap seal.

//greg//

TruChaos · Feb 8, 2005

"The hand primer pump only pushes fuel as far as the end of the soft lines. It's of no use trying to force fuel up the hardlines. It's not quite clear if the no-fuel condition was detected at the bottom of the hardline, the top of the hardline, or the output of the injector. Please clarify."

I'm not sure how the primer pump got into the discussion but that's not what I was referring to.

When checking the injection timing, the crankshaft is rotated until the fuel begins to rise at the first port on the fuel pump. Then the pump timing is read from the crank pulley at the pointer. While doing this, I noticed that at the rear port, the fuel would never rise regardless of the crankshaft position.

My thoughts were that perhaps the rear port wasn't functioning.

Tonight, I removed the top cover from the injection pump and took a look at the plungers. I cleaned each one and reassembled the pump. Now all three ports splash diesel when the engine is rotated.

However, the engine still knocks and blows smoke.

greg_g · Feb 9, 2005

( I'm not sure how the primer pump got into the discussion but that's not what I was referring to.)

You said "I bled the pump". Since that's the express purpose of the hand primer, I assumed that's what you meant. The fuel delivery assembly is actually three separate components ; it's a combination fuel pump, governor, and injection pump all in one unit. It's fed by soft lines on the fuel pump side, and compresses fuel through hardlines on the injector pump side. So when you have fuel delivery issues, it pays to be specific.

So I'll ask again. Is fuel actually getting to the top of the 3rd hardline? And if so, is the injector actually triggering a fuel spray? Because the knocking and black smoke makes it sound like you're still running on two cylinders.

//greg//

JohnS · Feb 9, 2005

I think you have been chasing the crappy fuel through the system /forums/images/graemlins/crazy.gif

Most likely, an injector is bad or dirty. As you are running, crack open each of the injector lines, on top of the pump, one at a time. Retighten the nut before proceeding to the next. If you notice a change, knock smoothes out, that is the one to change. Hope this helps.

TruChaos · Feb 16, 2005

I don't think I stated that I started out by cracking all the hard lines to see if there was a change in the misfire or sound and there wasn't. I then replaced the injectors which didn't fix the problem.

When I stated that I "bled the fuel pump", I did exactly that, I loosed both bleeder screws on the top of the fuel pump and bled the air out of the pump then continued bleeding the system down the fuel lines to the injectors.

When I stated that fuel wasn't reaching the third port on the fuel pump, this occurred while I was rotating the engine to check the fuel injection timing. It had nothing to do with the fuel system purge or primer use.

I removed the entire fuel system except for the fuel pump. I cleaned everything and reassembled it.

I partially disassembled the fuel pump and removed the plungers. I inspected and cleaned them all including the piston function at the bottom of the pump, they work fine. While there was no visible dirt, or contaminates, I still sprayed everything with carb clearer.

The one thing I did notice was that the poppet under the problem port seemed to stick for some reason. This appeared to be due to how it was machined and not debris or contaminates. I would clean it then poke it with a clean plastic spray can straw and it wouldn't open. Then it would drop out and I'd put it back in and it work freely again. Then stick again. I inspected it for burrs and saw nothing, nor could I detect any from running my finger over it. The orifice it was seated in seemed very smooth. I hit the poppet with some 400 grit sandpaper, cleaned and replaced it.

I started the engine and it still knocked. I gave the third port a couple light whacks with a small hammer for good measure and still nothing (thought it might free the poppet). I was checking the fuel system for air bubbles bleeding everything while the engine ran then suddenly the engine knocked like **** and died.

From all the fuel system purging, I had run it out of diesel. I added some diesel, purged and restarted the engine. It started and ran without knocking. It did continue to smoke for a time then the smoke stopped. I ran if for an hour and the engine now runs better than it ever has.

What it was is anyone's guess but it sure wasn't dirty fuel. I bled and flushed two gallons of very clean diesel through the system.

Problem solved.

Thanks for all the help and suggestions.