nonstoprc

My Feedback: (90)

The carb on my DL50 absolutely draws no fuel from the tank today, with choke fully closed, throttle wide open, and the filter screen removed. The engine has good compression. The pulse to the carb is good. The carb bolts are tight. I changed the diagram and it did not help.

I swapped the carb out and replaced it with a spare Walbro 201b. The fuel comes to the carb in 2 flips.

My question is what can go wrong with the original carb in this situation.

Wilki01

Check the fuel lines for an air leak.
I've been having issues with my gassers leaning out, for some air leaks

JoeAirPort

My Feedback: (41)

If the carb fixes it it's not the fuel lines.

rangerfredbob

My Feedback: (13)

if a carb swap fixes the flow, and you changed the diaphram I would look at the other side of the carb, that's where the reed valves for the fuel pump are, if one of those are dirty or worn out, it sure as heck isn't going to flow fuel...

pe reivers

probably the internal filter OR the pump membrane OR an air leak in the fuel-in nipple. A pressure test on the carb will show the leak. The pumper membrane must be inspected for curled valve petals. With the cover off, the internal filter can be checked as well.

Wilki01

Oops, for some reason, I didn't see the line about swapping out the carb. Too funny.

JoeAirPort

My Feedback: (41)

MY ZDZ 50 NG seems to have this same issue. It takes 20 flips to get the fuel from the tank to the carb fuel inlet. I wish I had put the new blue pump membrane on there when I had it apart. I'll have to try this.

Two flips to get it from the tank to the engine? Are you sure? Even my new DA 50 took more than that. At least 5.

pe reivers

My MVVS takes one or two flips (it fires on the second or third flip with choke on).

JoeAirPort

My Feedback: (41)

So you're saying that your fuel travels roughly 18-24 inches of fuel line in only 2 flips? That's the typical distance my tank is from my engine. That's incredible. Usually I only see it advance about 3-4 inches per flip.

pe reivers

No, I do not say that.
I say it takes two or three flips with choke on to fire, after a few days non-flying. That does not necessarily mean that the fuel suction line is dry! It is hidden from my view, so I cannot tell.

Andrew_S

My Feedback: (12)

Maybe the needle is stuck in the seat...take it all apart and spray some carb cleaner thru all of the orifices...Also maybe the mixture needles arre closed...

nonstoprc

My Feedback: (90)

I opened up the metering side of the carb and found the needle is somewhat sticky. That could be the root cause. On close examination of the needle tip with naked eyes I found nothing wrong. I do not know what material is used to build the tip. Could be rubber. If so, then the section of the tip contacting the seat got wear-off and the tip become "sticky". This is just a theory.

Now the interesting question is I do not want to pull the good carb from the DL50 to test this "bad" carb on fuel drawing capability. I figured I can use a small camera lens cleaning blower to provide pulses to the carb, close the two needles and see if the fuel comes to the carb. Will it work?

DMcQuinn

My Feedback: (13)

yes, but you need to have the needle valves open 1.5 turns each (at least one of them needs to be open a little for fuel to flow)

JoeAirPort

My Feedback: (41)

You could just remove the needle on the bad carb and install it on the engine. Plumb it up to a fuel tank and see if it draws fuel. That would test your theory that it's a sticky needle.

Below is a link that someone posted in a carb thread I started. Excellent material. You can see how the pump works. The engine does draw fuel through the needle during priming.

http://www.perkez.be/Walbro.pdf

PS: Also don't rule out the choke plate not seating well. If this happens you won't be able to draw fuel as fast. I followed a thread here about a guy that struggled for months with a ZDZ 160 that wouldn't draw fuel. It turned out his carb plate wasn't closing fully. It happens all the time.

nonstoprc

My Feedback: (90)

JoeAirPort,

That idea may work if the seat is the same across two carb bodies. What i found is that if the "bad" needle is moved to another carb, the stickness is not felt. So looks like the seating area also plays a role.

JoeAirPort

My Feedback: (41)

Hmmm sounds like it's the seat then. Wonder what would make the seat sticky? Gummed up? I just took apart a Walbro WT-201 and the needle was not sticky at all. Maybe it can be cleaned.

rangerfredbob

My Feedback: (13)

take a Q tip or something and some carb cleaner and clean it up... might have to take some of the cotton off, but should work fine

pe reivers

Ditto. Clean both needle tip AND seating area. Fuel gum is nasty stuff.

Rcpilot

My Feedback: (78)

What oil and ratio are you using?

nonstoprc

My Feedback: (90)

32:1 pennzoil air-cooled oil.

mrbigg

My Feedback: (21)

It's not the oil causing the problem then. I use the same stuff in 6 different engines with no problems. Some sit more than 6-7 months without being used.

JoeAirPort

My Feedback: (41)

Could be the fuel...old fuel can gum up that's for sure. I have read many reports of engines not drawing fuel after sitting all winter. My DA 50 used to do that. I was always able to free it up and get fuel flowing (plug vent and pump the tank up with pressure while flipping the prop).

nonstoprc

My Feedback: (90)

I have the habit of running the tank dry at the end of the day. The plane sits in the garage all day with temperature can easily reach over 100. On the other hand, my DA50 is fed the gas from the same tank and does not have the fuel draw problem.

RockiesGuy

[size=2]Hi there all; I got a ZDZ 50 ng engine off ebay..the old carburetor...and the engine was sent with no booklet..now ZDZ's website is out for a while...

can anyone tell me what are the low and hi end needles factory adjustments? ( how many turns)..got the engine running but it seems to me that there is a very fine tuning required!

I tryed RCS info but it is very general (no specifics)...I live in Colorado Springs (CO) and for sure altitude will affect this setting.

??

DMcQuinn

My Feedback: (13)

MaR/C0: Almost all 2C gasoline engines come with Walbro or Tillotson or Zama pumper carburetors. And these carbs usually have two needle valves. If you set these at 1.5 turns open, this is usually a good starting point to get the engine running. If the engine does not run with these settings, probably the problem is somewhere else (not the needle valve setting).