The carb on my 157 just quit working! It refuses to pump fuel any longer. I pulled the carb and pulled everything apart, needles, metering needle, carb screen, and cleaned out the carb with Briggs and Stratton carb cleaner. This stuff comes in an aerosol can that shoots a stream of cleaner at high velocity. All of the holes in the carb seemed to be clean. I reassembled and still nothing. I examined the pump diaphram and it looks pretty well stretched out so I'm assuming that's the problem.

I put on another carb from one of my other motors and it drew fuel immediately so I know that's the problem. The strange thing is I've never had a pump diaphram just wear out. And considering that this motor has less than 50 gallons through it makes it even stranger. I'm wondering if the new fuel blends might be the culprit.

Anyone else have a similiar experience?

I would suspect the fuel, I do know that Tillotson's don't dig on the blended fuels, after 50 gallons I would put a rebuild kit in it and call it good. FIFTY gallons??? I never had a plane last that long!!!

Tom

at 4- 5 flights to a gallon - 50 goes by pretty fast
128/4= 32 ozs
on my 40% model - 50 ozs per tankful so 40 into 128=3-4 flights per gallon
sluuuuurp

that alcohol/methanol/vodka you guys bump into the fuel - hard on any form of rubber

Super, I think you might be on to something about the Tillotson's. I have hundreds of gallons of fuel through Walbros with nary an issue. They must not use very chemical resistant membranes on Tillotsons.

I dont think its a fuel problem. There are thousands of tillisons out there on everyday things such as blowers, chainsaws, genarators, ect. This would totally wipe out a company if some blended fuel would not work. I can take one of the diaphrams and put it in solid alcohol and its just fine. I image you just have a bad pump that needs to be replaced or another issue going on. I had a carb one time do the exact same thing and never could figure it out. Ended up getting a new carb and everything was just fine.
Garrett

You're probably right Garrett so I'm trying to find the right kit for the HT-14A carb. So far I've found:
RK-1HT, RK-2HT, RK-3HT, RK-4HT and a partial kit number RK3HT.

My guess is that this carb had a small manufacturing filing that broke loose and has lodged itself in one of the check valves inside. If the kits contain the proper welch plugs I can go ahead and pull the carb completely apart and find the offending piece of aluminum.

I've tried over and over to get it to pump and all it does is pull the fuel up and push it back inside the fuel line. To me it's clear that a check valve is lodged open. I checked my fuel pump diaphram and there is no rupture on it. The metering diaphram looks perfect too so what does it leave? It has to be under one of the welch plugs.

Considering that this carb costs $90-95 I'm going to try and fix it. I found PDF files on how to properly remove the plugs and clean the carb completely so I feel confident that I can pull it off and if I can't I'll have a great learning experience trying.

Rich

Sounds good Rich. I have rebuilt them before and installed new plugs. Its not a big deal. I dont remember the numbers off hand but they are out there. Remember if you do end up buying a new carb you cant just go out and buy the same part number and expect it to perform like your carb. You can look into your carb and see the many different low end jet holes that help transition you to the high end. A stock carb will not have this. Also 3W changes the jetting and spring pressures from the stock carb a lot of times. I have the mp3 and mp4 carbs here at the house and both run just a hair different.
Garrett

I hear ya Garrett, a MP4 is the one that is screwed up right now and I bolted on a MO3 for the time being. It 'seems' to transition good, but I won't know until I fly it today.

In my quest to find out what the heck was going on with my motor I pulled the 157 off and stuck on a 150TOC in its place. That's how I discovered it was the carb because I transferred the carb onto the 150 and guess what the problem didn't go away. I was actually relieved to know the 157 was ok. Once I bolted on the MO3 the engine ran great. I supposed I could have done that in the first place but I wasn't convinced it was a carb problem.

Rich

The check valves are the little flapper things on the pump diaphram side. If they curl or get stiff the engine vacuumn will draw the fuel but it won't stay in the line.
Just install a new kit before you write it off as usless.

Well I'm having no luck finding the proper part number for the kit. I'm hoping that Gerhard has the kits because Cactus doesn't.

Ok I found it! Kit # DG-3HS/T

It can be found at:
http://m-and-d.com/

Just type in the part # and it pops up. In fact I typed in many numbers from that carb and the part popped up. Interestingly I found on the Tillotson website, the specs and part numbers for the 3W HT-14A carb. It's in a Excel spreadsheet. A complete diagram of the carb and individual part numbers.

http://www.tillotson.ie/

Select AFTERMARKET > Parts List > "click to download" > HT

After you download the file into Excel go to page 6. You can select the page and print it. Also be sure and print out Page 1 for the carb diagram to refer to.

I got my parts from M-and-D, slapped in the new gaskets and the carb works like new. Hooray!