Fuel system problems on 503

[Morph]

One of our guys who flew to the TFDC Fly in had a few engine issues coming back.

As they were crossing the Franshoek mountains the engine started running rough and revs dropped. He instantly switched on the electric fuel pump and the motor smoothed out. He switched it off after a while and the motor started playing up again. Switched the electric pump back on and it smoothed out. Now him being a sucker for punishment did this six times instead of just leaving the pump on and doing a precautionary to check it out. I have had this problem before and found the fuel filter to be blocked.

On landing he checked his fuel filter and it was fine

He previously had a problem, before the electric pump was installed and luckily made the field. This is the reason he installed the pump. He has checked his entire fuel system and everything seems fine.

Now, could it be a sticky needle and seat, preventing fuel from entering the float chamber? Would switching a pump on solve this problem?

Could it be the mechanical fuel pump? Perhaps grit or dirt in it

Cracks in the fuel pipes?

Where does he start

[kb]

was it humid / hot?? I also have a 503, and find that on ling distance on hot / humid days, she also runs rough at the bottom end of the rev's. when I land, and have a look, I can see water droplets on the OUTSIDE of the carbs. starting is also not easy after a flight as mentioned. Me thinks it's abit of carb icing.

[Morph]

I can see water droplets on the OUTSIDE of the carbs. starting is also not easy after a flight as mentioned. Me thinks it's abit of carb icing.

Yup, that's carb icing.

was it humid / hot??

No it was nice and cool, early morning, low humidity

[PMarshall]

Could be a pin hole in the diaphragm of a faulty non return valve in the mechanical pump. A leaking or too soft vaccume pipe could also cause this. I would relpace the lot if it has not been done for a few 100 hours.

[Aviation Engines]

What is the total hous of operation?
How often is the aircraft flown?
When last were the needles and needle jets replaced?
Have you checked for water in your fuel?
Carb icing is a reality, but if you are flying with others and you are the only one experiencing problems, very unlikely.
Try using AVGAS, there may be a problem with the quality of the fuel you're using.


Clearly the problem is one of fuel starvation, what we need to do is to find the cause.

1. Check the breather on the fuel tank, maybe blocked or too small
2. Ensure that the pick-up line inside the tank is not being sucked up against the walls of the tank
3. Check the fuels lines for any possibility of sucking air
4. Remove the float chamber, float lever and float valve, inspect for wear and dirt inside the seat.
5. Ensure correct position of the float lever (if not sure, attend my next training course) just kidding, call me.

If your fuel system is in perfect condition, I would then suspect some sort of damage/siezure of the internal components.

Remove the exhaust manifold and inspect the piston through the porrt for siezure while truning the crankshaft. Do the same on the intake side.

Call me at the office 011 455 4203 or 083 630 9406 to discuss further.
( I am busy with training courses from Thursday to Friday, leave a message on my cell and I will call you back)]

Regards
Niren

[Cloud Warrior]

Niren - please do not withhold your knowledge and experience from the rest of the forum due to a misunderstanding. I personally, as I am sure many others here also do, value your inputs greatly as well as those of other manufacturers/service providers/agents who use the forum.

Regards

Sebastian

P.S. Demon - maybe we should list some do's and don't with regards to forum etiquette / electronic communication. I know I have upset a few people in the work environment before due to my e-mails being interpreted incorrectly.

[Morph]

Thanks Niren,

I'll pass this information on to him.

[vincent]

I once had a similar problem on my 503.
After checking fuel lines and stripping and checking the carbs it was still the same, I was conviced it was the fuel pump that packed up. Stripped and checked the diafragm but found nothing wrong. Eventually as a last resort I checked the VACUUM PIPE from the crankcase to the fuel pump and found a pinhole in the pipe where it joins the crankcase. I promptly replaced all the pipes and the problem was solved
Hope you find the fault soon.

[Perry]

We have had the same problem here in Aus...

It all started at around 200hrs on our Airborne Edge 582. Similar symptoms as described in the posting.

We found it to be based upon the ageing of the mechanical pump and the head required to get the fuel to the carb (with less than a quarter tank) was at the outer limits of the capability of the pump.

Following the installation of a Facet electric pump all problems ceased.

Nowadays we rely on having an inline electric pump for takeoff.

Regards