Fuel pressure

by Richard Pingert in General Tech Discussion 9 years ago

When flying the fuel pressure gauge will stay at 3.8 to 4 lbs then drop to 2.5 and then back up again what do I look for

Re: Fuel pressure

by Roger Lee » 9 years ago

Roger Lee

126 5.12k 4.53k

Hi Richard,

What plane is it in and instrument system that is reading the oil pressure?

First you need to rule out whether this is a real fuel pressure drop or an electrical issue. It would be good to put a mechanical gauge inline and run the engine and see if the real fuel pressure matches your instrument panel readout. Sometimes the electrical system can change in resistance or a stray electrical interference from wires being bundled together. A bad or loose ground can cause issues at times.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Fuel pressure

by Richard Pingert » 9 years ago

Richard Pingert

5 8 0

Thank you Roger will try that and see what develops
Rick

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Re: Fuel pressure

by Richard Pingert » 9 years ago

Richard Pingert

5 8 0

Thanks Roger did what you said to check for and used manual gauge to check fuel pressure was 4 lbs and steady so to line off sender and drained reinstall problem was fixed
This is a great tool too use thanks again for your input
Rick

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Re: Fuel pressure

by Roger Lee » 9 years ago

Roger Lee

126 5.12k 4.53k

This is my own 2 cents and has nothing to do with Rotax.

Just food for thought.

I have found intermittent low pressure issues over the years with the fuel pressure senders. The senders that tend to hang down so the orifice is pointing upward and below the carbs seem to have these issues. If you use auto fuel the fuel sits in the hose for long periods, goes through many heating and cooling cycles. After about a year I find some of these have that small pressure sender orifice starting to plug from the old stale auto fuel. I had this issue the first year I owned my plane with intermittent low pressure alarms. I did the following and re-located my sender high up on the firewall. That was 7 years ago and I have never had an issue since and still have the same sender. No more killing vibration or stale fuel.

You have 3 choices. One replace the sender (last choice for me, but the sender could always be bad). Two, remove it and take a can of aerosol carb spray with the long plastic nozzle and hold it up against the sender orifice and give it 4-5 quick short blast of carb cleaner. Keep you face out of the way. :silly:
I have tried this and many engines and so far has worked 100% of the time.

The last thing you can do to help yourself after one of the previous two things is re-locate the fuel pressure sender so the orifice points down or at least horizonta to the engine and locate it high, equal to or higher than the carb balance tube.
This will allow the fuel to drain away from the sender orifice when the plane is sitting in the hangar overnight or for longer periods. When you start back up the fuel pressures right back up. All that I have done this mod to has never again had an issue and the sender's last for years.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Fuel pressure

by Richard Pingert » 9 years ago

Richard Pingert

5 8 0

Thanks Roger will try that little trick
Regards Rick

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Fuel pressure

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