High fuel pressure alarm.

[Eddie in NC]

Took a short flight and the high fuel pressure alarm went off on climb out. It is a 2007 CTSW. Pressure was 6.2 lbs and going back down and up for 4 or 5 minutes. Leveled off and headed back to the airport and it dropped to the normal 4.5 lbs and stayed that way for app. 15 minutes until I landed. Any ideas? Thanks Eddie

 

 

[Tom Baker]

What are the limits set for on the Dynon? If you have the new style fuel pump, the the upper limit for fuel pressure is 7.2 PSI. The old fuel pumps were lower. The limits in the Dynon should have been changed when the pump was changed, but often time they were not. In most cases the new pump will work okay with the old settings, but occasionally the pressure will go higher. I would change the top of the green to 6.5, yellow from 6.6 to 7.1, and set the red line at 7.2. On the bottom end 2.2 is the minimum, and it did not change.

[Eddie in NC]

Thanks Tom. I will check the logs to see if a new fuel pump was installed. I would think so but will look. I have put about 30 Hrs on the plane since buying it last year and this is the first time that I have seen it do that. It always shows around 4.5 lbs. The main reason for concern is that the Rotax manual says that 5.8 is the maximum.

[Eddie in NC]

There was a new fuel pump installed . Part # 899-115.

[Tom Baker]

The most current Rotax operators manual shows .5 bar, or 7.26 PSI for fuel pumps with serial number 11-0036 and after, That would be the new style fuel pump. 5.8 PSI was for the old style pump.

[Eddie in NC]

Thanks Tom. I will reset the Dynon this weekend.

[procharger]

I still want to know why is changes from startup to normal operating temps mine always

shows higher on first start up as it warms up drops back to around 4.5 ??

[Skunkworks85]

4 hours ago, procharger said:

I still want to know why is changes from startup to normal operating temps mine always

shows higher on first start up as it warms up drops back to around 4.5 ??

That is a good question, Possibly caused from the orifice on the return line increasing in diameter due to heat expansion? My Pressures exhibit the same behavior. 

[MileHighCTLS]

I find this thread interesting because my 2011 CTLS recently had a High Fuel Pressure alarm, when the Dynon showed my fuel pressure going up to 8.2 to 8.4, then back to normal. It was quite intermittent. I should mention the engine ran flawlessly during the entire time. Since, this happened after run-up, during taxi for takeoff, I decided not to fly.

Interestingly, this comes after several hours of trouble-free flying. However, last year, I had multiple fuel pressure alarms for Low Fuel Pressure! I changed out the sending unit thinking that was the problem. I used the old-style "VDO" sending units. At the time I replaced that sender, I was told there is an updated sender? Could that be my problem?

I know I am covering a lot of ground here, but any answers my fellow CTers may have will be much appreciated! 

[AGLyme]

Have your A&P review your fuel filters... for peace of mind.

[Roger Lee]

Two common things that cause this intermittent high fuel pressure. I have had this numerous times with owners.

These are easy to rule in or out. Usually the high alarms are from a poor ground or poor connection.

First take a pair of pliers and squeeze the two spade connectors on the sensor terminal EVEN if they feel firm. This drove me crazy for a month until I did this on my own plane once.

Second make sure the through the firewall ground bolt is TIGHT. Don't just feel it. Put a wrench on it. Double check the wires going through the firewall to make sure no wire has been rubbed through.

Last replace the sender. Usually a bad sender gives low alarms, but when other items are ruled out then give this a shot. VDO 360-043.   https://www.amazon.com/VDO-360-043-Pressure-Sender/dp/B004C10G02 

 

[Tom Baker]

1 hour ago, AGLyme said:

Have your A&P review your fuel filters... for peace of mind.

Fuel filter and high pressure is a fuel injected engine issue, it doesn't apply to the carbureted engines. 

[Roger Lee]

1 hour ago, Tom Baker said:

Fuel filter and high pressure is a fuel injected engine issue, it doesn't apply to the carbureted engines. 

I agree with Tom.

[AGLyme]

My bad, thx

[Tom Baker]

1 hour ago, AGLyme said:

My bad, thx

No problem, just trying to educate. Everyone likes to give advice, and pass along their experiences, that is a good thing. The problem is that sometimes the advice is predicated on something different than what the OP has. Unfortunately these airplanes are not a one size fits all, and what applies to yours might not work for someone else. For you high fuel pressure means you need to check the filter. For someone with a carbureted engine not so much. Trying to keep it all straight and paying attention to what someone is asking about can be mind numbing.  

[AGLyme]

all good Tom, agreed...