I am beginnng to see red

[hitech]

On a side note to the A&P's.

My RV (about 2k hours now do for a new engine) has always a strange issue that we have never been able to resolve.

When running on mechanical full pump only in level cruise some days the fuel pressure gauge will fluctuate from about 22 down to 12 and back up.
Turning on the electrical and things are rock steady.

Note the engine has never shown any indication of power change. Except for the time of a real mechanical pump failure. Only time I ever got cleared direct 52F over the center of DFW. No way was I going to fly under the bravo running only on electric.

Things we have tried.
1. Moving electric fuel pump from engine side of fire wall to internal. (was thinking possible vapor lock).
2. Replaced Mechanical pump.
3. Insulated all fuel lines.
4. Replace the sensor.
5. Replaced the gauge.
6. Rebuilt complete induction/servo system along with flow calibration to all cylinders.

Any ideas?

Dale

[FLS]

Did you post in the RV  forums?

[hitech]

Did you post in the RV  forums?

Years ago I believe.

Dale

[FLS]

A quick read there suggests it's not uncommon and not a problem. Cause is unknown but air pressure and temp are the suspects.

[hitech]

A quick read there suggests it's not uncommon and not a problem. Cause is unknown but air pressure and temp are the suspects.

We stopped trying to find it after the fuel pump move. That was 1200 hours ago.

HiTech

[Hetzer7]

On a side note to the A&P's.

My RV (about 2k hours now do for a new engine) has always a strange issue that we have never been able to resolve.

When running on mechanical full pump only in level cruise some days the fuel pressure gauge will fluctuate from about 22 down to 12 and back up.
Turning on the electrical and things are rock steady.

Note the engine has never shown any indication of power change. Except for the time of a real mechanical pump failure. Only time I ever got cleared direct 52F over the center of DFW. No way was I going to fly under the bravo running only on electric.

Things we have tried.
1. Moving electric fuel pump from engine side of fire wall to internal. (was thinking possible vapor lock).
2. Replaced Mechanical pump.
3. Insulated all fuel lines.
4. Replace the sensor.
5. Replaced the gauge.
6. Rebuilt complete induction/servo system along with flow calibration to all cylinders.

Any ideas?

Dale

Either you didn't say or I missed what exactly the engine is but thats really low fuel pressure to have in an injected motor, IO-360 Lycoming? If so they should run 40-60 psi at the fuel inlet.

For an O-360, fuel pressure should be 12-14 and max. 18psi, and I would check the carb float level tab adjustment; anyway thats where my thinking takes me <S>

[icepac]

If this issue cropped up only after climbing high enough for lower temperature or after running a pretty long while.......but not at first start, I would check if your tank is allowing air in such that it doesn't end up in a partial vacuum.

Just a shot in the dark.

[Peanut1]

Yep utter BS.

BTW there are a number of misleading stats in the article about 20% accidents vs 10% of fleet.

First it assumes all experimental are the same.

2nd it assumes the experimental class is flown the same amount as standard aircraft. My assumption would be that experimental get more hours then standard by a substantial amount.

HiTech

Uh.... rule 5 0r six???? forget what one lol

[saggs]

If this issue cropped up only after climbing high enough for lower temperature or after running a pretty long while.......but not at first start, I would check if your tank is allowing air in such that it doesn't end up in a partial vacuum.

Just a shot in the dark.

My first thought as well, check your fuel tank vents.

[hitech]

Either you didn't say or I missed what exactly the engine is but thats really low fuel pressure to have in an injected motor, IO-360 Lycoming? If so they should run 40-60 psi at the fuel inlet.

For an O-360, fuel pressure should be 12-14 and max. 18psi, and I would check the carb float level tab adjustment; anyway thats where my thinking takes me <S>

LYC IO-360-A2A

Yes it's really low but that is why it almost has to be false reading because there is no power change. When electric is on the gauge is steady, but no difference in engine sound in any way.

Also remember it rhythmically cycles. (6 - 10 sec range).


The plugged vent would make since except I would think you would see some type of engine change with that low of a drop.

Also remember it has been doing this for more than 10 years and 2000 hours.

HiTech

[Skyguns MKII]

LYC IO-360-A2A

Yes it's really low but that is why it almost has to be false reading because there is no power change. When electric is on the gauge is steady, but no difference in engine sound in any way.

Also remember it rhythmically cycles. (6 - 10 sec range).


The plugged vent would make since except I would think you would see some type of engine change with that low of a drop.

Also remember it has been doing this for more than 10 years and 2000 hours.

HiTech

Time to bust out our glencoes and 43.13s guys?