Fuel pressure issue, very perplexed, need help

[rocketbob]

Originally Posted by taverroi

Please help me if you can...what can I do?..suggestions?.. Please somebody...

Tango

Post pics of your fuel line routing. Some simple fuel line changes will likely fix this problem.

[Kevin Horton]

Where in your fuel system is the fuel pressure sensed?

[David-aviator]

Fuel is vaporizing in the line between the firewall and the pump inlet due to residual, radiating heat after landing. The fuel pump will not move vapor, only liquid. That's why the pressure is low. Shield the fuel line from after landing heat and the problem should go away.

With a cold engine start there is no residual heat and no problem, pressure is normal, all is well. In flight all is well because of air flow cooling through the area.

Its the only explanation that makes any sense.

[taverroi]

Sorry Guys been outta touch due to heavy work load.

Ok, I will take pics tommorow of fuel line rounting but havent figured out how to post them here on this forum

Fuel senser is mounted on the left most position of the firewall, right up against it (pilot side).

Fuel vaporization on the inlet line sounds most probable. I have purchased special fuel line insulation and have begun insulating all the fuel lines in there intirety. The inlet side line and line to the senser has was insulated today. In additon I ordered the fuel pump cooling shroud kit from vans and will install it when it arrives. Insulation of the outlet side fuel line will be accomplished tommorow. Ive also had a set of louvers for the bottom cowling made (delivered to me today) and will be installing these as well to assist in removing residual heat and to provide a cooler engine inviroment.

Anything else guys. Im taking all suggestions serious and am implimenting all thing possible for the best results possible and the best safty.

Very much apprieciate all of you.

Tango

[TS Flightlines]

get us some pics and we can help, as all Rv's are not created equal. If you still are having issues, fly it over to ridgeland---we have several people over here that can help out.
Tom

[taverroi]

Ok...All fuel lines insulated including the fuel line from the andair fuel valve running across the floor board to the firewall.

Test flight flawless...right up until landing...fuel pressure issue showed its ugly face again...it fell between 9 to 15 with slight fluctuation. Engine sputtered a bit after taxing for a while but it never shut off...like before...hmmm

I cant figure out for the life of me how to post pics. I took a bunch of the fuel line routing after insulation them and was gonna post them with this reply, but unless someone can give me a point by point direction I wont be able to. I've posted pics on other forum in this format before so I'm kinda confused as to why I can do it here. Help if you can.

My next actions are going to be (your opionions please) 1. fuel pump cooling shroud install. 2 Louver vents installed on the bottom of the cowling. 3. Exaust pipe heat protectors strategiclly located in areas of fuel lines.

Any other thoughts or suggestions? I'm confident to fly as this issue clearly does'n show itself initally or in flight...just after landing and taxing. But I would like to figure it out. Do you think I'll just have to live with it?

Tango

[RV8RIVETER]

Do you have a Van's gascolator?

A neighbor had a very similar issue with his IO-360 RV-6. He was getting air from the gascolator when he pulled the throttle back, but didn't show up until flying for a bit, usually on final. Once it was removed, no more problems.

[taverroi]

I dont think that I do. Iwill ckeck tommorow.

[DENMACRES]

I HAVE HAD TO INSULATE MY FUEL LINES ABOVE THE ENGINE. IT HELPED A LOT TAXIING AFTER LANDING. DENNIS -6, I-O360

[Fred.Stucklen]

Originally Posted by Bavafa

I totally agree. I have two other friends with the same setup/engine and flying with them have not seen such behavior, nor mine has ever done it and my min fuel pressure is set to 19 PSI. The rough start/running typically happens when you shut down the engine and heat builds up but not right after landing and while taxing. My 2 cents as usually.

So how much the same are they? Do you both have Mechanical fule pump cooling ? Do you both have fire sleeves on your fuel lines? What else might be different? Are you cowl exits exactly the same? How about the engine baffling? Are you both flying out of the same field under the same conditions?
From the original discription, I'd say that this is a taxi cooling issue for sure. The fact that the Aux pump brings the fuel pressure back up would seem to indicate a hot engine compartment causing vapor lock issues in the fuel lines within the engine campartment, probably BFORE the mechanical pump. The fact that a new high pressure pump didn't change the situation confirms it.
If you don't already have one, add an air blast tube flowing cool upper plentum air onto the mechanical fuel pump. Better yet, put a showd around the mechanical pump with air. Be sure that ALL you engine compartment fuel lines have fire sleeve and that they have air flow onto them.
FWITW, I've seen these issues before, and this is how I've mitigated them....