VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 09-09-2012, 01:31 PM
mike newall's Avatar
mike newall mike newall is offline
 
Join Date: Jan 2005
Location: Yorkshire, England
Posts: 2,052
Default Hot Rough Running

I'm noticing after a fuel stop, when I restart the engine it hesitates, surges and nearly quits. Runs like a bag of spanners - sorry, wrenches.....

Power check clears it and on take off, no problem.

I can't decide whether it is fuel vapour locking or a problem with hot P-Mags.

Any suggestions gratefully received
__________________
"I add a little excitement, a little spice to your lives, and all you do is complain!" - Q

Donated in 2020
Reply With Quote
  #2  
Old 09-09-2012, 01:37 PM
Geico266's Avatar
Geico266 Geico266 is offline
 
Join Date: Feb 2005
Location: Huskerland, USA
Posts: 5,862
Default

It would help if we knew what plane, engine, and fuel system you have, and what fuel you are burning.
__________________
RV-7 : In the hangar
RV-10 : In the hangar
RV-12 : Built and sold
RV-44 : 4 place helicopter on order.
Reply With Quote
  #3  
Old 09-09-2012, 01:52 PM
mike newall's Avatar
mike newall mike newall is offline
 
Join Date: Jan 2005
Location: Yorkshire, England
Posts: 2,052
Default

Sorry,

Used to be on my signature but I changed it.

RV7

Mattituck ECI motor, TMX IO-360, dual P-Mags, Silverhawk Fuel Injection.

Would never consider anything other than Avgas.......

The temperature spots on the P-Mags haven't gone black.
__________________
"I add a little excitement, a little spice to your lives, and all you do is complain!" - Q

Donated in 2020
Reply With Quote
  #4  
Old 09-09-2012, 01:55 PM
Squeak Squeak is offline
 
Join Date: Jan 2005
Location: Indiana
Posts: 270
Default Vapor Lock

Sounds like fuel vapor lock.
Reply With Quote
  #5  
Old 09-09-2012, 02:04 PM
RonB RonB is offline
 
Join Date: May 2006
Posts: 16
Default

Try leaning your mixture after startup. Not sure your location but I'm at 5000' and have to lean every time I stop for fuel. I also have the Silver Hawk system.

Ron B
Reply With Quote
  #6  
Old 09-09-2012, 02:07 PM
Cfrisella's Avatar
Cfrisella Cfrisella is offline
 
Join Date: Aug 2008
Location: Sun city, Ca.
Posts: 255
Default

I have pretty much the same setup and mine does the same thing. Don't think it would ever stop running, but sure not the same smooth sound. Also does it after landing towards the end of a long taxi while really leaned out. I've just assumed its the slow moving fuel in the injector lines getting too hot and boiling.
__________________
Cheers,
Chris Frisella
Www.boneheadcomposites.com
Reply With Quote
  #7  
Old 09-09-2012, 02:36 PM
az_gila's Avatar
az_gila az_gila is offline
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
Exclamation

Quote:
Originally Posted by RonB View Post
Try leaning your mixture after startup. Not sure your location but I'm at 5000' and have to lean every time I stop for fuel. I also have the Silver Hawk system.

Ron B
Highest spot in England is only 3200 ft.

And it's a nice hike up - Scafell Pike.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
Reply With Quote
  #8  
Old 09-09-2012, 03:20 PM
Andy Hill's Avatar
Andy Hill Andy Hill is offline
 
Join Date: Dec 2005
Posts: 976
Default

Quote:
I can't decide whether it is fuel vapour locking or a problem with hot P-Mags.
fuel vapour locking IMHO.

Fuel Pump on will help a bit...
__________________
Andy & Ellie Hill
RV-8 G-HILZ
RV-3B G-HILI very slow build
RV8tors
Reply With Quote
  #9  
Old 09-09-2012, 04:13 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,686
Default

If it was actual "vapor lock" no fuel would be getting to the servo and the engine would quit (vapor lock occurs prior to the engine pump and blocks fuel flow).

I think the most likely cause is fuel boiling in the fuel injector lines and fuel distribution manifold. This is a common problem on most FI engines on a quick-turn (especially in hot climates). Not much you can do about it unless you want to add a purge valve (circulates cool fuel up the to the manifold), or as you have done, clearing with some extra power to purge the hot fuel.

Just my 2c
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
Reply With Quote
  #10  
Old 09-09-2012, 05:56 PM
Dakbuster Dakbuster is offline
 
Join Date: Oct 2006
Location: Tauranga New Zealand
Posts: 26
Default

IMO Boiling fuel in the injector lines.
I have an IO-360. With dual P Mags. Runs well when cold but after flight and or a long taxi, engine runs with lots of missing and sounds terrible, to fix, apply power once the fuel starts flowing the missing seems to reduce BUT it won?t go away until full power for takeoff, that fixes it quickly.

FWIW Just after shut down the top of my cowl is nice and cool to touch but give it 5 minutes and you could fry eggs on it. The bottom cowl stays cool, inside, the exhaust is less than 1 inch away from the bottom cowl but you would never know it. I guess this just proves hot air rises and all this heat is boiling up those little fuel lines on top of the engine. I believe the fuel pressure in these lines is around 4psi and there is not much flow at idle so I think this is the reason for the rough running. I have got used to it now and don?t worry about it. I also open my oil door after shut down to let as much hot air out from behind the engine where my P mags are.
__________________
Bruce Black
New Zealand
RV6 finished and flying.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 05:35 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.