Home > VansAirForceForums

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

- Today's Posts | Insert Pics

Old 05-16-2018, 01:51 PM
6adan 6adan is offline
Join Date: Feb 2014
Location: Florence,Al.
Posts: 29
Default o320 running rich

New (not flying yet) RV6A engine starts very good but when you start to add power it becomes very rich running and bogs down. I pulled the carb off and checked float setting and it was good. Need some ideas on what else I could look for.

Thanks Dannie
Reply With Quote
Old 05-17-2018, 10:03 AM
Raymo's Avatar
Raymo Raymo is offline
Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 1,878

Does it run better if you lean the mixture during run-up?
RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ AFP FM-150 FI, 1 PMag, Vetterman Trombone Exh, SkyTech starter, PlanePower Alt
Catto 3 blade NLE, FlightLines Interior, James cowl, plenum & intake, Anti-Splat -14 seat mod and nose gear support
All lines by TSFlightLines

"The object of the game, gentlemen, is not to cheat death: the object is not to let him play."
Patrick Poteen, Sgt. U.S. Army
Reply With Quote
Old 05-17-2018, 12:45 PM
snopercod's Avatar
snopercod snopercod is offline
Join Date: Aug 2016
Location: Asheville, NC
Posts: 1,582

How do you know it's running rich? Can a bystander see black smoke coming out the stacks? Is this intermittent, as when you are pushing the throttle in - that could be your accelerator pump linkage is set wrong.
(2018 dues paid)
Reply With Quote
Old 05-17-2018, 01:44 PM
lr172 lr172 is offline
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 3,581

Most common reason for running excessively rich on a carb is a fuel level issue in the bowl. Too high of a fuel level in the bowl causes rich condition. Most typical reasons are that the float developed a leak (brass) or became saturated (composite float) or there is a piece of trash stuck in the needle/seat interface. On a new or rebuild carb, I would suspect an incorrect float height setting (accuracy is usually within a 32nd of an inch) or trash in the needle/seat. With new fuel plumbing, it would not be surprising to find junk in the needle/seat area, especially if you didn't flush the lines before connecting to the carb. I flushed two gallons through my fuel system with a filter before first start and got a lot of junk.

As others stated, be sure you are rich. A "bog" is most typically experienced when increasing throttle into a lean condition and is often due to insufficient enrichment from the accelerator pump. If the engine regains performance in a couple of seconds, it is the accel pump. If it continues to labor at noticably low power, it is a lean mixture. Lean conditions are typically not characterized as rough running until just about the point where the engine stops. An overly rich condition produces rough running with reduced power output and classic black colored exhaust and if bad enough cause the engine to roughly quit. Even inexperienced folks don't typically characterize the condition as a "bog."

Assuming this is not a transient accel pump issue, you can try accelerating into the bog condition and then pull slowly back on the red knob. If it eventually gets better, you're rich. If it just gets worse, you're lean. The mixture knob meters fuel out of the bowl and before the jets. Therefore it can compensate for the increase fuel flow due to the high level in the bowl.

RV-6A / IO-320, Flying as of 8/2015
RV-10 in progress

Last edited by lr172 : 05-17-2018 at 02:14 PM.
Reply With Quote
Old 06-15-2018, 06:30 PM
6adan 6adan is offline
Join Date: Feb 2014
Location: Florence,Al.
Posts: 29

Thanks for the response. We could tell it was running rich because of the black smoke and black plugs and just not running good with the throttle open. We are showing around 18 lb. of fuel pressure. Here is what we have done.
1 Installed a smaller main jet, this made it run better but we could not get the static RPM we should 1970 to 2000 is all it will do.
2 Got a new fuel pump and Rebuilt carb. This did not help.
3 Checked the prop to be sure it was not over pitched 68x76. It is correct according to Mr. Prince
Can anyone give some reasons why we can't get the RPM we should?
Reply With Quote
Old 06-15-2018, 07:14 PM
Jpm757 Jpm757 is offline
Join Date: May 2013
Location: Sherman, CT
Posts: 284

Fuel pressure 18 PSI? Way too high for a carbuerated engine. You should be running around 5-6 PSI. Sounds like you may have the wrong fuel pump.
RV6 completed 1991 sold.
RV7 #72018 N767T first flight 11/21/2017 170+ hrs.
IO-360M1B MT 3 blade, Dual AFS 5600.
1941 J3 Cub skis floats.
2019 dues gladly paid.

Last edited by Jpm757 : 06-15-2018 at 09:55 PM. Reason: Typo
Reply With Quote
Old 06-16-2018, 08:23 AM
Steve Melton's Avatar
Steve Melton Steve Melton is offline
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 1,903

Originally Posted by Jpm757 View Post
Fuel pressure 18 PSI? Way too high for a carbuerated engine. You should be running around 5-6 PSI. Sounds like you may have the wrong fuel pump.
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 700+ for all

Simplicity is the art in design.

see Amanda Melton for
Reply With Quote
Old 06-16-2018, 08:30 AM
robertahegy's Avatar
robertahegy robertahegy is offline
Moderator/Tech Counselor
Join Date: Jan 2005
Location: East Troy, WI
Posts: 1,939

Way too much fuel pressure. Those 0-320s can run on gravity feed with less than half a pound pressure. Fuel probably blowing right by the needle and seat.

Roberta Hegy
Built/Flew an RV-7A
Air Troy Estates, East Troy, WI
Ford Expedition and TRICE "Q"
Built Glen L "ZIP" Classic Outboard Runabout and Super Spartan Hydroplane
Glen L Torpedo
Reply With Quote
Old 06-16-2018, 12:06 PM
6adan 6adan is offline
Join Date: Feb 2014
Location: Florence,Al.
Posts: 29

I am thinking the Dynon reading on the fuel pump is not correct because this is the second FP and it is a new low pressure pump from Aircraft Spruce.
Reply With Quote

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 12:32 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.