VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics

  #1  
Old 03-10-2017, 11:35 AM
Dave Bernard's Avatar
Dave Bernard Dave Bernard is offline
 
Join Date: Dec 2010
Location: SLC UT
Posts: 68
Unhappy First start- no start.

What I had hoped would be a milestone day yesterday ended in disappointment...

I've got a new o-360, Dynon Skyview on my rv8.

We did the pre-oil procedure, put the plugs back in and out some gas in and prepared to start- the first interesting thing was the fuel pressure. Fuel pump came on and you could hear the fuel being pumped into the carb, but once it was full the pressure indication shot up to 17 psi or so. This seemed super high so I chalked it up to an indication problem, and shut off the pump. I have the facet pump from Vans which should only put out 6psi. The fitting from the engine fuel pump has the restrictor fitting installed.

We cranked multiple times, normal start, hot/flooded start, fuel pump on, fuel pump off, no dice. Not even a sniffle came from the engine, no indication of firing at all.

We drained the carb to see if it was contaminated with the preservation oil still, no dice, just fuel.

Pull the plugs, the bottom plugs were super oily which I suppose is normal for this new engine. Top plugs were wet but not oily. Cleaned and reinstalled. Not convinced the cylinders are getting fuel.

I didn't check the mag timing- the engine ran at the factory for a few hours before it was shipped, so I can't imagine the timing is wrong. My mag wiring goes from the Acs switch with pickoffs installed for Dynon tach indication to the mags with a shield ground pigtail there. I pulled the pickoffs to see if that was interfering, no luck.

The Dynon also showed 0 RPM during the start cycle, is that normal- do the RPMs not show until the engine is running?

Thoughts?
__________________
"Almost Done"

CAF Stearman pilot
Reply With Quote
  #2  
Old 03-10-2017, 11:45 AM
YellowJacket RV9 YellowJacket RV9 is offline
 
Join Date: Oct 2012
Location: Clearwater, FL KCLW
Posts: 1,281
Default

The fuel pressure is easy enough to verify with an cheap fuel pressure gauge plumbed in, although an indication error seems much more likely. An ignition issue would be my guess.

I would not take it for granted that the magnetos are timed correctly, as I recall some past posts here indicating that their engines arrived from Lycoming incorrectly timed or maybe even not at all.

Have you verified all the magneto wiring (p-leads properly grounding, leads to proper cyclinders, etc)? A timing check would help with this, and certainly be worth it. I was sure I had timed mine right the first time, and I was wrong

Chris
__________________
Chris Johnson
RV-9A - Done(ish) 4/5/16! Flying 4/7/16
Reply With Quote
  #3  
Old 03-10-2017, 11:47 AM
stancaruthers stancaruthers is offline
 
Join Date: Apr 2016
Location: Paradise tx
Posts: 192
Default Spark

When the grandson was 6, I would always have him hold the spark plug wire while I cranked the mower.....if he jumped or cried I was getting fire.
Reply With Quote
  #4  
Old 03-10-2017, 11:58 AM
Auburntsts's Avatar
Auburntsts Auburntsts is offline
 
Join Date: Jan 2005
Location: Tampa, FL
Posts: 2,861
Default

Of the 14 possible causes for hard starting listed in the Lycoming Trouble Shooting Guide, http://www.lycoming.com/node/17944 , 10 deal with the ignition system. My advice, look at the guide and methodically check and rule out systems as the culprit in a linear fashion. For example start with fuel and once that's ruled completely out as a problem, then and only then move on to the next potential item.
__________________
Todd "I drink and know things" Stovall
PP ASEL-IA
RV-10 N728TT - Flying!
WAR EAGLE!

Last edited by Auburntsts : 03-10-2017 at 12:02 PM.
Reply With Quote
  #5  
Old 03-10-2017, 12:00 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
Default

You need to confirm that fuel pressure! If you mistakenly got a high pressure pump installed that is putting out 17 PSI, that is your problem. The needle / seat in the carb cannot hold back anywhere near that pressure level and the carb bowl will overfill, causing a very rich mixture. The wet upper plugs (assuming it is gas and not oil), likely confirms the overly rich mixture.

Larry
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Reply With Quote
  #6  
Old 03-10-2017, 12:06 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
Default

comments in line below

Quote:
Originally Posted by Dave Bernard View Post
What I had hoped would be a milestone day yesterday ended in disappointment...

I've got a new o-360, Dynon Skyview on my rv8.

We did the pre-oil procedure, put the plugs back in and out some gas in and prepared to start- the first interesting thing was the fuel pressure. Fuel pump came on and you could hear the fuel being pumped into the carb, but once it was full the pressure indication shot up to 17 psi or so. This seemed super high so I chalked it up to an indication problem, and shut off the pump. I have the facet pump from Vans which should only put out 6psi. The fitting from the engine fuel pump has the restrictor fitting installed.

We cranked multiple times, normal start, hot/flooded start, fuel pump on, fuel pump off, no dice. Not even a sniffle came from the engine, no indication of firing at all.

We drained the carb to see if it was contaminated with the preservation oil still, no dice, just fuel.

Pull the plugs, the bottom plugs were super oily which I suppose is normal for this new engine. Top plugs were wet but not oily. Cleaned and reinstalled. Not convinced the cylinders are getting fuel.

What leads you to this conclusion? Did you smell gas when you pulled the plugs? They typically are only wet due to either oil or gas

I didn't check the mag timing- the engine ran at the factory for a few hours before it was shipped, so I can't imagine the timing is wrong. My mag wiring goes from the Acs switch with pickoffs installed for Dynon tach indication to the mags with a shield ground pigtail there. I pulled the pickoffs to see if that was interfering, no luck.

Mags could get bumped in shipping or installation. I would confirm the timing.


The Dynon also showed 0 RPM during the start cycle, is that normal- do the RPMs not show until the engine is running?

I would expect the Dynon to show RPM at cranking speeds. A 0 here could indicate incorrect EMS setup, wrong resistors installed or nothing being sensed on the P lead, which would mean the mag is not firing. You may want to consider wiring your P leads through mechanical switches until you confirm that your mags are firing. Bad switches and incorrect wiring seem to happen frequently with the keyed ign switch. P-lead switch should be open when you want a spark and closed (short to ground) when you don't.

Thoughts?
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 03-10-2017 at 02:05 PM.
Reply With Quote
  #7  
Old 03-10-2017, 01:53 PM
gasman gasman is offline
 
Join Date: Mar 2007
Location: Sonoma County
Posts: 3,821
Default

Check your ignition (mag) switch and make sure that you are not grounding your impulse mag also as you are cranking the starter.

As far as the high fuel pressure goes, it will need to be resolved later. Just run the pump till you see pressure (3#) then shut it off. The motor will run fine on the mechanical pump.

Do double check the timing.
__________________
VAF #897 Warren Moretti
2019 =VAF= Dues PAID
Reply With Quote
  #8  
Old 03-10-2017, 02:53 PM
Dave Bernard's Avatar
Dave Bernard Dave Bernard is offline
 
Join Date: Dec 2010
Location: SLC UT
Posts: 68
Default

172: nothing led to that conclusion- I just don't know. I assume it's getting gas to the cylinders but I'm not ruling out something weird with the carb.

The Fuel pressure deal was what I expected: the Dynon thought it had the 50psi sensor, which is why it was showing bad info... Switched to the 15psi sensor in hardware mapping and now showing 5 psi.

On to the ignition....
__________________
"Almost Done"

CAF Stearman pilot
Reply With Quote
  #9  
Old 03-10-2017, 03:03 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,516
Default

Quote:
Originally Posted by Dave Bernard View Post
172: nothing led to that conclusion- I just don't know. I assume it's getting gas to the cylinders but I'm not ruling out something weird with the carb.

The Fuel pressure deal was what I expected: the Dynon thought it had the 50psi sensor, which is why it was showing bad info... Switched to the 15psi sensor in hardware mapping and now showing 5 psi.

On to the ignition....
If you did not smell gas and have it dripping out, you can not be sure. Did you purge/test the fuel flow to the carb? One system test I worked on, 2 quarts of contaminated fluid came out. It was injected, so maybe a carb would be less. I would not just assume to have fuel, you need a positive indicator. Even to walking off with a wet plug and putting a match under it. Even 90% oil and water can smell like gasoline. Be sure, then move on. Pretty basic.

Keep at it, debugging is part of the process. It is necessary to a safe aircraft.
__________________
Bill

RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
Reply With Quote
  #10  
Old 03-10-2017, 06:37 PM
brad walton brad walton is offline
 
Join Date: Jul 2007
Location: Cypress, TX
Posts: 526
Default

My first start was also a nonstart. It was due to my misunderstanding of how to wire the mags as gasman suggested. When switch is in the "on" position or circuit is closed, the mags are grounded and won't fire. Open circuit equals not grounded and mags will fire
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 01:07 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.