Author Topic: MS 290 tank pressurizing  (Read 1412 times)

0 Members and 14 Guests are viewing this topic.

Offline farmboy

  • Moderator
  • Nitro Hotsaw
  • *******
  • Posts: 1170
  • Karma: 150
  • Location: Hayesville, NC

  • Total Badges: 31
    Badges: (View All)
    Level 6 Eighth year Anniversary Seventh year Anniversary Sixth year Anniversary 1000 Posts Old Browser
MS 290 tank pressurizing
« on: August 13, 2014, 10:54:59 pm »
Put a fuel line on it year or so ago been on the shelf since.  Got it out to service it as my other MS290 I sold keeps coming back w/little probs.  Told the guy I would swap it if he wanted or buy it back which I really don't want to do.  Fired it up 30 sec running gas was spewing out around the gas cap.  Shut off opened cap tightened made sure the flippys were locked 10 sec. gas spewing.  What the heck never had that happen before.  What causes that?  Bad carb diaphgram.  Plan on kitting it.
Shep

Share on Facebook Share on Twitter


Offline jmester

  • Global Moderator
  • Nitro Hotsaw
  • *******
  • Posts: 2106
  • Karma: 171
  • Location: MD

  • Total Badges: 36
    Badges: (View All)
    Tenth year Anniversary Nineth year Anniversary Eighth year Anniversary Seventh year Anniversary Sixth year Anniversary Level 6
Re: MS 290 tank pressurizing
« Reply #1 on: August 13, 2014, 11:04:33 pm »
Would say a tank vent or your flip cap is trash.
FEAR NO TREE. FEAR GOD.

Offline 660magnum

  • Global Moderator
  • Nitro Hotsaw
  • *******
  • Posts: 6437
  • Karma: 249
  • For The Love Of Chainsaws
  • Location: NCO

  • Total Badges: 39
    Badges: (View All)
    Seventh year Anniversary Sixth year Anniversary Fifth year Anniversary Fourth year Anniversary 5000 Posts Third year Anniversary
Re: MS 290 tank pressurizing
« Reply #2 on: August 13, 2014, 11:59:22 pm »
You could test the tank vent with your Vacuum/pressure test set up that you use to check engine crankcase pressure/vacuum integrity.

I checked the gas tank vent on the last chainsaw (025) I did with my Mity-Vac 6500 and the tank vent performed as the Workshop manual says it should. The vent passed both pressure and vacuum slowly. Use about 7 psi pressure or 15 inches of vacuum (About 1/2 atmosphere)

There should be nothing making gasoline pressure in your gas tank?  However, gasoline has a vapor pressure of 7 or 8 psi, so the tank should build pressure with the chainsaw just setting and not running if the vent is plugged? Running a chainsaw should not have an effect on tank pressure?
We should share what we know... someone may learn...
That knowledge can live after us... and that "Pays It Forward".
Be all that you can be . . .

Offline aclarke

  • Nitro Hotsaw
  • *******
  • Posts: 1676
  • Karma: 172

  • Total Badges: 25
    Badges: (View All)
    Fourth year Anniversary Third year Anniversary 1000 Posts Second year Anniversary Level 5 500 Posts
Re: MS 290 tank pressurizing
« Reply #3 on: August 14, 2014, 12:07:45 am »
Do the newer EPA vents let pressure out or just air in? Really high pop off pressure on new saws is in part too keep tank pressure from pushing fuel into the carb and vapors venting to the atmosphere from what I understand

Offline 660magnum

  • Global Moderator
  • Nitro Hotsaw
  • *******
  • Posts: 6437
  • Karma: 249
  • For The Love Of Chainsaws
  • Location: NCO

  • Total Badges: 39
    Badges: (View All)
    Seventh year Anniversary Sixth year Anniversary Fifth year Anniversary Fourth year Anniversary 5000 Posts Third year Anniversary
Re: MS 290 tank pressurizing
« Reply #4 on: August 14, 2014, 12:27:46 am »
Trying to consider how the MS 290 is made . . .

This is a clamshell design so there is not connection possibilities like a leaking gasket in the crankcase. The 290 has no gaskets about the engine except the exhaust gasket.

There are only two connections to the tank.
One is the fuel line
and the other is a combination vent line/primer bulb return line

There could be a problem with this combination system of the vent line but there would have to be additional air pumped into the tank some way to build pressure while running?

Normally, the purge pump is only pulling fuel through the carburetor, so the fuel itself is merely in a loop.

If the fuel line from the tank to the carburetor has a air leak, Then there could be a source of additional air? But with all that pressure there would certainly be a fuel leak also in the fuel line?
We should share what we know... someone may learn...
That knowledge can live after us... and that "Pays It Forward".
Be all that you can be . . .

 

Related Topics

  Subject / Started by Replies Last post
6 Replies
817 Views
Last post December 17, 2012, 05:29:48 pm
by Al Smith
8 Replies
2112 Views
Last post May 28, 2014, 06:14:37 am
by fordfairlane78
11 Replies
534 Views
Last post August 19, 2014, 08:19:54 pm
by basod
6 Replies
968 Views
Last post November 08, 2021, 02:24:00 pm
by partner
7 Replies
930 Views
Last post September 03, 2014, 09:35:37 am
by KilliansRedLeo
1 Replies
252 Views
Last post March 07, 2015, 12:41:37 pm
by Cut4fun .
0 Replies
151 Views
Last post April 23, 2015, 04:35:16 pm
by Giles
7 Replies
306 Views
Last post December 08, 2015, 12:07:28 pm
by Cut4fun .
1 Replies
409 Views
Last post February 25, 2016, 12:17:15 pm
by Cut4fun .
0 Replies
514 Views
Last post November 05, 2016, 05:11:07 pm
by blueflame