[AT] OT - JD STX38 fuel problems

[Larry D. Goss]

What you've described here sounds like a typical vapor pressure problem,
Mike.  Greg's suggestion about a different brand of fuel filter may
solve it.  Changing blends or octane ratings of gasoline may have the
same effect.  I've never been able to predictably determine when the
fuel supply system is going to react the way you are describing it.
When I replace the fuel filter on John Deere equipment, I always use the
OEM parts, but sometimes the filter fills and other times it doesn't.
The running condition can change simply because of changes in the
weather.  When I'm working on a customer's machine, I simply run the
engine with hood closed and with all the side panels in place until
everything is up to ordinary operating temperature.  If the engine
doesn't falter, I ship it back to the owner regardless of whether the
fuel filter fills while it's running.

Remember the good old days of vapor lock?

Larry

-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Mike S
Meulenberg
Sent: Wednesday, May 19, 2004 10:42 PM
To: at at lists.antique-tractor.com
Subject: Re: [AT] OT - JD STX38 fuel problems

I mowed again tonight, and here's what I observed:
1. When I last left the mower the filter was empty and the shutoff was
open, when I looked tonight
     the filter was full.
2. After mowing for a while the filter was empty, but it didn't quit.
3. About 3 hours after mowing the filter was again full.


I'm beginning  to wonder if the fuel filter is providing too much
resistance to flow for a little mower without a fuel pump. Maybe the
paper cartridge is too restrictive. I will check the carb again to look
for any signs of the float sticking.

Thanks,
Mike


On Tue, 18 May 2004 21:28:14 -0700 "Dean VP" <deanvp at att.net> writes:
> Mike:
> 
> Another thought. Is it possible that the float is hanging up in the 
> bowl
> because it has been bent accidentally to one side? Or the needle 
> getting
> stuck in the seat occasionally? Or the float isn't set quite right 
> to allow
> enough needle travel? Maybe due to heat?
> 
> Can you get to the hose that runs from the in-line filter to the 
> carburetor?
> If you take this connection loose at the carburetor is the flow 
> always good?
> 
> 
> This is the demarcation line. If the flow isn't good at the end of 
> the hose
> that connects to the carburetor then the problem is further back 
> towards the
> in-line filter and/or tank or lines. If the flow is good, then the 
> problem
> is in the carburetor. The parts list doesn't show how the hose 
> connects to
> the carburetor, but maybe there is some crud at the inlet point, 
> maybe a
> partially plugged screen or sticking float or needle valve. All it 
> would
> take is a small piece of crud at the needle and seat to cause the 
> symptoms
> you are experiencing. 
> 
> I keep thinking of a vapor lock but I've not seen that when one has 
> rubber
> hoses feeding the gas. 
> 
> Since you don't have the solenoid that shuts off the gas and you are 
> not
> losing fuel into the carburetor when the tractor is parked, then the 
> needle
> must always be shutting off the fuel flow properly. That kind of 
> precludes
> the possibility of some crud at the needle to seat interface and it 
> would
> flood occasionally too. Unless you are always shutting off the fuel 
> valve
> after each usage. 
> 
> To me checking the hose inlet to the carburetor will lead you to the
> problem.
> 
> Dean A. Van Peursem
> Snohomish, WA 98290
> 
> What people can dream, people can do! George W. Bush
> 
> www.deerelegacy.com
> 
> http://members.cox.net/classicweb/email.htm
> 
> 
> 
> 
> -----Original Message-----
> From: at-bounces at lists.antique-tractor.com
> [mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Dean VP
> Sent: Tuesday, May 18, 2004 9:58 AM
> To: 'Antique tractor email discussion group'
> Subject: RE: [AT] OT - JD STX38 fuel problems
> 
> Vaughn:
> 
> Seems to me it has everything to do with fuel flow if it is not 
> working
> properly. If the wiring is intermittent or the coil in the solenoid 
> has some
> windings that short out it may not be opening properly or staying 
> open
> properly during run time. It appears to be opened by turning on the 
> switch
> and is supposed to stay open until the switch is turned off. If it 
> isn't
> opening properly or is intermittent it would explain the symptoms 
> present.
> It may start acting up only after running for awhile as it heats up. 
> 
> 
> Dean A. Van Peursem
> Snohomish, WA 98290
> 
> What people can dream, people can do! George W. Bush
> 
> www.deerelegacy.com
> 
> http://members.cox.net/classicweb/email.htm
> 
> 
> 
> 
> -----Original Message-----
> From: at-bounces at lists.antique-tractor.com
> [mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Vaughn 
> Miller
> Sent: Tuesday, May 18, 2004 4:50 AM
> To: at at lists.antique-tractor.com
> Subject: RE: [AT] OT - JD STX38 fuel problems
> 
> The solenoid at the Carburetor bowl shuts off fuel to the main jet 
> to
> prevent backfire, and will have nothing to do with the flow into the
> carburetor.
> 
> Vaughn
> 
> >>> deanvp at att.net 5/18/04 1:21:01 AM >>>
> <snip>
> 4.) What does the solenoid do in the carburetor bowl? Does this just 
> let
> fuel flow when the switch is on? Doesn't look like a pump. Is this
> solenoid
> acting up? Wiring loose or corroded? This may be where the problem 
> is. Is
> the carburetor bowl clean inside? 
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