willysmjeeps.com

My M-38 has run perfectly for months now and suddenly it's as if
you're pulling the choke full out on a warm engine. Pulled the airhorn
and there's fuel even in the hose to the crossover tube!!
1. The float is set at .188 from the airhorn surface and it should be
.25 from the surface (excluding the gasket)-correct me if i'm wrong.
How the heck did it run so well at .188?? I can't imagine the float tang
bending during use..
2. The needle valve and seat appear clean and servicable.

I'll reset the float to .25 (excluding the gasket) this PM.

Ideas??

The YS in my M38A1 was flooding out because a pinhole leak had opened up in the casting between the fuel inlet area and the float chamber. Plugged it up and back in business. Not something you would expect to see.

Tim
http://i30.photobucket.com/albums/c318/ ... y_carb.jpg

You must sport 20/20 vision to have spotted that pinhole Tim.
I reset my float to .25 spec. The needle in the valve is a 3pc setup w/needle, spring and plunger, the spring was slightly compressed
so i stretched it maybe .032. Slapped it back together and we're
good to go. The smallest adjustments made a big difference-
finicky little devils..

Still no joy in YS637 land. Went for short drive yesterday +- 15mi
and still flooding. Pulled the top and drained just slightly less than
1-3/4 oz fuel from the bowl (55cc in a dose syringe). Then pulled the complete carb and see 1/4" raw fuel in the intake manifold.
Count on this to rear it's ugly head when you're preparing for
your 1st MV rally-Idaho Motor Pool June 05-08.

Are you using the needle only type or the needle and spring type for the float. You may need the spring type. What is the fuel pressure coming from the pump?

It is needle/spring type. I'll put it back together and get a pressure reading at the pump 1st oportunity. Can an accurate pressure reading be
obtained by simply cranking the engine w/starter or should i put it back
together and run it for best results..

It's a positive displacement pump, so spinning fast/slow does little to the pressure, only the rate of fuel transfer. Turning it over should be fine.

I have on the bench 2 different meters that belonged to my bro.
I've never used them or been instructed on their use-which begs the question, can i plug the meter hose direct to the fuel pump outlet line
or should it be "T"eed in to a complete closed system.. would it make a difference? I hope "the only dumb question
is the one not asked" axiom applies here..

RICKG wrote:

I have on the bench 2 different meters that belonged to my bro.
I've never used them or been instructed on their use-which begs the question, can i plug the meter hose direct to the fuel pump outlet line
or should it be "T"eed in to a complete closed system.. would it make a difference? I hope "the only dumb question
is the one not asked" axiom applies here..

Yes you can put the hose on the fuel pump outlet line, but if you don't have some sort of clamp on the hose and line it might blow off and squirt gas all over the place. I can't tell what the ranges in PSI are of the guages you have. If they are strictly for measureing vacuum, you can't use them to test for pressure. You must use a pressure gauge that measures in PSI. For a good test You will want to use a guage that has low pressure range like 0-20 or 0-30 PSI. Not one that reads to 0-100 PSI.

Thx guys for the replies-yes both gages read fuel pump pressure
in the low range 0-30psi. I'll hook it up tonite and reply back.

The gage in the top foto reads in the 0-10 psi range.
With that gage and a 20 sec crank with the starter it
builds up to 4 psi and holds steady. TM9 8012 pg 151
specs 4-5.25 psi @ 1800 rpm so i'm not experiencing
excessive pressure from the fuel pump. Based on this
i suspect the needle valve and seat aren't holding back the
fuel even tho the float level is set at .25". So i'm on the
hunt for a new needle valve and seat. I don't suppose
any of the vendors sell just the valve-probably will have
to purchase the whole rebuild kit.

Is the needle or seat damaged? IE scratches or burrs? Are you sure the float integrity is ok and it's not getting heavy with gas leaking into it?

Try the carburetor shop for a replacement needle & seat set.
http://www.thecarburetorshop.com/index.htm

wesk wrote:Is the needle or seat damaged? IE scratches or burrs? Are you sure the float integrity is ok and it's not getting heavy with gas leaking into it?

Try the carburetor shop for a replacement needle & seat set.
http://www.thecarburetorshop.com/index.htm

The spring inside the needle is slightly deformed. Float integrity is good.
Thx for the link-i'll give them a shout.

No joy @ the carb shop. Sold as complete kit only $125 + ship OUCH!!

Then and Now complete kit only $65 + ship. Placed my order with Tony
and my kit is on its way.

Is that kit the same as the dual application $55 kit that Midwest & AJP sell.
Or maybe the same as $35 G503 parts M38 or A1 specific kit?