How to Diagnose No Fuel at Carb 7.4

[Theom]

Engine information in my signature.

I'm getting no fuel at my carb and so the engine won't start, what are my next trouble shooting steps? I did an engine rebuild. All fuel components sat for a couple years. I have the original carbs, fuel pump, and fuel lines back on.

What I've done so far:
1) Syphoned all the gas out of the tank and put 15 gallons of fuel into the tank 2 months ago.
2) Removed fuel filter and filled to the rim with fresh gas, reinstalled the filter. (Brand new filter)
3) Turned over 5 to 7 seconds, 4 times. Checked for any signs of gas in the carb. There are none.
4) Prop open choke plate with a screw driver. (the longer of the three plates that goes across the whole carb). Manually pressed down the silver pin and looked for gas squirting out under the choke plate. No gas coming out.
5) Emptied fuel filter and turned over the engine for 5 seconds, 4 times. Checked fuel filter and it was still completely empty.

Would the next step be to unhook the pressurized fuel line coming out of the fuel pump and see if the pump is squirting fuel out?

(I've got spark now, so hopefully this is my last step to get it running)

 

[Theom]

This is the pin I pressed down on in step 4 above, to see if fuel would squirt out under the carb plate:

 

[Bt Doctur]

thats the accelerator pump .
place a oz or 2 directly into the carb to verify motor will start
use a remote tank connected to the fuel pump ,retest
If motor now runs work back to the tank
filter housings do corrode under the remote housing and leak air into the fuel lines, remove filter and run a finger on the underside
next is the anti-syphon valve at the tank

 

[Theom]

thats the accelerator pump .
place a oz or 2 directly into the carb to verify motor will start
use a remote tank connected to the fuel pump ,retest
If motor now runs work back to the tank
filter housings do corrode under the remote housing and leak air into the fuel lines, remove filter and run a finger on the underside
next is the anti-syphon valve at the tank

For this do you think it matter if I put the gas directly into the primary or the secondary barrels? (Large vs small) I assume primary is fine.

Any tips for how to connect a remote tank to the fuel pump since it has a threaded connection? I'm looking at getting an outboard remote fuel tank like this and then thinking I could just get a brass connection from home depot to put in the hose to connect it to my fuel pump if the one provided doesn't fit.

 

[Theom]

I put about 2 oz of fuel into the carb, turned it over for about 5 seconds. It sputtered a bit, and seemed like 1 or 2 cylinders fired off, but definitely didn't start.

The mating surface under the fuel filter is clean and smooth.

I removed what looks like my pickup tube (Image attached) where I thought the anti anti syphon valve would be but I don't see anything there. It's just a 90 degree hose connection and a tube. Light, liquid, and air pass freely both directions through it.

Should air pass all the way from my pickup tube to the carburetor freely? When I blow thru the hose that came off the pickup tube without much pressure I get bubbling/air in the carburetor.

I'll try the remote tank tomorrow when the stores open back up

 

[04fxdwgi25]

I would be focusing on the fuel pump or looking for an air leak on the line somewhere before the pump.

 

[kenny nunez]

When the engine was rebuilt did you install the fuel pump push rod that works the fuel pump?

 

[Bondo]

I put about 2 oz of fuel into the carb, turned it over for about 5 seconds. It sputtered a bit, and seemed like 1 or 2 cylinders fired off, but definitely didn't start.

The mating surface under the fuel filter is clean and smooth.

I removed what looks like my pickup tube (Image attached) where I thought the anti anti syphon valve would be but I don't see anything there. It's just a 90 degree hose connection and a tube. Light, liquid, and air pass freely both directions through it.

Should air pass all the way from my pickup tube to the carburetor freely? When I blow thru the hose that came off the pickup tube without much pressure I get bubbling/air in the carburetor.

I'll try the remote tank tomorrow when the stores open back up

Ayuh,..... Welcome Aboard,....... The aluminum barb fitting on the 90* fitting on the tank's diptube, should have a check-ball, 'n spring in it,....
That's the anti-siphon valve,....
You should not be able to easily blow through the fuel pump, as the fuel pump is nothing but a diaphragm, 'n 2 check-valves, 1 in, 'n 1 out,.....

 

[Bt Doctur]

and there could also be a stent filter inside the pickup tube thats clogged up, the tube unscrews from the fitting

 

[Theom]

When the engine was rebuilt did you install the fuel pump push rod that works the fuel pump?

Yes, the # 5 component in the image below was installed behind the fuel pump. I also put a new gasket on it.

 

[Theom]

Ayuh,..... Welcome Aboard,....... The aluminum barb fitting on the 90* fitting on the tank's diptube, should have a check-ball, 'n spring in it,....
That's the anti-siphon valve,....
You should not be able to easily blow through the fuel pump, as the fuel pump is nothing but a diaphragm, 'n 2 check-valves, 1 in, 'n 1 out,.....

Mine is just a plate 90 degree elbow, no anti-syphon valve. It looks like the pickup tube was cut or broken where it connects to the elbow and then LOTS of epoxy was used to reattach it.

I just ordered a new pickup tube, 90 degree elbow, and anti-syphon valve that I'll have tomorrow. I don't think this was keeping it from running, but at least I'll have the anti-syphon valve now and less restriction in the pickup tube from all the over flow epoxy.

I'm assuming being able to easily blow through the whole system is a sign my fuel pump is bad, so I ordered a new one that should come in tomorrow.

 

[Theom]

I took the fuel pump off. I can freely blow air into the inlet and thru the out side so I guess that means it has failed, but looking inside the gaskets and everything seems to be in decent shape to me. Although I don't know exactly how it's supposed to look:

 

[Theom]

In case anyone else comes to this thread, I think it's correct that you can blow through the fuel pump from the intake side to the fuel-out side. The one way valve prevents the fuel from going back out the intake and stops fuel from going into the fuel-out side, but air would pass all the way thru from the inside to the out side.

 

[Scott06]

In case anyone else comes to this thread, I think it's correct that you can blow through the fuel pump from the intake side to the fuel-out side. The one way valve prevents the fuel from going back out the intake and stops fuel from going into the fuel-out side, but air would pass all the way thru from the inside to the out side.

Yes the check valves flow from tank through pump to carb.
The diaphragms in that pump are fine unless the check valves are bad pump should work.

given you found the pick up tube was molested and goobered back together I’d start there

 

[Theom]

The fuel pump wasn't working because the small overflow connection was clogged and created too much pressure in one side of the pump so it couldn't operate. I cleaned out the clogged connection and then the pump worked. I also cleaned the epoxy out of the pickup tube, replaced the lines going from the fuel tank up to the filter and installed an anti syphon valve and now I've got fuel pumping through the system.

Thanks for all your help everyone.

 

[Scott06]

The fuel pump wasn't working because the small overflow connection was clogged and created too much pressure in one side of the pump so it couldn't operate. I cleaned out the clogged connection and then the pump worked. I also cleaned the epoxy out of the pickup tube, replaced the lines going from the fuel tank up to the filter and installed an anti syphon valve and now I've got fuel pumping through the system.

Thanks for all your help everyone.

no gas is coming out of that connection right? That should be connected via a Tygon tube to a nipple on the carb to dump fuel down throttle bores in event of a diaphragm rupture vs into the bilge