Vanguard 35 fuel issues

[BLES]

Hi guys. Haven't been around here much lately, but my health is a bit better so I may be "around" more.

Vanguard 613477-3048-G1 with only a handful of hours.
Engine runs fine when gravity fed from a test tank.

No fuel pumping to carb. Fuel gravity feeding out of tank and through filter toward pump. Nothing out of pump. Tried 2 more pumps (read posts about bad vacuum pumps). Hose from engine to pump is fine but seems weird that it's connected to intake just downstream from carb on these. Any suggestions? I know I could install an electric, but it did run a few hours with this setup.

Appreciate you guys and look forward to your thoughts.

BLES

[KE4AVB]

Bles, Not a whole info on the Big blocks fuel systems. But I would be looking a vacuum/pressure leak and this could be caused by poor valve clearance adjustment. Basically the intake has to develop enough vacuum and pressure pulses for the fuel to operate.

Now I did download and upload the service manual that cover the carbureted version of these engines. It listed as file "69_80114787 Vanguard BIG BLOCK 54, 61 Diagnostic and Repair Ver A" in the Briggs download section. But as I said it won't be of much help fuel wise.

[BLES]

I would be looking a vacuum/pressure leak and this could be caused by poor valve clearance adjustment..

I never even checked this. I'd guess it's got 5 or 10 hours on it. I guess it's worth a shot. Hopefully I can find specs. Likely .005"ish on intake?

[RoyM]

.004"-.006" on both.

[BLES]

Just curious... isn't the pulse line usually from the crankcase? I don't understand how it works on the intake manifold.

[KE4AVB]

Just curious... isn't the pulse line usually from the crankcase? I don't understand how it works on the intake manifold.

Yes normally that what Briggs has done.

But here they are attempting to use vacuum in the intake as the cylinders are pulling in fuel/air mix. Thus the throttle plate has to mostly closed or the choke closed to develop max vacuum to operate the fuel pump. Once the engine is running there plenty vacuum created by the running engine as the engine constantly pulling fuel/air mix everytime the cylinders are on the intake strokes.

SO try keeping the choke closed and try testing the pump this way.

[Skywatcher]

Hi BLES

If the engine runs fine on a gravity feed temporary fuel supply, you'll have maximum vacuum pulse at idle. If the pump is not delivering at least 4 oz per minute into a clean container at idle, this would suggest a fuel restriction problem further up-stream. Disconnect the inlet line from the pump and remove the fuel cap then blow the line back with 5 to 10 psi regulated air. If you don't hear bubbling in the fuel tank, you've got a plugged filter, a plugged line, broken or disconnected pick-up tube in the tank or a fuel valve turned off.

When you have the engine idling on a gravity feed fuel supply, disconnect the pulse hose from the fuel pump, the engine should start running rough or missing on one cylinder. If there's no change in the engine, you have a plugged vacuum pulse line. These pumps work on vacuum only, the vacuum pulses compress the spring under the diaphragm. The built in spring pushing back against the diaphragm is what gives you the actual fuel pressure. Hope this gives you a few ideas. All the best,

Sky

[BLES]

Thanks Sky.
I didn't remove the pulse line with it running, but I did check the hose (it's very short) - not plugged, pinched, or leaking.
When I remove the fuel inlet line from the pump and lower it a few inches to the fuel level in tank, it pours lots of fuel out. This is after the filter, too, so line and filter to pump should be good.?
I'm hoping to check valve clearances if I get back to it this weekend.
Thanks for your thoughts.
PS - I'm beginning to understand why I see so many of these with electric pumps installed. These are common on grain augers around here.

[KE4AVB]

Bles, I am learning a lot from this so please keep us update on your findings. But the electric fuel pumps use does makes more sense to me. Sorta like using vacuum operated fuel shutoffs on some equipment.

[Skywatcher]

Hi Again

Oh yes, the ubiquitous grain auger engine, lots of those around here too. What I've been doing for several years now is to install a marine outboard motor inline hand primer bulb pump between the fuel tank and the fuel filter. Operate the hand primer pump until resistance is felt (carburetor full), start the engine and away you go.

Most farmers around here are price driven, so a $25.00 hand pump trumps a $150.00 electric pump every time. If you do use an electric pump, make sure you obtain a low pressure pump (no greater than 5 psi) as a medium or high pressure pump will push the float needle off its seat and completely flood the engine. All the best,

Sky