engine and drivetrain Not Getting Fuel

[Flunder]

Suggest you carry a duplicate electric pump in your spares in the trunk. I had one quit on the back roads of the Eastern Shore late one night.

 

And why not keep the mechanical pump in the road spares too along with fuel line in appropriate

lenghths to splice the electric out of the system entirely if need be.

[worzella]

My favorite book as a kid...

 

So is the assumption that at some point you were filling with gas at a station and Mr. Fly decided to dive into the tank??

 

Or possible other ‘splanations:

 

- Fly got into fuel supply from station underground tank, tanker truck, Houston cracking tower at Exxon refinery

 

- Fly was sucked into carb and said “Hell no” and faught upstream through a jet into the bowl, burrowed through the filter down the line to tank

 

- But my favorite... he was prehistoric encased in amber and survived the oil well and Exxon refinery into the supply and out the pump

 

 

 

[marlin1881]

I read through all these posts, and what a great investigation it was!  I've got the same problem, but I didn't find a fly in the pickup tube.  I really wished I would have...

 

My car starts OK when cold, but very quick when it's warmed up.  I do have a see-through clear plastic fuel filter between the firewall and the mechanical pump on the cylinder head.

 

If the car has not been run for a while (overnight?) the fuel filter is completely full.  Once the motor is started, the filter starts to show some "air space", and eventually has mostly air.  At this point, the motor starts to sputter and mild backfire.  It's starving for fuel.

 

When I turn the motor off, within the next 5 minutes, all fuel is gone from the see-through filter.  But, after some time (overnight), the filter is completely filled again.  I can take the fuel line off the pump (vacuum side) and blow through it, and all fuel is pushed to the gas tank.  Then, I can hear it bubble in the tank as I continue to blow through the fuel line.

 

I've removed the pickup tube assembly, cleaned the bottom filter (I can barely see through it), and stuck stuff through the 90 degree neck in the pickup tube (wire, pipe cleaner).

 

I'll keep chasing through each supply line section until I find the restriction.

 

I guess I'll have to start with a different source of fuel at the tank (gas can with fuel hose), and connect to the plastic line by the right rear fender.

[John76]

Did you check the hose connection to the pick-up tube?  Should be air-tight and leak-free.

Also consider installing a check valve on the fuel line before the connection to the plastic line in the trunk. This helps keep fuel in the line all the way to the fuel pump (even though the fuel pump has a 1-way check valve).

When your warm engine is idling, look down the primary carb throat to see if fuel is dripping from the venturi.

If you see a drop of fuel, followed by a stumble in the idle speed ... you most likely have a bad (plastic) float or grit in the needle valve. 

Be sure your fuel tank is vented to atmosphere (normally through the vapor tank in the trunk and the charcoal canister in the engine bay). 

John

 

 

[marlin1881]

John76,

 

Good suggestions.

 

The hose connection on the pickup tube has the hard plastic inner sleeve, and my new gas line fits very tight over it, along with a hose clamp.  That looks good.

 

I don't have a check valve at the tank.  That might solve the problem of the see-thru filter getting emptied after I turn the engine off.  I still find it curious that the filter will fill up again after a few hours.

 

I've got a new Redline carb kit, diaphragms, and power valve. Everything is new in the carb.  But, I'll take a look down the primary throat.

 

I'll check the vent hoses again, but I even drove it around yesterday with the gas cap off.  The see-thru filter still slowly got a larger volume of air after 15 minutes of easy driving.

 

I'm still thinking I have some restriction in the supply side, even though I can push fuel and air both directions.  I'm wondering if there's just a little something somewhere that is restricting the fuel flow that I can't simulate with an air compressor.

 

And, for the see-thru filter to fill back up again, after an hour or so of the engine being off, tells me the fuel pump has a good check valve in keeping the vacuum side "pulling" fuel.

 

But, what could be "pulling" fuel out of the see-thru filter while I'm driving, and then completely empty it when the engine is off?

 

I suppose I could just replace the see-thru filter with a solid aluminum filter so I wouldn't be obsessed with this anymore...  😉

 

 

[jimk]

Thread is getting long and maybe it's been mentioned before.

A mechanical pump has two spring loaded wafer valves, suction and discharge.  Something could be lodged between the wafer and seat and the pump not holding the gas from the tank after shutdown.

To check the pump off the car, the suction nozzle should draw a vacuum when the pump is cycled and hold the vacuum.

The suction test could be done on the car but you'd need a helper to crank the engine.

[John76]

5 hours ago, marlin1881 said:

what could be "pulling" fuel out of the see-thru filter while I'm driving, and then completely empty it when the engine is off?

The carb float bowl is open to atmosphere through the air filter. When the engine is turned off, the fuel in the bowl evaporates quicky (thanks to the low Reid vapor pressure of winter blend gas). Picture alcohol in a pan on a warm stove...gone in no time!

So, when the gas level in the float bowl drops, the needle valve opens allowing air to vent the suction of the fuel trapped in the filter. Do you have a fuel return valve? When there is no vacuum applied to the valve, it is almost closed on the return line to the tank. Normally, fuel would remain in the fuel line and filter (after the pump) if the needle valve was closed.... just like holding your finger on a straw after dipping it into water.

Sound crazy???   That's my story and I'm stickin' to it.  😬

John

Edited April 17, 2023 by John76
Correction