Delphi Mechanical Fuel Pump stops pumping fuel

[David Downs]

I have replaced and checked everything related to fuel except dropping the tank. Replaced and checked all fuel lines, installed fuel filter at tank, blew air through fuel lines (including return), pulled vacuum on the metal fuel lines (held vacuum), drained tank, overhauled SU carbs, and can't keep fuel in the engine fuel filter. I removed the valve cover to check on the fuel pump cam lobe. I'm able to pump fuel by moving the pump lever by hand at the cam. Is it possible that I'm not getting enough lift from the mechanical pump cam lobe? Or is there an issue with Delphi pumps? There is plenty of fuel in the filter I installed at the tank. 

[Zed Head]

4 minutes ago, David Downs said:

can't keep fuel in the engine fuel filter. I removed the valve cover to check on the fuel pump cam lobe. I'm able to pump fuel by moving the pump lever by hand at the cam

Do the carburetor float bowls fill?  That's the objective.

You can have a bubble in the filter and still have plenty of fuel passing through it.  People get distracted by the bubble in the filter often.  It might not matter.  There are some recent threads about it.

[David Downs]

No fuel to carbs. If I crank the engine long enough fuel starts to pull to the filter. I can spray carb cleaner in the intake and she will fire.

[Zed Head]

17 minutes ago, David Downs said:

 Is it possible that I'm not getting enough lift from the mechanical pump cam lobe? Or is there an issue with Delphi pumps? 

Have you spun the engine with the valve cover off? See how far the cam moves the pump arm.  You said that you can pump it by hand so the diaphragm must be okay.

Take a picture of the pump on the engine.  Maybe you're missing a part or have the wrong spacer or something.

[David Downs]

49 minutes ago, Zed Head said:

Have you spun the engine with the valve cover off? See how far the cam moves the pump arm.  You said that you can pump it by hand so the diaphragm must be okay.

Take a picture of the pump on the engine.  Maybe you're missing a part or have the wrong spacer or something.

Yes, removed cover and cranked the motor over. Arm is moving, pump is new (3rd one), and the pump spacer is new as well. I will upload a few videos but not sure they will work since its from my iPhone.

FullSizeRender.MOV

Edited April 24, 2020 by David Downs
add more videos

[Zed Head]

The videos work fine on my Windows 10 machine.  The second one shows the filter body filing with gasoline,with a clicking noise in the background.  The first  video shows the pump arm moving on the eccentric as somebody spins the engine.  Can you connect the two videos with some words?  Were you moving the pump arm by hand in the second video?

And you didn't show the actually mounting of the pump.  I know that there are typically phenolic spacers that sit under the pump.  Maybe your pump is too far from the eccentric.

That's my at-the-moment guess.  The pump is sitting too far from the eccentric.

[David Downs]

2 minutes ago, Zed Head said:

The videos work fine on my Windows 10 machine.  The second one shows the filter body filing with gasoline,with a clicking noise in the background.  The first  video shows the pump arm moving on the eccentric as somebody spins the engine.  Can you connect the two videos with some words?  Were you moving the pump arm by hand in the second video?

And you didn't show the actually mounting of the pump.  I know that there are typically phenolic spacers that sit under the pump.  Maybe your pump is too far from the eccentric.

That's my at-the-moment guess.  The pump is sitting too far from the eccentric.

The first video is the engine turning over to show that the mechanical fuel pump cam lobe is functioning. The second video was me pumping the pump arm manually to pull fuel to the filter. Third video shows the fuel in the filter draining back to the tank filter after letting it sit for about a minute. 

[Zed Head]

There are only two videos, the first two you describe, then your voltmeter needle moving with your flashers after those.  But I get it now.  

Still, wondering about the mounting of the pump.

https://zcardepot.com/products/fuel-pump-spacer-plate-240z-260z

[motorman7]

The one video looks like the pump is working well.  Typically, I will disconnect one of the hoses going to the carb float bowls to see if fuel is pumping out.  That will tell you if the pump is working.  Put a rag or cup under hose to catch the fuel.

Edited April 24, 2020 by motorman7

[David Downs]

1 hour ago, motorman7 said:

The one video looks like the pump is working well.  Typically, I will disconnect one of the hoses going to the carb float bowls to see if fuel is pumping out.  That will tell you if the pump is working.  Put a rag or cup under hose to catch the fuel.

The pump spacer you posted is the exact one I purchased. I went back to the garage and manually pumped fuel through the entire system. I confirmed that fuel is pumping to the float bowls. Once I pumped fuel through the system I let it sit for a few minutes to see if the fuel would drain back toward the tank. This time the fuel remained in the engine bay fuel filter. So, I cranked the engine and she fired up. Now I'm even more puzzled because this is likely an intermittent problem. My next thing is to drop the tank and make sure I'm not picking up debris at the end of the pick up tube. 

[Zed Head]

3 hours ago, David Downs said:

can't keep fuel in the engine fuel filter. 

You didn't really say if you had a problem with the engine starting.  Sometimes people think things but don't actually write them down.

The drain back to the tank from your filter is not surprising.  It's higher than the tank.  The engine will start with what's in the float bowls and the filter will refill in a second.  I counted 9 clicks so that would be 18 revolutions of the engine.  Lets' say 20, for the math.  At 1200 RPM, that would be one second to refill the filter.

So, is this an actual operational problem or a "this bothers me" problem?

[SteveJ]

His car has stalled without restart except with starting fluid (knowledge of his problem from outside this forum). From how he has described it to me, I lean toward a fuel pick-up problem.