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David Downs

Delphi Mechanical Fuel Pump stops pumping fuel

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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. 

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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.

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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.

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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.

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Posted (edited)
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 by David Downs
add more videos

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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.

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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. 

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Posted (edited)

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 by motorman7

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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. 

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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?

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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.

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10 minutes ago, SteveJ said:

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.

Could also be a weak spark problem.  The empty filter might be a red herring.  Time to fish...

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21 minutes ago, Zed Head said:

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?

Sorry I wasn't clear. I will drop the tank and have it cleaned to make sure its not a tank pick up line issue. Has anyone installed a fuel check valve? This could help keep the fuel closer to the carbs with less cranking.

 

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3 minutes ago, Zed Head said:

Could also be a weak spark problem.  The empty filter might be a red herring.  Time to fish...

Interesting thought. Can you offer more details on what to look and test for? New coil? Would a weak spark cause fuel starvation?

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I had a problem with a weak ignition module, the engine would only start with fluid.  Then it would run fine.  That was on an EFI car though.  I had done some work and left two spark plugs disconnected so I had a clue about what the problem might be.

Only you know how the engine behaves when it restarts, or how it behaves when it stalls, but the only good reason for a no-start that is fuel-related would be if the float bowls emptied.  Just offering ideas.  If it fires right up and runs well on the first shot of fluid you have to wonder why it didn't start on the fuel that was in the bowls.  

More details!.....  What type of ignition are you running?

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17 hours ago, Zed Head said:

I had a problem with a weak ignition module, the engine would only start with fluid.  Then it would run fine.  That was on an EFI car though.  I had done some work and left two spark plugs disconnected so I had a clue about what the problem might be.

Only you know how the engine behaves when it restarts, or how it behaves when it stalls, but the only good reason for a no-start that is fuel-related would be if the float bowls emptied.  Just offering ideas.  If it fires right up and runs well on the first shot of fluid you have to wonder why it didn't start on the fuel that was in the bowls.  

More details!.....  What type of ignition are you running?

Pertronix and everything looks stock.

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There are other things you could check before dropping the tank.  The Pertronix is one of them.  You could also try an electric pump in the engine bay as a short test.  Another thought.  You might be able to keep the filter full by adding a length of hose in front of the filter that is higher than the filter.  It would depend on how strong the siphon effect is.  Or you could add a check valve in the engine bay.

Either way, don't be surprised if the problem is still there after the tank cleaning.  I don't think your symptoms really support a fuel supply problem.  Your "finger" pumping filled the filter in 9 stokes.  That's a pretty powerful pump action.

I would focus on the float bowls, not the filter.  See if they have fuel.  There's a thread about a float tuning tool that actually works like a sight glass.  You can see the fuel level in the bowls.  If you're planning to tune your carbs it might be worth doing first.  You could probably rig up a temporary "sight glass" also.

Just another view.

Edited by Zed Head

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This is the bothersome part.  I'm not an SU guy.  But the float bowls should not be siphoning empty with the filter's emptying.

image.png

Edited by Zed Head

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This is the cheapest and easiest way to get a close level of the float chambers.  $2 worth of clear hose from Lowes.  The red arrow in this pic.  The fuel in the hose should be even with the top of that rectangular boss on the side of the carb.

image.png

 

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3 hours ago, Zed Head said:

There are other things you could check before dropping the tank.  The Pertronix is one of them.  You could also try an electric pump in the engine bay as a short test.  Another thought.  You might be able to keep the filter full by adding a length of hose in front of the filter that is higher than the filter.  It would depend on how strong the siphon effect is.  Or you could add a check valve in the engine bay.

Either way, don't be surprised if the problem is still there after the tank cleaning.  I don't think your symptoms really support a fuel supply problem.  Your "finger" pumping filled the filter in 9 stokes.  That's a pretty powerful pump action.

I would focus on the float bowls, not the filter.  See if they have fuel.  There's a thread about a float tuning tool that actually works like a sight glass.  You can see the fuel level in the bowls.  If you're planning to tune your carbs it might be worth doing first.  You could probably rig up a temporary "sight glass" also.

Just another view.

Today I drove the car around and stopped at 2 locations. Once I left the second stop the pump stopped pumping. I confirmed this by opening up the float bowls and cranking the engine with the fuel line to carb off. I could not get any fuel to squirt from the carb hose. The carbs were rebuilt and floats adjusted per the instructions. I adjusted the floats again just in case they were set too low. Also, I removed the pump and manually pumped fuel back to the carbs to see if she would start. She fired up and ran out of fuel 200' from my last stop. I don't think I'm having an ignition problem because she always has great spark. My impression is the fuel pump is not getting enough motion. I believe the pump should pump on a 7mm lift. I think it needs more lift to get a full pumping stroke. Time to add an electric fuel pump.

Edited by David Downs
added more info

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1 hour ago, siteunseen said:

This is the cheapest and easiest way to get a close level of the float chambers.  $2 worth of clear hose from Lowes.  The red arrow in this pic.  The fuel in the hose should be even with the top of that rectangular boss on the side of the carb.

image.png

 

I will try this as well. Though I don't think this is my issue. At least I will have my floats at the correct level. Thank you!

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My cruddy tank would let me drive about a mile before clogging up the fram g2 I had right out of the tank. Took the front hose off at input of that filter. Blew like crazy with my mouth until it was gurgling in the tank then I could get back home, barely.

DSC00508.thumb.JPG.8f5227f5b139661bfbfb9f2f189ed916.JPG.jpg

DSC00522.thumb.JPG.9151659e7b68765efa1d87241aa9c22c.JPG.jpg

 

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57 minutes ago, siteunseen said:

My cruddy tank would let me drive about a mile before clogging up the fram g2 I had right out of the tank. Took the front hose off at input of that filter. Blew like crazy with my mouth until it was gurgling in the tank then I could get back home, barely.

DSC00508.thumb.JPG.8f5227f5b139661bfbfb9f2f189ed916.JPG.jpg

DSC00522.thumb.JPG.9151659e7b68765efa1d87241aa9c22c.JPG.jpg

 

It's possible my tank has debris. However, I can use a vacuum pump and suck fuel to the filter. I can remove the Delphi pump and hand pump fuel to the carbs as well. 

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