Technical Fuel pump

[peace4uno]

Hi! I have problem with the fuel pump, or it is some sort of leak that makes the pump work harder than before. To fix gasoline fume in the car, I ordered a new gasket for the pump. Used OEM number: 7743530. This gasket did not looked the same as the one I took off. The new one was wider, 21 mm. But it fitted nicely on. The problem is the sound of the pump, it now makes high frequency noise when the engine is running. The pump starts okey, it starts and stop before I turn the engine on. Then it makes the noise that I haven’t heard before.

I have looked over the fuel lines, but no leakage as I can see. I have measured the pressure out from the pump, and it is 2,5 bar.

The car starts and is running normal at 1000 rpm.

When I take it on the road, and I try to give some more throttle, and that is just over 3000 rpm, it will stall. Like it is lacking fuel.

So, I have now changed back to the old gasket, but it is still the same issue at 3000 rpm and the same noise.

Is it something that I could have missed at the assembly, that make the pump not work correctly, or is the pump itself that is broken?

How can I rule out something in this equation? Is it possible to check the pump itself, taking it out and put some 12 Volt on, and let it pump in water? I know it will work, because I have checked the return line as well.

Anyone experienced the same and can give me a hint on what is wrong. The car was running fine before I change the gasket, and that rules out the filter etc.

Is it possible to assembly the pump wrong, the arrow is pointing more or less the same way I remember it to be. I tried to be as gentle as I could, and I just don’t get how this could suddenly be broken.



The car is Fiat Barchetta, 97.

 

[bugsymike]

Does point to possible fault in reassembling pump.
Without looking at it, that is hard to tell though.
Any chance you dislodged some dirt which is blocking fuel to engine?
Can you read the fuel pressure when it gets to the 3000rpm stall point ?

 

[peace4uno]

Does point to possible fault in reassembling pump.
Without looking at it, that is hard to tell though.
Any chance you dislodged some dirt which is blocking fuel to engine?
Can you read the fuel pressure when it gets to the 3000rpm stall point ?

I haven't tried that yet. Still the noise from the pump is telling me that it is working hard, but what makes the pump work hard is the problem. I can't find any videos of someone assembly the pump with gasket. Possible I have mounted it wrong, but I can't find pictures of it or instruction on how it should be mounted.

 

[bugsymike]

I haven't tried that yet. Still the noise from the pump is telling me that it is working hard, but what makes the pump work hard is the problem. I can't find any videos of someone assembly the pump with gasket. Possible I have mounted it wrong, but I can't find pictures of it or instruction on how it should be mounted.

It is usually how the diaphragm is connected to the electro magnetic plunger, also when tightening screws how the diaphragm is positioned so it is not trying to jam and has free movement.
I wouldn't test it with water as you mentioned earlier, but when it is still wet with fuel you should feel a good suction on the input side and pressure when testing the outlet side.
Ideally they should hold these conditions for a short while after switching off to prove the valves are working well and also no leaks through diaphragm.
In the old days of SU pumps the depth the diapragm was screwed in affected the operation, but they had mechanical make and break points to activate.

 

[peace4uno]

It is usually how the diaphragm is connected to the electro magnetic plunger, also when tightening screws how the diaphragm is positioned so it is not trying to jam and has free movement.
I wouldn't test it with water as you mentioned earlier, but when it is still wet with fuel you should feel a good suction on the input side and pressure when testing the outlet side.
Ideally they should hold these conditions for a short while after switching off to prove the valves are working well and also no leaks through diaphragm.
In the old days of SU pumps the depth the diapragm was screwed in affected the operation, but they had mechanical make and break points to activate.

I’m not sure how the pump should sound like, if I try to run it outside the tank. Makes me think about the wiring and petrol fumes, not the best combination

Waste of money to buy a new one, if it is something else that is not working.

 

[peace4uno]

Should it be pressure or vacuum in the thank? In this case, if I remove the gasket, will it still work? Is the gasket just holding the pump, and to make it airtight from fumes leaking in the car? I guess it makes sense that there is no vacuum or pressure in the tank, but I’m no spesialist in this area.

That tells me that the pump is broken, but still not 100% sure

 

[bugsymike]

Should it be pressure or vacuum in the thank? In this case, if I remove the gasket, will it still work? Is the gasket just holding the pump, and to make it airtight from fumes leaking in the car? I guess it makes sense that there is no vacuum or pressure in the tank, but I’m no spesialist in this area.

That tells me that the pump is broken, but still not 100% sure

Sorry I think we are at cross purposes here.
I thought you had the electric pump apart, are you saying you only changed the rubber seal on the top of fuel sender/pump unit in the tank?
So you haven't had the actual pump apart?

 

[peace4uno]

Sorry I think we are at cross purposes here.
I thought you had the electric pump apart, are you saying you only changed the rubber seal on the top of fuel sender/pump unit in the tank?
So you haven't had the actual pump apart?

No.

 

[bugsymike]

No.

So is this what you fitted the seal to?
If so was there any sign of dirt or blockage to the fuel filter part, or is it possible you damaged the pipes inside it?
Is there any contamination inside the fuel tank?

 

[peace4uno]

So is this what you fitted the seal to?
If so was there any sign of dirt or blockage to the fuel filter part, or is it possible you damaged the pipes inside it?
Is there any contamination inside the fuel tank?

This looks like the same pump.
Some small particles in the tank, but surprisingly little. Any specific parts on the pump, that I should inspect. I must admit that I didn’t spent much time on it.

 

[bugsymike]

This looks like the same pump.
Some small particles in the tank, but surprisingly little. Any specific parts on the pump, that I should inspect. I must admit that I didn’t spent much time on it.

I think around the actual pump part there is a fine filter.
As this is the only filter in the system I should check inside the tank and that filter thoroughly.

 

[Steve gt]

I’m sure there is an aluminium fuel filter on the outside next to the fuel tank , that could be blocked making the pump struggle, try replacing that

 

[bugsymike]

I’m sure there is an aluminium fuel filter on the outside next to the fuel tank , that could be blocked making the pump struggle, try replacing that

Certainly worth checking for.

 

[Davefridge]

Should it be pressure or vacuum in the thank? In this case, if I remove the gasket, will it still work? Is the gasket just holding the pump, and to make it airtight from fumes leaking in the car? I guess it makes sense that there is no vacuum or pressure in the tank, but I’m no spesialist in this area.

That tells me that the pump is broken, but still not 100% sure

Usually there is pressure in the tank. Hiss when removing the cap is normal (I leave my cap a bit loose to stop fumes in the car). Can't do any harm, can it?

 

[bugsymike]

The seal around the fuel pump /sendor unit in tank must be air tight to prevent fumes inside the vehicle. Also if over filled tank fuel ,could leak from top of tank and would be a fire risk.
Fuel tank on older vehicles are vented externally via vent pipe, many modern vehicles have a controlled sealed system which is why you hear a venting noise when releasing filler cap.