62 250 GTE Fuel pump questions

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drew_1295
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Joined: Thu Dec 14, 2017 12:26 pm

62 250 GTE Fuel pump questions

Post by drew_1295 »

Hello all,

We have a 62 240 GTE in our collection that I've been doing some work to. I have found that the factory mechanical fuel pump was not pumping fuel and upon disassembly I noticed that it was in need of a new diaphragm so I went ahead and got the parts to rebuild it. Once rebuilt I re installed on the car and found that the pump was still not working! after doing some more testing I found that the rod that activates the fuel pump didn't have enough movement to actuate the pump. I have come to understand that the heat treat on the cam/gear that operates the fuel pump is not that great and the part is know to wear faster than it should causing it to not work the mechanical pump.

The factory electrical pump does work but I noticed something weird in doing all of this diagnosing. To me I would think that the electric pump would move fuel through the mechanical pump, through the fuel filter and then into the fuel rail and then out of the rear of the fuel rail and back to the tank. Currently its the exact opposite. The electric pump is pushing fuel into the carbs first from the rear of the fuel rail and then down to the mechanical pump.

Which is the correct way?

Thanks
Andrew
DWR46
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Re: 62 250 GTE Fuel pump questions

Post by DWR46 »

Andrew: The electric pump is operating correctly.
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tyang
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Re: 62 250 GTE Fuel pump questions

Post by tyang »

Hi Andrew,

The electric pump pushes fuel from the rear of the fuel rail and puts out about 3psi. How much does the pushrod move? Its total movement is only about 3mm, so it is critical to set a minimum amount of backlash on the pump lever .

Tom
'63 330 America #5053
drew_1295
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Re: 62 250 GTE Fuel pump questions

Post by drew_1295 »

Hi Tom, After reading your reply to my thread am I correct to assume that the car will not run on the electric fuel pump alone since its output is only 3 psi?

I noticed that when reassembling the mechanical pump that there was a lot of free movement in the lever before it actually started to actuate the diaphragm. How would I go about setting the correct back lash?

I would have to agree with you on the fuel pump push rod only moving about 3 mm. I had discussed this issues with a local guy and he suggested that the lobe on the fuel pump gear set had been worn down due to poor heat treat. Hopefully he was wrong in this case and due to me lack of knowledge in vintage Ferrari's I just didn't know about setting backlash on the fuel pump.
DWR46
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Re: 62 250 GTE Fuel pump questions

Post by DWR46 »

Andrew: The car will fun fine on the electric pump, 3 psi is plenty of pressure for the Weber carburetors. I seriously doubt the cam that drives the pushrod is worn ( I have never seen one wear measurably). I will let Tom address your other questions.
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tyang
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Re: 62 250 GTE Fuel pump questions

Post by tyang »

drew_1295 wrote: Thu Jan 06, 2022 2:07 pm Hi Tom, After reading your reply to my thread am I correct to assume that the car will not run on the electric fuel pump alone since its output is only 3 psi?

I noticed that when reassembling the mechanical pump that there was a lot of free movement in the lever before it actually started to actuate the diaphragm. How would I go about setting the correct back lash?

I would have to agree with you on the fuel pump push rod only moving about 3 mm. I had discussed this issues with a local guy and he suggested that the lobe on the fuel pump gear set had been worn down due to poor heat treat. Hopefully he was wrong in this case and due to me lack of knowledge in vintage Ferrari's I just didn't know about setting backlash on the fuel pump.
Hi Drew,

Like Dyke said, 3 psi is plenty to run the car.

There is a bakelite spacer between the body of the fuel pump and engine along with two gaskets. Measure the amount of pushrod travel or protrusion by turning over the engine with the fuel pump removed, and extrapolate how much material from the spacer needs to be removed. This can be done on a flat surface and some coarse sand paper. Try to keep the spacer square to the surface to avoid putting excess stress on the fuel pump body when mounting it. Removing too much material from the spacer risks over stressing the lever inside the fuel pump and breaking something, so be careful. 3mm is not a lot of room to play with.

I have a test rig that measures backlash and allows me to set and test the fuel pump off the car, but it can be done with trial and error on the car.

Good luck.

Tom
'63 330 America #5053
drew_1295
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Re: 62 250 GTE Fuel pump questions

Post by drew_1295 »

I've got something else weird going on then. The electric pump will get fuel to the carbs but not enough the fill the bowls. Car will only run on the choke circuit. Carbs were just rebuilt so I know they are not the problem. Ill start working on getting the mechanical pump corrected today.
DWR46
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Re: 62 250 GTE Fuel pump questions

Post by DWR46 »

Drew: If the engine will run on the choke circuit, then the carbs are getting fuel. Don't assume the carbs are OK. When something is wrong, always first go back to what you did last.
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