New Mechanical Fuel Pump

[joe7]

I had a similar problem with an electric pump. It would fill the carbs but after a short dive it would stall out. I was able to turn off the engine and leave the pump on to fill the carb bowls. I could drive about 1/4 mile and it would start to sputter and die. Redo the engine off, pump on, start off. Repeat as necessary. Fortunately I was very close to home. I found out that while the pump was pumping it didn't develop enough flow to keep the carbs full to keep it running. Another incident a friend had was the the mechanical pump was putting out too much pressure. So, too little pressure or too much?

[2cams70]

Drive it until it stalls. When it stalls take off the air cleaner and see if you get any fuel squirts from the accelerator pump or take the carb cover off and see what is in the fuel bowl. If you don't see a lot of fuel you know what your problem is!

[111Robin]

Drive it until it stalls. When it stalls take off the air cleaner and see if you get any fuel squirts from the accelerator pump or take the carb cover off and see what is in the fuel bowl. If you don't see a lot of fuel you know what your problem is!

I would if it ever broke down in a safe location, which it never has. Always on a blind bend or busy main road so the priority is always to get it moved to a safe location, normally by churning the starter in first gear, so by the time I get it to a safe place I have no idea if the fuel level will be representative of when it fails. I have now reverted to the fuel pump that was on it originally and the previous owner says they never had any issues so I have to assume the pump is ok. I really need to measure the pump delivery rate/pressure to confirm though.

[alan.barker]

I hope the mech pump has a glass dome and not one of the all metal ones which has too much pressure and floods carbs.
If the eletric pump you removed is a "Facet" throw it in "leslie's" Bin. They have an internal filter that clogs up, make lots of noise and need a pressure regulator.
Alan
P.s. after a short "dive" are you sure it didn't drown the carbs.

[111Robin]

It's an all metal pump. There are no indicators of flooding when it fails, no fuel dripping, no smell etc. I've never run an electric pump other than to empty the tank. Even on short runs, I have always run the car up to normal temperature in the garage before driving it. Operating the pump by hand on the bench I'm seeing about 2psi but it's difficult to get an accurate reading, it's certainly not excessive.
One thing I forgot, the car had and still has electronic ignition. I fitted a new Aldon Ignitor incase the previous one was faulty. However, I also made a new set of HT leads, copper cored, to replace the Accuspark suppressed leads that were on it. I remembered yesterday I had read you are not supposed to use copper leads with this type of ignition as the interference from the non suppressed leads can affect the ignition module. I confirmed this with Aldon. So I have reinstalled the suppressed leads. Unfortunately I don't think that this would have caused the type of breakdown I've been suffering. I hope I'm wrong but I have no confidence in it anymore. I need to pluck up courage to drive it now to see what happens.
Reading further into this, it is unlikely that the copper leads would have this type of effect on a hall effect ignition. Voltage spikes due to failed insulation could fry the unit but electrical interference would have no effect, so yet another red herring.

[alan.barker]

Hi Robin,
if you can find a mech pump with glass dome like original.
If it's secondhand you can get a kit to recondition it.
Alan

[111Robin]

Hi Robin,
if you can find a mech pump with glass dome like original.
If it's secondhand you can get a kit to recondition it.
Alan

I have one on its way Alan. I still have my doubts as this will be the third pump and the previous owner said he never had any issues with the car. If this doesn't work the only other thing I've changed is to have the Webers overhauled by Paul who has kindly offered to have a look at them for free if I send them down to him. That will probably be the next job on the list.

[alanr]

I would urge caution if buying secondhand glass bowl mechanical pumps.You will need the correct model glass bowl pump.
The pressure on these AC pumps varies quite a bit depending on which vehicle they were originally intended for and it could be that their suitablability for a twincam may be questionable without checking the pressure output before fitting.
A repair kit which doesn't to my knowledge have a replacement spring in it will not change the pressure output.

Alan.

[111Robin]

Alan it's a NOS pump of the correct type so will be fine. I seriously doubt it will make a difference but it will be one more thing I can eliminate. Next will be a new engine at this rate

[gjz30075]

If nothing else, you can observe the glass bowl when it quits. Should give some clues.

[mbell]

What ignition coil are you running? 3 ohm or 1.5ohm? Do you have ballast resistor fitted?

IF your running a 1.5 ohm with no ballast resistor or incorrectly wired ballast resistor your coil could be over heating.

[111Robin]

What ignition coil are you running? 3 ohm or 1.5ohm? Do you have ballast resistor fitted?

IF your running a 1.5 ohm with no ballast resistor or incorrectly wired ballast resistor your coil could be over heating.

3 ohm, no ballast resistor.

[alanr]

Re-Glass Bowl Mechanical Fuel pump.
The correct part numbers according to the AC catalogue of the time are given for the Elan and +2 :-
461-197 and/or 7971280.
The first number is usually on a plate and the latter number is usually on the lever arm.

Alan.

[111Robin]

Re-Glass Bowl Mechanical Fuel pump.
The correct part numbers according to the AC catalogue of the time are given for the Elan and +2 :-
461-197 and/or 7971280.
The first number is usually on a plate and the latter number is usually on the lever arm.

Alan.

Pump now fitted and running but yet to do a road test. I bought it from a very reputable source of nos parts so I'm happy it is the correct item. Whether or not it solves my problem I have serious doubts. I just have to hope that the next time it breaks down it's in a safe location where I can spend some time trying to diagnose the fault.

[Craven]

Using copper core leads with this type of ignition module requires the inclusion of resistive plug caps. If you ran copper leads without on this type of module it can be damaged in milliseconds.
Resistive plug caps ensure the coil always sees a terminating load as the reflected high voltage spike without finds its way back to the module.
FWIW