Fuel Flow Variation

[David Ramsbotham]

As part of my ongoing issue to get my early rubber bumper car running properly I have been examining fuel flow. My concern is that the poor flow reaching the carbs is insuffient to allow the HIFs to operate correctly.

Today I have done a number of tests.

1/ fuel flow at carbs. Best 0.85 litres a minute

2/fuel flow at pump. as above

3/ fuel flow at carbs using pump and an external tank, positioned at approx car tank height. 1.2 litres a minute.

As you can see I am loosing approx a third of the flow available through the tank pick up . I have tried blowing into tank but result remains the same. Does anyone know how pick up is configured in the tank ( which by the way is, I believe , fairly new )

The pump is a new electronic item purchased from MGB Hive nominal max rated at 1.5 litres a minute.

Cheers David.

[Paul Scott]

This might sound silly David.

Is this with fuel cap on or off?

I'm sure the cap has a breather system built in.

Just a thought, but as I say it may sound a bit silly & be totally wrong.

Regards
Paul

[David Ramsbotham]

Hi Paul,
Thanks for thought but tried cap both on and off with no difference in flow so at least the fuel cap works properly!
Cheers David.

[Mnripley]

Check the actual fuel pipe under the body and rubber hoses could be damaged or pipes sludged up. Fuel pick up pipe on some models have a suction filter, could be blocked.
Michael

[Charles Farran]

David,
This might have been covered already,but when you put the new fuel pump in did you use new hoses each side? If the old ones had deteriorated inside then bits of rubber could have become detached & with old waxy fuel clogged the copper tubing somewhere.
Incidentally, when you used a seperate tank & remote pump did you try to see if the engkne woukd run if connected directly to the front carb???!!!
Cheers, Charles

[David Ramsbotham]

The best flow measured was achieved using all the existing pipe work right through to the carbs so I believe the blockage is in the tank pick up.

I didn’t try to start the car using the external tank. Although this would have tested the low fuel flow theory, the installation was a bit Mickey Mouse to say the least and would not want to risk starting car!

Will try blowing compressed air down pick up tube ( cap off !) to see if It makes a difference. If this doesn’t work will fit later type fuel float level with integral pick up tube and blank off old pick up.

Cheers David.