Classic Alfa Forums

When I havn't used my car for a few days it can be difficut to start.

Seems the fuel drains back to the tank.( I have standard mech fuel pump.). Before I flatten the battery, I have used Easy Start.

Someone suggested a priming bulb?

Or maybe an electric fuel pump? But the mech one is fine.

I have a fuel filter before the carbs. Do they do a non return version?

Wondered what other people do?

Would like to know this too, as I’m new to them I don’t know whether it’s what they all do or if it’s something wrong.

Previous owner of mine fitted a non-return valve on the pipe near the tank, but it can still take a lot of cranking after sitting a week, I have considered another in the line between pump and carb, but not tried it yet, and not sure how the pump would cope with another restriction in the line.

I tried a non-return between pump and carbs but saw no improvement so took it back out. After a couple of weeks without use I crank her over for 15-20 secs then give 4 pumps on the throttle and job's normally a goodun.

I changed mine for an electric pump

Did you block off and remove the mechanical pump Or just remove the hoses?

I removed it and made a blanking plate

I remember years back, our A35 had a priming lever.
But now, priming bulbs seem to be on the market.

I find the battery is running flat after trying to start it, after several days lay off.

alfadave wrote: ↑

Fri Nov 13, 2020 1:46 pm

I remember years back, our A35 had a priming lever.
But now, priming bulbs seem to be on the market.

I find the battery is running flat after trying to start it, after several days lay off.

I run a cut out switch mounted into the plastic in front of the battery - didn't want to drill into any metal.

One of my classic cars a few years ago was hopeless so I replaced all the fuel pie and not only did it cure it but it accelerated much more smoothly. So a cheap fox that gave an excellent result. Then electronic ignition made it better still.

Pie = pipe

Fox =Fix.

Found I cannot talk and type.

I fully Hindustan

Got a bulb fuel primer here.
Dumb question.
Do I fit it between the tank and pump.

Or between the pump and carbs?

alfadave wrote: ↑

Thu Nov 19, 2020 8:17 pm

Got a bulb fuel primer here.
Dumb question.
Do I fit it between the tank and pump.

Or between the pump and carbs?

I think pump and carbs, more accessible, easier to check on, same as a diesel unit gets fuel right through the system.

Demon tweeks say they are for priming the fuel pump.
So, fitted between tank and pump?

If you fit it between the pump and the carbs then it is pressurised whenever the engine is running, if you fit it between the tank and the pump then it isn't, which is probably better !

justsuds wrote: ↑

Sat Nov 21, 2020 2:08 pm

If you fit it between the pump and the carbs then it is pressurised whenever the engine is running, if you fit it between the tank and the pump then it isn't, which is probably better !

Oh yes, Can see that point trumps mine !

I wonder if a non return valve at the tank is the best solution?

A more intelligent person than me agrees that a non return valve at the tank is the best solution.

I fitted an aluminium non return valve at the tank.
So far, the car wants to fire up straight away.

Used to be difficult to start after standing for a couple of weeks or more.......but its in regular use now, so might have to wait a bit for a proper result

I have always had an electric pump in the Green Machine, as the mechanical pump would have fouled on the chassis rails, but always with a fuel pressure regulator set at 1.5 psi - it is really easy to overpower the float chamber needle valves in the carbs. and overfuel the engine.

But here's the thing - your fuel might drain back into the tank from the pump, but the mech pump uses a reciprocating lever to operate a diaphragm and uses a non-return valve to deliver the fuel to the carb(s). So even with the engine standing for a few days I would have thought that there should always be some fuel between the pump and the carb. Also, the float chamber will have fuel in it and this should not drain away either (although given enough time it will evaporate).

So I am not sure that a priming bulb will help unless the non-return valve in the pump has failed, or the engine fails to catch on the fuel left in the carb float chamber.

Perhaps the fuel tank breather is blocked, causing a vacuum which prevents the fuel being sucked up by the pump?

Lauren

I fitted a new tank (when they were available!) and new breather not long ago.

So far, the engine seems to fire up immediately on turning the key. It used to need to turn over a few times previously.

The key test will be after it hasn't been run for say 10 days. But thats not likely to be soon.

I fitted a non return valve at the tank some time back. I have a mech fuel pump.
I've been away for a fortnight, and in the past I would have flattened the battery trying to start it.

Its clear now there is fuel at the carbs almost immediately, and the car fires up quickly.

A job I would recommend to anyone!

That's a nice result Dave, shows the value of a simple modification. A nice side benefit is to your starter motor and battery as they should also last longer!
With the warm weather and it being parked for 2 weeks that shows that it's not just fuel evaporising in the carbs, it must all have been slowly dribbling back despite the fuel pump being a version of a one way valve.
Good result

That's a nice result Dave, shows the value of a simple modification. A nice side benefit is to your starter motor and battery as they should also last longer!
With the warm weather and it being parked for 2 weeks that shows that it's not just fuel evaporising in the carbs, it must all have been slowly dribbling back despite the fuel pump being a version of a one way valve.
Good result

Non return valve at the tank has done the trick for me. Priming the pump is the real issue. It's not really up to dry operation to drag the fuel back up hence the prolonged cranking after a layoff.