Technical Electric Fuel pump + Mechanical FOR COLD START?

[ClassicFiat500]

My 652 Fiat 500 has been serviced & overhauled by a very reputable Abarth specialist MB Garage & runs much better for it apart from one thing, Starting is a nightmare due to the fact MB garage disconnected the electric pump & re fitted the original mechanical pump. The problem I have is when the car has been standing for a few days the mechanical pump has to fill the Weber DCO 40 with fuel obviously before it will start, this can take over 30 to 45 seconds putting a strain on the battery & starter. When the electric pump was connected as soon as the ignition is on the fuel fills the carb & fires up.
Spec on pump from Ricambio—-

• Pressure 2.1 PSI​
• Flow 27.5 Gallons per Hour (125 Litres per Hour)​
• Union fuel pipe size 5/16 inch / 8mm​

This pump is designed to be fitted near to the fuel tank of the vehicle. (not in the engine bay)

This pump is ideal for use with Dellorto or Weber carburettors, the low pressure eliminates the need for a pressure regulator.

My question is - Is it possible to fit a T piece into the fuel inlet near the carb, then connect the electric pump activated by a relay switch on the dash, when starting from cold, As soon as the carb is filled I could switch it off so the mechanical pump will take over, would I be forcing to much fuel into the carb?
I know the weber 40 is too big for the engine, but it runs great when its warm with no problem,
Looking forward to your valuable advise as usual Barry

 

[ClassicFiat500]

Set up with Weber 40View attachment 8D63A415-94D9-4D88-9EFC-27B9AA6E7050.jpeg

 

[The Whitakers]

Can you not fit a anti fuel return valve in between the pump and carb?

 

[fiat500]

Use it every day.

 

[the hobbler]

Use it every day.

A 'non-return' valve will not effect the runningof the engineas long as the valve is between the pump and the carb. If you fit it by the tank, the engine will not run at higher revs---the pump on the 500 is a 'pusher', not a 'puller' I concede that the float chamber on a FZD Dellorto is probably smaller than that on a 40DCOE, I have no problem starting unless the car has been standing for quite few weeks. I have no choke mechanism on my FZD, so utilize the fact that it has an accelerator pump; give the throttle about 3 slow pumps, count to 10 (to give the fuel time to vapourise) and then crank. If the car HAS been unused for some time, I pressurise the fuel-tank with an old tyre-pump to push fuel through to the (mechanical) pump.

 

[RalphM]

Is the pump now fitted new or have they just connected the one fitted that has been sat there?
if so maybe the pump needs a bit of tlc they are fitted with a diaphragm that can dry out over
time if not used and non return valves that can stick, had lots of cars with mechanical pumps
always started normally.

 

[ClassicFiat500]

A 'non-return' valve will not effect the runningof the engineas long as the valve is between the pump and the carb. If you fit it by the tank, the engine will not run at higher revs---the pump on the 500 is a 'pusher', not a 'puller' I concede that the float chamber on a FZD Dellorto is probably smaller than that on a 40DCOE, I have no problem starting unless the car has been standing for quite few weeks. I have no choke mechanism on my FZD, so utilize the fact that it has an accelerator pump; give the throttle about 3 slow pumps, count to 10 (to give the fuel time to vapourise) and then crank. If the car HAS been unused for some time, I pressurise the fuel-tank with an old tyre-pump to push fuel through to the (mechanical) pump.

Hi really appreciate your advise & knowledge, when you say you pressurise the tank with an old fuel pump can you elaborate on this. Just to let you know I have just started the car it was ok & runs well starting after turning it over for about 5 seconds then stops but after 3 goes it fires up & runs well, but as you say if I were to leave it for a week or two it needs a lot of turning over. Do you think a non return valve would be helpful ( if so could you recommend a good make) or is the petrol just evaporating in the carb which could leave a gunge in it. Or is it the old saying “USE IT OR LOOSE IT”
Barry

 

[the hobbler]

Hi really appreciate your advise & knowledge, when you say you pressurise the tank with an old fuel pump can you elaborate on this. Just to let you know I have just started the car it was ok & runs well starting after turning it over for about 5 seconds then stops but after 3 goes it fires up & runs well, but as you say if I were to leave it for a week or two it needs a lot of turning over. Do you think a non return valve would be helpful ( if so could you recommend a good make) or is the petrol just evaporating in the carb which could leave a gunge in it. Or is it the old saying “USE IT OR LOOSE IT”
Barry

(a) yes, I am a firm believer in using ones classic car as much as sensibly possible. (b) I use an old AIR pump (for pumping up tyres) to pressurise the tank---something my son asked me "to store for him". I just put the hose that you would normally attach to the tyre-valve into the filler kneck of the tank, hold some rag around the hose (to seal the tank) and let the pump run for a minute or two. When you take the rag away you might hear a slight rush of air ---the pressurised air in the tank escaping. This is normally enough to force fuel back through to the pump

 

[ClassicFiat500]

(a) yes, I am a firm believer in using ones classic car as much as sensibly possible. (b) I use an old AIR pump (for pumping up tyres) to pressurise the tank---something my son asked me "to store for him". I just put the hose that you would normally attach to the tyre-valve into the filler kneck of the tank, hold some rag around the hose (to seal the tank) and let the pump run for a minute or two. When you take the rag away you might hear a slight rush of air ---the pressurised air in the tank escaping. This is normally enough to force fuel back through to the pump

(a) yes, I am a firm believer in using ones classic car as much as sensibly possible. (b) I use an old AIR pump (for pumping up tyres) to pressurise the tank---something my son asked me "to store for him". I just put the hose that you would normally attach to the tyre-valve into the filler kneck of the tank, hold some rag around the hose (to seal the tank) and let the pump run for a minute or two. When you take the rag away you might hear a slight rush of air ---the pressurised air in the tank escaping. This is normally enough to force fuel back through to the pump

Hi Tom I can see the logic in pressurising the fuel tank, I have also been looking at the Piston head forum where a quite a few people with Weber carbs have encountered the same problem of fuel evaporation, one or two have said use a hand fuel pump primer. If this was fitted between the mechanical pump near the carb would you think i would be able to fill the carb with it enough? my only concern with it is - the safety of a rubber primer bulb, which is a similar scenario as fitting a plastic see through filter(would the rubber bulb perish )
Barry

 

[judderbar]

I think you are making this far too complicated. A correctly set up mechanical fuel system will not be making it so hard to start your car. Unless you are living in a very hot climate you will not need to be concerned about significant evaporation. I can see the logic of adding on something to fix a problem that is hard for you to personally fix but there are safety issues for you to think about. I think the abarth garage have some responsibility here since they decided to fix your car into this perhaps safer configuration for you which is now causing you headaches

 

[fiat500]

There should always be fuel available at the inlet for the mechanical pump. There was even a warning sticker, fitted by FIAT to that effect. Once started, fuel is delivered partly by gravity. So there should be no need to pressurise the tank in order to deliver fuel to the pump. It seems likely that the disc-valves inside the pump would be an obstacle to any separate priming-pump.

After a lay-up, the only thing that should need to happen is for the pump to pull in the standing fuel at its inlet and to deliver a full carb bowl. It's something which is quite normal on older cars. When my car has been sitting for any length of time, I prime it with two or three short bursts on the starter, which can even be done with the ignition turned off.

It seems likely that if you need to turn over the engine for an extended period in order to get fuel moving, you may have a loose pipe connection or porosity somewhere in the pipe-run.

 

[ClassicFiat500]

I think you are making this far too complicated. A correctly set up mechanical fuel system will not be making it so hard to start your car. Unless you are living in a very hot climate you will not need to be concerned about significant evaporation. I can see the logic of adding on something to fix a problem that is hard for you to personally fix but there are safety issues for you to think about. I think the abarth garage have some responsibility here since they decided to fix your car into this perhaps safer configuration for you which is now causing you headaches

Many thanks for your reply, Yes I partially agree with you, however 1st of all I know the carb is not the most ideal however as it came with the car & I have just spent quite a lot on having it set up & fully stripped & re built plus it runs great when its warm, it also starts fine after 24 to 36 hours or so but if I leave it for longer say a week the petrol seems to either drain off or evaporate this appears to be a common problem with Weber 40 carbs. (don’t think it actually evaporates as its only 8 degrees in my garage, it seems to drain off), if I fit an electric pump it fills the carb before the engine turns over then starts. As the mechanical pump has now been serviced and runs ok when warm I have been advised to keep it on. Hence the idea of just fitting a hand primer may resolve the problem.

 

[RalphM]

When I worked on Fords with DCOE carbs you never used the choke just 2 pumps
on the accelerator and turn the key, also the carbs were on anti vibration manifolds
that had to be set up with 7 thou clearance if memory serves, it's a long time ago,
or you would get flat spots due to fuel frothing.

 

[RDS]

For engines that are used daily and which have a pump that has the correct throw and us able to self-prime, then I have found mechanical pumps to be just about satisfactory. However for less frequent use especially on a specialty carb and to help diagnosing other problems, I found that fitting an electrical push pump with sufficient lift but of low pressure controlled by a relay, was one of the best things I did to my other fiat.

The carb is primed quickly, you can then squirt some fuel using the accelerator pedal into the manifold before cranking and the start up is much quicker.

 

[ClassicFiat500]

I have now re instated the electric pump & guess what, It now starts straight away, as you turn on the ignition you hear the fuel pump ticking, press the starter & off she goes, no waiting for the carb to fill up