Mechanical Fuel Pump & Priming
Discussion
My Dad and I recently bought a Formula Ford with a Kent engine.
When we bought it the previous owner told me that it was tough to get fuel up to the carb when the car has been sitting for a while. You'd be turning it over for ages flattening the tiny battery waiting for fuel to get up to the carb. He advised removing the air cleaner and squirting some fuel in the top to get it going.
I ran the car at Brands pre-lockdown and sure enough it was a bit of a pain. I didn't like the idea of squirting fuel in the top because I was worried about putting too much in and hosing the bores down, so I duly flattened the battery before resorting to the recommended method.
Once it was going it was on the button all day.
I suppose the issue is that the carb and possibly even the fuel pump are higher than the fuel level in the tank so the fuel drains back over time.
Is it typical to have a check valve in the fuel line to prevent this? If not, how else can I solve it? I can't imagine everyone else with a Kent FF is having to do the same engine start procedure!
When we bought it the previous owner told me that it was tough to get fuel up to the carb when the car has been sitting for a while. You'd be turning it over for ages flattening the tiny battery waiting for fuel to get up to the carb. He advised removing the air cleaner and squirting some fuel in the top to get it going.
I ran the car at Brands pre-lockdown and sure enough it was a bit of a pain. I didn't like the idea of squirting fuel in the top because I was worried about putting too much in and hosing the bores down, so I duly flattened the battery before resorting to the recommended method.
Once it was going it was on the button all day.
I suppose the issue is that the carb and possibly even the fuel pump are higher than the fuel level in the tank so the fuel drains back over time.
Is it typical to have a check valve in the fuel line to prevent this? If not, how else can I solve it? I can't imagine everyone else with a Kent FF is having to do the same engine start procedure!
Fuel should not drain back...carbs and mechanical pumps worked fine for daily stuff for decades. So there is no reason it should not work.
Check the obvious.
Restrictions from tank to pump.
Check the pump does indeed work.
And ensure line and any filters to the carb are good.
And dump the "tiny battery" and fit a good one.
Check the obvious.
Restrictions from tank to pump.
Check the pump does indeed work.
And ensure line and any filters to the carb are good.
And dump the "tiny battery" and fit a good one.
HustleRussell said:
Will check the regs but I suspect that if electric fuel pumps were permitted the car would have one
Ah, good point.The carbs bowls should retain quite a bit of fuel, even if the fuel line is leaking back I would have thought, enough to start it. You sure there are no fuel leaks.
tapkaJohnD said:
In FF, are you allowed an accessory battery, connected by an Anderson plug?
Then, you can have full size battery for start up, even on the grid, if your crew will bring it.
JOhn
My car does have the Anderson connector. Using a battery tender used to be absolutely necessary and a lot of people still do it... however the little AGM batteries used these days have enough power to start and run the car all weekend with little or no topping up provided the engine is able to start promptly. Then, you can have full size battery for start up, even on the grid, if your crew will bring it.
JOhn
I’m not going to have a crew so I will be making do without a battery tender.
It would help if even for the first start of the weekend but the car is taking so long to start due to the fuel drain back / evaporation issue that I’d want to rectify it for the sake of the starter motor and wiring as much as the battery. I think the starter motor is an inertia type as well but I’ll need to check that.
Currently thinking that I need to make sure there’s no way for air to get into the fuel lines upstream of the pump but apart from that I’m not sure what I can do... I’ve gone off the idea of a non return valve a bit because it’s an extra thing to go wrong and two extra joins in the fuel line...
I think I need to find out if this is an issue which will manifest overnight or whether it’s only when the car isn’t run for weeks because if it’s the latter I’ll probably just work around it like the previous owner did- get the car running in the workshop before I set off for the weekend and / or squirty bottle of fuel.
PositronicRay said:
Don't those pumps have a diaphragm? If so replace that 1st.
Before thinking of that, make sure the pump's valves are seating properly. For a pump to work it must have NRVs before and after the pumping chamber. It is they which also prevent fuel draining back into the tank so fitting an additional NRV, as suggested above, is not addressing the real problem.
Leave it long enough not to fire (overnight ?), open up the float bowl and see if there is fuel in them, if not, turn it over for 30s, then check if the bowls are full. Then you can see if its a problem getting fuel to the carbs or a carb issue
Need to step through the performance of each part, somethings not right. Is the vent to the top of the bowl blocked ?, is the needle valve on the float sticking, is the suction pipe to the pump leaking so it pulls in air and prevents effective priming, so many individual little possibilities.
Sounds like a lot of fun. Did you see Tiff Needell's lockdown video about his FF? Worth a watch.
Back in the day when most ordinary cars still had mechanical fuel pumps, they were pretty much a consumable item. Either the diaphragm would go or the internal valves would start to fail, leading to lots of cranking as you describe.
So I would try a new pump, if it's the sort that doesn't come apart, or a strip and rebuild if it does.
Back in the day when most ordinary cars still had mechanical fuel pumps, they were pretty much a consumable item. Either the diaphragm would go or the internal valves would start to fail, leading to lots of cranking as you describe.
So I would try a new pump, if it's the sort that doesn't come apart, or a strip and rebuild if it does.
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