Fuel pump/ lack of fuel

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Fuel pump/ lack of fuel

Post by scimitargtc » Wed Apr 17, 2019 3:01 pm

So the saga continues with getting my 79 6a restarted. Got the stuck choke flaps sorted all put back together but no fuel to carb. Blew air down from the pump inlet pipe back to the tank which is new stainless via c/borough and has about 4 gallons of fuel in it and enough noise and vapour out of the filler cap(open) to suggest no blockages. Blew air thru pump and it’s going thru but leaving off the outlet pipe to carb and cranking it in 5 second bursts over20 seconds no fuel is coming out. Ideas? Did have pump off, could I have refitted it either arm over/ under the ‘drive’ peg in error, could I have fitted the fuel lines wrong way round at the tank? Am 60 on Friday and really really want to have it going then if humanly possible


1979 se6a auto pas 3.0v6 (unnamed)
1998 Range Rover 4.6 v8 auto (unnamed)
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Fuel pump/ lack of fuel

Post by scimmy_man » Wed Apr 17, 2019 3:10 pm

They can take a while to prime, try a teaspoon of fuel in the carb inlet,
the cough is often enough to prime it.


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Fuel pump/ lack of fuel

Post by Roger Pennington » Wed Apr 17, 2019 3:18 pm

Have you got a means of applying suction to the fuel pump inlet pipe? (perhaps replace it with a length of clear pipe so you can see the fuel coming!). If you can suck up petrol through it, then that will confirm whether the pipe is on the correct stub from the tank.

Also if you dip the pump inlet pipe into a bottle with petrol in it, then put the outlet in an empty bottle, then operate the pump, if the pump is working you should see petrol pumping through.

If it's stood for a long time, it's not unknown for the valves in the pump to dry out, the second test above should eliminate that.


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Fuel pump/ lack of fuel

Post by peter freeman » Wed Apr 17, 2019 3:21 pm

Fit a electric pump - you can fit it in series with the mechanical pump and with a push button use it to prime the carb.



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Fuel pump/ lack of fuel

Post by scimitargtc » Wed Apr 17, 2019 3:23 pm

2 replies within an hour, fantastic! Can get her to fire briefly by chucking fuel down the throat but obviously no fuel is being sucked up raptors fill the bowl... sucking sounds like a plan with a manual air bed pump will update shortly


1979 se6a auto pas 3.0v6 (unnamed)
1998 Range Rover 4.6 v8 auto (unnamed)
2016 Nissan QashQai 1.6 Tekna CVT dci ("Quentin")
2019 Skoda Cititgo MPI SEL Greentech ("Clyde")
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Fuel pump/ lack of fuel

Post by b.c.flat hat » Wed Apr 17, 2019 4:54 pm

It takes about a full ten seconds to get fuel to the float chambers when mine has been standing for over a couple of days. Modern fuel seems to evaporate so much faster now.



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Fuel pump/ lack of fuel

Post by scimitargtc » Wed Apr 17, 2019 8:20 pm

No fuel when sucking so just reviewed the workshop manual. And tomorrow will check fuel lines... what difference is there for the 2 stubs on the tank, if 1 is a return why? Is it just a higher point than the ‘feed’ supply?


1979 se6a auto pas 3.0v6 (unnamed)
1998 Range Rover 4.6 v8 auto (unnamed)
2016 Nissan QashQai 1.6 Tekna CVT dci ("Quentin")
2019 Skoda Cititgo MPI SEL Greentech ("Clyde")
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Fuel pump/ lack of fuel

Post by scimmy_man » Wed Apr 17, 2019 8:39 pm

blow down it, you should hear bubbling if on the right way


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Fuel pump/ lack of fuel

Post by scimitargtc » Wed Apr 17, 2019 8:59 pm

When pumping an airline down the pipe l adding to the pump there certainly was bubbling but also so7nded like the tank was being pressurised when starting to pump air in despite flap being unlatched


1979 se6a auto pas 3.0v6 (unnamed)
1998 Range Rover 4.6 v8 auto (unnamed)
2016 Nissan QashQai 1.6 Tekna CVT dci ("Quentin")
2019 Skoda Cititgo MPI SEL Greentech ("Clyde")
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Fuel pump/ lack of fuel

Post by Old and Slow » Wed Apr 17, 2019 9:44 pm

Is it possible for a non-return valve in the fuel pump to get stuck in the open position? If so it will negate any pumping action.


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Fuel pump/ lack of fuel

Post by scimitargtc » Wed Apr 17, 2019 9:46 pm

Can feel air pumping it both ways thru the pump more when pumping 5he correct direction


1979 se6a auto pas 3.0v6 (unnamed)
1998 Range Rover 4.6 v8 auto (unnamed)
2016 Nissan QashQai 1.6 Tekna CVT dci ("Quentin")
2019 Skoda Cititgo MPI SEL Greentech ("Clyde")
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Fuel pump/ lack of fuel

Post by Roger Pennington » Wed Apr 17, 2019 10:02 pm

Old and Slow wrote:
Wed Apr 17, 2019 9:44 pm
Is it possible for a non-return valve in the fuel pump to get stuck in the open position? If so it will negate any pumping action.
Roger Pennington wrote:
Wed Apr 17, 2019 3:18 pm
If it's stood for a long time, it's not unknown for the valves in the pump to dry out, the second test above should eliminate that.
Most mechanical pumps are extremely simple with just a diaphragm and a pair of non-return valves. As the diaphragm goes down it creates a vacuum, the input valve opens and the output valve closes, petrol is sucked in. Then as the diaphragm pushes up, the input valve closes and the output valve opens, and petrol pumps out to the carb. As mentioned, if the pump is left to dry out the valve can get dry or sticky and stop working, that's why I suggested working the pump in isolation, to prove that it actually does still pump.

Have you tried the test with petrol?
scimitargtc wrote:
Wed Apr 17, 2019 8:20 pm
No fuel when sucking so just reviewed the workshop manual. And tomorrow will check fuel lines... what difference is there for the 2 stubs on the tank, if 1 is a return why? Is it just a higher point than the ‘feed’ supply?
Yes, the supply side goes to the bottom of the tank, so that it can pick up all the petrol, the return just dumps fuel back into the tank, so doesn't actually need to go very far.


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Fuel pump/ lack of fuel

Post by scimitargtc » Wed Apr 17, 2019 10:07 pm

Thanks roger basic physics and gravity will check how I plumbed in the new tank first thing tomorrow, recall I’d thought I’d carefully put the fuel lines in but who knows :o


1979 se6a auto pas 3.0v6 (unnamed)
1998 Range Rover 4.6 v8 auto (unnamed)
2016 Nissan QashQai 1.6 Tekna CVT dci ("Quentin")
2019 Skoda Cititgo MPI SEL Greentech ("Clyde")
Space for 5 more! Money for none!!

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Fuel pump/ lack of fuel

Post by gtcse8 » Thu Apr 18, 2019 8:04 am

scimitargtc wrote:
Wed Apr 17, 2019 3:01 pm
Am 60 on Friday
Happy Joint Birthday, but your a couple of years ahead of me. :W

Go to the Bottom of Board Index page tomorrow and see who else is celebrating. :lol:
Last edited by gtcse8 on Thu Apr 18, 2019 8:37 am, edited 1 time in total.


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scimitargtc
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Fuel pump/ lack of fuel

Post by scimitargtc » Thu Apr 18, 2019 8:27 am

Thanks mark


1979 se6a auto pas 3.0v6 (unnamed)
1998 Range Rover 4.6 v8 auto (unnamed)
2016 Nissan QashQai 1.6 Tekna CVT dci ("Quentin")
2019 Skoda Cititgo MPI SEL Greentech ("Clyde")
Space for 5 more! Money for none!!

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