700 double pumper on a road car

GJUK · Post by **GJUK** » Tue Aug 19, 14 10:44 pm

Thank you.

GJUK · Post by **GJUK** » Wed Aug 20, 14 3:37 pm

I've ordered a fuel pressure gauge and fittings from torque, they should be here tomorrow.

I've also been reading up, could this be an issue (read from another forum with someone having a similar issue)

Blocked off fuel tank vent causing excess pressure to build in the tank and push the fuel pressure up

I have no fuel return from the carb to tank.

That said if my fuel pressure is too high (especially when running at high rpm as it is mechanical) maybe this is the problem...

Will find out soon

Jon

Dave81 · Post by **Dave81** » Wed Aug 20, 14 8:45 pm

GJUK wrote:I've ordered a fuel pressure gauge and fittings from torque, they should be here tomorrow.

I've also been reading up, could this be an issue (read from another forum with someone having a similar issue)

Blocked off fuel tank vent causing excess pressure to build in the tank and push the fuel pressure up
I have no fuel return from the carb to tank.

That said if my fuel pressure is too high (especially when running at high rpm as it is mechanical) maybe this is the problem...

Will find out soon

Jon

Jon,

Can you post the link to Torque on eBay as I can't find it?

Cheers Mate!

db · Post by db » Wed Aug 20, 14 9:06 pm

GJUK wrote:
I have no fuel return from the carb to tank.

Jon

Neither do I- depends on the type of pump/ reg you have.
My return line is from my pump (mounted next to the tank in the trunk). I'm told this can heat up the fuel though and is noisier than a system that has a return from the carb.

GJUK · Post by **GJUK** » Wed Aug 20, 14 9:10 pm

Thanks, I appear to have no return at all. so it's a dead end and if the psi is a little high.... could cause leaking from the booster.

God I've learnt a lot about carbs in the past 3 weeks.

Torques.

http://www.ebay.co.uk/usr/torques_uk?_t ... 7675.l2559

J

Dave81 · Post by **Dave81** » Wed Aug 20, 14 9:25 pm

GJUK wrote:Thanks, I appear to have no return at all. so it's a dead end and if the psi is a little high.... could cause leaking from the booster.

God I've learnt a lot about carbs in the past 3 weeks.

Torques.

http://www.ebay.co.uk/usr/torques_uk?_t ... 7675.l2559

J

Thanks.....

Dave-R · Post by **Dave-R** » Wed Aug 20, 14 9:50 pm

You don't need a return with a mechanical pump.

GJUK · Post by **GJUK** » Wed Aug 20, 14 9:56 pm

Thanks Dave.

Mossy68 · Post by **Mossy68** » Wed Aug 20, 14 10:00 pm

Dave wrote:You don't need a return with a mechanical pump.

Dave.
As most our cars run mech fuel pumps ,which from my knowledge and experience prove to be reliable, then what could cause one to over fuel / increase pressure ?

Bozwell · Post by **Bozwell** » Wed Aug 20, 14 10:44 pm

looks like secondary float too high.

primary float height is quite critical for slow running and progression but with the secondaries the air speed is already up so you can go a little lower on the float height without ill effect.

GJUK · Post by **GJUK** » Wed Aug 20, 14 10:56 pm

Bozwell thanks, I will be trying this along with my fuel regulator tomorrow when all the car parts arrive at work, much to the receptionists joy.

Dave-R · Post by **Dave-R** » Thu Aug 21, 14 8:36 am

Mossy68 wrote:
Dave wrote:You don't need a return with a mechanical pump.
Dave.
As most our cars run mech fuel pumps ,which from my knowledge and experience prove to be reliable, then what could cause one to over fuel / increase pressure ?

RPM.

You increase engine speed and it pumps faster. A stock pump does self regulate to a degree (they are weak) but aftermarket pumps in particular are built to deliver more fuel so you need a regulator to give you a constant pressure. Otherwise it is just going to go up and down with rpm.

GJUK · Post by **GJUK** » Thu Aug 21, 14 8:45 am

Dave wrote:
Mossy68 wrote:
Dave wrote:You don't need a return with a mechanical pump.
Dave.
As most our cars run mech fuel pumps ,which from my knowledge and experience prove to be reliable, then what could cause one to over fuel / increase pressure ?
RPM.

You increase engine speed and it pumps faster. A stock pump does self regulate to a degree (they are weak) but aftermarket pumps in particular are built to deliver more fuel so you need a regulator to give you a constant pressure. Otherwise it is just going to go up and down with rpm.

Ahhh, you see it is not an original pump (it looks new). I was told that they self regulate but with aftermarket parts I guess you never know.

My regulator fittings are here today so fingers crossed guys... Really hope this fixes it.

Thanks for all your help.

Jon

Dave-R · Post by **Dave-R** » Thu Aug 21, 14 9:48 am

An aftermarket pump can easily deliver 8psi of pressure without a regulator.

Dave-R · Post by **Dave-R** » Thu Aug 21, 14 9:51 am

A simple cheap in-line pressure gauge in the fuel line to the carb will allow you to set the regulator pressure. Try it at 6 psi and set both fuel bowls to only JUST weeping out of the sight plug holes. Not dribbling out.