Correct Fuel Pump??

JimMet · Post by **JimMet** » Thu Jan 04, 2007 8:50 pm

I have an RV8 in my hilux, which was already fitted when i bought it. Occasionally i have problems with it stalling and i think it's something to do with the fuel supply, as there never seems to be very much fuel in the filter.

I'm not sure if the fuel pump is the correct one. I took some pictures of it but i haven't got the ability to put them on. It's roughly 4 inches square and kind of gold coloured. There is no markings on it, apart from a few US patent numbers.

At the moment there is a T-junction just before the filter to accommodate a return back to the fuel tank, which exists from the original toyota engine. The fuel pump runs at all times when the ignition is on.

Should this T-junction be there at all? Or should there just be a pump that keeps the pressure in the fuel lines constant at all times?

Any help is greatly appreciated!! Cheers.
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Post by **katanaman** » Thu Jan 04, 2007 9:47 pm

put the pictures on something like photobucket and paste the links they give you on here.

Sounds like a holley pump to me but cant be sure specially the sizes your giving so follow above and let us have a look. Is there anything between the return line and the supply line to restrict the flow? There should be a restrictor or better still a regulator on it although you should be able to run the pump without any return. What carb are you running?

Ian Anderson · Post by **Ian Anderson** » Fri Jan 05, 2007 2:27 pm

Perhaps a Facit low pressure
see
http://www.rallydesign.co.uk/catalog/pr ... ts_id=1698

That said Marki sounds right - should be a resstrictor / regulator there

Ian

JimMet · Post by **JimMet** » Fri Jan 05, 2007 3:15 pm

The pump in the link above is the same (or at least looks the same) as the one I have.

There is nothing between the return line and the supply line to restrict flow. Where is a good place to get a regulator from and where should it be fitted?

It's running on twin SU carbs.

Post by **katanaman** » Fri Jan 05, 2007 3:58 pm

I would drop the return line and just run it straight the regulation on the pump itself should be ok.

Ian Anderson · Post by **Ian Anderson** » Fri Jan 05, 2007 4:41 pm

Also make sure you have the right pump as the come in different flow rates and perhaps the pump you have is not man enough to keepup with the engine

Also you don't say where the pump is located - should be near the tank as they prefer to push rather than suck. If it is sucking it could be running on vapour and that will not help anything.

Ian

JimMet · Post by **JimMet** » Fri Jan 05, 2007 6:49 pm

The pump is right next to the tank.

If the pump is the same as the one in the link above is it powerful enough to keep up with this engine (3.5 RV8)??

I'll do away with the return line.

Ian Anderson · Post by **Ian Anderson** » Fri Jan 05, 2007 7:59 pm

Jim

3 flow rates on the pump variety
see
http://www.rallydesign.co.uk/catalog/in ... th=281_282

Note I'm not advertising rally design just know I found their site useful in the past.

There is a formula for calculating fuel useage and it is something like 12cc per minute per HP (Memory on this number so don't shoot the grey cells)

So 300HP engine needs a max flow rate of something like 45gallons per hour(12*300*60 = 216000cc/hr = 216 l per hour = 48 gal per hour)

But that is at full power and how often do you use full power for an hour without tapping off but gives a good indication of what is needed in those "mad moments"

So your pump may be good or not.

Take the pipe off at the carb stick the end in a drum and run the pump for say half a minute and see how much it flows and calculate to see if it will cope with your estimate of your engine power

Cheers
Ian

Post by **katanaman** » Fri Jan 05, 2007 8:48 pm

Before you go getting all complicated fix your current bad installation and see what happens. Returning fuel the way you are could lead to zero fuel pressure and most of the fuel returning to the tank way before it gets to your carbs.
The not much fuel in the filter part I wouldn't bother about either. if its one of those clear filters and its on its side the fuel will only come up just past the inlet/outlet as the other bit is air locked. that's the way all filters are its just the clear ones people can see and panic.

Paul B · Post by **Paul B** » Fri Jan 05, 2007 10:52 pm

katanaman wrote:Before you go getting all complicated fix your current bad installation and see what happens. Returning fuel the way you are could lead to zero fuel pressure and most of the fuel returning to the tank way before it gets to your carbs.
The not much fuel in the filter part I wouldn't bother about either. if its one of those clear filters and its on its side the fuel will only come up just past the inlet/outlet as the other bit is air locked. that's the way all filters are its just the clear ones people can see and panic.

That's my approach too. The 38 Dgas carb I used to have on my 3.5 was 'supposed' to have a return to the tank, but no two people could give me the same reason why, so I blocked it and all was well with the world. Apparently it is for letting fuel circulate and cool, but you do lose a certain amount of flow/pressure through it.

There is talk of the carb flooding if the return is blocked, but I think a faulty needle valve in the carb is the answer there, unless a tiny Facet can put out 6psi or more.

toughy V8 · Post by **toughy V8** » Sat Jan 06, 2007 6:21 pm

ive got the holleyred pump on mine with no regulator, holley say that you dont need one, it pumps 7psi, 95 gph free flow or 67gph at 5psi should be good enough for most rovers

JimMet · Post by **JimMet** » Sun Jan 07, 2007 2:39 pm

I did away with the return and its running much better now, no more stalling. Thanks for all your help guys!!!!

Post by **katanaman** » Sun Jan 07, 2007 6:59 pm

glad it worked out for you.