im putting on twin webbers and am using twin electric fuel pumps in parralel (off a MQ nissan patrol, if any one has specs on these i would love to hear from them), im afraid there going to pump too much petrol and want to run a return to the tank. i just saw a set up in one of the discussion where the fuel line to carbies ran accross the top of the firewall which i think i will do, but what is the best method of running the overflow back to the tank? should i get another standard fuel line and use it alongside the other? where should the return go back to? i want to mount pumps at back near tank, can i run the return into a "T" joint just before the pumps? or am i better off trying to run it back into the tank? thanks for any advice,
Michael


p.s. im asking this without having looked at the fuel line setup at the petrol tank and having no real idea where i could mount the fuel pumps yet. yep im lazy and its too cold outside

u think its cold in AUS it was under 4degrees celcuis all day here in NZ well to answer your question personly i would run it back to the tank with another fuel line and join it to the the top of the tank drill a hole in the top of the tank and get a peice of pipe the size u want and solder it on

P.S do this while tank is out of car and if it goes wrong dont blame me OK

<small>[ Edited by rally-a-coupe on 2002/6/17 20:28:31 ]</small>

Please don't weld fuel tanks if you value your body in its entirety.

any other tips guys? surely heaps of you guys have done it? or dont you run a line back?

Firstly I would be getting on to a Nissan workshop and getting the specs for the flow rates on the fuel pumps. I think the twin pumps will be over kill but you could install them so that if one sucks a kumara you can flick a switch and kick the second one into life...Second I'd buy a good quality fuel pressure regulator, Webers don't like too much pressure, 4psi will be enough. If you are worried about fuel surge make a tank (250mL) and mount it on the firewall to fed the carbs . If you run a return line any fittings added to the tank should be soldered NOT welded, the old metal will have absorbed fuel and will ignite quite happily. The tank should be flushed with water for an hour at least and then filled with an inert gas like argon(from a Mig welder). While your'e doing the return you may as well enlarge the the outlet to ensure a good feed to the pump. Hope this helps....

As Stirlingmac said check the flow rates. This will tell you how much fuel you are gonna send up to the carbs and you will also need to know/find out how much fuel you actually need at the carbs. The return line could go back to the tank but if you use a surge tank you could send the return line to that so as to save you stuffing about with your old tank (ie new attachments). You will have an overflow on the surge tank back to the Datto tank. Seeing as the Datto tank doesnt have an in tank fuel pump, put one in between the Datto tank and the surge tank. Then use a larger capacity pump from the surge tank to the fuel rail. A fuel pressure regulator sounds like a good idea too.
One thing I cant understand is why mount a surge tank in the engine bay? This sounds far more dangerous than mounting it in the boot where there is much more space. Most of the stuff you need can be sourced from wreckers and a surge tank can range between $150-$300. Using a surge tank will save you a lot of bother with your old tank.

In my Ford ute I have an EFI pump supplying a Weber and I have had no real dramas. I have not bothered with a surge tank as the ute doesnt really undergo enough hard cornering to warrent the use of one. Surge tanks stop fuel surges and the starving affect when the fuel sloshes about when going hard around corners. If there was no surge tank, go around a corner hard and the fuel might not get picked up.

The surge tank on the firewall is for feeding the fuel bowls on the sidedrafts which are prone to running out of fuel when cornering hard. By mounting the tank higher than the carbs gives a reserve amount of petrol should the pump suck air momentarily while howling around a corner. The tank is only as dangerous as the regular fuel lines as it is only regulated pump pressure (4psi). Fuel injection is a completely different story and requires higher rated fittings and hose. In this situation I would mount the surge tank in the rear as FI runs around 55psi and the pumps can also get very noisey. I don't really understand why you would run an FI pump on a carbed engine it must be regulated to hell or the fuel will be screaming around it's circuit and eventually could lift the needle off it's seat in the fuel bowl causing flooding. When it comes to fixing problems I go for simple (read that as cheap) solutions, making a tank for me is easy and as an engineer I can't believe the prices charged by some outfits for surge tanks and similar stuff...

twin nissan patrol electric fuel pumps? crikey! that's some serious flow brother, what are you running, a Rolls Royce Merlin?
the tank outlet is only 1/4" so unless you enlarge it as stirlingmac suggested I'd say that's overkill, especially in a rally car which isn't full throttle 90% of the time like a race car. my A15 with 45s uses the factory mechanical pump and runs fine. the main benefit I can see of electric pumps is that they fill the fuel bowls before you start, making life much easier on the battery.

yeah maybe it is overkil, guy at an auto shop told me to set pressure regulator on 3 kpa or mpa? whateverer the units are. he said i dont need a return and he knew one of the pumps can push upto 5 kpa or mpa so ill be keeping one as a spare. he also told me one pump new costs $200 i got two for $45 . not too keen on the comment about rally cars being not on full throttle 90% time. i reckon it would be bloody close to 90% and always right on redline. theres no time to back off thats for sure. when you are hitting the brakes youre still reving the car quite high with engine braking aswell. anyway thanks guys for ya 2 cents

Yeah, now I get what your on about with the surge tank on the firewall.
Nah i dont have my FI pump regulated. I only have the occasional problem with spluttering whether thats to do with the pump i dont know. The only reason I run it is becasue the motor was from an EFI car and my old motor was carb. This one is carb but has no place for a mechanical pump on the new engine. Why didnt I go EFI? Couldnt afford it. Might do it later.

Im studying to be an engineer, people charge so much for something that costs next to nothing if you have the skill. I spose thats like everything really.