Hi everyone,

Along with my 2.1Slowboy stroker block and AMS GT35 modification (among other goodies which i will sure post when done), I'm custom fabricating an in-tank twin walbro pump setup.

I've succeeded to fit the two pumps and joined them with a Y-Connection to the stock fuel hose that goes to the fuel rail. The pumps go on a stock pump-frame whereby I have cut the stock pump chassis and fitted the new pumps now.

The pumps are electrically connected to the stock harness in parallel. The stock fuel return and air ventilation remains.

However, I've had some mysterious behaviour being that when I start the car using the first walbro i have a constant 3.2bar pressure (50psi). However, when i hook up the twin pump, the pressure is very erratic and does not go above 2bar (15psi), after which the pumps will stall and the engine will stop.

Any ideas of what could be the problem?

I wanted to ask, are the pumps wired directly to a constant 12V current or are they hooked to some electronic control thru the ECU?

Your comments appreciated..

new twin pump set..
http://evolve.ae/forum/userpix/366_image0k80_1.jpg

external filter..
http://evolve.ae/forum/userpix/366_imagek081_2.jpg

Wael

 

Do you have both pumps hooked up to the same stock pump wiring? It is clear that the first pump is working, but I'd check to see if (1) the second pump is working or defective, and (2) how much electric current draw down you are seeing when the second pump starts up. You may be overloading the electric circuit and wiring and not getting enough current to run both pumps at the same time the way you have them wired up. Are you turning the second pump on and off with a pressure sensor, or are they both supposed to run all the time?

 

Sounds like CO VR4 has it right. Most of the aftermarket kits have a low pressure switch that triggers the second pump wired in through a relay if I am not mistaken. I may be wrong as it has been known to happen.

Josh

 

I think the stock ECU has a low speed/high speed pump switching system. Maybe with both pumps in the tank, the low speed does not provide enough juice?

 

http://www.atpturbo.com/Merchant2/me...egory_Code=BCS

Something like that, to turn on 2nd pump when a certain boost is reached

 

The Evo does have a LO HI voltage system for the fuel pump.

I think it is possible for the two pumps to not be getting enough current to run them.

Its a bad idea to run two high flow pumps off the factory wiring. Use the factory wiring to trigger two fused relays to run the pumps.

Two Walbro 255L HP pumps feeding the factory feed line and returning through the factory regulator and line will create about 70 psi of fuel pressure at idle. Staging the pumps or upgrading lines and regulator is the only way to get the pressure at idle under control.

If you are not returning fuel to the tank through the factory siphon fitting (hooked up correctly of course), you will not be pulling fuel from the opposite side of the tank and you will not have fuel on the pump side of the tank when your tank gets to a little under half a tank.

 

Ivan couldn't of said it any better to have constant proper fuel control.

 

OK, thanks guys for so much positive response..

I will run two fused relays to trigger the pumps. But i am only worried that if i do that, how will the pumps run if the ECU is supplying low current at sometime as COVR4 is saying?

I do have an aftermarked SARD fuel pressure regulator. Stock fuel supply line, stock return, stock fuel rail, stock electric socket..

I would have loved if someone can guide me either shcematically or step-by-step on how to go about it. I have seen the link of the pressure switch Liqquid has posted, but how do i go about that! Thanks..

I will investigate more and let you know..

Wael

 

Good luck wael...bravo on being creative and fabricating parts for your evo...hope it turns out the way you wanted..

**my lazyass just went the easy way with a buschur twin pump setup** lol

 

Pump 1 you can run with the stock wiring, pump 2 needs to be hooked up to be activated via relay or pressure switch for a consistant turn on point. This way pump 1 will work inline with the stock relay for Hi and Lo amp runs and pump two will turn on wide open when needed. I hope this makes better sense of what is being said.

 

Ok GTVEVO, I get what you mean! I'll work on that basis, thanks for the explanation.. Now, we have to find a pressure switch!

I guess I will use ur system, and run pump2 on a pressure switch to trigger after 1bar (14psi) manifold boost. I am aiming for 2bars (~30psi) as maximum boost.

Thanks again!

Wael

 

If you do a search for the Buschur system description, I think you'll find that Buschur uses a relay to turn on the second pump, but it still needs to be wired so that you have sufficient current to each pump, or you'll have exactly the same problem you have now. This is NOT just the factory HI/LOW output problem. It can be a basic problem of how much current/amperage the wires can handle maximum, and whether you can run both pumps off the same wiring. Many people used to run larger wire to make their pump voltage higher capacity in DSMs for this very reason. All of the fuel pumps are VERY sensitive to having adequate voltage. You can see this from a comparison of what the pump will flow at 12V compared to 13.4V or 14V. The difference is MAJOR.

The reason Buschur uses a relay to turn on the second pump at a predetermined positive boost level is that it avoids having to increase the return line size, which is necessary if you run both pumps all the time because at lower pressure most of the fuel is bypassed and returned to the tank. It also avoids the need for an adjustable fuel pressure regulator...

 

If you use the AEM you can use a relay to control the exact turn on as I do, if you do not you will probably need a hobs switch to auto activate the pump at a desired pressure. Either way pump 1 runs on the stock wiring to retain Hi/Lo speed and pump 2 runs on its own wiring (not the stock) to again be clear. Sorry I didn't include the wiring in my earlier post so I wanted to be sure you are aware. CO_VR4 expains the reasons above.

 

It's also wise to have a fail safe so that if one pump fails or something happens to it's circuit (if wired independently) of the other, to automatically shut off the other pump. It would suck for one pump to malfunction when you were making a pull at the track for example and you end up starving the motor of fuel by all the load being transferred to the only functioning pump. Nice way to kill a motor.

 

Can you post pics of the actual assembly and not just the top/outside of it? You can't see anything in the pics you posted, it'd be cool to see how you modified the stock assy and mounted the pumps!