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Discussion Starter #1
I noticed yesterday that my fuel pressure dropped quite a bit. Is this normal for the twin walbros to get heated and lose capacity when outside temperature is up or the fuel tank is below half full? this would not be too good if I was to run someone with a low tank of gas.
 

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I'm the only one that I've seen with this problem, but when I ran my pumps off of the battery my fuel pressure would drop after starting the car. It would go down around 8 psi after a few minutes of running. I ended up hooking the walbros back up to the stock fuel pressure ecu and with regulated voltage my fuel pressure is stable now. Try it if you don't find another solution.
 

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how big of a drop are were talking here? i had an issue with one of my rubber lines in the tank after installing my 2 pumps and could'nt get more then 33psi...one of the lines was split..replaced both lines to be safe and now its solid at 43psi... i also only run one pump at anything under 2psi i believe, once over that the other one turns on..

jay
 

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braddman said:
Mine idles at a steady 35psi with twin 850gph Walbros.
if i have a t04r and 850cc injectors what would the recommended fuel pressure be? i am running twin 255lph walbro
 

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You shoudln't see pressure drop. In fact on my car I had so much fuel at idle I couldn't bypass enough of it. I now stage my pumps. I run two totally seperate lines to the front to my rail...
 

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Discussion Starter #7
jaynite said:
how big of a drop are were talking here? i had an issue with one of my rubber lines in the tank after installing my 2 pumps and could'nt get more then 33psi...one of the lines was split..replaced both lines to be safe and now its solid at 43psi... i also only run one pump at anything under 2psi i believe, once over that the other one turns on..

jay
I think about 7lbs of fuel pressure drop. When the tank is full I do not see this problem. I think the pumps are heating up and not as efficient as cold. BTW, this is twin walbro into a -8 braided line.
 

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Discussion Starter #8
supra400hptt said:
I'm the only one that I've seen with this problem, but when I ran my pumps off of the battery my fuel pressure would drop after starting the car. It would go down around 8 psi after a few minutes of running. I ended up hooking the walbros back up to the stock fuel pressure ecu and with regulated voltage my fuel pressure is stable now. Try it if you don't find another solution.
I ran the pumps off the batery since I thought the ECU did not provide enough power for 2 pumps.
 

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Dual walbros and -8 here also. My pressure would be in the low 30s at start up, a few minutes latter start to drop a psi or two at a time until it ended up in the low to mid 20s. Drove me nuts. I changed pumps, regulator, put in a fuel cooler and finally rewired the pumps to the stock fuel ecu. Problem solved.

There have been several discussions on running two pumps on the stock fuel ecu. Don't do it with MKIV pumps. Ok in my experience with two walbros. Search for those threads if you want to read more.
 

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How did you wire that? Almost everyone I know running dual pumps triggers relays off of the fuel ECU, and direct power to the relays which power the pumps directly.

turbomkiv said:
I ran the pumps off the batery since I thought the ECU did not provide enough power for 2 pumps.
 

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Discussion Starter #11
silvino said:
How did you wire that? Almost everyone I know running dual pumps triggers relays off of the fuel ECU, and direct power to the relays which power the pumps directly.
I used the ecu to trigger the two relays also.
 

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Discussion Starter #12
supra400hptt said:
Dual walbros and -8 here also. My pressure would be in the low 30s at start up, a few minutes latter start to drop a psi or two at a time until it ended up in the low to mid 20s. Drove me nuts. I changed pumps, regulator, put in a fuel cooler and finally rewired the pumps to the stock fuel ecu. Problem solved.

There have been several discussions on running two pumps on the stock fuel ecu. Don't do it with MKIV pumps. Ok in my experience with two walbros. Search for those threads if you want to read more.

It is interesting that you are powering both pumps with the stock ecu power. I would like to resolve this problem too. May be I will monitor the fuel pressure when the tank is full and see if this problem exist there. Thanks.
 

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One OEM pump draws about the same amperage as two Walbro however I've been told not to lower voltage on the Walbro pumps. Fuel pressure shouldn't be dropping unless the pumps are having trouble keeping up or the regulator isn't compensating for the lowered flow when hot. One thing I found on my regulator was that it leaked vac - BAD. The adjusting screw on top had to be sealed with Teflon goop to solve that. Make sure you aren't at either end of your adjustment range too. I trigger one Walbro with my fuel ECU to a relay and another through an output on my AEM.
 

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so if i understand this correctly. if i plug both of my walbros up to the stock power line i will create like a lag of power? and in return i will be running slow.
 

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You will also probably overpower those tiny little lines (possibly melting the insulation off) and/or starve those pumps of power.
 

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so i need to upgrade the wire feeding the pumps. and put in -6 fuel lines. that will support my 700hp? that is my goal.
 

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Some online shops sell kits but you basically need:

-Decent sized power line from battery
-two relays
-a pair of blade fuses and holders
-other wiring to wire up the fuel ecu to relay, the power to relay and power from relay to each pump

If you really don't know what I'm saying already, you should buy a kit from one of the online stores and use their instructions.
 

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It sounds like he already has the pumps wired correctly --> Using 12v relays (from the battery) triggered by the fuel pump ecu. I ran ONE of my walbro pumps through the stock pump wiring, and for the other walbro, I did the relay method triggered by the pump ecu.

I've seen people run 2 walbros off stock wiring and get away with it because walbros draw half the current than stock pumps. You could also replace the stock wiring (to the pumps) with thicker gauge wire.

On another note, I thought there were a few issues of people losing FP on a hot day after the car has warmed up. The walbros would be flowing so much fuel that it would heat the FPR and cause a drop in FP. I have not seen this problem on my setup though.
 

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My Walboro pumps are setup just like mav7 has his. I have never had any loss of fuel pressure.
 

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i run my dual walboros on the stock fuel ecu.. I ran new wire inside the tank to the stock connector and ran new wire outside the tank using the stock connecters (depinning). I grounded my pumps on the pump hanger and used the old +/- at +/+ for the 2 new pumps.
 
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