Fuel System issues: Ultimate fuel system with Denso pump
 

I am having issues with my fuel system I am running a rx7store ultimate fuel pump system with 750cc prims and 1688cc secondary's and a Denso pump stock wired. The probblem I am having is it's running lean hitting 12's on my AFR at 6000rpm 10psi of boost innovative hand held. My duty cycles are at 70%.

What I have done so far was replace my fuel filter and increased my FPR from 34-38psi at idle. When I tried to increase it higher than 38psi the guage started to fluctuate. I just got done checking my voltage to my fuel pump todat and it's at 7 volts even when I rev to 5k any comments and sugestions would be appreciated. I want to figure out the problem before I do the fuel pump rewire.

it is mostly because there are so much resistance within the stock wiring harness. It has been known with this issue. Therefore IT is NOT necessary in trying to figure out the problem when everyone know that it's within the crappy harness the FD has.

So, why not save time and do the fuel pump rewiring? It will save you alot of time, and get the problem fixed xD

-AzEKnightz

Rewire the fuel pump and try again...

http://www.memeticians.com/2008/05/2...5986b5e6c1.jpg

http://www.memeticians.com/2008/05/2...5986b5e6c1.jpg

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I am pretty sure there is a fuel pump resistor (located under the brake master cylinder) that decreases the voltage the fuel pump gets until certain conditions are met.

Either way, rewiring your fuel pump is a GREAT idea.:nod:

I rewired it today :) I will check tonight for AFR's hopefully the problem is solved.

Do you rewire the hole harness? or is there just a portion of the harness that is removed and rewired? Im having the same problem with the same setup.

you basically add a relay and re-wire the positive and negative directly (from battery and a good ground) to control the pump whenever the key is turned on. So the pump is fully running whenever the key is on the "on" position.

-AzEKnightz

That's really not necessary. You can use the factory fuel pump wire, the one that used to power the pump, to trigger the relay. Then you don't have the electrical drain (and potential safety issue) of triggering the fuel pump from the ignition circuit.

Of course the factory pump wires can be reused. However, if you want a clear good circuit, a separate rewiring would be necessary.

However, about the electrical drain, many people when doing a battery relocation would add a separate fuse box and hook up the "key-on" feature so there wouldnt be any electrical drain per your statement. Of course, if not done correctly there will be plenty problems.

But the best way would be a brand new electrical circuit with new wirings wouldn't you agreed?

I already agreed with you saying it is not necessary. For those who aren't as anal as I am, just reusing the original factory wiring would be efficient but with a potential of old brittle wires with a higher resistance that's all.

-AzEKnightz

considering how little amperage the coil in a relay draws, I'm not really concerned about the factory wire triggering it unless the car is a real basketcase found-in-barn type. When using the stock wire to trigger the pump, the fuel pump is controlled by the ECU and won't turn on unless there is a tach signal for safety reasons.

anyone have pics? Just trying to get a good idea on the best way of going about it.

Couldn't you just cut out the resistor and splice in a wire in it's place? I don't beleive mine is getting the full volts either and it's something I have to do in the futurre.

There's a whole thread on rewiring the fuel pump.