TrueGS300

I'm considering a way to get the fuel pump to prime when turning the key to the run position before cranking. A lot of cars do that, but I've noticed on these cars it does not. The fuel pump is only first active when cranking. This is fine for the stock dead head system that holds pressure. However in a return system, this makes a great deal of cranking necessary to build up pressure to start. I've been putting my starter through hell every time I need to star the car.

So here are my options. I can find a key on power source and run it directly to the pump, but it will always power the pump. Not like normal cars that would prime up and then deactivate it if the key was going to stay on but not running for whatever reason, like doing diagnostics or something. So getting into something a little more advanced, would there be some kind of relayed way to wire something like this up?

The next option I can think of is to run that same key on power wire with a switch in it so I can run the pump when I turn the key on, and if needed switch it off. Otherwise I should just be able to leave the switch "on" and start the car after a few seconds of priming, and it would turn off after the key goes to the off position. So no harm right?

Anyone have any better ideas I haven't thought of? Maybe someone has come up with something? I'd hate to have a jank looking switch in the car, but might be what I have to do.

Scigheras

Not sure on what kind of engine management you are but if you have a capable standalone I would just set all of this up electronically through the ECU. No extra wiring or relays needed.

firelizard

iTrader: (1)

If you want to avoid a physical switch, I reckon you could do a relay like you were thinking. Using a switched power source, like you would for a radio turn-on.

TrueGS300

I have an AEM infinity ecu. This one still goes through the factory ecu with a p&p harness, so I don't think it's going to be possible, but I'll ask my tuner about it.
'

KyleH

iTrader: (1)

I can't take any credit for this, but here's the solve that someone on the Facebooks shared with me. This resulted in the pump running anytime the key is in the "on" position.

It has the added benefit of knowing the pump is always running at full voltage.

TrueGS300

Interesting, I'll look into this, thanks ! Do you know where this is on the car though?

KyleH

iTrader: (1)

I do now, LOL. Just behind backseat, drivers side. Pull the little plastic retaining clips in the trunk for access and you'll see it.

TrueGS300

I am getting around to doing this. Do you think this defeats the need for a hotwire kit? I have one from deatschwerks, but it seems this splicing mod is known as the "12v mod" which in addition to key on power, would likely send running (alternator volts) to the pump once running yes? I might not need the kotwire/relay kit if our cars already have this setup from the fuel controller and just having to wire it right.

TrueGS300

So to answer my own question, I started with wiring the pump controller wires as shown above. It worked and the fuel pump primes with key on. I did test at the pump and found that 12.7 (Battery voltage) is all that's supplied to the pump while running. So wanting alternator volts going to the 525lph pump I have, I went ahead and installed my Deatschwerks hotwire kit. This is a very simple kit and something I've installed on other vehicles in the past with success. However I am not seeing alternator volts at the pump. I'm not sure whats wrong because it's really not possible for there not to be alt volts at it now.. I was showing 13.8V at the battery, and only 12.8V at the pump when checking.. The hotwire kit sends a wire directly from the battery to a relay, chassis ground to the relay, and the other two wires just split the pump power wire and are connected in series.

I shouldn't need to put the wiring back to normal at the fuel pump controller right? At this point everything should be bypassed and alternator voltage going to the battery. I do have a relay tester, it tests good, and the ground is good. I went to a spot where other grounds are, and even sanded the spot good for the best contact possible. Car starts and runs fine, but only seeing 12.8V. Any thoughts?

Dazz

Did you get this resolved? I am getting ready to run dual 325lph fuel pumps for my surge tank. Need the best way to power the 2 fuel pumps.

TrueGS300

No I never quite saw the voltage I want at the pump. Higher than factory but not by much. I think I need to upgrade my alternator soon too. I'll be looking into the hot wire setup again one day. But for now it's as good as I can get it. Id still do what I did though. It's good to have big pumps prime up before cranking. And the hotwire kit sends a thick wire directly from the battery (or alt) to the pump via a relay. So regardless of what I measured, I do know it's at it's best voltage possible and that's what you want. Maybe it's better under load/rpm. I just wasn't that able to test it the day I was working on it or really go that far into it.

KyleH

iTrader: (1)

To add on to this - I ran the kit from Radium. When the north pole moves back north, I'll start my car to confirm the voltage for you - but I am seeing close to alternator voltage (well over 13 volts as I recall) at the plug of the fuel pump.

When I eventually go dual pumps, I'm intending to drive my startup/idle/cruise (smaller) pump with the stock wiring harness. I'll juice the secondary pump with a trigger from the Haltech that will be on the higher amperage line.

TrueGS300

I will see here shortly how my setup works. Nervous about it. I wanted to avoid dual pumps and all the wiring/tuning for them. The thing that scares me about dual pumps I've read is that if one fails when you hit it hard into boost, you lean out hard and it's over for your engine. If you're on one pump and it fails, the car sputters out and dies. So Ideally if one big pump can support your goal, it might be safest. Also for those of us modifying our stock hangers, there is no room for dual pumps. I had a difficult time getting my one 525 pump in and the fittings placed on top plus routing the conjugated ptfe hose inside etc. for the pump and the return line to the jet valve. If you are going for upwards of 800hp I'd say a real dual or triple pump hanger is worth it for the simplicity of making two or more pumps work.

P.S. Kyle, I'm getting a list of the fittings I used to modify my hanger as you requested since you've decided to build your own hanger. Going to post it here so others can see too. But as I mentioned, it might not be good for someone that wants more then one pump.

KyleH

iTrader: (1)

A fair concern. But depending on the ECU you're running, you may be able to put failsafe strategies in place that will help prevent this outcome. I'm thinking like fuel pressure or AFR target relative to boost/RPM/TPS. Example - if AFR exceeds 12.8 when RPM > 3,000 and Boost > 10psi, reduce boost solenoid duty cycle to 0%. I'm looking forward to running dual pumps. I think reducing the demand and full duty cycle relying on a single pump will increase confidence in the fuel pressure/consistency and longevity of the pumps. But hey if I can get to my target with the single pump, less hassle, complexity, and cost - well that'd be great too!

KyleH

iTrader: (1)

As a quick follow-up to an earlier post in this thread, I wanted to confirm the voltage found at the pump plug with the direct battery (via relay) connection. I measured a healthy 14.00 volts with the engine running.