Help with fuel pump voltage (have I been misinformed?)

[Butter Face]

As it stands I am struggling to get the fuelling right on my Supercharged Civic Type R (EP3).

My fuel system is currently setup as below

Warlbro 300l/ph in tank pump - Specs here - http://www.glencoeltd.co.uk/walbro-motorsport-upgr...
Sytec rising rate FPR
Fuel rail modified with return, 6mm return line to tank
Standard fuel supply line.

I have been told (which I now think may be wrong) that my voltage at the pump is too low. I have checked wiring, replaced relays and fuses through the system.

When measured yesterday, the battery was charging at 14.5v and the measurement at the pump was 12.1v (see pic below) which is what I have been told is too low..



But I can't see how that can be too low? Surely the system runs at 12v? And the description from the website above says that the voltage for the pump is 12v?



Any help would be appreciated so I can get this sorted!!

[Butter Face]

I think I have found my own answer, there is a flow chart on the wesbite that shows voltage from 13.2-13.7v, so I am down on where it needs to be. Hmmmmmmmmmmmm

[Butter Face]

Thanks MT.

I have considered that I will need to run a new wiring setup. It's just a PITA!

Luckily (I think) the battery is in the boot, so I could run a live from that to a relay to feed the fuel pump?

TBH I may leave this to someone who knows it a bit better, don't want to fry anything!

[Butter Face]

Done some more testing tonight.

Fuse box - 13.6 volts at idle
Fuel pump relay, 12.8 in, 12.8 out
Fuel pump - 11.9

So seem to be losing volts from fuse box- relay and relay-pump.

[Butter Face]

Cheers for all the input.

This pump is sold as a direct fit so I would assume that the wiring should be man enough.

I am going to do a test to see how many amps the pump is drawing. If I can't get any luck I will take it to a local auto electrician next week.

[Butter Face]

As an update..

We wired the pump to the battery (13.74 volts) and pump was getting 13.34v so all ok there.

Checked the original wiring with no load and all running 13.74v volts. Also check for continuity and no resistance so wiring itself is fine.

As soon as original wiring on the pump it dropped to 11.9v at the pump!

So either the pump is faulty (but I have been told has been tested out of the car and al ok) or just the wiring is not man enough?

My solution is the run a live from the battery to the pump via a relay, the switch for this I will run from the current 12v supply for the pump so I will not be bypassing the existing relays/fuel cut off?

Any thoughts?

[Butter Face]

mk1turbo16v said:

Use the original fuel pump feed as the +ve trigger for the relay, fuel pump will cut out as usual.

Yes that's what I was thinking. Cheers for the confirmation that will work.

[Butter Face]

fatjon said:

Unless your pump is right on the borderline of what the engine needs this will make no difference. I think you are barking up the wrong tree. Unless you are also running injectors that are too small and hitting 100% duty cycle in which case a tiny drop in fuel pressure will matter. In that case the solution lies in fitting the right size injectors and addressing the fuel pump size/wiring so you have some overhead capacity without going lean.

I have RC 650cc injectors, nowhere near the duty cycle unfortunately.

I believe that my issue is twofold.

The voltage is too low to the pump, hence it not flowing enough fuel
The original fuel line is too small, as above.

Cheers

[Butter Face]

Thanks Jon, I think I will address both issues at the same time.

Might as well do a belts and braces, upgrade the wiring so the pump is running the best it cam whilst also making it's life easier with a larger fuel pipe.

[Butter Face]

Hi mate.

The issue (as I understand it) is that the fuel pressure is dropping off at higher RPM, so at 5k+ RPM where my rising rate FPR should be upping the fuel pressure with the boost, the pressure is dropping off (I can't tell you exactly what it should be/is as TBH it's all been pretty confusing for me)

My understanding is that the engine is just not getting enough fuel at higher RPM, the pump is flat out but is restricted as to how much it can flow by the power it's getting/fuel pipe restriction.

I'm no technical expert at all, I am going by the information from various sources that tells me the pump isn't getting enough power and as such when the engine/injectors need it, it isn't there.

Hope that makes sense!

[Butter Face]

stevieturbo said:

Butter Face said:

Hi mate.

The issue (as I understand it) is that the fuel pressure is dropping off at higher RPM, so at 5k+ RPM where my rising rate FPR should be upping the fuel pressure with the boost, the pressure is dropping off (I can't tell you exactly what it should be/is as TBH it's all been pretty confusing for me)

My understanding is that the engine is just not getting enough fuel at higher RPM, the pump is flat out but is restricted as to how much it can flow by the power it's getting/fuel pipe restriction.

I'm no technical expert at all, I am going by the information from various sources that tells me the pump isn't getting enough power and as such when the engine/injectors need it, it isn't there.

Hope that makes sense!

Upload a datalog showing these items.

What base pressure are you running and how well does fuel pressure rise with manifold pressure, and when it deviates...by how much ?

You've stated duty cycles are fine....so almost regardless of fuel pressure there doesnt seem to be a lack of ability to feed fuel to the engine. Unless fuel pressure is dropping insanely...in which case in injector duties could not be behaving normally. So there has to be a red flag here somewhere.

As with any remote diagnosis, proper information is needed. At the minute there is to a degree conflicting information.
Fuel pressure dropping a little on it's own is no big deal. Not always ideal, but no big deal. But as it depends on many other factors...far more information is needed here.

Exactly how much power is the car making ? ( although that could be another dyno debate in itself ) and what fuel ?

Power is 320bho using Tesco Momentum 99. The rest of the questions I will have to clarify and update at a later date but I will come back ASAP.

[Butter Face]

Off the top of my head I believe that the anticipated fuel pressure at max RPM was wanting to be 4.5 bar but at the moment the pump is struggling to achieve 3.2 bar. I can't be sure and need to sit down with my guy and write it all down.

Appreciate the help so far!