Mkii Ute Fuel Pumps

[F6 UTE]

FLOW is not the issue with the stock pump. Pressure caused by boost affects flow in that the relief valve can't handle the extra pressure put on it..

The pump flows enough fuel, how much I don't know, but when boost is raised, pressure against the relief valve is raised, Relief valve does it's job, diverts flow to fuel tank to relieve pressure.

The stock pump will flow what you need it to. If you modify it (relief valve ).

If you don't modify it, you'll fix the problem somewhat with an inline pump..

New intank will fix the problem, Modified Stock pump will fix the problem, External surge tank + external pump will fix the problem.

[Trough Lolly]

what if I keep the boost under 15psi... will that help? as u said in your earlier post 15+ was making the valve "pop" .. ??

[F6 UTE]

what if I keep the boost under 15psi... will that help?  as u said in your earlier post 15+ was making the valve "pop" .. ??

<{POST_SNAPBACK}>

Yes, maybe on yours it will too. BUT I'm not running an ideal tune, and don't want to risk the valve 'popping' under and circumstance.

Every pump will react with each tune differently, ie: when boost comes on as opposed to rpm/load etc etc.. If you accelerate hard in 1st,2nd,3rd, there's not as much load as winding her up at low rpm in a high gear ( going up hills for eg. ) and different environments/tunes will have different effects on pressures..

Also we have noticed different pumps react to different pressures. Some XR pumps handle well more than some f6 pumps, my F6 pump is ok- same as XR - check F6 Tornado's post..

I wouldn't recommend running a stock pump at that level of power.., it's best left to the dyno, or a fuel pressure gauge as to see when your particular pump 'fails'. Fails aint the right word though, it's just doing what it's designed to do.

[cobrav8]

Great technical reply - but one question.

Why does the F6 seem to get different mention than the XR6T so much? Surely both once edited are equal (ignoring differences in rods etc). As far as I was aware the only difference between the two is an intercooler, and some extra boost?

[F6 UTE]

As far as I was aware the only difference between the two is an intercooler, and some extra boost?

<{POST_SNAPBACK}>

Yes, that's why.

As for why the foon get's better results in general????

I don't think anyone here has fitted a foon intercooler and edit to there 'T' yet have they??

[F6_Tornado]

F6 tornado... thanks for that HUGE informative post but after that much info going thru such a little brain im a bit lost now!! lol..

basically summing up, the stock in-tank pump will be sufficient IF a inline pump is added to help take the stress off the relief valve of the in-tanker??

excuse my lack of brains this week I got that much going thru my head about this bloody car im at the point of exploding!

<{POST_SNAPBACK}>

Trough Lolly thanks for that my question exactly, though if the in tanker doesn't have enough grunt the inline pump will be starved also wouldn't it.

<{POST_SNAPBACK}>

Not necessarily.

That all depends on how its setup and if the inline pump has a surge tank.

The trick is to know what’s wrong and why you run out of fuel so you can address that and not tear up money on more parts and add more complexity with inline pumps, surge tanks etc.

In this case the only thing wrong with the Fuel pump is the relief valve blowing off at to lower pressure and allowing flow to dump back into the tank when you need it at the fuel rail.

I suppose once you start using more than 3 ltr a min (about 20mins of fuel from a full tank) then time to change the pump out apart from that the pump is quite OK. If the relief is modded!

Changing the in-tank pump means cutting wires, changing fuel lines, adapting the new pump to fit as they don’t drop straight in sadly.

My preferred option is to simply use the original pump and mod the relief valve but something that should only be done by a qualified mechanic and to ensure the relief is set correctly once modified to protect the pumps internal components and the entire fuel system.

Too many just change the pump out!! As that and $$$$ fixes it! But they only presume it has a flow problem….sadly 99% of them don’t even realize it’s the Pump relief valve not the pump.

Another simple test is to stick your head close to the fuel tank while someone slowly squeezes the return fuel line and @ 450~550kpa you will hear a noise in the tank as the relief blows off confirming that fuel is being dumped into the tank and as such the engine starves for fuel at the rail and leans out.

Also think about this:

The relief valve is on top of the pump and when it goes off the fuel squirts up and outward away from the swirl pot.

In the normal fuel circuit the return fuel runs back into the swirl pot adding to the volume to minimize fuel starvation when the tank is low as the swirl pot may well only be sitting in a few inches of fuel.

Picture the relief valve blowing off and the fuel squirting up and outward from the swirl pot….. This intern contributes to fuel starvation under load when the tank is low in fuel volume as the relief valve tries to empty the swirl pot.

And so the problems Go on and on and on!!!

Before doing any of this you should set your mind at rest and fit a gauge and do some testing. This will then justify what you need to do to rectify the problem without spending a lot of cash in the process.

Besides you might also learn something which is good for all.

[cobrav8]

As far as I was aware the only difference between the two is an intercooler, and some extra boost?

<{POST_SNAPBACK}>

Yes, that's why.

As for why the foon get's better results in general????

I don't think anyone here has fitted a foon intercooler and edit to there 'T' yet have they??

<{POST_SNAPBACK}>

They probably havnt because it is cheaper to buy a bigger aftermarket intercooler. The base edits for a Typhoon and a XR6T with an after market intercooler must be the same - nothing else to differentiate them is there?

[F6_Tornado]

what if I keep the boost under 15psi... will that help?  as u said in your earlier post 15+ was making the valve "pop" .. ??

<{POST_SNAPBACK}>

If you read my first post you will notice that even the F6 with only 3 psi more than a STD XR6T can set the relief valve off on “some” Factory pumps.

They all vary and in this case F6 UTE’s pump is way better than my STD pump so keep it in mind….they all vary so some people get away with it and some don’t from factory.

My second Factory fuel pump relief was way higher than the first and the problem was then not evident with STD HP

Mod it to 300rwks and it’s over the edge again and a Problem even with a factory pump with a Higher STD relief setting.

Some will handle 15 psi yet other will struggle with as low as 8~9 psi

[F6_Tornado]

Great technical reply - but one question.

Why does the F6 seem to get different mention than the XR6T so much?  Surely both once edited are equal (ignoring differences in rods etc).  As far as I was aware the only difference between the two is an intercooler, and some extra boost?

<{POST_SNAPBACK}>

The only reason I compared the F6 to the XR6T was the STD XR6T has 6 PSI boost and the STD F6 has 9 PSI boost.

Modded with nothing else you can run a Higher boost on the F6 than an XR6T due to the F6 having dual air intake and a bigger cooler.

The point here is fuel pressure is a variable and is grossly affected by boost pressure and this is the point most people are neglecting to get a grip on and addressing.

Just put a gauge in and test … you will be surprised as many other will.

[Eugene]

WOW, what a Post, or series of posts.

Some great info here.

I have been worried about my fuel pump for a while, and after reading the above, I will do a pressure check this afternoon and see how it goes.

I am sure my car has fuel supply probs,

If I use my 293rwkw tune, when pushed hard for extended runs of constant flat out running, the car will alot of the times loose power, back off for a few seconds and its fine again, it will do it in hot or cold weather etc etc, I am only running 11psi boost so I dont think its overboost.

When I run the 277rwkw map it shows no signs of doing it, ever, lower boost and fuel map, so less fuel required, no Probs.

A fuel pressure check should tell me.