Just installed a new pump. problems.

[Bass Junky]

Hey guys and girls.

I just had a 650hp Walbro Pump fitted to my R34GT-T

Problem.

After changing gear, there is a slight surge-backoff-surge feel, only on light throttle applications.

Also, my fuel economy went to the sh1tehouse. Half a tank, 100klms.

What is the problem?

Is the return line too small to handle all that fuel and it's pumping it all through the engine and out the exhaust pipe?

Is my pump sus?

What is the surge?

Is this all related?

IS the earth going to swap magnetic polar ends soon and is this the only warning we are going to get?

So many questions.

BASS OUT

[Bass Junky]

PS. Changed my Oxy sensor just recently, so it's not that.

[Abo Bob]

Do you have an aftermarket regulator?

[Bass Junky]

Nope stock.

But as far as I know, the stock one should just relieve ayn extra flow or pressure back to tank.

[Doctor]

Sounds like your pump is working a little too well. I think its fouling your plugs mate.

Get it on the dyno and it should show your are running as rich as buggery.

[Bass Junky]

But shouldn't the Standard regulator just dump what it doesn't need, ie extra pressure or flow to the return line?

Plently of people here are running big pumps with standard regs.....

[Sydneykid]

I would check the fuel pressure at the rail under load. Changed the fuel filter lately?

[Bass Junky]

SK

I was waiting with baited breath for your response.

What would be the standard pressure in the rail at idle?

What would be the standard pressure in the rail on load? I don't have a dyno, how would I check this???

Fuel Filter..... So for instance if the fuel filter is blocked, this would do what compared to a clean one?

[Sydneykid]

SK

I was waiting with baited breath for your response.

What would be the standard pressure in the rail at idle?

What would be the standard pressure in the rail on load?  I don't have a dyno, how would I check this???

Fuel Filter.....  So for instance if the fuel filter is blocked, this would do what compared to a clean one?

Oh I feel so humble, baited breath was it? :cuddle:

Standard pressure is 36-38 psi at idle, you don't need a dyno to check that, just a fuel pressure gauge. Pressure whilst under load (has boost) can be checked by jacking the car up and running it against the brake (hand and foot) for a quick burst. The fuel pressure should stay the same at 36-38 psi above boost. So if you get 10 psi boost, the gauge should read 46-48 psi. Don't do it for too long though, the brakes and water temp don't like it.

Fuel filter is just a check, I have heard of so many Skylines lately with old, unchanged, dirty fuel filters causing bad running. They are such a cheap item, often overlooked for more exotic hardware, that can hurt you.

Hope that helps

[T0nyGTSt]

Standard reg. and a Bosch 044 is no problem.

You need to get it dyno tuned.

I have an 044 + Apexi/Nismo reg. and I dyno'ed it a day after I had the pump put in. Fuel consumption is normal.

T.

[Sydneykid]

Standard reg. and a Bosch 044 is no problem.

You need to get it dyno tuned.

I have an 044 + Apexi/Nismo reg. and I dyno'ed it a day after I had the pump put in. Fuel consumption is normal.

T.

Hi Tony, I have replaced a number of fuel pumps with both larger and smaller capacity pumps and not had to tune the car. If there are no pre existing issues or problems, the tune should not change one little bit.

[T0nyGTSt]

See this I don't get...

Big pump therefore more flow.

But the reg. should still provide the 'cork' to stop the flow.

So I'm guessing the performance aspect of a big pump and no other mods is that the increased flow makes the motor get more fuel, more quickly so the car feels more 'surgey', more responsive?

When the new pump went into my car it did feel more surgey, like more kick, response off the line.

But that could be just a flawed impression.

T.

[Sydneykid]

See this I don't get...

Big pump therefore more flow.

But the reg. should still provide the 'cork' to stop the flow.

So I'm guessing the performance aspect of a big pump and no other mods is that the increased flow makes the motor get more fuel, more quickly so the car feels more 'surgey', more responsive?

When the new pump went into my car it did feel more surgey, like more kick, response off the line.

But that could be just a flawed impression.

T.

Hi Tony, the fuel pressure regulator is not really a "cork to stop flow" its more like a flood gate that opens to bypass the flow.

[paulr33]

has the o2 sensor been checked with a voltimeter? i know you said its been changed but who did it? would only take a few seconds to check with a multimeter

[Bass Junky]

My mechanics changed the Oxy sensor.

I'll have the fuel pressure checked today.

Thanks for the help guys.

[Abo Bob]

I wait with bated breath for the day I smell your baited breath Bass

I know this doesn't help.

I don't know anything.

I don't own or work for a workshop (because I would have to pay them.)

[Bass Junky]

cheeky bugger

[Bass Junky]

Okay, just had a pressure gauge on the line.

Car primes to about 50psi, then when it starts it stay up at 50psi for about 15 seconds.

Then it drops back to abuot 35psi.

Then when driving around, the pressure rises as it should with boost.

My mechanic says that they have a two stage pressure function. Seems to make sence as when I change gear and the car starts to spool (mind you, I'm hardly on the throttle at all) the guage drops back a few psi and then flicks up again to about 45psi.

Is this normal?

Could my pneumatic boost control be playing havoc with the fuel pressure?

BASS OUT

[Sydneykid]

Okay, just had a pressure gauge on the line.

Car primes to about 50psi, then when it starts it stay up at 50psi for about 15 seconds.

Then it drops back to abuot 35psi.

Then when driving around, the pressure rises as it should with boost.

My mechanic says that they have a two stage pressure function.  Seems to make sence as when I change gear and the car starts to spool (mind you, I'm hardly on the throttle at all) the guage drops back a few psi and then flicks up again to about 45psi.

Is this normal?

Could my pneumatic boost control be playing havoc with the fuel pressure?

BASS OUT

Sounds normal to me Bass, when you change gear the boost escapes via the BOV. This removes boost pressure from the fuel pressure regulator and it drops the fuel pressure in the fuel rail accordingly.

I have no idea what this means though...

My mechanic says that they have a two stage pressure function

"Two stage" I wonder what he means by that, the fuel pressure varies with boost so it has "multiple stages". The fuel pump has 2 voltage levels, maybe that's what he means.

:cooldance

[Bass Junky]

yep,

Two voltages