# Overfuelling rather largly perhaps?



## G40tee (Feb 25, 2008)

My walbro (cough rubbish) fuel pump gave up the ghost and i have replaced it with an 044.

Took the car for a quick spin and at about 6k rpm im getting misfiring and huge fuel clouds out the back of the car.

The car didnt do this before, could this just be the plugs blackening up and not sparking? or is it a separate coilpack issue. Am hoping it is the first.

The car will be going back up to TR Racing when it can to get the map adjusted for the new fuelling but just want to make sure its that before i go buying things again! :s


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## JapFreak786 (Aug 29, 2003)

sounds like the rpm that you get the misfire,have your's been replaced since new or not?


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## kismetcapitan (Nov 25, 2005)

what's your fuel pressure? different pumps, different pressure. you've got to adjust for it. With a higher fuel pressure, your injectors just went up a size.

In other words, you need to balance out your fuel system, no remap needed.


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## G40tee (Feb 25, 2008)

How would i balance out my fuel system?

i dont have adjustable fpr or anything like that, just stock fuel system bar pump and injectors.

the car is still cutting out like it did before. i am also going to try some other coilpacks and ignition amplifier next week. Which you never know may sort the misfire.


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## kismetcapitan (Nov 25, 2005)

you need an adjustable fuel pressure regulator, and you need to calibrate it to 3 bars rail pressure at idle with the vacuum reference hose disconnected. Different pumps flow differently; a Walbro may have been close to stock, but a Bosch 044 definitely is not.

or am I misunderstanding something about flow, and that the stock non-adjustable fuel regulator will always produce 3 bars, regardless of how much fuel in liters per hour you're throwing at it?

One sure way to tell is to drive with a wideband lambda. If the AFR plummets right before misfiring, it's the fuel pressure. If it plummets only immediately after the misfiring starts, you've got ignition problems and might be blowing out your spark.

In any event, it may seem serious but it's quite easy to sort out. Just take it down to tweenierob I'm sure he'll have it diagnosed within minutes.

misfiring consistently at 6000rpm, what turbos and boost? It could be blowing out spark come to think of it. Hope it's not though - new coilpacks and ignition amp and spark plugs will cost a hell of a lot more than a simple Nismo fuel pressure regulator that takes ten painfree minutes to install.


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## G40tee (Feb 25, 2008)

it is going to robs at the end of the month but wouldnt mind having a look at the problem before then.

GTSS turbos and 1.6 bar. I am not using many revs etc whilst i have the problem, topping out at about 5k rpm and rarley coming on boost.

Even when not on boost the car is still cutting out intermittently, it will suddenly not accelerate and lose all throttle response, only blipping once everytime the throttle is put through full travel. It will then sort itself out and can carry on driving.

We thought this was an issue with the fuel pump as there was no fuel in the lines when that happened, but now there is fuel in the lines so cant be the same issue. Previously the car would not start sometimes but i dont have that issue now it just cuts out.

Which is what leads me to a broken down ignition amp etc. But would that cause complete spark failure or just misfiring. 

I am trialling Listerofsmegs coilpacks and ignition amp so money will not be an issue atm until the problem is diagnosed.


What i thought with fprs would be that they held a common pressure regardless of flow! i mean that it just me assuming so may be completely wrong. I mean the injector timing will still be the same but the pump must be pushing more fuel through them in the same time, meaning that the rail pressure must be higher?! the car does feel flatter than before


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## rb30r34 (Jun 30, 2008)

kismetcapitan said:


> you need an adjustable fuel pressure regulator.


If a car has EFI it has an adjustable fuel pressure regulator.

Get rob to remap it. Thats all it needs, just like you would need a remap if you changed your turbos. Fuel pumps are no different.


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## Asim R32GTR (Sep 24, 2003)

G40tee said:


> the car is still cutting out like it did before.


So you are saying the car did this before you changed the fuelpump?


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## G40tee (Feb 25, 2008)

Asim R32GTR said:


> So you are saying the car did this before you changed the fuelpump?


yes.

the car will occaisionally lose power and will not respond to throttle input, if it does it will only blip once with every full travel cycle of the pedal and not keep revving if you see what i mean.

i went out with aaron34 last night and we tried to plug in the datalogic but for some reason it would not connect to my car cant figure out why but checked all the coilpacks etc and it doesnt seem like my misfire is related to them.

by the looks of it the misfire is fuel related, the fact the car cuts out seems like it is fuel related as well as all the ignition side seems to be working fine. I am going to change the fuel filter tomorrow as because the pump stopped working the hoses were sucks dry so could have picked up some rubbish somewhere along the line so could be clogging it.

I hate annoying little issues like that, if the misfire is mapping related that is fine as it is booked in with rob to get the map altered soon.

the cutting out is an issue i want to cure asap as it is very annoying. Will do it at any speed and revs. just lose total throttle control, sometimes only does it for a second and if you hold the pedal at a gentle depression it will bring it back sometimes it wont and have to turn off and back on again.


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## tweenierob (Aug 5, 2003)

Sudden loss of power is not going to be the fuel pump, you should have called me before doing unnessecary changes . 
Fuel pump will be gradual loss of power as the fuel in the rail gets used.

Rob


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## gtr-loz (Feb 10, 2006)

i would of thought that the stock regulator will flow stock pressure the adjustable pressure reg is only really needed when upping the fuel pressure

clouds of black smoke hits that the fueling is not the problem as its the overfueling thats causing the black smoke


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## G40tee (Feb 25, 2008)

rob, to be honest i hate calling you when every little thing happens, the main reason i thought it was the pump is that it completely stopped working once, took the pump out, connected it straight to a battery and it started working again. But carried on doing the same thing cutting out etc.

So i think there was a fault with the pump anyway but even if not have never been keen on the walbro anyway if im honest! was a last minute addition as you remember! :S

I am going to change the fuel filter tomorrow but may give you a call after to see if you have any ideas i can try before taking up your time! 

I hate little issues like this! Its blatently something simple! (well i bloody hope it is! haha) There is no way it can be big, i mean engine is basically new, likewise for turbos and nothing has been maxxed out. i rarely give it any stick to be honest! have spent most time fixing stupid little things! haha oh the joys of skyline ownership!


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## kismetcapitan (Nov 25, 2005)

par for the course. After the build is finished, in my experience you run through about six month of teething problems and sorting little things here and there, even though the car is drivable. you learn a LOT about the car during this process.


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## G40tee (Feb 25, 2008)

oh yeah definately its part of owning the car, i can only learn about it and what symptoms are and how to cure them by them happening, which is part of the reason for wanting to find the problem and cure it myself with help from others rather than just taking it back to Rob and the boys.

yeah i may not get it right all the time but hey thats life! obviously major things that could affect things built by them i wouldnt try to get involved with as dont want that responsibility on my head whilst im still new in the game but hey!  

Dont think ill ever be as anal as you have been Toby with yours but i like to know what is what, have never been one of those people to buy a car and get other people doing it all for you, i do like to get my hands dirty every now and again.


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## kingsley (Aug 26, 2002)

G40tee said:


> Even when not on boost the car is still cutting out intermittently, it will suddenly not accelerate and lose all throttle response, only blipping once everytime the throttle is put through full travel. It will then sort itself out and can carry on driving.


Does your car still have AFMs?

Cheers,
Kingsley.


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## G40tee (Feb 25, 2008)

it does yes, i havent tried new ones yet.

i looked at the voltage of them at idle, one is reading .97v and the other about 1.23v is there supposed to be that much difference in voltage between the two?

I havent seen the voltages of them when the problem has arisen as im too busy trying to get the power back as ill start holding up traffic.


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## kingsley (Aug 26, 2002)

The reason I asked is that when one of my AFMs started playing up, the symptoms were that the car drove normally most of the time, though sometimes it would fail to respond when I put my foot down from, say, cruise at 3000rpm in 5th. It would stutter and hesitate a bit then pick up. It drove perfectly through town etc. I set the AVC-R to monitor injector duty and noticed that whenever it did this, the duty would rise up from what it was on cruise (10 - 15%) up to about 50%. I guessed it was probably an AFM from this, as if one of them was intermittently giving a maxxed out signal. When I took the car to Abbey and they tested it, it turned out that I was right.

Of course yours might not be that. It just sounded a bit like the symptoms I'd had when mine started playing up.


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## G40tee (Feb 25, 2008)

I spoke to a couple of people about afms and they said when theirs have gone the car doesnt really work at all, cuts out when pressing the accelerator etc, is interesting that yours didnt do that.

i will try it and swap them with some working ones etc, there is no harm in trying and it is a simple thing to do.

am going to change the fuel filter probably on thursday when i next have the chance as more than likely that is full of crap when the hoses went dry etc. which wont be helping matters.

i have injector duty monitored on my hand controller but when the car starts having issues i dont really look at it i have to admit. If the car has restarted without me having to turn it off and on and i have glanced at the controller the injector duty hasnt seemed any higher than what id expect from how i was driving. Have been staying off boost really whilst it needs a map alteration so the duty never really goes about 20%.


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## kingsley (Aug 26, 2002)

Maybe the AFMs of the other people you spoke to failed totally. I think mine must have developed an intermittent connection somewhere.

Handily, the AVC-R has a graph mode as well as a digital readout so you can see a scrolling graph covering the last 30 seconds or thereabouts. That made it much easier to see what was going on. It would have been a lot harder if I only had a digital readout and was looking at constantly changing numbers.


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## G40tee (Feb 25, 2008)

i have the power fc which has a graph function as well.

madden checked it out when we were driving and there was no sudden change in afm readout when the issues started up. The car would just cut out when idling when hot (doing increasingly now) and when driving the car is really messing around. I get bad misfires at about 5500rpm, which we have now gone back to possible coilpack problems so will be trying some replacement ones on sunday/monday but it just keeps losing power and throttle input when driving.)

It is one hell of an annoying problem, it has got to be a sensor somewhere that is causing the instant cut out of the power, the ignition feed stays live, the pfc keeps powered up etc and there are no strange knock readings, no spikes in injector duty, you can hear the fuel pump going, no crazy afm voltages or o2 sensor voltages etc.


ARGHHHHHH!


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