AAN Running mega lean

[HMS-S6]

Hi guys . . . . again

Had the day off today for a data log on the S6 and thankfully it performed awfully for them!

They came back to me and informed me that its running awfully weak, aside from Lambda sensor and MAF sensor, or fuel pressure what could cause this?

[Jamo]

Things to check: Fuel filter, fuel pump, fuel pressure regulator, vaccum leak to fuel pressure regulater, injectors, rubbish ecu map.

I'd try and do a realy mod to the fuel pump to make sure it's getting 14v instead of 12v

[HMS-S6]

Things to check: Fuel filter, fuel pump, fuel pressure regulator, vaccum leak to fuel pressure regulater, injectors, rubbish ecu map.

I'd try and do a realy mod to the fuel pump to make sure it's getting 14v instead of 12v

Hi Jamo,

I have been running the car with a fuel pressure gauge all day and it was showing 4.5 - 5 Bar on boost every time!

And it has performed the same on 3 ecu's

[Jamo]

but your running lean, you need to investigate with open eyes forget about fuel pressure readings.

[HMS-S6]

but your running lean, you need to investigate with open eyes forget about fuel pressure readings.

But surely if the pressure is there in the rail, the filter (which is new) the pump and regulator are ok else it would be incorrect??

I totally take on board injectors - do they fail/get dirty often on these cars?

[Jamo]

Why does it? your running lean, you can't rule anything out IMO

I do technical diagnosis for a living, it's the golden rule don't assume it is working if there is a fault condition in place

[Sleeper_Avant]

as above, its got a fault matey, asume nothing!

on another thread you said it starts poorly also right?

fuel pump, no ifs or buts, try it and get back to me

oh and as Jamo says, pump should get 14v not 12, i seen MANY MANY big power and standard Cosworths die due to wiring faults and not getting the 14v they need.
(and when i say die i mean melted pistons and shagged blocks/heads! i have unfortunatly ben there too with a 480+ car, it will only happen to you once......lol!)

[Sleeper_Avant]

Also what gains is the lambda showing, and what are the temps the engine is running at when readings are given?

i get massive ammounts of cars with weird lambda readings and its due to dodgy water temp sensors fooling ECU`s into thinking temps are incorrect (mostly late VW`s actually!!)

[HMS-S6]

Well i still have the other car which is running right, so i guess i could swap the pumps over (after reading the voltage supply), then swap the ect sensor too, daft as it sounds i'm still glad that its narrowed down to weak running!!

Sorry Jamo i wasn't just dismissing your suggestions, i'm just tired of getting my hopes up with every possible fault, and then struggling for time to look into every possibitily Plus being a mechanic working for someone as opposed to self employed, it sufferes in a way, from 'mechanics car syndrome' as in, i'm able to steel ten minutes here, five there between jobs etc, and often it's left at the garage over night while i use a coustomers car!!

[HMS-S6]

With having future plans for the car, if i do replace the fuel pump, is t worth fitting a bosch 044 now? and i so, do they fit in the existing basket?

[GazzaG60]

044 is worth it. if you plan on 360hp plus.

has the maf been checked. is it clean. a dirty maf can cause lean issues. along with many other things.

[merlin's S4]

With having future plans for the car, if i do replace the fuel pump, is t worth fitting a bosch 044 now? and i so, do they fit in the existing basket?

Yes it is worth it and no it won't fit the standard basket. See here; http://www.s2forum.com/forum/showthr...ght=notes+pump

But as stated check your voltage first. You may find fitting a relay inline to the pump helps. There is a guide here somewhere.

[HMS-S6]

Gazza, thanks fo the input, the car was on a new MAF and just incase changed to the one from the known good car i have. Ang yeh one day i want upwards of 360hp.

Merlin, thanks for that, wil look it up, and yeh i checked the voltage just now and it was 13.8 v. I was going to switch pumps from the good car, but that also has 170,000 on it so i thing i'd be wasting my time and better wait for a new pump.

[GazzaG60]

for ref on the pump. i have no relay circuit and use an 044 with factory wiring and no issues contrary to popular belief.

its a bit of a difficult one this.

running lean can be so many things.

in the past on boost ive seen.

throttle body- not seeing WOT. can be throttle pot or cable.
poor injectors. not that common.
a weak FPR pressure line. common. this is very important coming on boost. you should be seeing the fpr pressure + boost. so bout 5-5.2 bar fuel pressure on boost. a few pin holes in the vac line will cause a lean condition on boost potentially.
fuel filter. an easy change and worthwhile.

id hazard a guess at one of those ro start if it runs fine and curises ok.

[HMS-S6]

for ref on the pump. i have no relay circuit and use an 044 with factory wiring and no issues contrary to popular belief.

its a bit of a difficult one this.

running lean can be so many things.

in the past on boost ive seen.

throttle body- not seeing WOT. can be throttle pot or cable.
poor injectors. not that common.
a weak FPR pressure line. common. this is very important coming on boost. you should be seeing the fpr pressure + boost. so bout 5-5.2 bar fuel pressure on boost. a few pin holes in the vac line will cause a lean condition on boost potentially.
fuel filter. an easy change and worthwhile.

id hazard a guess at one of those ro start if it runs fine and curises ok.

Hi Gazza, thanks again.

The throttle pot checked out ok yeaterday, going to 100% every time
I had a vacuum pump on the fpr line yestarday and it help a vacuum perfect!
It runs to 5 bar on boost but people have still pointed towards fuel pump, which i've not ruled ut at all, just not got one!!
And the fuel filter was changed 10k ago.
Brings me back to injectors - something i've never looked into, but have an asnu cleaner at work so will be ripping them out later!!!