Help again! Polo 6n 1.4 Very high consumption

VAG Fan
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by VAG Fan »

Sorry, I missed that you had already changed the coolant temp sensor. Not sure about the MAP - somebody else would have to advise. My idea was triggered by what you wrote about summer and winter.
Mark R.
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2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by missioner »

If the fuel pressures are lower than spec, then your main culprit is the fuel pump.

OP you mentioned earlier in the thread that the car has over 300k on the clock, I doubt the pump has ever been replaced.

I have yet to find a car that can tell you it's fuel pump is faulty by diagnostic computer and it's reasonably common type of wear and tear failure.

By contrast fuel injectors are very rare items that get replaced due to being worn out.
'87 Golf 1 Olde Skewl OEM+
Jasondj
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by Jasondj »

missioner wrote:If the fuel pressures are lower than spec, then your main culprit is the fuel pump.

OP you mentioned earlier in the thread that the car has over 300k on the clock, I doubt the pump has ever been replaced.

I have yet to find a car that can tell you it's fuel pump is faulty by diagnostic computer and it's reasonably common type of wear and tear failure.

By contrast fuel injectors are very rare items that get replaced due to being worn out.
Went trough the records and nothing states that the pump was replaced (intensive records was kept by previous owner(Woolworths))

Ok so car was on the dyno. When i picked up the car the guys who done the testing left but they wrote down the following values, which makes no sense to me.

Startup: 13.8:1
Idle: 16.0:1
Underload: 15.6:1

They wrote down car is running lean.

This means that either my pump is shot/blocked seeing that the pressure is also lower than normal. While im at it, should i replace the fuel pressure regulator?



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panic-mechanic
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by panic-mechanic »

fuel pressure regulators rarely fail. do the pump first. A very lean car will use fuel because you use a lot bigger throttle opening than needed.
Swop the pump and take it from there.
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Mal_Jan
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by Mal_Jan »

Hi Jason

I have exactly the same issue as you, don't know about the fuel consumption yet as we bought the car with this issue.

I just posted a topic with my issue and the list of things I've done.

I read you had the car in for testing, the fuel pressure is lowish as was mine. Fitted the new pump and the pressure was correct but never thought of putting in on a dyno to get the air fuel ratio readings. I've changed everything i can think of that's related to fuel and spark.

Looks like we are in the same boat
VAG Fan
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by VAG Fan »

Jasondj wrote:Startup: 13.8:1
Idle: 16.0:1
Underload: 15.6:1
I am surprised that idle is leaner than load. If the pump is to blame, I would expect the under-delivery of fuel to be worst under load (high flow), not idle. But that's just a comment from the sideline. :geek:
Mark R.
- - - - - - - - - -
2004 VW Golf TDI, type 1J, AHF, 317k (2016-current) --- daily
1990 VW Fox, type 16, HM, 304k (2005-current) --- spare runaround
Previous:
1992 Audi 500 SE, type C4, AAR (2001-2020) --- nice while it lasted
1983 VW Golf GTS, type 17, FR (1992-2005) --- most fun car I've ever had
1978 Audi 100 GLS 5E, type 43, WC (1991-92) --- died in the side of a Rekord who cut me off
- - - - - - - - - -
Mal_Jan
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by Mal_Jan »

panic-mechanic wrote:fuel pressure regulators rarely fail. do the pump first. A very lean car will use fuel because you use a lot bigger throttle opening than needed.
Swop the pump and take it from there.
Thanks Panic

New pump is ordered and will be here friday, will fit it the evening and see how things goes.

Thanks a lot
Mal_Jan
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by Mal_Jan »

Mal_Jan wrote:Hi Jason

I have exactly the same issue as you, don't know about the fuel consumption yet as we bought the car with this issue.

I just posted a topic with my issue and the list of things I've done.

I read you had the car in for testing, the fuel pressure is lowish as was mine. Fitted the new pump and the pressure was correct but never thought of putting in on a dyno to get the air fuel ratio readings. I've changed everything i can think of that's related to fuel and spark.

Looks like we are in the same boat

More Jan

Ek het jou post gaan op soek, lyk my ons is wel in die selfde boot. Ek hoop net nie probleem kom reg met die pomp, so ver wys als na die pomp toe.

Jy het natuurlik baie meer as ek vervang en die probleem is nogsteeds daar. Het jy als op een slag gedoen?
Mal_Jan
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by Mal_Jan »

VAG Fan wrote:
Jasondj wrote:Startup: 13.8:1
Idle: 16.0:1
Underload: 15.6:1
I am surprised that idle is leaner than load. If the pump is to blame, I would expect the under-delivery of fuel to be worst under load (high flow), not idle. But that's just a comment from the sideline. :geek:
That's how i also understand it, did a few reading on the mixtures last night. It should be worse under load and not the other way around. They might have written down it down incorrectly (Idle and load) but so far both test leans towards the pump.
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by panic-mechanic »

The demand on th pump is low at idle. But already that is lean and they would normallynidle around 15'S odd.
Under load the fuelling should go to somewhere in the 13's and some mp9 will even do 12's
So comparing that it is much worse how lean it is compared to the at idle reading.
Stephan van Tonder - Jhb - Putfontein Benoni
'05 Audi A6 3.0L TDI Avant
'09 Touareg 3l TDI
'13 VW CC 2l tdi (repair project)
'05 Touareg v10

Perfect Power dealer. I do dyno tuning.
Jasondj
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Re: Help again! Polo 6n 1.4 Very high consumption

Post by Jasondj »

Got the pump yesterday evening. A day sooner than i thought.

Well installed the pump, took me about 40min. Longest part was opening the housing the pump was in, those plastics get so brittle.

Well, took the car for a nice 60km drive last night. I noticed a few things. Throttle response a little better, i can feel i give less throttle to drive 120, in fact i just touched the pedal to drive 100km/h. Going up hill where i know the car use to cut out nothing happened and the best part of all, this morning, no difficult cold start. Im so chuffed its sorted.

Thanks Panic and others for the advice.




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