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Author: Subject: Seat Leon 1.4 tsi fuel pressure problem.
omega 24 v6

posted on 25/1/16 at 07:41 PM Reply With Quote
Seat Leon 1.4 tsi fuel pressure problem.

Good evening all.
I had a problem today with my leon. 1.4tsi 09 plate but facelift bodywork.

It had just completed a round trip of 70 miles no problems. It was then parked up for about an hour and a half.

It was restarted no problem and then run for about half a mile ( with the side lights on) I then turned on the headlights and almost immediately it started to kangaroo under accleration. When I pulled over it cut out ( misfires and backfires as well ).
I tried twice restarting it but nothing other than erratic reving ( with pedal down) and cutting out with backfires as well.

I got out and opened bonnet to have a look and all was looking ok. Got back in and it started and ran ok ( eml on now though and it wasnt before, even during the episode) ran fine all the way home for another 15 miles.

A generic Fault code reader came up with P0192 ( fuel pressure input low). And I cleared the codes and put out the eml.

Now I doubt the headlights going on was the issue and just a coincidence. So the only thing I can come up with is that when I opened the door to get out the lift pump in the tank then reprimed the system and it started after that.
Hopefully it was just an airlock ( 3/4 tank fuel) but I doubt it.

The pump seems to run as it always has when the drivers door is opened

I will try running it again tomorrow and see if all is OK.
Anyone got any ideas???





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Dingz

posted on 25/1/16 at 11:03 PM Reply With Quote
Bit of a long shot but could the battery be on its way out? turning the headlights on dropped the voltage and confused the ECU?





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nick205

posted on 26/1/16 at 08:43 AM Reply With Quote
I'd wait and see if it happens again, could be a random fault.

Oddly enough having always annually replaced my diesel filter in my Passat TDI and restarted the car without a problem the last time I did it the car wouldn't start. Very annoying and it flattened the battery trying. I took the battery out recharged it, manually filled the filter can with diesel and the car started good as gold first time. The bummer turned out to be the locked radio for which I had to pay the VW dealer 28 to unlock and give me the code). Not the end of the world, but very irritating all the same.






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britishtrident

posted on 26/1/16 at 11:04 AM Reply With Quote
The charging system should properly checked out as well as the fuel system.
The electric fuel pumps faults are often intermittent faults that are difficult to reproduce, the the high-tech check for these is to look at the current flow wave to each pump using an oscilloscope with a DC current clamp.





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britishtrident

posted on 26/1/16 at 11:07 AM Reply With Quote
quote:
Originally posted by Dingz
Bit of a long shot but could the battery be on its way out? turning the headlights on dropped the voltage and confused the ECU?



Not a longshot at all intermittent connections in the charging system or excessive alternator ripple play havoc with signals to ecu,





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nick205

posted on 26/1/16 at 11:08 AM Reply With Quote
Must admit I'm no expert on petrol systems, but VW (and I guess Seat) diesel systems changed with the introduction of CR fuel systems. As I understand it PD systems had an in-tank pump that runs with IGN on and primes the system. CR systems don't have this and need to be primed manually if air enters the system.

Perhaps petrol systems have a similar setup and air got in the system - seems odd given the reported fuel levels though.






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omega 24 v6

posted on 26/1/16 at 12:19 PM Reply With Quote
Mmm thanks for the replies so far.
I didn't think it would be connected but I only use the car like once every 3 weeks sometimes less. I did have an instance of a totally flat battery i.e. not even warning lights on the dash.
Recharged the battery ( trickle only) and local motor factors said it checked out ok. Been OK since as well.
I might have to just run it and see what happens. Trouble is its only ever used for long must do journeys. the rest of the time everyone uses my disco2.
Thanks for the replies so far.





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nick205

posted on 26/1/16 at 01:14 PM Reply With Quote
Might be worth talking to a Seat garage to see if they have any ideas to try.






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omega 24 v6

posted on 26/1/16 at 06:01 PM Reply With Quote
Running fine again now and codes deleted and not reshowing. BUT i'd rather have found why it did it.





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obfripper

posted on 26/1/16 at 09:10 PM Reply With Quote
The kangarooing you had was by design, as when the given fault code occurs the hp fuel pump pressure regulator valve shuts down, so the hp circuit pressure is equalised to the low pressure circuit, this is to prevent damage to the engine due to unknown fuel pressure, and enable limp home driving.
From this occuring followed by a complete non start it would indicate you had no fuel pressure being supplied by the lift pump when the car would not restart, cycling the ignition allowed the pump to restart & the fault code status to become intermittent so you were able to drive as normal.
The pump operation voltage is regulated by PWM, a weak pump could operate correctly at full voltage (priming pulse) but stall at minimum load voltage.
There is no low pressure circuit pressure sensor, so a low pressure circuit failure would not have a related fault code and would instead trigger the code you had.

It's also possible that the bypass pressure regulator in the fuel filter was sticking open, make sure if you replace the filter that the new one is the current spec 6.6 bar pressure regulator version, also the non fsi models have an identical looking filter with lower pressure ratings - these will cause you plenty of fault codes if accidentally used.

Dave

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omega 24 v6

posted on 26/1/16 at 10:34 PM Reply With Quote
Thanks Dave that sort of makes sense. The filter has been in for 16months though and first its done it. Its a genuine filter as well. Just hoping its not going to become an issue though. With regards to the non start / the engine would start but was lumpy as hell and certainly undriveable. With backfires as well.
Hope its just a glitch but from your description I'd be looking at new fuel filter first then poss lift pump. A mate has vagcom so I might borrow his laptop and do some live data if it reocurrs.
Thanks
Gary

E.T.A it certainly wasn't in limp home mode even with the light on. Drove just like it always did.

[Edited on 26/1/16 by omega 24 v6]





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nick205

posted on 27/1/16 at 09:14 AM Reply With Quote
As mentioned above, I've changed my Passat's TDI PD fuel filter every year (from what I can see VW talk about every 40k miles). For the cost 5 of doing it and the benefit's in driveability (sp?) I can't see it as not worth doing, the old filters are black and very dirty when removed.

Check the priming sequence before you do it, but replacing the fuel filter can't hurt.






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omega 24 v6

posted on 27/3/16 at 04:42 PM Reply With Quote
Well I'm ashamed to say I haven't had time to do anything to this car yet. Although I have been running it and its done about 300miles since the last occurance. Its done it again today though. Same scenario same symptoms. Need to get my hands dirty this week I think.
Would Vagcom Narrow it down a bit Dave?? generic code reader just comes up with P0192.





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obfripper

posted on 27/3/16 at 06:20 PM Reply With Quote
The code will likely be the same with vagcom but it will give a subcode that may help in narrowing down the fault and possibly relevant freeze frame data, however you'll be able to check the desired/actual fuel pressures with vagcom and do this while driving with an assistant, iirc vagcom will let you graph the data which makes it easier to spot an irregularity.

The actual pressure value will closely follow the desired value in a 50-150 bar range, any spikes or sudden random drops in the actual pressure can indicate a sensor/wiring issue, the actual pressure being correct at idle but falling low under acceleration indicates a restriction in the flow.
When it falls into limp mode the actual pressure will drop to 6.6 bar and remain there regardless of rpm/load, if it drops lower than this there is a lift pump/low fuel pressure regulator fault.

Have a good read of this for some in depth workings of your engine.

If you manage to log data while the fault is occuring or get a subcode/freezeframe data, post a screenshot or datalog, I'll have a good look and point you in the right direction if possible.

Dave

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omega 24 v6

posted on 27/3/16 at 07:08 PM Reply With Quote
Cheers Dave. thinking of changing the car this year so don't want to be throwing expensive parts at it unless required LOL.





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