VW polo 1.4 cuts out and won't restart.

fred888

Member
Joined
Nov 7, 2018
Location
Lanark
TDI
VW Polo 1.4 TDI
Hi guys.
I'm a newbie to this forum so I would like to introduce myself and request some assistance with a problem which would have me tearing my hair out - if I had any.
We have a Polo 1.4 TDI (3 cylinder) 2006 which has become unstable.
Firstly a bit of background history:
The car's been perfect for the past 3 years of our ownership.
Our daughter borrowed it and managed to fill the tank with petrol!!!!!
She didn't realise until she'd driven 100 yards and it stopped.
We managed to drain the system and refill with diesel.
The engine eventually started and after settling down, seemed fine.
However, on the way home it cut out and took about half an hour before starting again.
So now, when cold it'll start first turn of the key but when warmed up, won't restart. (Until cooled down)
Also, if I drive at a decent speed, then coast - the revs drop to zero. Restarts on lift of clutch pedal.
I think it could cut out at any time when idling in traffic.
I've replaced the fuel pump (in tank). No difference.
Replaced the fuel filter. No difference.
Now I'm suspecting air in the system or a blockage in a fuel line somewhere.
A difference I have noticed since the petrol debacle is that there is no whoosh sound when the ignition key is turned (fuel system priming). This sound was always there when the car was running perfectly.
I'm looking at the fuel return system now but don't fully understand what a couple of objects are: 1. An electrical sensor/valve near the tandem pump on the return pipe. 2. A cylindrical block clipped to the coolant expansion tank where the supply and return pipes are all connected. My manual doesn't mention either of these. Any info on these would be greatly appreciated.
Most of the stuff on the internet relates to the 4 cylinder engine so no help there.
Hopefully my symptoms listed above will ring a bell with someone. I'm almost at my wit's end.
Any suggestions welcomed.
Thanks
 

JB05

Top Post Dawg
Joined
Oct 20, 2005
Location
Il.USA
TDI
Golf,2005,anthracite blue
The sensor sounds like it could be a fuel temperature sensor. That is all I can offer.
 

fred888

Member
Joined
Nov 7, 2018
Location
Lanark
TDI
VW Polo 1.4 TDI
Thanks JB.
Yes, It could be.
But it's held in to a plastic housing with a beefy looking circlip which made me think 'valve'.
It's weird I can't find pictures and descriptions of it anywhere.

The other one clipped to the coolant tank is like a little cylindrical manifold where the feed and return pipes come together.

Cheers
 

fred888

Member
Joined
Nov 7, 2018
Location
Lanark
TDI
VW Polo 1.4 TDI
Thanks Dannyboy.

Yeah. When I got the call to tell me what she's done, my shoulders dropped. Then she revealed that she'd run the engine and I nearly burst into tears! LOL
We didn't drain the lines. Stuck at the side of the road with failing light. The engine started after refilling the tank with a bit of smoke but not as much as you'd expect. After a couple of mins she was idling sweet with normal response to the throttle. I think the relay is ok as I get the glow plug light when the ignition is switched on. The fuel pump is priming. I can hear it beneath the rear seat. But I only get the 'whoosh' of liquid sound after I take it out and refit it. She starts first turn of the key when cold and performs normally until the temp guage is up to normal. Then if I coast at driving speed, the revs drop to zero. If I stop the engine, it won't restart until cold. So the fuel temp sensor may possibly be the culprit. Or maybe the petrol, being a solvent cause some crud to create a blockage somewhere. I'm going to try disconnecting the return pipe to see if anything comes out when the engine runs.
Cheers
 

fred888

Member
Joined
Nov 7, 2018
Location
Lanark
TDI
VW Polo 1.4 TDI
Just thought: If the fault was at the fuel temp sensor, surely I'd get a EML or a fault code.
No light and no code.
The other item I need to identify is clipped to the expansion tank and has the supply hoses in/out and return hoses in/out. Could this be a check valve?
Going to try disconnecting the hoses to check flow.
 

k_pt

Veteran Member
Joined
Oct 13, 2017
Location
pt
TDI
VW MKIV TDI
To diagnose the fuel temp sensor you just need to read the values, and see if it's make sense, usually around 70°C

You gotta think about the route of the fuel. And anything that have been busted probably is mechanic, no electric.

Petrol is not as lubricant as diesel, and pumps usually fail when petrol is used on a diesel car, I would be checking tandem pump.

Also check the pdf bellow:
http://pics.tdiclub.com/data/517/PD_fuel_delivery_check.pdf.

A compression test on the engine and a pressure test on the tandem pump could help you.
 

fred888

Member
Joined
Nov 7, 2018
Location
Lanark
TDI
VW Polo 1.4 TDI
Thanks k_pt.
The PDF looks like an interesting read but I think I'll read it over a few times so I have complete understanding.
There are a few differences between my car and those shown in the photographs.
My fuel filter has only two connections (from the lift pump and to the tandem pump).
I don't have the little doohickey shown on the fuel filter pic - the one with return lines 3+4. However, I have a cylindrical object clipped to the expansion bottle which intercepts the supply and return pipes. I'll need to research what this does. (is it a check valve maybe?)
It's very possible that the petrol has damaged one or various components and the car is only good for scrap. It's just annoying that it seems to run nicely until switched off - then it won't restart for about half an hour. It could be temperature or pressure related.
With regards to compression and tandem pump testing, I think I may need to get the local professionals to do that for me.
Thank you for your input.
It's greatly appreciated.
 

eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
There's a pressure valve at the end of the injector line on the return line. Not sure why it would act up under temperature other than the fuel is warmer and flows easier.
 

fred888

Member
Joined
Nov 7, 2018
Location
Lanark
TDI
VW Polo 1.4 TDI
Thanks Eddie.
I was thinking that maybe the solvent effect of the petrol could have washed dirt through the line and caused something to block or seize up.
I found a part number stamped into the side of the item in question but an internet search came up with nothing. A trip to the local VW parts department is my next move I think.

Cheers
 

eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
Thanks Eddie.
I was thinking that maybe the solvent effect of the petrol could have washed dirt through the line and caused something to block or seize up.
I found a part number stamped into the side of the item in question but an internet search came up with nothing. A trip to the local VW parts department is my next move I think.

Cheers
Yeah, that valve might have some weakness to petrol or get clogged also, it should be listed in the pdf. Didn't check if the one you were give is the same as the one in my signature, good article though!
 

Chopsueydoey

New member
Joined
Feb 9, 2020
Location
Grimsby
TDI
Polo 1.4 tdi octavia 1.9 tdi vw t5 1.9tdi
Hello got the same problem as this post is there a fix to what it was changed fuel filter and t piece just put another tandem pump on cranks for abit when cold then fstarts but cuts out once warm then won't start again until cooled any help would be much appreciated
 
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