A2 90Tdi slow starting problems

KIBOURED

KIBOURED

Member
Hi All, I have been reading various threads about problems with slow staring on A2 diesels but haven't found an agreeable solution. Symptoms are, leave the car a few days and it will only start after cranking it for 30~45 seconds, once started it's perfect, no smoke, just perfect. Stop it and it will restart with no issues. Leave it another 2 days and the process repeats itself. I have fitted a new filter and recently had all 3 injectors replaced, also replaced the wiring loom inside the rocker cover about a year back. Once started you could drive it Australia without incident. It's as though the fuel is slipping back to the tank. It's certainly not electrical so has anyone found the definitive answer to this problem. Some have said there's an air leak somewhere in the fuel line but the lines look good and there's no signs of any fuel leak. Slowly running out of ideas so any help from the community would be really appreciated. Rich
 
It is highly possible that the fuel is draining back to the tank. The tandem pump could be worn and allowing the fuel vaccuum to leak through it, the fuel filter may be letting in air, or some or all the fuel pipe could have aged and become porous or cracked. To see if there is fuel still in the line you will have to replace the section of rubber pipe between the metal fuel pipe and the tandem pump with a piece of fuel grade clear plastic tube. When you disconnect the fuel will return to the tank so the next start may be even worse by the time the fuel is sucked by the tandem. But after that if you see bubbles in the clear plastic air is getting in the system or the level dropping back then its probably the tandem pump failing.
 
Have you checked the casing on the fuel filter? If it's the plastic type they are very easily broken when replacing or checking the element.
 
May I ask if you replaced the injector yourself? Is it a DIY job? Where did you purchase new injectors?
 
Hello Rich,

I own an Audi a2 1.4tdi ATL. I encountered similar experiences with cold starts after the car has sat for a few days. A couple of good suggestions have been made. I’d like to add replacing the bushings of the injectors. There are a few rubber grommets on the injector which become brittle over time and cannot hold the vaccuum anymore. I.E. false air comes in the fuel distribution lines. Under normal circumstances the vaccuum holds the fuel set as it is. The long start sessions (30-45 sec) are needed to pump the fuel al the way up to the injectors again.
Per injector it probably is around 10-15£ and is a DIY job. There are howto’s to be found online.
Since I had these replaced, no more sorrows again on starting the ATL. Hope this helps.
Kind regards
Duncan
 
audifan said:
It is highly possible that the fuel is draining back to the tank. The tandem pump could be worn and allowing the fuel vaccuum to leak through it, the fuel filter may be letting in air, or some or all the fuel pipe could have aged and become porous or cracked. To see if there is fuel still in the line you will have to replace the section of rubber pipe between the metal fuel pipe and the tandem pump with a piece of fuel grade clear plastic tube. When you disconnect the fuel will return to the tank so the next start may be even worse by the time the fuel is sucked by the tandem. But after that if you see bubbles in the clear plastic air is getting in the system or the level dropping back then its probably the tandem pump failing.
Click to expand...

So just searching back though old posts because I have an intermittent version of the same problem here in that sometimes and it appears to be completely random, the engine fails to start first time. It spins over, catches for a second and stops, this can happen anything between once and five times except for last Saturday when it must have been 20 times before resorting to Easy Start and even that took a few attempts.
If the theory about vacuum in the tank pulling the fuel back is valid (ignoring root cause of potential split hoses, weak pump, injector seal issues), then presumably releasing the vacuum in the tank when stopping then engine would prove it? Worth a try perhaps.
 
As the tandem is higher than the tank, gravity lets the fuel drain back down the feed line if the tandem is not air tight. If you replace the short length of rubber fuel tube to the inlet side of the tandem pump with diesel proof clear tubing, you can check if the fuel is draining back as the line of fuel can be seen moving further away from the tandem. If on the other hand the tandem is air tight then if air is getting in say from the filter then you would see bubbles rising in the clear tube with the engine running.
 
The fuel lines have a check valve built in to them. If this fails, it's quite likely that fuel will drain back into the tank - why else would it be there? Also, even with a leak at the pump that allows air in or out and does not allow fuel to leak, if the check vale is working, fuel shouldn't drain back to the tank. So either replace the line with the check valve (?) or splice a Lupo 3L check valve (165 201 542 B) into the line. The Lupo 3L check valve is situated just above the cambelt cover in the inlet from the filter to the pump:

fuel line; fuel filter Lupo / Lupo 3L TDI (LU) 2001 year Volkswagen EUROPA 201025

fuel line<br/>fuel filter Lupo / Lupo 3L TDI (LU) 2001 year Volkswagen EUROPA 201025 spare parts
volkswagen.7zap.com volkswagen.7zap.com

If you do the latter, make sure the arrow on the valve points in the correct direction!

RAB
 
No check valves in the 1.4 tdi fuel lines. So there must be a reason not fitted to those engines.
 
audifan said:
No check valves in the 1.4 tdi fuel lines. So there must be a reason not fitted to those engines.
Click to expand...

Agreed, I searched through the parts diagrams last night. I have been thinking about trying the Lupo one way valve, but have been trying to establish the root cause before I just hide it. At the moment I'm considering replacing the tandem pump as it has done over 192K miles.
Anyone know where I can get clear fuel (diesel) pipe?
 
Re: previous post & fuel pipe, stupid question obvs., anyone know what size is required as I don't have the car here to measure?
 
I would say your tandem is well worn by now.
As for the plastic pipe something like this....

www.thehosemaster.co.uk

Clear PVC Diesel, Oil, Fuel Hose

This is a transparent unreinforced PVC tube designed for Petrol, diesel, oils and biofuels. This is suitable for fuel lines on motor mowers and similar light duty non-pressure applications.
www.thehosemaster.co.uk www.thehosemaster.co.uk
 
audifan said:
No check valves in the 1.4 tdi fuel lines. So there must be a reason not fitted to those engines.
Click to expand...
The check valve seems to be in the tank sender:

Starting problem bhc diesel

My fuel tank sender unit arrived from Kaz. Gave it a quick clean and did a couple of tests to try and understand how it works. A youtube video on golf starting from cold problems suggested it was not uncommon for the unit to contribute to fuel delivery problems so I was intrigued to know how...
www.a2oc.net

So if that has failed, you can change the sender or do what I suggested.

RAB
 
Well I have taken the sender apart in the past (which was clean) but I didn't check what is probably the return vavle on it. I have also checked the fuel filter, changed the crank sesnor and the fuel temp sensor and just now I confirmed that there is no obvious vacuum in the tank. However, I have also ordered some clear fuel hose, so that is next step.
 
AndyP said:
Well I have taken the sender apart in the past (which was clean) but I didn't check what is probably the return vavle on it. I have also checked the fuel filter, changed the crank sesnor and the fuel temp sensor and just now I confirmed that there is no obvious vacuum in the tank. However, I have also ordered some clear fuel hose, so that is next step.
Click to expand...
Any updates on this AndyP, did you fit the clear hose and do you have a photo of where you installed it? Maybe you have photos of the line with fuel and without, if that was the failure mode. TIA
 
jonjo said:
Any updates on this AndyP, did you fit the clear hose and do you have a photo of where you installed it? Maybe you have photos of the line with fuel and without, if that was the failure mode. TIA
Click to expand...
Nope, gave up on that theory because I decided it wasn't a fuel supply problem. May latest thought is that it's imobiliser related as that more closely matches the symptoms - just waiting for it to happen again to grab the error codes.
 
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