Audi A3 2.0 TDI starting issue ..

[Dan3222]

I would say give yourself 2 hours to replace the pump. It should be located under the rear seat which should just pull up, a sharp tug.

-Clean up with hover and collect all the spare change lurking under the seat. Clean well arond the top of the tank/fuel housing.

-Disconnect battery earth to be safe or just be cautious when removing electrical connections

-Remove the fuel hoses, press the button to release each hose connector.

- carefully tap the massive plastic nut holding the pump housing (again make sure you have removed all debris before removing, u don’t want that in the tank.

- Replace the pump and put back together.

-Prime the pump and the the fuel pipe by turning the ignition on several times without engaging the starter motor. Leave in position 2 for 5 seconds.  You should hear the pump working for approx 5 seconds.

- try starting her up.

- my only tip on a diesel is try to have the engine warm before you do all this work. Because of the chance of air being in the system. A warm engine usually fires better than a cold one. Easier starting. Great advice when changing a fuel filter too.

SHould you take on this mission, this message should not explode 😉

[samroach]

im competant enough to change the in tank fuel pump ,  is there anyway  of testing them ? spoke to diesal tech and he said to take it back and they will have another look at it, told him he can have it all week to monitor it better ... will let him have another look before i bite the bullet and buy anything else .. im hoping he does look after me after the injetor seals he fitted did nothing 

[Dan3222]

Yeah good if they will take another look. Why not suggest you pay for a pump and they fit for free? Especially as you may not have needed the injector seals......... though it’s not bad that they have been changed.

they would be able to change a pump in less than an hour!?!

[samroach]

right guys 

 

update to my woes ..fuel fileter changed . vacuum pump refurbed .. injector seals replaced and today i fitted a new fuel pump and the fecking thing is still dont want to start ... put the back end up in the air on ramps and starts first turn of the key every time put it level and it dont want to start ... runs mint and starts ok once it had its initail run in a morning .. what next he sighs ? no fault codes coming up when scanned 

[Dan3222]

Simon, I am really sorry about this. I was absolutely sure it was going to be the primary pump. 

I have been going through this in my head for a while now and the more I think about it it still has to be fuel related. If it was low compression in a cylinder, glow plugs, dodgy injector etc then the parking the rear of the car up would make no difference to how easily it starts. Even cold start timing or fuelling issues have been outruled by parking to rear up in the air. I even thought about the injector loom being an issue but again elevation of the rear would/should make no difference. 

I was going to say that it must now be the tandem pump but it seems you have already refurbed that. Have you tried clamping any of the hoses yet? one per night to see if it identifies an issue.

i will have a read around the T5 forum a bit more and see if any of the long long threads on there can offer an alternative theory. Will have to do it later on tonight though as I have to put my T5 back together. 5 hours graft yesterday just to get to and remove the alternator. What a mare of a job.

Once again, apologies for any suggestions from this forum (and me) on how you have spent pennies on this problem. Of course we are only trying to help. When I got my first T5 I was sold a lemon. It had come with a £3200 receipt for a auto gearbox rebuild. Once it was delivered to me I took it for a test drive and it shook really bad under any load at all. The forum first suggested drive shafts but I knew it was that but changed them anyway. No difference. Took it in to a gearbox specialist. They rebuilt it again at a cost of £3700. Still no difference. I changed the fuel filter £70!! It was sorted. It turned out to be partially blocked, letting enough fuel through to start and gently accelerate but starved fuel on bigger demands creating a vibration through the engine due to lack of fuel.  My point, he sighs, I feel your pain!!

[cliffcoggin]

Like Dan, I still believe the problem is lack of fuel at the injectors during starter cranking. Unfortunately I don't have the practical experience of working on a A3 fuel system so all I can offer is logical deductive reasoning.

[1] We have all assumed the primary pump is now working because you changed it, but is that true? Have you tested it to ensure it actually delivers fuel? Even if you can hear it buzzing or whining or whatever noise it is supposed to make, it doesn't necessarily mean it is pumping fuel. I hate to say this but the only way to be certain is to remove it and test it with a bucket of fuel and some short pieces of hose. (There is a distinct fire risk to this operation but I believe you to be competent enough to set it up safely. You eliminate the risk by testing with water but then you have the problem of getting rid of the water from the pump before re-installing it.)

[2] Is there a second fuel filter that has not been changed? Some cars have more than one.

[3] Is the tank vent clear? If it isn't, a partial vacuum can be generated in the tank which will actively try to pull fuel backwards. You can test this immediately after a long run by opening the cap and listening for the inrush of air. (Some cars used to vent through a valve in the cap; many now have a separate vent hose running from the tank to a level above the filler.)

I wish you luck. I'll add more suggestions if any occur to me.

[Magnet]

Hello Simon,

I would be running out of ideas with this on a DIY basis, but it sounds as if you have a generally low fuel pressure - but that becomes a guess only. 

On the basis of additional simple things, is it worth renewing the fuel pump relay? Just incase!

Kind regards,

Gareth.

[Dan3222]

Cliff has a point, you could test the pump is working but you can do this without removing it. I use and glass milk bottle for this, take the feed pipe off at the tandem pump leaving the other end connected to the filter obviously, place end of pipe in the bottle.  Turn ignition on for 5 seconds, repeat. You should see fuel start to fill the milk bottle.

[samroach]

Hi guys

i have took the car back to the deisal specialist 1 /04/2019 and they have called me today after checking the system again 2/04/2019 .. they are now suggesting its the tandem pump , which is going to cost £420 to replace and refit . i told them i was told by yourselves it was the injector seals which cost me £260 now your telling me its the tandem pump but they cant guarantee me this will cure it . i changed all the seals and gaskets in the pump which didnt make 1 bit of differance , im confident i did the work propely to the tandem pump as i am quiet savvy with engines and mechanics , i wont be happy if i give them the go ahead and it dont cure it as that will take me to £680 for wrong diagnosis .. do i buy a 2nd hand pump or bite the bullit ???... 

[cliffcoggin]

It sounds to me that your specialist is guessing, or to put it another way, they are taking you for a ride. If they are incapable of testing the existing pump I have to regard them as incompetent. Unfortunately I have no further suggestions to add those already presented on this forum. Have you tried all of those?

As for a fitting a secondhand pump, that would only be adding another unknown factor into the problem. Test the one you have.

[samroach]

hi clifford 

i dont have much faith in the diesal place to be honest , they were supposedly testing the pump this afternoon , is there a way of testing them ? i can buy 10 2nd hand pumps for what they want to charge me as i have looked on eBay .. i have overhauled the vacuum pump and fitted it so im confident enough to fit a 2nd hand one .. im proper loathed to pay out that much as i have nearly spent as much having the car looked at then i did to buy it 

[samroach]

hi again guys 

i rang the deisal guy this morniing and the tandem pump i refurbed seems to have passed the test they performed overnight , and they are carrying out more test of the system , i am now wondering if it the injector seals they first diagnosed that they have fitted that have failed ???.... 

[samroach]

the saga continues with an anti climax 

 

had the call today from diesal place and they cant find the problem ... they have rechecked injector seals and replaced 2 of them again for minor marks on them , they now seem to think it  could be  a worn cylinder head were the injectors seat , i am well and truely at a loss now and dont know what avenue to take next 

[Dan3222]

That doesn’t make too much sense to me,  why does it start ok if back is up when parked overnight? 

Asking again, have you tried clamping the pipes yet?

[samroach]

Hi Dan

im picking it back up tom from them , the only saving grace is they aint charging me this time , he did say that clamping the pipes might be the only way to stop it , im not convince on his prognosis either . were would you suggest clamping the pipes ? ill put a picture up of the system when i get it back tom so you can give me some pointers if you dont mind

 

[Dan3222]

I would normally say the feed to the filter. But your aim here is to see if clamping makes a difference. Try one hose one night, another hose another night, see if you get different results. Just remember to remove it before starting the engine.

At least they didn’t charge you for this work this time.

[cliffcoggin]

2 hours ago, samroach said:

, they now seem to think it  could be  a worn cylinder head were the injectors seat ,

There's a powerful aroma of something familiar coming from your diesel place that I am trying to identify. Ah, I remember now. It's BS.

Do the job yourself Sam, or find somebody trustworthy.

[samroach]

hi clifford 

i get contradictory theorys everytime i speak to the guy , there supposed to be the best round here  and been going for 40 odd years , im not to savvy on the workings or diesals but im rapidly learning ......the injector seals he changed didnt make i bit of differance .. i will be doing a crash course in learning though and starting with clamping the pipes tom evening 

[Dan3222]

Any progress Simon?

[samroach]

hi Dan

i have clamped the fuel line were it goes into the vacuum pump and the car starts the next day everytime i have done it , i fitted a none return valve there which hasnt cured it ,  , I looked on the web and found a 12 volt fuel cut off valve (anti theft valve ) which i want to fit to see if that works better as im not sure it the air leak where ever it is is pulling it the same direction the 1 way valve , the fuel cut off valve will hopefully stop anything passing through it , i need to find a 12 volt supply that becomes live under the bonnet when the ignition is turned on ... im not savvy with electrics though so any help would be apreaciated 

 

[samroach]

the 12 volt supply is needed to activate the solenoid on the fuel cut off valve to open it 

[Dan3222]

Well in some ways that is a total result. It confirms what parking the rear up has done. It’s fuel running back.

You have done the two things that I would have suggested to do, replace primary pump and then look at tandem pump. Shame you had to pay for the injector stuff though but still you know that is done for the future anyway.... silver linings and all.

We really need someone like Ndziel to come on and tell you where to go for ignition 12v feed. Electrics are not in any way something I can help with.

If you have a multimeter you could have a play, or even better a bulb on cables that would light up for you so you can see what comes live and what doesn’t. However, that’s easy for me to say sitting on the sofa!

[san-iok]

Hi Sam,

 

Have you managed to fix starting problems.  Have VW BKD same problem, all forums saying about running fuel back to the tank but not even one posted or solved it .!

Thanks,

 

Alex

[John Long68]

Was wondering if anyone has the solution to this starting problem on the A3 as I have the exact same issue on mine but am struggling to solve it. 
Any help appreciated. 

Edited October 5, 2022 by John Long68

[ChayD]

I had a similar problem with my A3 (170 PD engine), after many months of head scratching and cursing Audi, it turns out one of the rubber fuel lines was perished (if i recall correctly, it was the one that goes between the metal fuel lines crossing the top of the engine and the in-line fuel temperature sensor); it was barely visible by eye unless you took the hose off and bent it, but it let in just enough air to cause fuel to drain back. Replaced all the rubber lines with off the shelf stuff from Halfords, and it's been fine ever since. Admittedly the car has a ton of other issues, but at least it starts!

Edited April 3, 2023 by ChayD