Audi 2.5 2001

**johnkarl** · 25-05-2021,07:17 PM

I have just bought an Audi 2.5 tdi with a few problems, i am focusing on one problem at a time as i am old and not as mobile as i once was. I would like a little help in diagnosing the next fault i have on my list, [ already done quite a few jobs on it ]. This problem is to do with cold start or if car has been left for a while. It takes 9 or 10 seconds to start on a morning, but runs great when it fires up, engine is smooth and has full power, if i switch it off for a couple of minuets then restart, it fires straight up and runs great, the longer i leave it the longer it takes to start, up to a maximum of 10 seconds when totally cold, i have checked the leak back pipes and they are in good condition and all dry, no signs of a leak anywhere, does anyone know where i should start looking next, the car has no code faults showing, any help would be appreciated on this matter, i have looked on our forum for quite a while but haven't found the same problem as mine, engine has done 157k

**Crasher** · 26-05-2021,11:57 AM

Remove and test the glow plugs but take great care as they love snapping. Even if they test OK, do not re-use them. My business partner has a 2005 Allroad and this was having hot start problems, I checked the cranking RPM (pump plug disconnected) and the cranking RPM was too low but this can also cause cold starting. The AKE engine should have pressure check valves in the return lines from injectors 1 and 4 back to the pump, often these are missing or the wrong way around and non AKE units can benefit from them being retro fitted, part number 059 130 789, these are £37.26 inc VAT retail from any Audi dealer.

**johnkarl** · 27-05-2021,05:29 PM

Originally Posted by Crasher

Remove and test the glow plugs but take great care as they love snapping. Even if they test OK, do not re-use them. My business partner has a 2005 Allroad and this was having hot start problems, I checked the cranking RPM (pump plug disconnected) and the cranking RPM was too low but this can also cause cold starting. The AKE engine should have pressure check valves in the return lines from injectors 1 and 4 back to the pump, often these are missing or the wrong way around and non AKE units can benefit from them being retro fitted, part number 059 130 789, these are £37.26 inc VAT retail from any Audi dealer.

Thank you for your reply, will have them checked, but it feels like no fuel to me, as after it has started i can switch it off after 5 seconds of running and it starts straight up and runs fine, [ i was wondering if there was a lift pump on this model [2001 2.5 tdi ]

**Crasher** · 27-05-2021,08:52 PM

Is it an AKE and are the check valves there?

**johnkarl** · 28-05-2021,04:44 PM

i have never heard of check valves and as new to these vehicles i don't know if it is an AKE, please would you explain please, as this is my first allroad audi, how would i be able to tell?, thanks again

**MFGF** · 28-05-2021,06:48 PM

Originally Posted by johnkarl

i have never heard of check valves and as new to these vehicles i don't know if it is an AKE, please would you explain please, as this is my first allroad audi, how would i be able to tell?, thanks again

Your car should have a build sticker in the spare wheel well in the boot, and/or on the inside cover of your service book. This sticker lists the engine code and gearbox code, along with lots of other useful stuff like the paint code, interior colour code and codes for all the options fitted to the car.

Regarding the check valves, Crasher mentioned these a couple of posts ago - "The AKE engine should have pressure check valves in the return lines from injectors 1 and 4 back to the pump, often these are missing or the wrong way around and non AKE units can benefit from them being retro fitted, part number 059 130 789, these are £37.26 inc VAT retail from any Audi dealer." It's worth tracing the fuel return lines to see if they are fitted. If they are faulty, missing, or fitted the wrong way around, I'm guessing this can mean fuel pressure can drop when the pump isn't running, and the long crank time is as a result of fuel pressure having to build up again.

Cheers!

MF.

**johnkarl** · 28-05-2021,10:17 PM

It has the sticker in my service book and it is an AKE engine, i will check to see if it has these fitted on Sunday as am fishing all day tomorrow, thanks for your help and information on this matter, do you know if it has a lift pump in the tank on this model as i seem to have what looks like a brand new lift pump in the box with a few other spares i got with the car, thanks again

**Crasher** · 29-05-2021,02:20 PM

There is a pump in the tank but it is not a lift pump... I know, confusing; it actually has two pumps, one electric and the other “suction jet” (6) and the system is designed to keep a swirl pot of fuel the the tanks right side, full of fuel and is necessary due to the saddle bag design of the pump which also requires two level senders. The VEP then draws fuel from the pot.

**johnkarl** · 29-05-2021,08:32 PM

OMG what have i gotten myself into he he he, thanks for your reply Crasher mate, will the failure of any of these components cause my problem mate

**Crasher** · 30-05-2021,12:47 PM

If the circulation pump or relay fail, this starts to cause lowish fuel level running problems which it did on my business partners 2005 AllRoad and as on the same car, a slow starter can also cause poor cold starting as can failed glow plugs and faulty/missing return line check valves. IF after cranking when it starts you get a puff of smoke then that can be glow plugs or the Commencement Of Injection fuel pump timing.