How to solve a hot start problem 2.5tdi

[myth]

I have a hot start problem with my AFB engine that's buggering me for some time, but I can't find exact info about this, mostly theories.

So, the symptoms are long cranking when hot, but the problem is intermittent. By long cranking I mean about 5 seconds of cranking before it fires right up. Cold start is fine. Also, I must add that this problem occurred progressively. At first, it was once a week, now, it's 2-3 times a day.

By now,I have checked the timing, the TCS and also tried another S-H ECU, to no avail. Unplugging the TCS improves the start, but with a lot of black smoke.

The possible fixes are:

1. Remap the ECU.
I can't find how to do it myself and I can't find a local tuner. I tried with another ECU, but it was the same problem. Maybe it got the same problem?

2. Recoding the ECU with auto trans.
I tried logging in on my ECU with the code 26262 but it just doesn't seem to accept ANY coding I try. The login code is accepted, but the coding jumps back to 01002.

3. Bypass the TCS while cranking using a relay, but apparently the ECU uses the cranking information to afterglow the glowplugs for a few minutes even when the engine is hot. I found more information here
99.5 long crank when hot... Fixed for about 8 bucks! - TDIClub Forums
also check this post
TDIClub Forums - View Single Post - 99.5 long crank when hot... Fixed for about 8 bucks!

Am I going in the right direction? Can it be a different solution to this damn intermittent problem? Can it be the Injection Pump itself? I must mention there are no fault codes.

Any info is greatly appreciated!

 

[myth]

Bump!

 

[CHRISTOPHÉ]

I have started to get this problem in the last few weeks, since changing the fuel filter. I was debating bleeding the injectors and checking the returns are not perished. I'm not sure if this will help but it's my next step I think.

 

[adamss24]

Buy a genuine Hengst or Bosch filter and new plastic tee valve from local dealer- it will solve you start ! No amount of bleeding will help there, either you used a cheap filter or the seals on the tee are flipped/pinched !

 

[CHRISTOPHÉ]

I used a Bosch filter so must be the connections to it. I'll change them. Cheers chris nice one

 

[myth]

Ahh... the famous tee connection...

I will change it, just to rule this out too, BUT it doesn't make sense. Why? Because:
1. There are no bubble in fuel lines
2. The filter is dry-like-sahara. It is covered is a small amount of dust
3. If it is leaking, then it should affect the cold start.
4. My problem is intermittent. I shut off the engine after a long run, then want to restart it within seconds since I stopped it and it's struggling.

 

[myth]

I've changed the tee and it's the same as before.

 

[myth]

I solved the problem with the #3 solution from the first post.

I have created an advanced version, fully automatic and without the glow plugs to glow after hot start. The cold start is not affected at all. If someone is interested, I can post details into solving this problem.

 

[myth]

I'm back with (new?) a problem. Since I made that modification to the starting problem, I found another problem on my car.

The return line from the #4 injector was cracked and the surrounding zone was always wet. I always thought it was oil vapors from the oil filler cap and was ignored. I replaced it and the starting improved, but I'm still not pleased.

Here is a video of the cranking:
https://www.youtube.com/watch?v=IWDzaEAtDVY&feature=youtu.be

 

[adamss24]

Get a fresh battery and new starter, it seems to me you don't have enough amps to crank the engine fast enough... Never had a v6 tdi engine crank this slow before...

 

[myth]

I've changed the battery to a Bosch 100ah in 11.dec.2013. So it must be the starter then!

 

[myth]

@Adamss24, you were right about the cranking speed. It was too low. I found the culprit was the injection pump

I changed the injection pump and before it fired it up ( until I managed to bleed the system) already it was cranking faster. After the system was free of air, it started much much faster. Also, the engine pulls better. Looking back at all the problems and headaches it gave to me... it's just mindf**k. The "refurbished" job that was done was pure bulls**t.

Also, the timing belt was forced until now... and the fuel consumption should improve.

 

[CHRISTOPHÉ]

Myth just wondered if you had part number of the replacement T please.

 

[myth]

AUDI A6/AVANT [A6] (EUROPE) 1998: ENGINE: 12735. FUEL FILTER

If that doesn't work, it's 057127247A on this picture http://i.imgur.com/PSeuIFO.png