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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old April 4th, 2011, 12:19   #121
Hamman
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Well done!
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Old May 15th, 2011, 04:14   #122
Y_Cymro
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Hi
I want to try the "Hamman mod" on my UK 2.5 Audi B5. It has a four-wire CTS. Can anyone tell me which wire to cut? There are two blue coloured - one with a red trace and the other with brown, one white/brown and the last is white/brown (IIRC).
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Old May 16th, 2011, 08:50   #123
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Originally Posted by Y_Cymro View Post
Hi
I want to try the "Hamman mod" on my UK 2.5 Audi B5. It has a four-wire CTS. Can anyone tell me which wire to cut? There are two blue coloured - one with a red trace and the other with brown, one white/brown and the last is white/brown (IIRC).
I can confirm that it's pin 3 that should be cut as detailed earlier in this thread.
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Old June 26th, 2011, 09:41   #124
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all sounds great. I'm going to make a switch with a 10kohm resistor, and one with a 3300ohm resister. if the 3300 don't work i'll swap it with the 10k. my question about automating it with a relay using the Start cir on the ignition. will this affect it when it is actually cold? if i'm using a 3300ohm resistor the ECU thinks its just cool, not cold and there for does not activate the GPs. If it actually COLD and I do need the GPs will this affect my cold starts? I live in Nor Cal and I do get snow a little in the winter. gets down to around 25f at times, but most of the time I wont need the GPs anyhow
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Old July 7th, 2011, 13:33   #125
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I just saw this on the VAG-COM website, towards the end of the document... I wonder if there is anything to it......

Channel 5: starting conditions
  • Though undocumented, this channel effects the injected quantity the ECU allows when starting.
  • You may want to experiment with it as a temporary fix for bad-start problems
http://www.ross-tech.com/vag-com/cars/tdi.html
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Old July 9th, 2011, 16:36   #126
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I just bought a A4 TDI with the hard start when warm problem, dealer took it back and sent it to their mechanic to get a new IP. It didn't fix the problem. Keep in mind this was NOT a TDI, or even a VW specific mechanic. When I got the car back a week later it still has the problem, but very erratic. sometimes its hard to start when cold now and not hard when its warm, sometimes it goes back to the hard starting when warm, but starts fine when cold. Sometimes its hard to start hot and cold, sometimes it starts fine for a couple days. I have the switch with the 3300ohm resistor all set up to install
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Old October 20th, 2011, 07:15   #127
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2000 golf TDI 275,000, hard to start when hot, cranking for like 5+seconds, I went threw all the scenario's on this post, nothing seemed to work. But then I found the "hammer mod". it worked! I changed the IQ and it started right up hot, cold ,warm, or upside down! I did not have a vagcom to set it like they show you so i did it by feel, now she runs great. here is a link
http://forums.tdiclub.com/showthread.php?t=258297. hope this works for you. also, the special socket it calls for that is like 20 bucks, you can just mail me the 20 bucks! just take an old cheap socket i dont remember the size its an odd ball that is slightly smaller almost will fit but wont and take your hammer and "beat it on" persay and there you go i left mine on there after i was done because i see in the future that i will have to adjust as the miles increase. my pump is loud its had alot of what ever will burn threw it

Last edited by kdavis80s; October 20th, 2011 at 07:27.
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Old October 27th, 2011, 16:42   #128
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Hi, I'm new to this forum. The reason I found this forum is that I was searching for answers about why my 99.5 TDI starts hard when hot. I've checked everything with the VAG COM, and timing, coolant temp, Injection quantity, etc., all seem to be where they should be. I have been reading about the Hamman fix for this problem, and I'm starting to think it's the way to go, but, I was wondering if using a newer ECM would fix this problem? I have an ECM for an '01 that I was going to try. Does anyone see any potential problems with trying the newer ECM?
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Old October 28th, 2011, 07:01   #129
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Are there any major differences between a 99.5 and an 01 ECM?
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Old October 28th, 2011, 07:07   #130
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Yes. They are not compatible. 80 pins on the 99.5 and 121 on the 01.
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Old October 28th, 2011, 07:31   #131
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So what you're saying is either I get my ECM reflashed or I do the resistor trick? Can the dealer do a flash that would solve this problem?
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Old October 28th, 2011, 09:39   #132
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They probably won't even acknowledge the problem.
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Old October 28th, 2011, 09:42   #133
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Quote:
Originally Posted by Rockcrusher6 View Post
So what you're saying is either I get my ECM reflashed or I do the resistor trick? Can the dealer do a flash that would solve this problem?
The dealer probably won't even acknowledge the real problem. Also, it's more than just a reflash. The ECU needs to come out and a new, programmable chip soldered in.
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Old July 2nd, 2012, 12:09   #134
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Quote:
Originally Posted by Eric Dow View Post
Readings with different resisters Here's some observations of this fix.

1st, the worry about reduced mileage and extra fuel consumption... Don't worry, I have some facts to back this one Nope, no problem with extra fuel or reduced mileage. I checked in VAG-COM and also did before and after resistance readings. With the documented proceedure, the resister is in Parallel with the factory temp switch/sender. This means that the electricity will take the lowest resistance path. As the temp goes up, the switch/sender actually lowers the resistance, so the 10k or 4.7k ohm resister actuall get's ignored. When the switch is thrown, the temp goes down to the following, and right back to real temp as soon as released:

10k ohm = -15 degrees cel. Not necessary, too low and turns on glow cycle
4.7k ohm = 2.7 degrees cel. This is good, only starts short glow cycle
3.28k ohm = ~24 degrees cel. This is probably the best setting IMO. It doesn't cycle the glow plugs, but does modify injection timimg and starts real easy.
1.67k ohm = 56 degrees cel. on the warming up side.
Somewhere between 3.28 and 1.67 is where the ECU will stop considering the car cold and assist starting.

So, what I'm getting at is this, no codes with this mod, no lasting affects past the release of the switch after starting. So if you have replaced the temp sender, starter, battery and confirmed that your injection timing is good, and don't want to do any more with your pump, or fear that it's on it's way out, give this one a try

P.S. On the New Beetle, it's cleaner to splice the ECU side of the circuit. You can make it totally invisable and put the switch anywhere ya like.

I did this modification yesterday, after putting it off for over 2 years in my 2002 Jetta GLS TDI. I had always noted that on my Scan gauge II, if the temp was above 130F, it was hard to start, 5 seconds of turn over before it caught and ran, if it was 120F about 3 seconds, and if it was 110F, it pretty much fired up instantly.

In these pictures, you can see how pushing the button with a 3.3k 1/4 watt resistor tricks the ECM into seeing 110F, which does not activate the glow plugs at all... simply push the button with your left hand, mounted on the left side of the steering column, and start the car normally, and the car fires up instantly now.






The results, it takes a second for the temp to register on Scan Gauge, there was a bit of a lag, I'd removed my finger from the button in the lower left of the picture.






This modification is a complete success on my 2002, it works flawlessly in hot start mode now, fires up instantly.

Why it works... a diesel will start if the timing is close, warm or cold, if there is fuel. With the timing map shown here, the fueling map keeps looking for options and seeks an option that will work... so it goes through a lot of options if your start rpms are 250 and your temps are above 40C,, closer to 70C, which is where zero fuel is sent by the ECM to the injector pump. You are fooling the fueling map, not the timing of the pump at start, which is static.

So you need a resistor that will fool the ECU temporarily, by pushing the button first, before you turn the ignitions on. The ECM then "reads" that temp, and selects a fuel map and quantity for that start temperature. Once your motor is up and fires, your rpms instantly increase above the 0 fuel level that is at start rpms of 250 and above 40F.



At 250 rpm, regardless of temp, this fuel map should have 19- 21mg of fuel being shown all the way down the 250 rpm column, as well as down to 200 rpm. It doesn't, hence the motor starves for fuel while the fuel map hunts and pecks as the motor cranks to find a solution for fueling that works.

Last edited by Niner; July 2nd, 2012 at 19:46.
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Old July 2nd, 2012, 12:19   #135
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****FIXED****

After many years of dealing with this, I finally have it fixed. It took 10 minutes to pull my ECU and stick in a Malone Tuned ECU. ONE CRANK!!! and it starts right up.

It would like to send the cost of the tune to VWAG.
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