Hard to start when hot

Y_Cymro

New member
Joined
May 14, 2011
Location
Wales
TDI
Audi 2.5 tdi
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).
 

Y_Cymro

New member
Joined
May 14, 2011
Location
Wales
TDI
Audi 2.5 tdi
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.
 

nostopin

Active member
Joined
Jun 24, 2011
Location
Emerald Triangle, Nor Cal
TDI
99.5 Jetta GL TDI
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
 

STRANGETDI

Veteran Member
Joined
Sep 20, 2001
Location
East Hampton, CT
TDI
2013 Audi A3 S-Line Premium Plus Quattro - APR Stage II
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
 

nostopin

Active member
Joined
Jun 24, 2011
Location
Emerald Triangle, Nor Cal
TDI
99.5 Jetta GL TDI
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
 

kdavis80s

Well-known member
Joined
Sep 21, 2011
Location
IL
TDI
2000 Golf 460,000
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
 
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Rockcrusher6

Member
Joined
Aug 24, 2011
Location
CT
TDI
99.5 Jetta
New ECM??

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?
 

Rockcrusher6

Member
Joined
Aug 24, 2011
Location
CT
TDI
99.5 Jetta
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?
 

whitedog

Veteran Member
Joined
Jul 12, 2004
Location
Bend, Oregon
TDI
2004 Jetta that I fill by myself
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.
 

Niner

duplicate account, banned
Joined
Jun 3, 2011
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.
 
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PB_NB

Veteran Member
Joined
Nov 20, 2007
Location
Vancouver, B.C.
TDI
1999 New Beetle
****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.
 

Niner

duplicate account, banned
Joined
Jun 3, 2011
I think we've been saying a tune fixes this for the past 10 years, lol.
I'll take $4 in parts and a little of my time, thank you, instead of something illegal on an on the road car... tunes are for Off Road use only, not public streets. I think that should be said every day, as a reminder...
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
I'll take $4 in parts and a little of my time, thank you, instead of something illegal on an on the road car... tunes are for Off Road use only, not public streets. I think that should be said every day, as a reminder...
no, tunes are for custom applications, including street and/or off-road use. Most of the big rigs on the road use tunes.
The diesel cars, as delivered to North America are way dumbed down.
 

LNXGUY

Top Post Dawg
Joined
Jan 10, 2004
Location
Barrie, Ont, Canada
TDI
'05 Jetta TDI Wagon
I'll take $4 in parts and a little of my time, thank you, instead of something illegal on an on the road car... tunes are for Off Road use only, not public streets. I think that should be said every day, as a reminder...
Huh? Since when is upgrading the stock ECU illegal?

Time to get your facts straight bud.
 

HopefulFred

Veteran Member
Joined
Sep 5, 2002
Location
Atlanta, GA
TDI
Golf, 2006, Indigo Blue
I haven't been a regular poster or reader here in a few years, so pardon me if this is the wrong place for this remark... My experience is with my 2006 Golf - BEW.

I began having a hot start problem (extended crank time) a few weeks ago. Most days I only start the car twice, so it wasn't a big concern. Associated with the extended crank time was an unstable, slightly high idle. I was searching around the forums, and came to this thread. I was concerned about the hassle of butchering my wiring harness, but more bothersome to me was the idea that I've driven the car for almost seven years (this is my seventh summer) and this is the first time I've had any such problem, so I couldn't shake the idea that something had broken; replace the broken part, right? Why find a work-around when the solution could be so straight-forward?

Thinking it through, I was pretty confident that I was going to put a new coolant temp sensor in it. The cost and trouble was minimal, and it was the solution that made sense to me. Before I got around to it, I got a MIL. P0128. Reset it. Second trip after reset, it's back. So I put a new ECT in it, some fresh G12+, and three days later it's good as new.

Especially given VW's ECT history, I'm surprised this isn't everyone's first move. In any case, it worked for me. :)

Fred
 

whitedog

Veteran Member
Joined
Jul 12, 2004
Location
Bend, Oregon
TDI
2004 Jetta that I fill by myself
I haven't been a regular poster or reader here in a few years, so pardon me if this is the wrong place for this remark... My experience is with my 2006 Golf - BEW.

I began having a hot start problem (extended crank time) a few weeks ago. Most days I only start the car twice, so it wasn't a big concern. Associated with the extended crank time was an unstable, slightly high idle. I was searching around the forums, and came to this thread. I was concerned about the hassle of butchering my wiring harness, but more bothersome to me was the idea that I've driven the car for almost seven years (this is my seventh summer) and this is the first time I've had any such problem, so I couldn't shake the idea that something had broken; replace the broken part, right? Why find a work-around when the solution could be so straight-forward?

Thinking it through, I was pretty confident that I was going to put a new coolant temp sensor in it. The cost and trouble was minimal, and it was the solution that made sense to me. Before I got around to it, I got a MIL. P0128. Reset it. Second trip after reset, it's back. So I put a new ECT in it, some fresh G12+, and three days later it's good as new.

Especially given VW's ECT history, I'm surprised this isn't everyone's first move. In any case, it worked for me. :)

Fred
Fred, that's great news for an 06 BEW, but it's a known issue for the earl ALH ECUs to have this software issue.
 

nostopin

Active member
Joined
Jun 24, 2011
Location
Emerald Triangle, Nor Cal
TDI
99.5 Jetta GL TDI
I'll take $4 in parts and a little of my time, thank you, instead of something illegal on an on the road car... tunes are for Off Road use only, not public streets. I think that should be said every day, as a reminder...

So if Tuning/fixing your ECU is illegal, does that make fuel additives illegal too? how about aftermarket fog lights?
 

paulp1919

Member
Joined
Jun 24, 2013
Location
Uk
TDI
Passat 2004 tdi 130bhp
I haven't been a regular poster or reader here in a few years, so pardon me if this is the wrong place for this remark... My experience is with my 2006 Golf - BEW.

I began having a hot start problem (extended crank time) a few weeks ago. Most days I only start the car twice, so it wasn't a big concern. Associated with the extended crank time was an unstable, slightly high idle. I was searching around the forums, and came to this thread. I was concerned about the hassle of butchering my wiring harness, but more bothersome to me was the idea that I've driven the car for almost seven years (this is my seventh summer) and this is the first time I've had any such problem, so I couldn't shake the idea that something had broken; replace the broken part, right? Why find a work-around when the solution could be so straight-forward?

Thinking it through, I was pretty confident that I was going to put a new coolant temp sensor in it. The cost and trouble was minimal, and it was the solution that made sense to me. Before I got around to it, I got a MIL. P0128. Reset it. Second trip after reset, it's back. So I put a new ECT in it, some fresh G12+, and three days later it's good as new.

Especially given VW's ECT history, I'm surprised this isn't everyone's first move. In any case, it worked for me. :)

Fred
Hi Fred,
what does ECT mean? Is this the same as the CTS - Coolant temperature sensor? I also have on going starting problems. Infact when fully warmed up it dosnt start. Very inconvenient I can tell you. I have already replaced my CTS with no result. However it might be faulty as I didn't buy from a dealer.
However hopefully this thread will help me. I am getting desperate
 

wsc

Well-known member
Joined
Jan 3, 2015
Location
Cypress Texas (Houston)
TDI
99.5 Jetta, 06 Jetta (Totaled), 14 Passat.
Solved the Issue with my 99.5 using the relay and resistor

My 99.5 had very extended cranking times when hot. Unplugging the temp sensor made it crank instantly. I used the Hammond mod (using a relay triggered from the starter solenoid to make the make the ECU see a 10kohm resistor rather than the sensor.) She cranks right up now!!
 

JDSwan87

Black Swamp Thing
Joined
Feb 9, 2014
Location
Michigan near Toledo
TDI
2001 Jetta TDI, 5 speed Lagoon Blue Metallic(sold); 2005 Jetta TDI Wagon auto
My 99.5 had very extended cranking times when hot. Unplugging the temp sensor made it crank instantly. I used the Hammond mod (using a relay triggered from the starter solenoid to make the make the ECU see a 10kohm resistor rather than the sensor.) She cranks right up now!!
Or you could just have the "99.5 hot start fix" done by a tuner...:rolleyes:
 

wsc

Well-known member
Joined
Jan 3, 2015
Location
Cypress Texas (Houston)
TDI
99.5 Jetta, 06 Jetta (Totaled), 14 Passat.
Absolutely. The problem I have with the tune solution is I won't be able to settle for the stock tune. The next thing you know, I'm at Stage 3 and need bigger injectors and a stronger clutch. :eek:.
 

JDSwan87

Black Swamp Thing
Joined
Feb 9, 2014
Location
Michigan near Toledo
TDI
2001 Jetta TDI, 5 speed Lagoon Blue Metallic(sold); 2005 Jetta TDI Wagon auto
Absolutely. The problem I have with the tune solution is I won't be able to settle for the stock tune. The next thing you know, I'm at Stage 3 and need bigger injectors and a stronger clutch. :eek:.
Lol!! I know the feeling!!
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Subscribed ......... as I am working on a hard start issue with a 99 NB..

Interestingly, I tackled this suspected starting issue with my ALH in the Vanagon using a double relay set-up. Too bad I didn't find this Thread back in the day!

One relay is Normally Closed and the other Normally Open. The N/O relay would close during the "start" position of the ignition which routed the #3 circuit thru a resistor, thus, the ECU saw a colder temp! The instant the ignition was released to the "ON" position, the N/O relay 'opened' and the N/C relay snapped closed switching the #3 circuit back to it's original route!

However, my ECU always threw a DTC relating to the temp sensor!

Here is a little of my R&D to address the issue.......

Below, is a pic of the ALH Engine Temp Sensor wiring schematic. As stated numerous times in this Thread, the CTS is really two sensors in one: G62 (left side in pic) provides info to the ECU (back ground). G2 (right side in pic) provides data to the cluster for the temp gauge.



I have a pic of the relays....... will find and post!
 
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AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
This is a look at the double relay set-up with resistor in the #3 circuit wire. The resistor is there to the left in that wire that loops down.




 
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