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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 August 16th, 2009, 13:22   #106
auditdiman
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Default hammon mod

going to do this on my audi a3 asap
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Old September 7th, 2010, 13:50   #107
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Well it's over a year since the last post on this thread - and that's about as long as MY hot starting problem has been bugging me! Disconnect the ETS and instant start, replace the ETS with new and back to where I was .
Read about slow cranking so linked up to another car (engine running) with jump leads to ensure good power available - no difference, still 5sec+ before start.
I'm only on 119k miles with a well cared for engine (I've had it since 46k).
I've read about the wiring mods to trick the ECU (tempting) and about the possible blocking up of the inlet manifold and resulting poor airflow but reluctant to start down that road just yet.
Did ANYONE get to the root cause of the problem or do we blame the software?
The car is a 1998 Sharan with a 1.9tdi AFN engine and I really want to run it for a couple more years. Any more solutions/ideas out there?
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Old September 7th, 2010, 20:31   #108
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Smither, have a look into this thread and others and you will see that the early mk4's have a different ecu map. It seems to be dependent on rpm (250) before it begins fueling (if my memory serves me).

I installed the hammon mod and put a relay into it to automate the process. There was an improvement but still not what I expected. Then I did my timing belt and while I was into the engine, I changed the starter. This made all the difference as the cranking speed went up. It would appear that starter motors slow down as they get older making this problem more apparent.

Now it starts right up at any temp. I still have the mod installed and there doesn't seem to be any ill effects.

I think there is a way to change the ecu map with some help from the tuners on this forum.

Good luck!
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Old September 8th, 2010, 14:18   #109
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Many thanks for this PB. When I posted my thread last night I had got to post 250 out of over 500! I'm about to read on for further insights. I'm tempted to strip down, clean and lube the starter motor and check/clean the battery contacts, earthing straps and starter connections. But if I have no joy there the Hamman mod seems well endorsed so I may end up doing as you have done. Thanks for replying.
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Old September 8th, 2010, 18:01   #110
turbocharged798
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I changed my clutch and now no more hard hot starts! The DMF must be messing with the cranking speed or somthing...
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Old September 27th, 2010, 13:25   #111
smither01
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I checked out the resistance on all the earthing and that seems good. So I'm doing the 'kid the ECU it's cold' mod. When I checked out the 4 contacts on the engine temp sensor it seems there are two separate readings one approx half the other. They go up and down together reading approx 6k and 3k ohms at close to zero and dropping to 920 and 440 at almost boiling point. Room temp reading are 2.4k and 1.2k. I have two relays and propose to wire in two additional resistors (one in each circuit) which operate in series with the ETS when the relay is activated. I'm going to operate it by a push to make switch so both readings go up at the same time and the resistors I've chosen (2.2k and 1.5k) should make the ECU think it is about 10 degrees C. Cold enough to make the injection pump squirt straight off but not so cold as to set glow plugs running. I'm not running the relay from the starter just yet, but might add that refinement later. I don't want it thinking its -15 degrees C when its only just zero!
Does anyone know why there are 4 wires, two circuits and which circuits go to what? Obviously one goes to the ECU, what about the other?
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Old October 7th, 2010, 13:34   #112
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Well I bit the bullet and did what I said I'd do with two relays and resistors in series with the ETS and Hey Presto! It works a treat. I have a neat little PTM switch and when, from experience, I know it's going to be reluctant to start I just press and hold while turning the starter and then let go. I feel like I'm years out of date looking back at the start date of the thread and the original Hammon mod - but I'm back up and running and am happy about that even if no one else in the world reads this posting!!
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Old October 7th, 2010, 18:55   #113
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Smither;

Glad to hear the mod is working! To answer your question about what the wires do IIRC, one pair sends the temp signal to the ECU and the other pair send the signal to the temp guage on the dash.

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Old November 21st, 2010, 13:06   #114
bddumptrk
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Thanks Hamman for your great invention of how to (Quickly) solve this hard to start when warm problem,without spending alot of bucks.
I just installed the push button system you designed on my 1999 TDI Bettle and it starts better than it ever has,it fires instance when button is pressed.
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Old November 27th, 2010, 14:01   #115
Jetta Diesel Guy
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Default This will put the resistor in parellel. This will alter the coolant temp at all times

Quote:
Originally Posted by TornadoRed View Post









You need a switch that has a N/C and N/O contacts. One side of the resistor needs to go to ground to the ECU reads the resistance
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Old November 27th, 2010, 14:13   #116
Jetta Diesel Guy
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Default Tried this according to diagram, doesn't work

Quote:
Originally Posted by dqa View Post
I was trying to use your drawing and instructions in combination with the drawing by MCathcart of the Hamman mod on this thread (post #316):

Hard to start when hot issue...

Unfortunately, besides your using a Bosch-style relay and MCathcart using a Radio Shack ice cube, the wiring also seems to be different - you run the resistor from Normally Open to Common, while MC runs it from Normally Open to Normally Closed.

These may be trivial differences, but since I have a pretty weak grasp of auto electrical systems and relay terminology, and I also wasn't sure about where the starter wire would be found, I had to abort my planned mod this past weekend.

I was wondering if you or another knowledgable member could provide some more specifics to help the more ignorant among us. Now that I have a Bosch instead of a RS, I'm ignoring the MCathcart diagram altogether. Having placed your 5-step instructions next to your diagram without confusion introduced from the other diagram, it makes much more sense. However, I need more detailed instructions on steps 3 & 4:A. How do find the starter solenoid wire? (Visual descriptions, references to Bentley, Haynes, or ETKA all acceptable)
B. Where would I find "a good ground"?
C. What is the preferred way to tap into the starter solenoid wire?

And one last question...does intermittent failure of my dash engine temp gauge have anything to do with this, or does it just mean that my blue coolant temp sensor is 3 years old and putting in for retirement?
Everything is good with this except the resistor needs to be grounded for the ECU to read it. I made that correction on my car works great.
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Old November 29th, 2010, 08:12   #117
Trek_tdi
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Default I solved Problem Changing another stuff

Guys I’m new trough this forum, but I will try to help as much as I can solving issues.

I bought a 2000 TDI with the same issue (hard to start when hot) so I decided to start reading allot about the problem, and I got to a conclusion:


-I replaced the timing belt, pulleys, water pump, cleaned the egr valve, changed transmission fluid (manual tranny) also replaced diesel filter and problems of hot start are gone, now it fires up right away and no more crank for long period.

I thing that timing belt was old enough to expand when hot, and start jumping at least 1 pulley tooth so allot of crank time will be requiredv

Hope this can help someone else out
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Old February 22nd, 2011, 14:25   #118
big3s_nv
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I'd like to know what wires to tap into and where the resistor can be easily found.I just did a Head gasket job along with rod bearings and rings.The thing runs great but the hot start problem is a PITA. Going to get a Ross-Tech Vag Com real soon too. I do have a flashing glow plug light and the check engine light as well.
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Old March 29th, 2011, 12:40   #119
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Quote:
Originally Posted by Jetta Diesel Guy View Post
Everything is good with this except the resistor needs to be grounded for the ECU to read it. I made that correction on my car works great.
I would like to know more about why the resistor needs to be grounded before I proceed with the relay modification below.

http://i508.photobucket.com/albums/s...7/hotstart.png
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Old April 4th, 2011, 11:39   #120
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After a lot of planning, I finally got to do the Relay version of the Hamman mod on my 98 Audi A3, over the weekend. It was done in the same way as the pic in the previous post. It works perfectly too and has almost breathed new life into the car...sort of. I was able to mount the relay in a box that has 2 relays in it already, and run the earth and start signal wires along some trunking that goes to the ECU.
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