Hard to start when hot

dataiv

Veteran Member
Joined
Feb 12, 2005
Location
Ottawa, ON
TDI
2015 Golf Wagon TDI 6MT
hydromen, the CTS plug is indeed a bit hidden. Find the coolant hose that comes out of the driver's side of the head and look behind that (towards the firewall). The plug is back there.
 

poor1

Veteran Member
Joined
May 3, 2003
Location
UK
TDI
MK4
Hot start

My apologies in advance for double posting but there are two threads running on the same subject and I want to make sure that this is seen by all those with an interest in te subject:

With regard to the Relay and Button solution to this problem.

It would be useful to have a made-up four way cable which could be connected between a male plug to going into the sensor socket and a female socket going into the the male plug which normally goes into the senor. The appropriate cable in-between the sensor socket and plug would connect up to the relay and ECU in the normal way. This would obviate the necessity of actually cutting a cable in the original wiring harness connecting the sensor to the main wiring harness. It would also have the added advantage that if the link was removed it would leave the original wiring exactly as it was.

I hope this makes sense. Picture http://pics.tdiclub.com/showphoto.ph...43863&cat=4042
- please disregard colour coding of cables - only included for illustration purposes and are NOT correct.

The question is I wonder whether it is possible to get hold of a male and female socket to construct the link.
 
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Friar

Veteran Member
Joined
Sep 17, 2005
Location
North York, ON Canada
TDI
2006 Jetta TDI, 5spd
I just had the same problem. It was resolved with a new battery, the old one was only 2 yrs old but wasn't holding a high enuf charge... warranty replacement!
 

LNXGUY

Top Post Dawg
Joined
Jan 10, 2004
Location
Barrie, Ont, Canada
TDI
'05 Jetta TDI Wagon
Friar said:
I just had the same problem. It was resolved with a new battery, the old one was only 2 yrs old but wasn't holding a high enuf charge... warranty replacement!
That will work for a bit, but you'll have hot start problems soon enough :)
 

poor1

Veteran Member
Joined
May 3, 2003
Location
UK
TDI
MK4
With regard to my Post 94, it appears that the socket which fits onto the temperature sensor itself is available as VW Part 357 919 754. A plug to replicate the sensor is more problematic. Can anyone be of assistance in locating a manufacturer or supplier please?. The sensor itself is a VW part 078 919 501B (dated 1999) and is manufactured by BEHR in Germany.

I have tried dismantling a temperature sensor, but the sensor side is totally encapsulated and having ground out the interior of the sensor, leaving the connecting pins intact, cannot see a way of attaching connections, by soldering or mechanic means.

If a 'breakout line' such as I am trying to devise could be conveniently set up, it would be the most convenient way of introducing a device (button or relay)to circumvent the sensor in the TDI hot start issue.

Thanks for the note about a new battery - I am not convinced that is the answer.
 

andy198712

Well-known member
Joined
Jan 22, 2009
Location
Cornwall, UK
TDI
VW AHF 110
A derv specialst surguested fuel pump to me was a normal cause for this in most diesels, its an expensive unit though!
 

jackbombay

Top Post Dawg
Joined
Mar 12, 2002
Location
Diesel knows best
TDI
A4 Jetta
andy198712 said:
A derv specialst surguested fuel pump to me was a normal cause for this in most diesels...
With the 99.5's the pump in not the problem (although it can be), it is a well known software problem that is responsible for the hard start when hot issue of the 99.5s. The resistor tricks the ECU to fix/avoid the ecu, but if set-up right the resistor does nothing except when the car is being started.
 

andy198712

Well-known member
Joined
Jan 22, 2009
Location
Cornwall, UK
TDI
VW AHF 110
mine does it, and its fixed if you unplug the temp sensor, BUT i have the EU ECU, so just saying, fitting an EU ECU wont fix the issue.

if that was what some people were surguesting ;)
 

LNXGUY

Top Post Dawg
Joined
Jan 10, 2004
Location
Barrie, Ont, Canada
TDI
'05 Jetta TDI Wagon
andy198712 said:
mine does it, and its fixed if you unplug the temp sensor, BUT i have the EU ECU, so just saying, fitting an EU ECU wont fix the issue.

if that was what some people were surguesting ;)
They are suggesting model specific code, not just an EU ECU....

I think the ARL base code fixes the issue and I am sure there are others...

Your ECU obviously still has this issue, regardless if it's a EU ECU or not.
 

Adnan

New member
Joined
Feb 2, 2009
Location
Bulgaria
TDI
AGR
Hot engine start it's discuset on Bulgaria as well. It's as know as programer bug in VW here is the one table sorry it's not mine so i just copy it :





There is calling MAPING of electronical part of fuel pump who send fuel. As you can see when starter run on 200 RPM and temperature is above 15.0 (C!) fuel pump do not send any fuel to cilenders.
Now i'm asking does anyone of you know how to map the fuel pump.

There is one more solution which is very lamer one. Always can change setting from VAG COM to auto gear option. Then hot engine start is gone but on 2't gear car is not running as it should be.
 
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auditdiman

Member
Joined
Aug 8, 2009
Location
uk
TDI
audi a3 2.0ltr tdi 54 plate
a3 2.0 tdi

thinking of doing this to my 54 plate audi a3 are wires the same colour on sensor ?
 

smither01

New member
Joined
Nov 3, 2009
Location
LEEDS
TDI
SHARAN 1.9 110BHP
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?
 

PB_NB

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

smither01

New member
Joined
Nov 3, 2009
Location
LEEDS
TDI
SHARAN 1.9 110BHP
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.
 

turbocharged798

Veteran Member
Joined
May 21, 2009
Location
Ellenville, NY
TDI
99.5 black ALH Jetta;09 Gasser Jetta
I changed my clutch and now no more hard hot starts! The DMF must be messing with the cranking speed or somthing...
 

smither01

New member
Joined
Nov 3, 2009
Location
LEEDS
TDI
SHARAN 1.9 110BHP
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?
 

smither01

New member
Joined
Nov 3, 2009
Location
LEEDS
TDI
SHARAN 1.9 110BHP
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!!:D
 

Hamman

Veteran Member
Joined
Oct 4, 1999
Location
Warren, OH
TDI
No TDI's, but an '84 Rabbit diesel
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.

Dave
 

bddumptrk

Member
Joined
Jan 17, 2009
Location
NC
TDI
1999 Beetle
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.
 

Jetta Diesel Guy

New member
Joined
Nov 26, 2010
Location
Michigan
TDI
Jetta
Tried this according to diagram, doesn't work

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.
 

Trek_tdi

New member
Joined
Nov 28, 2010
Location
@ chiwas
TDI
2000 jetta
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:mad:

Hope this can help someone else out :confused:
 

big3s_nv

Member
Joined
Apr 13, 2003
Location
Southern Ohio
TDI
1996 Passat wagon
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.
 

paddy737

Member
Joined
Feb 5, 2008
Location
ireland
TDI
1997 a3 tdi
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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