Hard to start when hot issue.....

crankshaft positions sensor or camshaft position sensor. it must be crankshaft if it is down by the oil cooler. how does it get its information? optical, magnetic?

I am planning to buy one and replace mine. Got an appointment at the VW dealer today to pick up some break pads and discs. I will ask them about this part and try and order it for replacement.
Will keep you guys updated, if anyone else tried/trying to replace it let us know too.

ps: i think it gets it electricaly trough a selenoid.. It says here that it uses the "Hall effect" A difference in currents..

Hall Effect sensors are pretty durable; my Mustang utilizes one in the distributor. I can’t see it malfunctioning intermittently when cold vs. warm, etc. Does this sensor have a vag-com channel we can check out. I would imagine it is too fast to show on the screen when the engine is running.

Hard start - Hamman's fix

OK- how about using a "on delay" relay instead of a momentary push button?

rskovira, My exact thoughts for a week now. Screw the switch, use a 12 volt relay and operate it by the starter solenoid. It would work exactly like pressing the "button" at the same time you hit the starter (hot or cold)... I don't see a problem. Connect the wires across the NC contacts and then jump the resistor from the common and to the NO and walla, you have it. Doing it this way you don't have to run the wires into the cabin, everything stays under the hood. Radio Quack has a 12V relay (or just dig one of of the junk box). I should have a couple Ford relays or old air cooled VW's laying around.

Captain Mike

fascinating... use the starter relay to trigger a 2nd relay to break continuity to the engine temp sensor.
Only when the clutch is depressed, and the key is in the start position would the circuit be interrupted. Will the computer register the fault if that occurs?

I recently had to finally replace the starter on my 99.5 I also had hot start issue's. Wasn't a prob with the temp sensor though, as the car would still take 5-6 seconds to start whether the sensor was connected or not. I know, atleast what my prob was... the starter. I had to grease my old unit in order to get rid of the 5-6 start delay, once I installed the new starter, she starts right up, hot/cold doesn't matter. I still think there is an issue with the software on the 99.5 cars. The combination of a older start + software leads to some funky probs.

I have purchased a new engine speed/crank angle sensor for my 99.5 Jetta, and will install it this weekend. I have had the hot start problem, and have replaced the battery and the starter, and have checked the injection timing. I will post the result of the R&R once it is done.

Michael_Akamatsu said:

I have purchased a new engine speed/crank angle sensor for my 99.5 Jetta, and will install it this weekend. I have had the hot start problem, and have replaced the battery and the starter, and have checked the injection timing. I will post the result of the R&R once it is done.

Click to expand...

I for 1 am very interested in your findings. Let us know if the sensor solves your problem. Then we will have to figure out a way to diagnos whether its a starter or a sensor. There must be a vag-com measureing block for this.........????? Anybody got any ideas??

I think if you unplug the coolant temp sensor and the car starts right away when hot, you can rule out the starter being bad.

Relay

MCathcart, I was looking at the relay hookup a little differently. What does the resistor from the common to NO do? With your hook up the relay is de-energized after releasing the stater solenoid right? Before you hit the starter solenoid do you think the signal from the ETS would have any influence before its interrupted by the relay opening?

rskovira said:

MCathcart, I was looking at the relay hookup a little differently. What does the resistor from the common to NO do? With your hook up the relay is de-energized after releasing the stater solenoid right? Before you hit the starter solenoid do you think the signal from the ETS would have any influence before its interrupted by the relay opening?

Click to expand...

I need to draw it out per the original information. I think he used a Normally Closed pushbutton and added the resistor across the two poles, when you pressed the button the switch opened and the resistor was used (to tell the computer, I'm Cold) and the car was started. Since the computer is used to the value of the temperature changing, I don't think it would throw an error code. To re-think the relay. Use a Normally Closed set of contacts, the temperature sensor wires are soldered to the NC contacts and then the resistor is soldered across the same terminals. If it's Cold and the sensor tells the computer to fire the Glow Plugs, you'd wait for the light to Go Off and start the car normally (and the relay) would still tell the computer its Cold. (No problem.) If it's Hot, as soon as you crank the starter the relay (resistor) tells the Computer it's COLD and you crank faster. How 'bout it? Yea or No? I can make a drawing or even wire a relay and try it out.

Captain Mike
(Yes, I can repair Yanmar's too!)

Relay

MCathcart,

Yep I understand and agree. I know that when I unhook my ETS its amazing the difference in cranking speed and start up. Since the resistance is not there when I unhook the sensor, is that why the wait to start light does not come on and the CEL is thrown. Otherwise everything else functions as if a cold engine? Don't understand why the engine turns faster with the ETS unpluged. I'm off to Radio Shack.

Thanks

I noticed a great improvement in starting with the euro RCII software. The car often starts as soon as the key hits start, and occasionally has to crank for just a moment.... much better then before.

-Jason

Relay sound like a good idea!

That relay sounds like the way to go if you are trying to avoid pushing a little button each time you start hot... My only thought is that with the
10k ohm resistor in the circuit, you will add that resistance to the curcuit
every time you start the car - even when it's cold. I don't know what the normal parameters of the ECM are for input from the temp sensor, but
there's a change it will trigger a CEL, because the resistance is going to
be added between the temp sensor and the resistor...... To avoid this
you could switch out the temp sensor's resistance in some way with the relay, but again - even a momentary loss of all resistance might trigger a CEL.

On another note, I agree with Jason, finding that the RC2 eliminates any
warm start problem. (The sprint 205's don't seem to hurt much either )


Dave

I wasn't able to change the engine speed sensor on my 99.5 Jetta this weekend. There is a star head bolt holding it in place, for which I don't have a socket. My tools were stolen in a burglary and my friend from whom I am borrowing tools is on vacation. So it will have to wait until weekend after next. In the meantime, I cleaned the three ground connections on the black cable from the battery to the transaxle. This did help the starting situation at all temperatures. But it still needs improvement.

Please be patient all. I will post results weekend after next.

Michael_Akamatsu said:

I have purchased a new engine speed/crank angle sensor for my 99.5 Jetta, and will install it this weekend. I have had the hot start problem, and have replaced the battery and the starter, and have checked the injection timing. I will post the result of the R&R once it is done.

Click to expand...

Hello Michael,

Have you been able to change the part yet..? If yes how did it go..?

Greets,
Ker

Ker,

Please see my post that is just ahead of yours.

Michael

Sorry thanks for the update!
Goodluck then Michael!

Joining the hard to start when hot club

Ok, sounds like i've started having the same problem. i had a bad fuel temp sensor and changed that out. but only help a little.

Timing is good, and actualy set it to the top of the timing range just recently, and still no diffrence.

~5 second crank before it will start, pull the engine temp sensor and it starts right up. seems it cranks pretty fast when hot but i cant tell how fast (rpm).

I understand that the ecm does not allow fuel to be injected if the engine is not turning over 250 rpm. I do wonder if pulling the coolant temp sensor disables the "no injection under 250 rpm"? It would think it would as i'm sure under extreem cold its hard to get the engine cranking over 250 rpm.

anyone know of there is there a good way to see if the pump is getting told to inject while cranking. would be an interesting test. I was thinking of either monitoring the fuel cutoff or the quantity adjuster singnal. but i'm not sure how it disables the injection below 250 rpm.

I'm very interested in the crank angle outcome as well.

My thought is that maybe all these aproches center around the ecm/ecu thinking its ok to inject fuel or not based on temp and rpm etc...? thoughts anyone?

I, for one, am waiting on results from Michael_Akamatsu . He has taken it upon himself to play guinea pig.

add me to the list of hard(er)-starting when warm issue, but on a '04 PD. Just stop at Starbucks, be back in 5 min, go to start-up, cranks a good 3 seconds till it fires. in the morning when it's been sitting overnight, and not that cold out here in GA, it fires right up.

so it's not just the ALHs that are plagued; seems like an electronic issue, something with the sensors. if some of these coolant sensors are used on the older and newer style motors, they may be the culprit. i'm all ears as to what to try.

mine is driving me crazy. in the morning fires right up, when warm it takes 4-8 seconds of cranking. I have hooked up the battery charger in the garage when warm and it still takes too long when warm. Sounds like another reason to Rocketchip.

I have the same problem with a 99 Bug with 103000 miles. I just change the timing belt at 87000 and that didn't make any differance. It only does the 5 second crank before starting when I shut it off after driving for an hour and then restarting after it has sit for 5 to 10 minutes. If I wait for 30 minutes after shutting it off it starts right up. I was thinking maybe a relay isn't pulling in when warm?

Hard to start when hot

Yes & add me to the list.

My 99.5 Jetta had the same problem after VW dealer replaced a faulty injector pump at 130,00Km's
Gave me the run around & many reasons why it was doing it. I allowed them to do the following;

1. replace the glow plug rely & harness
2. Clean the intake manifold
3. Replace the throttle pedal
4. Check the timing

When they had run out of excuses & I out of money they said your compression is low on all cylinders. At this point I told them to go sling there hook. That car starts first turn @ -40'C without being plugged in That is not the sign of a low compression.

I have since found a good VW shop (Tony's Auto, Calgary) who is very good but has not solved the problem yet. He uses the TDIClub for problem solving. When he replaced my timing belt he checked out the timming & set it as advised by the club. This as not helped.

Since then for the past 20,000Km's I have just lived with it trying to think what else it could be. I decided to try somthing out. After the engine was at operating temprature at about 15 K.P.H. I turn the engine off & let it coast for about 5 secound & let the clutch out in 5th this way I knew the engine was turning over slowly. The engine fires right up? this proves the sensors & starter motor are not at fault.
Any suggestion.

I installed the engine speed sensor today. The car is starting better, but not perfectly, when hot. Unfortunately, I had an electrical ground problem that I fixed at the same time, so this was not a well controlled experiment. I would say, let me live with the new speed sensor for a few days. That will give me a better idea of how effective the swap was. I will post again sometime in the coming week. For now, don't go out a buy an engine speed sensor thinking it will solve your hot start problem. The jury is still out on this one.

On my problem, i checked my battery voltage, it was sitting at about 12.2 volts after a long drive.
replaced the battery with a 94r from auto zone.
started better, but still not great. voltage on the new battery was 12.5 when i installed it
after a 200 mile trip the voltage measured 13.2 The voltage dips to 10.5 on starup, but started much better.
the highest voltage measured when driving was 13.6 and would be around 13.4 most of the time.
I am suspecting a week alternator as i would expect the charging voltage to be closer to 14v.
I'll give it another day or two before i do more work.

i'm curious what voltage others have on their battteries who have a hot starting problem. (running and/or off)

sidsnot said:

Since then for the past 20,000Km's I have just lived with it trying to think what else it could be. I decided to try somthing out. After the engine was at operating temprature at about 15 K.P.H. I turn the engine off & let it coast for about 5 secound & let the clutch out in 5th this way I knew the engine was turning over slowly. The engine fires right up? this proves the sensors & starter motor are not at fault.
Any suggestion.

Click to expand...

I've had an odd thought in the back of my head for a while that perhaps when the engine is turnning over the voltage drops low enough to cause the sensors / ecu problems.

seems your test backs up my theory some as the voltage would be higher if your not turning over the engine with the starter.

Do you know what your battery voltage is before you try to start, and what it is when you are turning over the engine and lastly when it is running?

I've given some thought to perhaps isolating the circuits for the ecu/sensors from the starter/glowplugs with an isolated auxilary battery in a similar fashion to the isolation circuits used for some high power audio applications. but that would be a last resort for me.

Guys, you might not agree with what I'm going to say but after owning 4 Tdi's for 9 years and teaching Trouble Shooting 101 for 15 years I can honestly say this;

1. A higher Amperage Battery WILL Decrease Your Cranking Time. i.e. Engine spinns faster therefore it Cranks Better.

2. In two of the Tdi's (1998 and 1999 Beetle Tdi's I've owned) a High Amperage Battery Helped but DID NOT Solve the problem. (5 Seconds turned to 3 seconds cranking time.) Our 2000 Jetta Tdi would start INSTANTLY Hot or Cold. I mean just Bump the Starter and it was Running. All three cars were driven 124k, 124k and 145k.

3. If you read back through all the Stuff in this thread what you'll learn is If you Disconnect your Temp Sensor, the Engine Will Crank Faster. Also the people who are using different computers or custom software, their engines Crank better (quicker).

If you want to do the battery/starter thing, that's OK. I'd suggest Increasing the Battery Cable Size and making sure your Starter is A-OK... Put in the Highest Amperage Battery that you can find and Go for it. It will help!

*****If you want to do a quick Voltage Test. Connect at Battery Charger to your ECU fuse (or control power) and try cranking the engine. The ECU will get a constant voltage during cranking!***** I haven't tried it but it's worth a try!

Best of luck!

Mike C.

voltage

ZapBuzz said:

i'm curious what voltage others have on their battteries who have a hot starting problem. (running and/or off)

Click to expand...

With the engine off, 12.75V. With the engine running, 14.1V.

99.5 Jetta 5sp with hot start problem.