New TDI owner in over my head, bought a project car

KillyMcGee · Apr 15, 2015

2001 TDI M5

Lets not go heavy into the "you should have" and "why didn't you check this before buying" part of the ordeal.

I own the car now and want to make as good of a situation out of what looks like a crappy one.

The car ran great when it was warm. Now it won't start unless the engine is warmed up, or unless the coolant sensor is unplugged and you wait ~10 seconds before cranking. Outside temp is 60-70 degree F. No smoke when starting, idles fine. The pump is excessively loud, i do have another pump and rebuild kit. I do not have VCDS software though.

How likely is it that my compression is down or could it be some other issue that doesn't involve me having to do an engine rebuild?

Thanks in advance.

waltzconmigo · Apr 15, 2015

welcome to tdiclub killy, I am NOT sure about this, so do a search first, but iirc your problem sounds similar to the thermostatic tee issue, search for this term or cold start. sorry I could not be more helpful, hopefully someone more knowledgeable will chime in shortly. good luck getting this resolved.

edited to add---it is always helpful to give a more specific location so that members can offer assistance or access to VCDS.

turbobrick240 · Apr 15, 2015

May be a glowplug issue. Pretty easy fix if that is the problem.

maxmoo · Apr 15, 2015

don't panic and do something drastic....like rebuild the engine before you hook up vcds.
# 1 buy a vcds
# 2 check that all 4 glowplugs are actually working
...may just need a new temp sensor.

fossill · Apr 15, 2015

http://forums.tdiclub.com/showthread.php?t=121675

fossill · Apr 15, 2015

And while we are at it, here's a great reference for anything else that ails it:

http://forums.tdiclub.com/showthread.php?t=60705

Ol'Rattler · Apr 16, 2015

A VG site for learning about anything TDI's.

http://www.myturbodiesel.com/wiki/index/

no-blue-screen · Apr 16, 2015

Another option is to find someone close to you with VAG COM to scan the car. Purchasing a VAG COM is a good idea though as it is a very powerful tool and will help the gurus on this forum to steer you in the right direction.

jettawreck · Apr 16, 2015

As mentioned, get VCDS. Anytime you get into a project you need the proper tools. You need it, you will use it regularily if you intend to be a VW owner for any length of time.
GPs/CTS shouldn't be much of an issue whether they are really working or not given the ambient temps stated.
Air leak(s), physical static cam/crank/IP timing issues can make for those starting symptoms as could IP internal issues.

KillyMcGee · Apr 16, 2015

VCDS it is then. I appreciate in input and will get the right tool to see if i can pinpoint whats causing my issues. Until then the car will remain parked.

jettawreck · Apr 16, 2015

In your initial post you said, " Now it won't start unless the engine is warmed up, or unless the coolant sensor is unplugged".
Does this mean when you first got it, it started OK and not now, or that it just never started well.
Clarify that if you would. Any smoke while cranking prior to starting?

Concat · Apr 16, 2015

KillyMcGee said:
VCDS it is then. I appreciate in input and will get the right tool to see if i can pinpoint whats causing my issues. Until then the car will remain parked.

VCDS is pretty critical for a TDI project car

For the price, it's a pretty powerful tool.

KillyMcGee · Apr 16, 2015

jettawreck said:
In your initial post you said, " Now it won't start unless the engine is warmed up, or unless the coolant sensor is unplugged".
Does this mean when you first got it, it started OK and not now, or that it just never started well.
Clarify that if you would. Any smoke while cranking prior to starting?

I saw no smoke when starting or when car is running and put under a load. When I got the car it started fine but I now know it was because the temp sensor is unplugged. I started it, looked it over and then drove it home knowing it had a few issues. Those we will work on later. I haven't driven it anywhere since I bought it other then when I drove it home. I was looking it over better at the house and see the temp sensor is unplugged. So when plugged up the car wouldn't start. Unplugged and it will, and after the car reaches normal operating temp it will restart with temp sensor plugged in.

Ol'Rattler · Apr 16, 2015

replace the coolant sensor.....................

KillyMcGee · Apr 17, 2015

Ol'Rattler said:
replace the coolant sensor.....................

I thought that if the temp was over 40 degrees that the glow plugs wouldn't come on when you go to start the car so the fact that the glow plugs aren't coming on when the temp was 60 outside and they do when i unplug it would tell me it likely works. I'm all for replacing stuff, but have throw way too many parts at problems without fixing stuff because it "could" have been that.

Waiting on VCDS and to get back home from outta town work to check more stuff.

jettawreck · Apr 17, 2015

KillyMcGee said:
I thought that if the temp was over 40 degrees that the glow plugs wouldn't come on when you go to start the car so the fact that the glow plugs aren't coming on when the temp was 60 outside and they do when i unplug it would tell me it likely works. I'm all for replacing stuff, but have throw way too many parts at problems without fixing stuff because it "could" have been that.

Waiting on VCDS and to get back home from outta town work to check more stuff.

CTS are very inexpensive and were a common fail item on the early ones.
Glow Plugs may come on at any temp and even after starting they may/will cycle some for mainly emissions reasons. The "GP light" isn't an indicator of GP operation and is really a "wait to start" indicator. Some folks have wired in an indicator light to show actual GP duration.
But, since your ambient temps are 60-70* the GP cycle would be so brief even with a properly working CTS that probably has no bearing on your starting issue. With the CTS disconnected the ECU defaults to its max low temp (something like -45*F IIRC) cycling the GPs to maximum time. That's masking the real issue by making starting easier with much higher than needed temps in the cylinder. I would suspect very retarded injection timing or low compression.

Ol'Rattler · Apr 17, 2015

Not really rocket science here. If unplugging the CTS causes the car to start normally, there must be something wrong with the CTS.

I think you are way over thinking this. You don't need VCDS or some elaborate troubleshooting scheme. Just replace your CTS already. Cheap, simple and will eliminate at least one aspect of your problem.

Apparently, the glowplugs come on at warm ambient temps, or unplugging the CTS would make no difference.

It just kills me that folks put so much faith in VCDS. All it's going to do is verify something you have already confirmed. A really great tool and very necessary in some situations, but why bother with it when observed symptoms have already indicated the problem?

Would you do a scan to confirm a flat tire?

no-blue-screen · Apr 17, 2015

Ol'Rattler said:
Not really rocket science here. If unplugging the CTS causes the car to start normally, there must be something wrong with the CTS.

I think you are way over thinking this. You don't need VCDS or some elaborate troubleshooting scheme. Just replace your CTS already. Cheap, simple and will eliminate at least one aspect of your problem.

Apparently, the glowplugs come on at warm ambient temps, or unplugging the CTS would make no difference.

It just kills me that folks put so much faith in VCDS. All it's going to do is verify something you have already confirmed. A really great tool and very necessary in some situations, but why bother with it when observed symptoms have already indicated the problem?

Would you do a scan to confirm a flat tire?

I have to agree here. At the minimum the CTS is bad and needs to be replaced regardless if it fixes the problem or not. Just my two cents.

jettawreck · Apr 17, 2015

no-blue-screen said:
I have to agree here. At the minimum the CTS is bad and needs to be replaced regardless if it fixes the problem or not. Just my two cents.

New CTS can't hurt and doesn't cost much.
Don't think it is the issue though.

JDSwan87 · Apr 17, 2015

http://forums.tdiclub.com/showthread.php?t=438491

maxmoo · Apr 17, 2015

jettawreck said:
CTS are very inexpensive and were a common fail item on the early ones.
Glow Plugs may come on at any temp and even after starting they may/will cycle some for mainly emissions reasons. The "GP light" isn't an indicator of GP operation and is really a "wait to start" indicator. Some folks have wired in an indicator light to show actual GP duration.
But, since your ambient temps are 60-70* the GP cycle would be so brief even with a properly working CTS that probably has no bearing on your starting issue. With the CTS disconnected the ECU defaults to its max low temp (something like -45*F IIRC) cycling the GPs to maximum time. That's masking the real issue by making starting easier with much higher than needed temps in the cylinder. I would suspect very retarded injection timing or low compression.[/QUOTE]
good info

csstevej · Apr 17, 2015

Agreed with jetta ,retarded injection . You should be able to unplug your GP harness and even at 0 F should still start with no real issue other than a slightly longer crank and rough idle for a few seconds.
If timing is correct starting should be no issue whether GPS work or not.

no-blue-screen · Apr 18, 2015

Does anyone know how the CTS measures temperature? Could there be a situation where when cold...it is sending an abnormally high temp to the ECU? Would the ECU prevent the car from starting if it detected an overheating condition?

Let's hope its not low compression. Wouldn't low compression also be joined by smoke from the tailpipe?

csstevej · Apr 18, 2015

Do yourself a favor.......forget about the CTS for now. Make sure that the mechanical timing is correct first.
Hang a bottle of clean fuel from an bottle like an IV set up directly to the IP to bypass the fuel filter.....thereby ensureing you have good fuel going to the IP with a slight head pressure , and see if the car starts.
See then if the IP is making a racket and how the starting is.......my .02.

For your above comment ..... The CTS works by changing the resistenance internally when the temp,changes......the colder it gets the lower the resistenance... The hotter it gets the higher the resistenance.
And no the EcU will not prevent you from starting if it senses an over heat condition.

no-blue-screen · Apr 18, 2015

csstevej said:
Do yourself a favor.......forget about the CTS for now. Make sure that the mechanical timing is correct first.
Hang a bottle of clean fuel from an bottle like an IV set up directly to the IP to bypass the fuel filter.....thereby ensureing you have good fuel going to the IP with a slight head pressure , and see if the car starts.
See then if the IP is making a racket and how the starting is.......my .02.

For your above comment ..... The CTS works by changing the resistenance internally when the temp,changes......the colder it gets the lower the resistenance... The hotter it gets the higher the resistenance.
And no the EcU will not prevent you from starting if it senses an over hate condition.

Okay, this is good to know. For some reason I thought it wasn't cranking when the CTS was connected.

Ol'Rattler · Apr 18, 2015

csstevej said:
Do yourself a favor.......forget about the CTS for now. Make sure that the mechanical timing is correct first.
Hang a bottle of clean fuel from an bottle like an IV set up directly to the IP to bypass the fuel filter.....thereby ensureing you have good fuel going to the IP with a slight head pressure , and see if the car starts.
See then if the IP is making a racket and how the starting is.......my .02.

For your above comment ..... The CTS works by changing the resistenance internally when the temp,changes......the colder it gets the lower the resistenance... The hotter it gets the higher the resistenance.
And no the EcU will not prevent you from starting if it senses an over hate condition.

Wow. I don't get it. The OP has an observed and confirmed problem. why wouldn't he fix that before continuing with troubleshooting?

Mechanical timing is a great thing to verify, but I don't think it is indicated here. Mechanical timing probably has absolutely nothing to do with the OP's problem.

What is an "over hate" condition? AFAIK, internal combustion engines do not feel emotion.

jettawreck · Apr 18, 2015

Ol'Rattler said:
Wow. I don't get it. The OP has an observed and confirmed problem. why wouldn't he fix that before continuing with troubleshooting?

Mechanical timing is a great thing to verify, but I don't think it is indicated here. What is an "over hate" condition? AFAIK, internal combustion engines do not feel emotion.

I'm guessing his autospell turned a spelling error of overheat (?) into "over hate". My phone does some crazy stuff that way sometimes when I send a text.

The CTS may be faulty, but at 60-70* it's not the issue.
He hasn't confirmed anything about the CTS other than it starts with the CTS disconnected. That default makes the ECU to have GPs stay on as if it were -40*F. If it gave the ECU the correct temo (and it may be doing as it should) the GPs would stay on very very briefly, not even needed. Lots of TDIs that have poor injection timing or other issues and have cold start problems will start better with the CTS unplugged. Doesn't mean the sensor is bad. It's a "fix" for some other issue.
But, as said before. They are inexpensive and easy to replace, so replace if questionable.

Ol'Rattler · Apr 18, 2015

Oh, IDK. we really don't need to over think this stuff. It could be that if the CTS has a direct short to ground, it might have something to do with the problem.

Unless there is a ground path issue, all the OP would have to do is plug in a new sensor for troubleshooting purposes.

My money is on fix what you know what is not right before continuing. We can guess all day about how the GP systems works, but why bother? If there is a known problem, address it first.

I feel like I'm riding on the short bus here...............

csstevej · Apr 18, 2015

Ol'Rattler said:
Oh, IDK. we really don't need to over think this stuff. It could be that if the CTS has a direct short to ground, it might have something to do with the problem.

Unless there is a ground path issue, all the OP would have to do is plug in a new sensor for troubleshooting purposes.

My money is on fix what you know what is not right before continuing. We can guess all day about how the GP systems works, but why bother? If there is a known problem, address it first.

I feel like I'm riding on the short bus here...............

Seriously.....you think the GPS are the issue here........WOW!!!

KillyMcGee · Apr 20, 2015

Hooked up Vgcs and temp sensor showed -39 I think. Which makes sense as it was unplugged. I started it up and plugged in sensor. The cts shows the correct temperature. Once it reached about 80c I did timing test and my timing was retarded off of the chart. I shut it off and after a few tries it is as close to the center line as I can get it. It does bounce around a little bit though. Usually by a number or two but sometimes jumps 4-5. Is this
Art normal? The car starts fine now though.

New TDI owner in over my head, bought a project car

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