Audi TT Forum banner

crank but no start - RPM sensor

1 reading
16K views 59 replies 8 participants last post by  OUTTEA  
#1 ·
I have a "crank but no start" situation. I replace spark plugs because they are pretty old. I also replaced camshaft position sensor. Still does not start. I am using a blue tooth OBDII product called "MadPower" with the Torque pro android app. I see no fault codes. What I do notice on the Torque pro app is that the Throttle position and coolant temp gages are responding. The Revs remains at 0. The air conditioner code monitor shows a little flunctuation in RPMs and so does the dash gage. I am suspecting a crankshaft position sensor failure. It bit more of a pain to replace. Can anyone explain why I see RPM on the dash but not in the OBDII tool and if I should suspect the crank position sensor.
Thank you
 
#2 ·
Normally when you are cranking the rev counter should show approx 300revs if not then the sensor should be replaced, can you hear the fuel pump priming up before you are cranking if not then its probably a fuel pump issue under the rear seat drivers side.

Stevie
 
#5 ·
Hello Hoggy,
The dashpod rev counter moves to just below 500 while cranking. The OBDII shows 0 revs while cranking. The climate control, C28 (*corrected from C27) goes up to about 140. Other realtime data on OBDII shows ok data; Throttle position fluctuates and coolant temperature is equivalent to my garage temperature.
I was also experiencing a momentary drop in power when accelerating between 3000 and 4000 wth throttle about 3/4 way down.
I wonder if the OBDII is no reading correctly on the revs or if the dash and climate control and dash pod use a different input.
Thanks again outdoor stevie and Hoggy.
 
#7 ·
Since your rev counter needle is moving when cranking then that's good. You need to check if the fuel pump is priming before cranking it only primes for about 2 seconds when you turn the key to 'on' so you need to listen for it carefully! and you can only do it once every hour you don't get a second chance to hear it build up the pressure, so if your pump is very quiet you will need to remove the base of the rear seat and listen very carefully you should be able to hear it with the seat out, if not then you may have a fuel pump issue.
Have you replaced the fuel filter at all ever?

Stevie
 
#8 ·
Stevie,
I had the fuel filter replaced quite a while ago, about 70,000 miles. I have 190,000 miles on this one. I do smell lots of fuel after trying to crank a couple times. I get no spark at all.... I think the blue tooth OBDII scanner might not be working correctly. Going to get an Autel wired one today.
Thanks!!!
Ed
 
#9 ·
UPDATE:
The new Autel wired diagnostics scanner does report about 230 revs while cranking and not starting. The blue tooth did not report revs. I still smell fuel after about 3 long tries to start. Put car on 2 amp trickle charge until I can work on it again. Will look into a fuel filter replacement anyway, beside smelling fuel. Now that I spent all my extra money on diagnostic tools, I have to wait a few days before buying the new fuel filter. [smiley=bigcry.gif]
Anything else that this could be and not throw a code? Ignition? Mass Air???
Thanks,
Ed
 
#10 ·
Folks,
New fuel filter put in. Still does not start.
"Crank but not start" condition persists.
One thing that I had done recently, was many vacuum hoses were brittle and leaking. Had them replaced in the shop.
Ran great for 2 weeks. Had slight hesitations sometimes between 3,000 and 4,000 rpm with throttle down past 3/4 of the way. Then suddenly one morning about to drive to work, just sputtered briefly and since then not even a hint of a spark happening.
My OBDII's, both of them, show no codes, show rpm is ok at about 230 while cranking. I replaced the cam position sensor. I also replaced the spark plugs.

Any more ideas and also how to test the ignition system?

thank you very much,
Edward
 
#11 ·
OUTTEA said:
Any more ideas and also how to test the ignition system? thank you very much, Edward
Hi, Remove fuse 32 for injectors.
Remove a plug, connect it back in coil, earth plug on cam cover/engine somewhere, while spinning engine over plug should spark.
Have you checked Fuses No. 10,32,34 & 43. Have you checked you have fuel at the injectors.
Have you checked the engine control relay J271. No 2 relay under the bonnet.
Hoggy :D
 
#12 ·
Hoggy,

I did check fuses 10,32,34 & 43. They are listed as:
10 - 10A - S-Contact (don't know what S-contact means)
32 - 10A - Engine timing: petrol
34 - 10A - Engine timing: petrol
43 - 10A - Engine timing: petrol

I also checked #28 - 20A Fuel pump
29 - 15A - engine timing: petrol
37 - 20A - engine timing: petrol
all are OK!
I'm alone so doing the spark check will have to wait.
I'm very curious about the J271 No. 2 relay.
I did some research and believe I found this relay. I am not sure how to test it or which of the two relays it is.
They are located in a small plastic box under the hood (bonnet for you?) I took a pic and attached. They are numbered 100 black and 428 gray. Are one of these the J271 No. 2 relay????
The reading I did indicates this could be the problem.
thanks Hoggy for taking your time to reply and read.
Edward
 

Attachments

#13 ·
With 4 small jars you can lift the fuel rail and crank to check fuel delivery.

Also I'd say remove the fuel pressure regulator and check its gauze's are not completely blocked.

Hoggys spark check is worth doing any neighbour you could borrow to crank while you can look at the plug?

Where are you based maybe a forum member is local to help

or a test you may be able to set up with cable ties in some form to hold some thick cable on the exposed plug thread and connect to ground and then try in the dark so you can look for the spark from the drivers seat looking through the windscreen

With cable you should be able to position the plug to be in line of sight

Looks like left hand drive so ignition switch means sitting inside I guess.
 
#14 ·
Hi, if I might chip in here,the two relays shown in your pic the left hand one marked 100 is the SAI pump relay and the right hand one is the j271. oddly the Bentley manual confirms this but shows the relays in the opposite position :?: hope that helps :)
 
#15 ·
LesRSV said:
Hi, if I might chip in here,the two relays shown in your pic the left hand one marked 100 is the SAI pump relay and the right hand one is the j271. oddly the Bentley manual confirms this but shows the relays in the opposite position :?: hope that helps :)
Hi, As above.
You will need another pair of hands but you should hear/feel relay pull in as Ign switched on.
There is also the recent problem of corroded wires at ECU causing a no start prob, when everything appears O.K.
Hoggy. :D
 
#16 ·
Hoggy,

The corroded wires on the ECM. Would that be the connections under the windshield wiper where I think the ECM is tucked away at?

I'll be working on this a bit more on Friday and Saturday. Really miss driving my little OUTTEA.

thanks all for all the ideas etc. so far!
 
#17 ·
OUTTEA said:
Hoggy,

The corroded wires on the ECM. Would that be the connections under the windshield wiper where I think the ECM is tucked away at?

I'll be working on this a bit more on Friday and Saturday. Really miss driving my little OUTTEA.

thanks all for all the ideas etc. so far!
Hi, Yes, under the wipers, there have been at least 2 occasions when covering has been stripped back they have found corroded broken cables & the relay J271 has also been another cause.
Hoggy. :D
 
#18 ·
Hoggy said:
LesRSV said:
Hi, if I might chip in here,the two relays shown in your pic the left hand one marked 100 is the SAI pump relay and the right hand one is the j271. oddly the Bentley manual confirms this but shows the relays in the opposite position :?: hope that helps :)
Hi, As above.
You will need another pair of hands but you should hear/feel relay pull in as Ign switched on.
There is also the recent problem of corroded wires at ECU causing a no start prob, when everything appears O.K.
Hoggy. :D
I rigged up a test [see pic] for spark. There is no spark. Notice the driver extension in the plug hole. It has the old spark plug slightly screwed in. One of the cranks, I did get what seemed like one cylinder that fired. I have the new J271 relay in place also. We don't have much corrosion issues here in the desert, but I will look into finding the ECU and checking the wires.
thoughts?
thanks!!!
Ed
 

Attachments

#19 ·
OUTTEA said:
Hoggy said:
LesRSV said:
Hi, if I might chip in here,the two relays shown in your pic the left hand one marked 100 is the SAI pump relay and the right hand one is the j271. oddly the Bentley manual confirms this but shows the relays in the opposite position :?: hope that helps :)
Hi, As above.
You will need another pair of hands but you should hear/feel relay pull in as Ign switched on.
There is also the recent problem of corroded wires at ECU causing a no start prob, when everything appears O.K.
Hoggy. :D
I rigged up a test [see pic] for spark. There is no spark. Notice the driver extension in the plug hole. It has the old spark plug slightly screwed in. One of the cranks, I did get what seemed like one cylinder that fired. I have the new J271 relay in place also. We don't have much corrosion issues here in the desert, but I will look into finding the ECU and checking the wires.
thoughts?
thanks!!!
Ed
Got down into the ECM area to check for corrosion on connectors. Ran out of time tonight.
There is a bracket of some sort on the connector on the right that I have not seen in videos I found. Not sure how to get it out of the way so I can pull the plug on the right. I have not pulled the plug [longer one] on the left yet.
The plastic tubes connecting the washer fluid broke off on the panel that I had to remove once the wiper arms came off. I think I can rig those tubes up, but what a pain in the arse. LOL See pics of the ECU for comments.
Thanks!
Ed
 

Attachments

#21 ·
Ok Folks,
Got to spend a little more time on this situation:
I was able to check the condition of one of two connectors on the ECU (Computer). Really clean on the larger one inside. No sign of corrosion. The other seems to be factory sealed in the way the bracket in integrated. Appears I would have to split some metal welds to re-seat the other connector for inspection.
I was checking the fuseable links [see pic] and noticed that the middle cable has seriously oxidized inside the crimp on fitting. I found some description that show this fuse is for the cooling fan/control module.
Any more hints tips would be appreciated.
thanks,
Ed
 

Attachments

#22 ·
Hoggy said:
OUTTEA said:
Hoggy,

The corroded wires on the ECM. Would that be the connections under the windshield wiper where I think the ECM is tucked away at?

I'll be working on this a bit more on Friday and Saturday. Really miss driving my little OUTTEA.

thanks all for all the ideas etc. so far!
Hi, Yes, under the wipers, there have been at least 2 occasions when covering has been stripped back they have found corroded broken cables & the relay J271 has also been another cause.
Hoggy. :D
Hoggy,

The connector that I was able to pull has a plastic housing covering what appears to be a printed circuit board that has various cables going into it for the connector. Is this the area where you mention "covering has been stripped back"? It does look a bit dirty inside of the cover, but I did not remove it entirely as of yet.

Thanks,
Ed
 
#23 ·
There has been the odd issue in the past with the cable going to the ECU, you need to strip the covering tape from the cable to examine the wires inside the cable as far down the cable as you can as the moisture gets in under the tape and rots the wire away over a period of time so gently cut and peel it away if one of the wires is rotten it will be fragile and may already be broken which is giving you the issue.

Stevie
 
#24 ·
Stevie,

Thanks for the reply on this!
I had been using a blue tooth OBDII and a wired one, neither of which would show any errors. I used a different app [OBD Car Doctor Pro] for the blue tooth and saw the P0321 error in the pending codes. I have not replaced the crankshaft sensor because I would see about 230 reading on the climate control and the RPM on the dash would move a little. I did replace the cam shaft sense [easy one to do] already. I have yet to see any RPM on the OBD tools. So now I am wondering which ghost in the machine is exciting the RPM data. LOL!
Could be another week until I replace the crank sensor and examine ECU cables, but of course, more feedback is always welcomed!
Cheers,
Ed
 
#26 ·
Did you try popping your timing belt cover off and make sure the belt looks good?