The story goes on - CPS mystery - SaabCentral Forums
* site search:  
Home Saab Pictures Saab Classifieds Saab Dealer Listings Saab Forum Saab Forum

Go Back   SaabCentral Forums > Saab Classic 900, 1979-1993 & '94 Convertible > Saab Classic 900 Workshop
Saab Classic 900 Workshop Classic Saab 900 (1979-1993 & '94 Convertible) Technical Forum.

SaabCentral.com is the premier Saab Forum on the internet. Registered Users do not see the above ads.
Reply
 
Thread Tools Display Modes
  #1  
Old 18-03-07
Goran9000 Goran9000 is offline
Active Member
 
Join Date: Jan 2006                                                
Location: Sydney, Australia
My Saabs: 9000CD '95, 9000 '89, 900i '89
Posts: 86
Default The story goes on - CPS mystery

Hello,

In my previous thread (http://www.saabcentral.com/forums/sh...ad.php?t=95661) I've described how crankshaft position sensor got destoyed by a broken alternator belt on my father's 900i '88 (LH2.4 EZK)

Unfortunatelly, the story goes on and right now is driving me mad .

I've bought replacement sensor and happily went on putting everything back together thinking that problem is sovled . However, as you all probably know, problems on these cars have a mind of their own and this one refuses to die - the whole thing simply doesn't work .

There is still some problem around crankshaft position sensor. It's supply line (pin 4 on EZK control unit) sits on 12V with sensor disconnected,
but it drops down to 8.3 as soon as you connect the sensor . Consequnetly, sensor doesn't work and it's output (pin 24) just hangs at 2.3V all the time.

The power supply of EZK box itself is fine, so my first guess was that it actually got damaged when sensor was destroyed. However, that was not the case.

Since we've got two idential cars I was able to swap components and confirm that all of the following are OK:

- EZK control unit
- The crankshaft position sensor (one I've bought as replacement)
- Iginition amplifier
- Ignition coil
- LH ECU
- AMM

I've tried disconnecting the knock sensor, but it made no difference.

I've suspected wiring problem on EZK to CPS lines, so I've pulled all wires out of those cable conduits and carefully inspected every single one, but with no result.

After all this, out of desperation I've removed all other wires coming from the EZK box (lines going to amplifier, knock sensor, LH ECU and test sockets). I've done this to eliminate possibility of wiring problem somewhere else.

Anyway, at the end I was left with only 5 wires on EZK box: its power supply (+12V), ground and 3 wires for CPS, and even then the sensor supply was still at 8.3V.


Now, what am I missing here ?
The whole thing just doesn't add up. I mean, the whole ignition system is relatively simple - there are only 4 things connected to EZK control unit: CPS, knock sensor, ignition amplifier and LH ECU. All of these, including EZK box itself are fine. Wiring between them is fine. Now I've runned out of things to check.

What else is there that could confuse control unit so it cannot operate CPS?

Is there ANYTHING else that could have got damaged when CPS was destroyed ?

Please help

Thanks
Goran
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old 19-03-07
Rodentmaster's Avatar
Rodentmaster Rodentmaster is offline
Saab Lunatic
 
Join Date: Aug 2004                                                
Location: Australia
My Saabs: ....................empty.
Posts: 2,203
Default

When you say..........

'replacement sensor'.....where did you source it from, SAAB? Jaycar? Dick Smith?
Did you actually swap crank pulse sensors between cars???
Big job considering what needs to be removed to get the sensors out.....!
Typically, a hall element sensor draws virtually no current to speak of and so to see the voltage drop you quoted indicates that there is a substantial current draw to create that voltage drop.
That to me suggests a wiring error on first evaluation.

What is the voltage readings with old sensor back reconnected?
__________________
Quote:
Woah! Don't expect men to talk to your face if you patronise that establishment!
RodentMaster, post links responsibly!
Eat the Pudding!
------------
ODE to the N\A
"I have not TURBINE to compress my buttocks, O lord,
Pity will be thine when thoust can crap on with boost.
We of the 'N\A - N\A' knowst nil of the pulling glory,
Yea, to post, thy blight the day of those who pressurise their pipes,
Alas, suck be mine that my chariot breathes,
Strike me down for mine is an unworthy existance"

Reply With Quote Quick reply to this message
  #3  
Old 19-03-07
Goran9000 Goran9000 is offline
Active Member
 
Join Date: Jan 2006                                                
Location: Sydney, Australia
My Saabs: 9000CD '95, 9000 '89, 900i '89
Posts: 86
Default

Hello Rodentmaster and thanks for replying

Sorry I didn't gave enough details, I guess the frustration got the better of me.

I've got the replacement sensor from wreckers, so its 2nd hand. However, it is 100% OK since I've checked it on another car. I've done it simply by plugging it in on the connector under the inlet manifold and testing it with a piece of metal. It works perfectly, supply voltage is on 12V and it produces nice 5V when triggered (0 otherwise). Also, I've tried all possible combinations of swapping components (replacement sensor with EZK control units from both cars, sensor on working car with both control units etc.) and everything is fine.

There is no old sensor, it was smashed to pieces when alternator belt snapped.

You are absolutely right, that sort of voltage drop really looks like wiring thing - that was also my first guess. But, as I've said, I've checked every mm of wires going from control unit to the sensor and it's all fine.

I am guessing that when old sensor got smashed something else also got damaged, but I have no idea what and where.

Cheers
Goran
Reply With Quote Quick reply to this message
  #4  
Old 20-03-07
gurn's Avatar
gurn gurn is offline
Senior Member
 
Join Date: Feb 2007                                                
Location: Nashville Tn.
My Saabs: 96 900s ragtop;91 900s;92 9000s
Posts: 240
Default

Did you try swaping the crankshaft pully with the ignition field rotor from one car to another? Thats about the only other part I can think of.
__________________
"SAAB people are the best." Glenn Beck
Reply With Quote Quick reply to this message
  #5  
Old 20-03-07
skilpadda's Avatar
skilpadda skilpadda is offline
Senior Member
 
Join Date: Feb 2004                                                
Location: Mosjoen, Norway
Posts: 242
Default

You will have to change that 12v supply wire.
__________________
`78 99 T
`87 900 T16 "Aero" cab. (my wifes)
`91 900S
`78 MF 148 4wd

99T project-http://www.saabcentral.com/forums/sh...ad.php?t=84245
Reply With Quote Quick reply to this message
  #6  
Old 20-03-07
Rodentmaster's Avatar
Rodentmaster Rodentmaster is offline
Saab Lunatic
 
Join Date: Aug 2004                                                
Location: Australia
My Saabs: ....................empty.
Posts: 2,203
Default

I must say...........

something doesn't quite add up here but still,..............I can't see or touch the car...!

One thing that does spring to mind is a thread here some time ago where the alt belt destroyed itself and in the process damaged the underside of the loom near the top corner of the head. (See red arrow)
I'm sure this has nothing to do with the crank pulse sensor but that is a side effect of belt damage not often picked up.
Attached Thumbnails
Click image for larger version

Name:	IdleAirFlow.jpg
Views:	32
Size:	29.3 KB
ID:	7112  
__________________
Quote:
Woah! Don't expect men to talk to your face if you patronise that establishment!
RodentMaster, post links responsibly!
Eat the Pudding!
------------
ODE to the N\A
"I have not TURBINE to compress my buttocks, O lord,
Pity will be thine when thoust can crap on with boost.
We of the 'N\A - N\A' knowst nil of the pulling glory,
Yea, to post, thy blight the day of those who pressurise their pipes,
Alas, suck be mine that my chariot breathes,
Strike me down for mine is an unworthy existance"

Reply With Quote Quick reply to this message
  #7  
Old 20-03-07
ShadowWorks's Avatar
ShadowWorks ShadowWorks is offline
Banned
 
Join Date: Jul 2005                                                
Location: Holographic Universe
My Saabs: The Black Night, 900T
Posts: 5,841
Default

Can I have your EZK number, I just want to check something, It could be a bad ground in some place, have you replaced the coolant temp sensor or even checked its values at cold and warm?

Is your fuel pump in good working order?

Silly things I know but you never know.

It sounds like you have a real SOB of a gremlin!
Reply With Quote Quick reply to this message
  #8  
Old 20-03-07
Rodentmaster's Avatar
Rodentmaster Rodentmaster is offline
Saab Lunatic
 
Join Date: Aug 2004                                                
Location: Australia
My Saabs: ....................empty.
Posts: 2,203
Default

Goran,

You won't see Pin 4 of the EZK unit go to +12v with the CPS connected.
Pin 4 of the EZK is fed through a voltage drop bleed from the +12v supply.
My car with a healthy battery displays +10V approx at pin 4 EZK.

I found some drawings I started when my crank sensor went two years ago. I tried to reverse map the EZK unit circuit but could only get so far due to the unique items Bosch used in the EZKs. All but two I.C.s are proprietry items to Bosch and to that end, no details are available. I was able to nut out a lot around the edges, so to speak, but trying to work out the analog to digital process...

I would assume that the dead car ( the one not starting ), may have a relatively weaker battery at this point, from all the cranking, down time and testing etc..
So, if I was to use my car as a quick reference, I noted about 2 to 2.5 volts drop from supply to the sensor. With that scenario and apply it in reverse to your car, 8.3 say 8.5 volts, (taking into account possible ground differences, meter accuracy etc.) add the 2, maybe 2.5 volts and that should represent a rough indication of the same voltage as the battery. +11 volts ??
I'm willing to guess that if the battery was fully charged, you would see close to the 10 volts at the sensor.



This is a waveform of the crank pulse from the sensor and output to the LH unit. The top waveform is the crank pulse. It is only 5 volts p-p. I think the 2.3 volt reading you noted for the signal will be O.K., it will change as the signal starts to generate.

As GURN queried, did you change the pulley at all? Cutouts in tact? Replace the alternator bushes?

Don't give up....!
__________________
Quote:
Woah! Don't expect men to talk to your face if you patronise that establishment!
RodentMaster, post links responsibly!
Eat the Pudding!
------------
ODE to the N\A
"I have not TURBINE to compress my buttocks, O lord,
Pity will be thine when thoust can crap on with boost.
We of the 'N\A - N\A' knowst nil of the pulling glory,
Yea, to post, thy blight the day of those who pressurise their pipes,
Alas, suck be mine that my chariot breathes,
Strike me down for mine is an unworthy existance"

Reply With Quote Quick reply to this message
  #9  
Old 20-03-07
Goran9000 Goran9000 is offline
Active Member
 
Join Date: Jan 2006                                                
Location: Sydney, Australia
My Saabs: 9000CD '95, 9000 '89, 900i '89
Posts: 86
Default

Thanks guys, I really appreciate your help

Gurn - I had to buy new a shutter plate (or rotor) because old one was bent out of shape quite badly (because pieces of broken belt got entangled there).

Skilpadda - yes, I will change all three wires going to the sensor from EZK box. However, since I've checked them both visually and electrically, I don't think it will make any difference.

ShadowWorks - the BOSCH number of EZK control unit is 0 227 400 150. Fuel pump is fine (well, it worked so far and it was never noisy). I've never touched cooland temp. sensor, but I will check it if you think it might have anything to do with all this. Bad ground is plausible, but where ? I'll go over all grounding points to make sure everything is in order.

Rodentmaster - You are correct, "healthy" power supply of CPS is 10V. However, in my case it is 12V with sensor disconected and 8.3 when you connect the sensor. I should add that it drops fairly slowly - it takes few seconds to reach 8.3V so you can watch on multimeter as it drops.

Unfortunatelly, I've fully charged the battery, so it's not that (that would be too easy)

It looks I haven't explain state of the signal line properly. It sits on 2.3V constantly -both with empty sensor and when you put piece of metal in it.
In other words, sensor doesn't trigger so I don't have that square wave, just flat 2.3V.

I know what you mean about bosch stuff, several years ago I've tried to figure out LH ECU, but I just couln't find any info on the components.

No, I am not giving up (well, it's not like I have any choice), I'll fix the damn thing somehow.

Thanks for the advice and encouragment.

Cheers
Goran
Reply With Quote Quick reply to this message
  #10  
Old 04-04-07
gurn's Avatar
gurn gurn is offline
Senior Member
 
Join Date: Feb 2007                                                
Location: Nashville Tn.
My Saabs: 96 900s ragtop;91 900s;92 9000s
Posts: 240
Default

Did you ever get it fixed? I'm having the same problems with my 91 2.1
__________________
"SAAB people are the best." Glenn Beck
Reply With Quote Quick reply to this message
  #11  
Old 04-04-07
SteveTheFolkie's Avatar
SteveTheFolkie SteveTheFolkie is offline
Saab Lunatic
 
Join Date: Jan 2006                                                
Location: Pennsylvania, USA
My Saabs: 1987 900 8V
Posts: 4,078
Default

I'm sure you've checked this - but when the alternator belt was flailing around it didn't knock off a ground wire somewhere else, did it? edit (danged "post posting" ideas) - you say you charged the battery - are you certain the battery is good and doesn't have a dead cell so you're getting a sharp drop off in amperage when you put a load on it?

Feel free to consider either suggestion as "Gawd almighty that's dumb" - but it appears that you've eliminated the other obvious possiblities.

Last edited by SteveTheFolkie; 04-04-07 at 03:02 PM.
Reply With Quote Quick reply to this message
  #12  
Old 04-04-07
ShadowWorks's Avatar
ShadowWorks ShadowWorks is offline
Banned
 
Join Date: Jul 2005                                                
Location: Holographic Universe
My Saabs: The Black Night, 900T
Posts: 5,841
Default

It has to be something stupid and so small that your over looking it, I'm a professional at this
Reply With Quote Quick reply to this message
  #13  
Old 09-04-07
Goran9000 Goran9000 is offline
Active Member
 
Join Date: Jan 2006                                                
Location: Sydney, Australia
My Saabs: 9000CD '95, 9000 '89, 900i '89
Posts: 86
Default

I've got it !!!


It took me three weeks but I've got it (although I was only able to work on Saturdays so it's not that bad).

Sure enough, it was a stupid thing - an incredibly stupid thing (just as ShadowWorks predicted).
The worst part is that the answer was right in front of me all the time and all my work was unnecessary (I've completely pulled apart all wiring looms belonging to the ignition system and cut all wires coming to EZK box - it took me half a day just to assemble everything back together . Not to mention mental stress and frustration ).

The problem was that they've changed the layout of CPS wires somewhere along the years. More precisely, power supply and signal lines were swapped around . All I had to do was to cut and swap these two lines and everything was fine !

Now, I'm guessing that change occurred between '88 and '89 models. However, since I've bought sensor from wreckers I am not sure from which model it actually came from.
Anyway, if anyone is changing crankshaft position sensor just be aware of this issue.

Well, I suppose the whole exercise wasn't totally pointless since I've fixed few loose connections along the way and cleaned all earthing points. And I've learned something new, which I guess is most important anyway .

Cheers
Goran
Reply With Quote Quick reply to this message
  #14  
Old 09-04-07
Rodentmaster's Avatar
Rodentmaster Rodentmaster is offline
Saab Lunatic
 
Join Date: Aug 2004                                                
Location: Australia
My Saabs: ....................empty.
Posts: 2,203
Default

TOP STUFF!

Great patience and persistence pays big rewards in the end.

Well Done!
__________________
Quote:
Woah! Don't expect men to talk to your face if you patronise that establishment!
RodentMaster, post links responsibly!
Eat the Pudding!
------------
ODE to the N\A
"I have not TURBINE to compress my buttocks, O lord,
Pity will be thine when thoust can crap on with boost.
We of the 'N\A - N\A' knowst nil of the pulling glory,
Yea, to post, thy blight the day of those who pressurise their pipes,
Alas, suck be mine that my chariot breathes,
Strike me down for mine is an unworthy existance"

Reply With Quote Quick reply to this message
  #15  
Old 09-04-07
SteveTheFolkie's Avatar
SteveTheFolkie SteveTheFolkie is offline
Saab Lunatic
 
Join Date: Jan 2006                                                
Location: Pennsylvania, USA
My Saabs: 1987 900 8V
Posts: 4,078
Default

Quote:
Originally Posted by Goran9000
Sure enough, it was a stupid thing - an incredibly stupid thing
GREAT JOB ... AND .... let he who has not had a moment of Gestalt and shame when faced by an ignition problem be the first to pick on you for this .... I missed a "Yes" concert in 1978 because I ignored my girlfriend's advice to 'replace the condensor' on my (non-running) VW (she knew NOTHING about cars - I doubt if she could have IDENTIFIED a condensor).... SHE went to the concert with a mutual friend (who had a running car) .... two days later I replaced the condensor and the car started ..... (I'd re-wired the entire primary ignition circut by then, replaced everything BUT the condensor and enhanced the vocabulary of my parents neighbors small children by then) ...
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Bookmarks

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the SaabCentral Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 03:21 AM.



Powered by vBulletin® Copyright ©2000 - 2014, vBulletin Solutions, Inc.

top of page | sitemap | email us



copyright © 2003 - 2011 saabcentral.com, All rights reserved http://www.whiter.co.uk - valid xhtml - valid css
SaabCentral is an independently run website and is not affiliated in any way to Saab Automobile AB.


Garage Plus vBulletin Plugins by Drive Thru Online, Inc.