How to replace CrankShaft Sensor

[cookan]

Hi,
sorry for the amature question but my Leon 1.8 has been a bit iffy starting for a few months now. Problem seemed to start off a while back with a bit of a spluttery/sluggish start every now and again but one day I got in and it turned over and wouldn't fire up at all. I moved it on the starter, rocked it a bit, tried all the doors, tried patiently doing everything slowly with the key/ignition/door locks incase it was immobiliser related, but it wouldn't start. When the AA man turned up, it started first time of course. He couldn't diagnose a fualt that wasn't there but suspected crankshaft sensor.

A couple of times within the last few months it's failed to start but each time it's recovered after my usual war dance until today when my wife got stuck in camberley.Tried everything to no avail and the AA man this time diagnosed no signal from CPS Sensor apparently using his computer.

So....I'd like to replace this myself and by all accounts it involves dismantling loads of the engine bay (according to AA).

I'm not sure it can be that difficult...so thought I'd ask you guys ! (I'm no mechanic but I did drop the engine out of a Skoda with my wife once, to replace a spigot bearing...so I guess I fall into the practical, but no experience or knowledge category ;-) - we were successful with the spigot replacement btw ;-) )

From reading other posts, seems some confusion over which is the camshaft and which is the crankshaft, so thought I'd post my pics of where I rekon it is...that is...bolted into the front of the engine, in the void between the oil filter and the engine...I took on pic from above, and a close up from underneath with my phone close to the oil filter)

Not sure if this forum is allowing me to post images but the links are below this line...

https://picasaweb.google.com/lh/photo/hh6Cc3mI7LNDcQWj0gmPVU-V7q28XGSt5kT3KHnXlkU?feat=directlink

https://picasaweb.google.com/lh/photo/ezaR1e_-T8sUvKdsGZ4DpU-V7q28XGSt5kT3KHnXlkU?feat=directlink

AA man made it sound like it would be a pain to get to but I rekon I could get a socket to that without much trouble (anyone able to tell me what mm size it is to save me rounding it battling with the rust would be helpful !).

If that is the one I need to remove...I suspect it's the routing of the cable that becomes the bigger issue for me ? Seems it meanders between some pipes at the front of the engine before dissappearing under the exhaust manifold (I haven't taken the engine cover off yet so maybe it looks more tricky than it is...).

So...any idiot guide would be very helpful...it's not so much the not knowing how to do it...it's more the pain I'll feel if I start a job and find I have to give up ! so if I have to dismantle engine brackets, drop gearboxes out and generally have my engine supported on various bits of masonry..I'll have to resign myself to failure ;-)

cheers,
Ant.

 

[m0rk]

Your arrow points in the right direction, but you've photographed a knock sensor

The crank sensor is right at the end of the engine block, at the gearbox end.

Access is best from beneath

 

[cookan]

thanks for the quick response M0rk !

Just to confirm, that close up is taken from underneath the car, pointing front to back. Not particularly clear I know, but the oil filter is on the left (got some white text written on it) and the sensor I thought was the crankshaft sensor is setback on the right hand side of the engine, left of the gearbox. It has a nut/bolt head above it as opposed to through it (all the knock sensors I've been looking at to check seem to have bolts through the centre)

I jacked the car up further and couldn't find anything else in the area between the engine block and gearbox..only other sensors/plugs I saw looked more like they were connected with the gearbox, or on the actual starter motor..but maybe I'm all over the place ;-)

I'll take a look tomorrow in the daylight..

 

[m0rk]

Sorry, I looked at the photo again... that's a crank sensor.

 

[cookan]

thanks mate, so I'm on the right track then.

 

[cookan]

right...I've managed to remove the CrankShaft Sensor...nothing obviuously wrong with it but I guess that'd be far to easy ;-) I'm about to pick up £40 worth of sensor from Guildford but wanted to check something...

I've read a few things today that would suggest a faulty cam shaft sensor could allow the engine to run without cutting out, but then not start again.....but with a crankshaft sensor, if it developed the fault whilst the engine was running, it would cut the engine...

My leon has never cut out whilst running, it has always been a starting issue...oddly enough it started fine this morning despite refusing yesterday even after a 45 min tow home and an hour of me tinkering....

I managed toget the fault code from the AA guy today

P1398 No Engine RPM Signal

It's a 2001 Seat Leon 1.8 Petrol (APG engine code).

this still point to crankshaft sensor (or wiring from it) ? before I splash out 40 quid !

many thanks,
Ant.

 

[BearAttack]

P1398 No Engine RPM Signal

That sounds like the crank sensor to me - where the ecu takes its primary speed reading from.

EDIT: On second thoughts if you try and start it with the sensor completely disconnected, what happens, does it throw another fault saying speed sensor failure?

 

[cookan]

well..I've replaced the sensor and it 'still' starts, so a bit of an anticlimax ;-) We'll see with time I guess...if it happens again, I'll find somewhere that'll check the fault code with and without the sensor plugged in, see if it's the same fault (i.e that the fault code he got, does relate to that particular sensor).

So for people like me, steps were

1) borrow a 10mm allen key to remove the plastic engine cover on the top of the engine...luckily I had a friend that had one !
2) remove the plastic trim on the underside of the engine..luckily, mine was held on by only one screw at the front, and a second toward the nearside suspension..the rest was held on by luck.

3) at the front of the engine, under the lip of the exhaust manifold could be seen a bracket holding 3 plugs..middle one on mine was the crankshaft sensor and happened to be light grey (with a black/brown plug going to a knock sensor on the right. The 3rd plug I've no idea on).

4) before removing any plugs, I decided to attempt to remove the sensor first...I cleaned around it as much as I could first.
I could feel the cable going to the sensor and the little bolt head above it using my right hand feeling down slightly under but to the front of the engine block just behind and to the right of the oil filter. 10mm socket to remove the bolt which came out quite easily. Twist and jiggle the sensor out was difficult from above with right hand but lying down underneath the car, jacked up a little under its crankcase I was able to much more easily twist and turn it around. Took a while to actually pull it free...note, there's a rubber o-ring on it, and it's magnetic...so once it's turning in its socket, just needs a little force to pull it out against the resistance of the o-ring and magnet.

5) with the sensor free, I cleaned up the area again. At this point, looking from above front of the engine...you can actually see the opening where the sensor fits..so can see if the surfaces are clean.

6) With that done, I decided to then check I could remove the plug. I stuck a flat bladed screwdriver into the plug from the sensor side of the plug, to depress the locking tab so I could remove the plug from its socket. Note it was easier to do that having popped the plug and the plug to the right, out of the bracket so they were both free to move around.

7) the cable could be seen running through 3 clips. I tied some string to the plug before easing it and the cable out, down through the space to finally remove it all from underneath the car (leaving the end of the string underneath the car so I could tie the plug from the new sensor to it to pull back up through the engine...not really needed but gave me the confidence that i'd be able to work out the route it took in the first place)

8) refitting was easy (I put the new sensor in situe so I knew it fitted) before coaxing the cable back between the various pipes and up through the engine...with the help of the string ;-) )


thanks for the help guys...I'm sure I'll be back at some point ! (maybe to try to solve the 'all the windows open when I lock my door' problem ;-) )

Ant.

 

[Don87]

Dude let me know how you get on with this, i have the exact same problem with starting, only mines not never started or thrown up any coded simular to yours, it just struggles or cranks over for a drawn out period ever time i start!

 

[beechey]

did it work??? may have the same issue

 

[cookan]

Happy to say I've not had a problem since.

 

[munkimafia]

Not sure if you are still a member on the boards, but did the solution remain? I have exactly the same problem, so ken to see if thats the fix.

 

[cookan]

Hi,
yup, no 'non-start' problems since doing this.

on a secondary point, our Seat was very lumpy until warm..it would jump and choke when first driven. I thought this was related to the temperature gauge at first which never read warm so replaced the temperature sensor first. That didn't fix the issue and about a year later I changed the thermostat which fixed the temperature gauge (it had obviously failed open so the car never got up to temperature) but still the same problem.

In the end, my mechanic found the MAF sensor wasn't working correctly. Since replacing that, car has been running fine on the mornings and also, the persistent engine warning light has stayed off!

Ant.

 

[Crafoo]

It's a good job I'm not a gambling man, I'd have said for certain that a member with 7 posts who signed up in 2011 would not be replying here.

Top man

 

[cookan]

still got the seat ;-)

Ant.

 

[Crafoo]

Excellent

If you reply a few more times we'll double your post count in the last 4 years within 15 minutes

 

[cookan]

well..touch wood the seat doesn't need any more head scratching for a while...unlike the Mazda Bongo I also own !

 

[nd-photo.nl]

FYI, I replaced mine this weekend, pics:

Crankshaft sensor closeup by ND-Photo.nl, on Flickr

That hose is my PCV ventilation (to air).

Crankshaft Sensor position by ND-Photo.nl, on Flickr

New vs Old sensor. Notice the grime and filthyness on the old sensor. Would probably work after a good clean, but I prefer new shiny parts

New vs Old by ND-Photo.nl, on Flickr[/QUOTE]

 

[Muzza1742]

Just changed mine on sat, wanted to say thanks for all the photos in the thread - helped no end!