Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: SR-71Blackbird on 18 July 2016, 21:46:36

Title: Jumping rev counter 1998 2.5TD Auto
Post by: SR-71Blackbird on 18 July 2016, 21:46:36: Hi all,

I have a jumping rev counter on my 1998 2.5TD Auto. Mostly it is fine but sometimes it just jumps around from 0 - max etc.

Is this likely to be a crankshaft sensor failing?

Is there a way I can test this and is there a guide/images anywhere on how to replace it?

Thanks

Alex
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: zirk on 19 July 2016, 14:11:25: Its a TD so most likely something wiring related, my first call would be to pull the Dash Clocks out, ElectroLube the main connector and firmly refit.

(Edit, if you cant get your hands on ElectroLube Spray, a good clean with some Meths and cotton buds on the connector pins and socket should suffice)
Title: Re: Jumping rev counter 1998 2.5TD Auto - Creates "Automatic Transmission Fault"
Post by: SR-71Blackbird on 31 July 2016, 17:45:33: Hi all,

Getting a bit more serious now.

When the rev jumps around abit and then sits on 0 even when moving (should be around 2000rpm lets say) it causes the "Automatic Transmission Fault" check light to come on on the Display. I then stop, turn the engine off and on again and it clears but I want to get it solved.

Is it likely to be a failing crankshaft sensor? If so is there a guide or images of where this is and how to change it etc? I saw a Post where TheBoy says

http://oldsite.omegaowners.com/forum/YaBB.pl?num=1246733913

"crank sensor on TD is under starter motor. Never known one to fail. The sensor has a connector on it, might be worth giving that a clean, as that tractor blood tends to get everywhere."

Any pics or guidance of how to replace it and where it is?

Thanks as always all.

Alex
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: X30XE on 31 July 2016, 21:10:11: I doubt it. No feed from the CPS is an immediate engine shutdown condition in my experience.

Dodgy rev counter and dodgy idle... These may be two seperate issues that just happen to occur together sometimes. Or a more complex wiring fault causing both.
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: X30XE on 31 July 2016, 21:13:38: http://www.omegaowners.com/forum/index.php?topic=135078

See post from Nick W re: rev counter function...
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: Kevin Wood on 01 August 2016, 12:39:21: Quote from: X30XE on 31 July 2016, 21:10:11
I doubt it. No feed from the CPS is an immediate engine shutdown condition in my experience.

Dodgy rev counter and dodgy idle... These may be two seperate issues that just happen to occur together sometimes. Or a more complex wiring fault causing both.

No necessarily on a TD, as the engine has a conventional mechanical injection pump, so it can run without. Given that the autobox is complaining, in addition to the rev counter, I'd tend to go with the RPM indication from the engine ECU being to pot, which might well be a crank sensor problem.
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: SR-71Blackbird on 01 August 2016, 14:25:59: Thanks Kevin,

I have ordered another Crankshaft position sensor.

I went under the car the other day (forgot to take a picture damn) but there is a sensor that seems to be clipped to the starter motor and goes to the transmission. Is this the Crankshaft sensor and cable? I didn't take it out or disconnect as I was unsure.

Thanks very much in advance.

Alex
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: TheBoy on 01 August 2016, 18:54:23: It sits right next to the starter motor, is about 3inches long. Fitting lengthways, so goes through the engine casing, and presumably is picking up something on the flexplate.

Cable is a 2 pin connector, plugs straight into the sensor.
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: TheBoy on 01 August 2016, 19:10:32: Here's a pic, sorry not overly clear, as its an old pic of swapping my engine

(http://images.omegaowners.com/images/theboy/project_tb2/IMG_2226.JPG)

But you can see under starter motor :y
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: SR-71Blackbird on 02 August 2016, 11:56:25: Thanks guys,

I will see what I can see when the part arrives.

Great picture btw, I think I can see the bit you mean, under the starter and then the other end of the cable must connect somewhere too but I will just follow the cable back and see.

Fingers crossed this solves it.

I will report back when I have had a go.

Thanks

Alex
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: TheBoy on 02 August 2016, 19:59:02: Cable is part of engine loom, sensor has a socket on end, no cable
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: SR-71Blackbird on 04 August 2016, 15:50:54: OK my sensor just arrived and it has a cable attached to it, not removable and it has a 3 pin connection. I take it this is not correct?

Thanks
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: Kevin Wood on 04 August 2016, 16:25:12: Quote from: TheBoy on 01 August 2016, 19:10:32
(http://images.omegaowners.com/images/theboy/project_tb2/IMG_2226.JPG)

Oh, what fun and games we had with that tractor donk! :)
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: TheBoy on 04 August 2016, 21:16:58: Quote from: SR-71Blackbird on 04 August 2016, 15:50:54
OK my sensor just arrived and it has a cable attached to it, not removable and it has a 3 pin connection. I take it this is not correct?

Thanks
Not like that on the U25DT and X25DT engines I've seen.
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: TheBoy on 04 August 2016, 21:17:33: Quote from: Kevin Wood on 04 August 2016, 16:25:12
Quote from: TheBoy on 01 August 2016, 19:10:32
(http://images.omegaowners.com/images/theboy/project_tb2/IMG_2226.JPG)

Oh, what fun and games we had with that tractor donk! :)
Notice the fine weather in that picture, unlike "that day" ;D
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: Kevin Wood on 04 August 2016, 22:55:53: Ahh, yes. And no LFF64 under the car complaining about the damp while we ~~drank tea in the garage~~ also got horribly wet. ;)
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: SR-71Blackbird on 18 August 2016, 08:16:23: OK I replaced the Crankshaft Sensor and no change guys.

After max 30-60 mins the revs can start jumping and then it just gets worse until the revs fall to zero and the Automatic Transmission Fault kicks in.

TheBoy, you said you think it could be a wiring issue, it does seem (can't be sure) to start after going over bumpy roads and then it just gets worse.

I can see that the wire for the crankshaft sensor goes back into a bigger wiring loom and that is still wrapped together etc.

Shall I try to zip tie the wire to the wiring loom more securely/stop the sensor wire moving when going over bumps? Any other ideas please?

Thanks all
Title: Re: Jumping rev counter 1998 2.5TD Auto
Post by: TheBoy on 18 August 2016, 21:09:13: No other connectors in that loom until it gets to the large connectors near the battery.