Probable failing Crank Position Sensor

[Stephen Edwin]

My recent query about how to change the crank position sensor was not just idle curiosity. The 240 SE B200F has for a while been sometimes not quick to start. As if it had damp. Once under way it has behaved well. Other times it has started on the button.

This afternoon to come home it took about half a dozen tries. Every time it fired but would not hold the revolutions. And then it did work so I drove the car and it behaved basically perfick. None of which fits with damp.

(No signs of damp in the atmosphete this lovely sunny day. I confess I didn't do a dispersant spray on the HT.)

I remind myself that:

Originally Posted by Clifford Pope

In my experience they [Note by Stephen now: The context was the ignition amplifier] either work or fail totally.
I've had two fail, on different cars. One was nearing home when the engine suddenly stopped dead, and nothing would make it restart. I swapped in a spare amplifier and it started first shot and was trouble-free afterwards.

The other cut out while the car was idling in the drive. Again, a replacement fixed it.

I've once had a AMM fail. The car suddenly started running badly, spluttered, the lambda light came on, and it cut out. It started again, and ran reasonably well, not quite up to par. Diagnosis showed it was the AMM.
I think when they fail the system switches to a limp-home mode, which is a default setting which is almost OK - useable, but poor.

Poor or erratic starting I've found is usually the CPS. I had trouble with one over a period. Mostly the car started instantly, at other times it refused to start, but always did eventually. Once started it ran fine. I think it might be the wires or the insulation fraying, so might depend on engine movement, rather than a fault actually in the sensor body.

The fuel pump relay can go at any time, either spasmodically or suddenly. So too can fuse contacts. As in my experience this is easily the most common cause of poor starting or misfiring, I'd always;
1) - twiddle fuses 4 and 6
2) - jump terminals 4 and 6 with your handy short lead with a clip on each end. This bypasses the relay and runs the pumps continuously.
3) swap the amplifier

Those are quick tests, done in seconds, with a good chance of getting you moving.

The air mass meter was new less than a year, less than 1,000 miles ago.

The fuel relay fuses are good, blade fuses newer than the air mass meter. And once started the engine ran good so I'm not doubting the relay, yet.

Not a total engine stop as would usually be for the amplifier.

So I reckon, reasonably likely to be the crank position sensor?

.

[AlexO]

Stephen, apologies for not remembering what vintage your car is but isn't this fairly straightforward to diagnose if you've got a diagnostic box? When my CPS went a couple of years back that pretty much solved it right away.

[Clifford Pope]

It's code 2-1-4 I've just looked up. It seems pretty specific.

(If your black OBD box works. Mine has never shown anything, even after swapping for a known working one)

[Stephen Edwin]

Thank you both.

Oops. I forgot this might show on the diagnostic box....

I will check. If there is no code, what else might the symptoms indicate?

[Stephen Edwin]

Interesting.

ECU code: 3-2-2 Mass Air Flow sensor burn off signal missing or faulty. (MAF wiring fault).

EZK code: 1-1-1

I suppose I should start by cleaning and wiggling the air mass meter connector?

Or....?

[Stephen Edwin]

I haven't been able to do much today. I have been told by FRF Volvo dealer parts department that the ECU is available from Volvo Classic Parts. They also said this model of ECU doesn't fail very often. Obviously I hope this is a wiring issue....although that can be difficult to trace.

Next I think I must get out my multimeter and check if the ECU does provide a burn off voltage when the engine is switched off. And check the Air Mass Meter connection is firmly seated.

Where is the ECU please and, what does it look like? I should check if that is seated OK in its connector(s).

[Dirty Rooster]

Originally Posted by Stephen Edwin

So I reckon, reasonably likely to be the crank position sensor?.

Those symptoms do NOT sound, to me, like the CPS.

[Stephen Edwin]

Originally Posted by Dirty Rooster

Those symptoms do NOT sound, to me, like the CPS.

Thank you.

At the moment we have :

1. Those starting symptoms.
2. Lean running indicated by the very recent MOT Lambda results.
3. Good or maybe excellent low CO and particles MOT results.
4. Lower than usual mpg for a while now.
5. 2-1-4 code
6. Lambda (engine management?) warning light is NOT illuminated.
7. I have noticed the gizmo is damaged. I can never remember the name. It is under the inlet manifold and has a tube that goes down in to the oil sump. I've got a new one ready.

Otherwise, all seems to be good. But this is worrying me. I don't currently need to use the car and other non-car stuff is overwhelming me. So I will be slow re this problem. But questions are weighing on my mind:

What checks can I do beyond my plan to check for a burn off signal and check connections are well seated for MAF and ECU?

Where is the ECU and what does it look like?

Is this the sort of thing that a garage could do more specific tests to solve? If one can find a garage with the experience re these cars.

Is there a test device that I could use, beyond the built in code reader?

[Clifford Pope]

I agree it doesn't sound like CPS. In my experience the car either starts perfectly as normal or totally fails to fire. After retrying, when it does start eventually, it runs perfectly. You wonder how there can possibly be anything wrong - until next time it does it.

I don't see how there can be no light displayed on the dash but codes on the black box. I thought that was what the light meant - there are codes waiting to be read. Presumably the bulb works and it comes on with ignition before starting? Anyway, there are codes, which ought to help.

It's hard to say where to go next, but the lambda sensor looks a likely culprit? They don't last forever, get tired and sluggish, or the wires perish from heat and movement. They are quite cheap I recall. (Tip for removal if you can't budge it - remove the cat section of pipe, clamp the sensor shank in a heavy vice with the cat upside down on top, then just use the pipe as a hefty lever.)

The unit underneath the inlet manifold with a pipe into the sump is the black box oil separator. The pipe on top connects to the flame trap, and then to the air intake. The thin pipe from the side of the flame trap connects to the inlet manifold. It is all part of the engine block/sump breather system.
If any part of it is blocked, or connection leaking, then either won't be breathing properly, or the little inlet pipe will be drawing in too much air.
The box itself condenses any oil mist from the sump and lets it dribble back down the pipe.
The box is notorious for gradually filling up with baked carbon, like a disgusting old smoker's pipe. It can't really be cleaned effectively if choked.
If it's broken and letting air be drawn in, can that affect the mixture?

(Tip for removal. It gets fragile with age, especially the oil pipe, and if you break it in removal the bits fall into the sump. It needs a straight vertical pull to clear the rubber seal, but there is hardly any clearance under the manifold.
Some advocate removing the manifold. My trick is to cut off the lug on top which holds a clamp for a wiring harness. If the replacement won't go back in, cut it's lug off and use cable ties to hold the harness.)

Sorry, I can't think of anything else. I'm out of my depth beyond basic CPS, Ign Amplifier, and Lambda sensor replacement, and not very good with the codes.

[Stephen Edwin]

Originally Posted by Clifford Pope

I agree it doesn't sound like CPS. In my experience the car either starts perfectly as normal or totally fails to fire. After retrying, when it does start eventually, it runs perfectly. You wonder how there can possibly be anything wrong - until next time it does it.

I don't see how there can be no light displayed on the dash but codes on the black box. I thought that was what the light meant - there are codes waiting to be read. Presumably the bulb works and it comes on with ignition before starting? Anyway, there are codes, which ought to help.

It's hard to say where to go next, but the lambda sensor looks a likely culprit? They don't last forever, get tired and sluggish, or the wires perish from heat and movement. They are quite cheap I recall. (Tip for removal if you can't budge it - remove the cat section of pipe, clamp the sensor shank in a heavy vice with the cat upside down on top, then just use the pipe as a hefty lever.)

The unit underneath the inlet manifold with a pipe into the sump is the black box oil separator. The pipe on top connects to the flame trap, and then to the air intake. The thin pipe from the side of the flame trap connects to the inlet manifold. It is all part of the engine block/sump breather system.
If any part of it is blocked, or connection leaking, then either won't be breathing properly, or the little inlet pipe will be drawing in too much air.
The box itself condenses any oil mist from the sump and lets it dribble back down the pipe.
The box is notorious for gradually filling up with baked carbon, like a disgusting old smoker's pipe. It can't really be cleaned effectively if choked.
If it's broken and letting air be drawn in, can that affect the mixture?

(Tip for removal. It gets fragile with age, especially the oil pipe, and if you break it in removal the bits fall into the sump. It needs a straight vertical pull to clear the rubber seal, but there is hardly any clearance under the manifold.
Some advocate removing the manifold. My trick is to cut off the lug on top which holds a clamp for a wiring harness. If the replacement won't go back in, cut it's lug off and use cable ties to hold the harness.)

Sorry, I can't think of anything else. I'm out of my depth beyond basic CPS, Ign Amplifier, and Lambda sensor replacement, and not very good with the codes.

Thanks Clifford. Ahem. If you are ever out of your depth I should give up hope for myself. !!!!

So the opinions increase, not the CPS. And I think that could be said to be because the car does not even try to start when CPS is playing up. Nothing like damp symptoms. ANd of course the code is wrong.

I tried the car this evening. Yes the Lambda light was on when I turned the ignition on, and went off when I started the car. And. The car started quickly and easily.

I'll clear the code, run the engine, check the code reader again. And check with a multi meter for a burn off signal, before and after wiggling the MAF connector.

Where is that ECU please and what does it look like? So I can check that connection.

*****

Aha the oil separator, thanks. I'm wondering which bits I should remove or perhaps detach to get good access and how to detach them "efficiently" and without disturbing e.g. the fuel supply. That should perhaps give a better chance of a straight pull?