VR6 engine speed/position sensors

[bcstudent 0]

My mate's 1993 (distributor) Corrado VR6 has just died again. A few weeks ago it stranded him outside another mate's house when it lost it's ability to spark and refused to start when it was time to leave. After a couple of hours of poking and wiggling it became clear the the fuel pump was doing its job but, while it would turn over fine, it failed to start. We pushed it into the drive and left it. A couple of hours later the mate whose house it was tried again and it started.

 

It's been fine until today when it did the same thing again, but this time leaving him stranded at work 20 miles away from home. The RAC recovered the car and suggested the engine speed sensor was at fault (after almost no tests apparently, including no VAG-COM).

 

By the way, it's never hesitated or cut-out whilst driving. It just fails to start sometimes.

 

Anyway, he's ordered what he described to me as a "crank position sensor" for £40. I was under the (possibly misguided) impression that the non-coilpack VR6 had a Hall sensor rather than a crank position sensor.

 

I'd appreciate it if someone in the know could tell me what year of VR6 had what in the way of crank/cam/Hall sensors and what their function is on the car exactly.

 

Thanks in advance.

[dr_mat 0]

Crank position sensor is one-HUNDRED and forty pounds, so I doubt he's getting one for forty quid.

The VR6 sensors are:

 

crank position: £140, engine will not produce fuel or spark without it

cam position (aka hall sender): £40, timing will be off, loss of power without it

knock sensors: ~£50 each - two of - one on the front, one on the back of the block. See above.

 

And yes, the dizzy VR has the hall sensor included in the dizzy.

 

It is quite possible his crank sensor is faulty, and tbh once the engine has stopped turning, it's hard to diagnose. Stick it on an oscilloscope and you should see a nice square wave. Typically if they're failing the waveform gets indistinct and typically it's worse when the block is hot, and comes back to normal-ish when everything cools down.

 

I think, but could be wrong, that pretty much any other sensor being dead would just mean the car runs *badly*, but without the crank sensor you're going nowhere.

 

Check for spark. If there's spark then the crank sensor is fine.

[bcstudent 0]

It was the price that concerned me the most after reading the £140-mutterings in the other 'fuel but no spark' threads. Hence this thread to find out what he may have bought. The 'crank position sensor' description were his words, not mine. It seems to me that the dealer has sold him a cam position sensor for a coil-pack VR6. Clearly not ideal!

 

The thing is, the fault has been intermittent and has only (so far) happened when cold. There's deffinitely fuel at the rail but no spark when the fault occurs. From what I can gather, it's likely to be either the crank position sensor or the ECU relay causing the problem.

 

Oh yeah, where does the crank position sensor live on the engine?

[RW1 0]

Oh yeah, where does the crank position sensor live on the engine?

Front nearside on block above sump pan lip (near the front engine mount)

 

.

[Supercharged 2]

Have you ruled out imobiliser if fitted and ignition switch?

 

Change the critical relays anyway if they have not been done along with the BTS...

 

You need to VAGCOM it before spending money on a Crank sensor or dizzy as they are both over £100...

 

Also maybe worth checking oil is not contaminating the hall sender in the dizzy...

 

The crank sensor (G28) plugs in on the lower right hand side of the block held in by a single bolt...

[dr_mat 0]

When you say "there's fuel at the rail" - well yeah, but are the injectors putting fuel in the cylinders? If there's no spark I suspect they're not.

Definitely worth checking that ECU relay from what I've heard on here.

[fla 9]

Yep, change teh ECU relay, if only to rule it out. Its only £12 from teh stealers so not too pricey unlike teh sensors. Plus i would suggest you do the wd40 trick - spray the relay spades and reseat the relay in the panel a few times to ensure the panel contacts are clean. Then deffo stick it on VAGCOM.