HELP! Any Electrical gurus around Oxford?

[poll250 0]

I've posted about this a few times before but it seems to be getting more random.

 

My car completely died today 3 times on the way to work.

 

Once going round a large roundabout it cut out completely while still on the throttle, it restarted after 10 mins.

 

2nd time I was slowing for a toll bridge and it started stuttering a bit, lifting my foot to 'jump' start it while still at about 20mph didn't really work (as it normally should). It restarted after 25 mins, I left it idling for a couple of mins to check everything was ok and it just died, and would not restart.

 

By this time my dad had arrived as I had a meeting I needed to get to, so I left it until lunchtime. Just picked it up and it was fine on the drive home.

 

There's no kind of pattern to when it will do this, it's done it randomly through spring, summer and now autumn. Most relays and other parts on the car have been changed, so I'm guessing it's either an earth issue, or the battery is goosed?

 

Is there anyone around Oxford who is good with tracking down electrical problems, I really don't trust any garages to track this down properly without costing me an arm and a leg.

[ninja_motors 10]

Is it not a fuel feed problem? Crank Sensor as suggested sounds a good bet

Edited November 8, 2011 by ninja_motors

[Kevin Bacon 5]

That is classic crank sensor failure. Eventually it will get so bad it won't start at all.

[poll250 0]

Dang, the crank sensor was brand new 18 months ago.

 

Is there a way to test it?

[Kevin Bacon 5]

Really? Was it a proper VW one, or a cheap chinese copy from "World car parts" or ebay?

 

Hmmm, well in light of that it's unlikely to be the crank sensor if it's a new VAG one *. I'm assuming you have a Walbro in-tank pump? When it's doing one of it's can't start, won't start tricks, can you hear the pump on the ignition? I have the same pump and it's very audible on the key!!

 

* - You can indeed test it. Remove it and connect pins 1 and 2 to a voltmeter and then wave a peice of steel in front of it with no more than 2 or 3mm air gap. You should see a voltage spike of 0.7-1V as you wave the metal past it.

[poll250 0]

re: the other thread, The CAM sensor was new, not the Crank sensor!

 

It is a Walbro in tank pump, and when 'IT' happens, I can't normally hear the pump prime. I know when it's about to start again, because when I turn the key the pump starts priming, although it can take a couple of further goes/mins to start after the pump initially priming.

 

Am I right in thinking that the ECU sends a signal to the fuel pump relay before it sends one to the Crank sensor? How do the two interact so that if the Crank sensor is duff, the pump doesn't prime?

 

If there is sufficient pressure in the fuel rail, do you always need the pump to prime in order for the car to fire up? I would imagine there would be residual fuel in the injectors/ fuel rail to restart the car immediately after dying.

 

Thanks for the help so far :)

 

---------- Post added at 04:05 PM ---------- Previous post was at 03:18 PM ----------

 

I just went and disconnected the Crank sensor, and tried to start the car,I heard the fuel pump prime and there was a ticking from a relay, and obviously the car cranked, but didn't fire. Hmmm, I don't wanna splash 110 on a new sensor if it's not gonna fix it!

[DANG60 0]

I had a similar problem with a mk3 golf gti turned out to be the Ecu control relay. Worth a try, it was only about a tenner 3 years ago.

[Kevin Bacon 5]

It could be the fuel pump relay if the pump is only heard working intermittantly. It's number 167. you can also bypass that by running a couple male spades across the 2 fat terminals on the fuseboard and see if it starts then.

 

If you disconnect the crank sensor it will never start! Without a signal from that it won't fire the injectors or coils at all.

 

As I said before that kind of random cutting out and reluctance to start again is definitely symptomatic of a failing crank sensor, but start with the cheaper things first, such as the ECU and fuel pump relays.

[poll250 0]

I only disconnected the crank sensor to see if it had an effect on he fuel pump priming, which it didn't :)

 

Both the ecu and fuel pump relay have been replaced.

 

Curious!

 

Btw does anyone have the part number for the crank sensor?

Edited November 8, 2011 by poll250

[mikkijayne 0]

Have you changed the ignition switch yet?

 

The crank sensor is 021 906 433A. The seal for it is 021 906 445.