VR6 - No Spark...

[Steve B 0]

Hi, have a bit of a problem with which i would like some advice please..

 

I use my VR once or twice a week. Last used last wednesday it didnt start first time as usual, instead took a 2nd attempt.

 

Go to start it today and it wont start.

 

Now it turns over fine, the following things happen:

 

Fuel pump gives a quick whirl

Turns over, but wont fire.

Fuel pump relay keeps making and breaking during cranking...

Ive tried a working fuel pump relay from another car to make sure that is ok - same thing happens.

 

Ive made sure all relays are seated, fuses are intact.

 

There is no spark at the plugs (from the two i have tried) when holding them to inlet...

 

This suggests coilpack to me, but i understand there are other causes that could be involved.

 

Any help or advise would be appreciated, The car is a 94 VR6 with 66K on the clock, condition is inkeeping with mileage...

 

Also if anyone has any ideas for me to try then i would be grateful, or if anyone has a working coilpack to hand in the Southampton/ Pompey area id be much abliged if i could give that a whirl before spending out on a possible red herring...

 

 

Thanks in advance

[bcstudent 0]

As far as I'm aware it's rare for the entire coil pack to die at the same time. I have a friend with an earlier distributor-engine'd Corrado VR6 with the same problem. He's had the entire fusebox and all relays replaced (long story) and that hasn't cured the problem.

[Kevin Bacon 5]

Can you smell fuel when it's cranking over? If not it's the crank sensor that's gone. When that goes the ECU blocks both the spark and fuel.

 

Now the bad news. Replacement crank sensors are a scandalous £135+VAT from the dealer....and it's dealer only!

 

I have got a known working one (12 months old) which you can have if it proves to be that.

 

Actually, what age is your VR? If it's a 95 it will have a factory immobiliser, but generally when that goes, the engine will start and then immediately stop again, with an error in the ECU of "Engine start blocked by immobiliser".

[Steve B 0]

Thanks for the replies...

 

Its not an immob prob i dont think, ive dealth with them before and this doesnt seem to be sharing the same symptoms.

 

There is no apparent smell of fuel that i noted, i assume that since the fuel pump is priming that fuel is not the issue, the ECU shutting down the feed does sound viable in this case tho.

 

Ive got the battery on charge at the mo due to the good old problems associated with continual cranking... i shall be taking an indepth look on the weekend, and a mate is gonna hook up vag com.

 

Could you please advise me how to locate and test the crank position sensor, am i wright in thinking this should output a pulse in line with crank rotation?

 

I had a quick look last nite but cannot seem to see it, that said i dont know what it looks like so any help/ pics would be much appreciated!!

 

Also what codes are tell tell for the Crank position sensor having failed?

 

 

Many thanks again.

[dr_mat 0]

Trouble is the ECU will always throw a "No Signal" error on the crank sensor if the engine is not turning when you read the codes. If you see "open circuit" or "short to ground" or similar, then you'll know for sure.

 

And yes, if you put a 'scope on the crank sensor output and turn the engine on the starter you should see a nice clean square wave with a gap once per rev..

[fla 9]

Steve B, check the injectors for power when you're cranking it - its abit fiddly to get one of the end connectors out of the ful rail (brown in colour). Anyway, stick a voltmeter across it and if there is no power then check the spark to see if you have ignition, as per Haywires note.

The crank sensor is located at the front of the engine block, on the underside towards the radiator . You'' recognise it by a 5mm thick black lead coming away from the engine block. It may still be ok - certainly give it a clean and clean the sensor mating surface with emery, spray some WD40 on it and see how you get on. The other thing to check is relay 109 for the ecu - remove clean and spray the spade connectors. Then reseat a few times. Check this by applying 12v directly and see if it chatters at all (which it shouldnt). HTH

[Reggit 0]

I've had a similar problem to this; here's my experience.

 

Turn engine over, no start but fuel injection relay switching.

 

Disconnected engine speed sensor - obviously no start, but fuel injection relay not switching.

 

Therefore I assumed speed sensor was good.

 

My problem was quite intermittent, but I finally traced it to the car being damp inside. I had a leaking tailgate, after fixing that and drying car out the problem never returned, except for the time I forgot to close tailgate and it rained heavily.

 

I assumed there was moisture buildup on relay contacts, indead removing all the relays and giving the board a good spray of WD40 before replacing the relays would usually effect a temporary cure.

 

My car is also rarely used.

[Steve B 0]

Cheers for the response guys...

 

Ive got hold of a scope, so i shall check the crank shaft sensor after work tommorow or sat.

 

I think i saw a picture of one with it having three pins, does anyone happen to know which pins the signal should be output on.

 

I havent yet taken a look at it, so forgive me if its obvious, jus wanna get as much ammo as poss for the weekend session....

 

I took a look a relay 109 the other day, i think ill take another look tho since you mention it - i assume it just latched when ignition is applied?

 

 

Thanks again, any more comments more than welcome!

[Steve B 0]

Ive just managed to pop out take a look:

 

Relay 109 is working fine, latches and holds, and give +12 when held.

 

Also had a quick poke around for this crank shaft sensor - am i right in thinkin its an absolute sod to get at, seen a chuky wire going from a plug to the block, cant even see the sensor and apart from strippin the front end, dont see how i can..

 

I havent had the engine covers off yet, again i shall do this tommorow - any more info on sensor location (or possibly pics?) would be cool - sorry to labour the point...

 

 

Thanks

[Kevin Bacon 5]

Crank sensor is easy.....follow the wires on the front engine mount. You want the wire with the white plug. Follow it down to block, it's right next to the bell housing. Probably best to jack the front up so you can see it better.

 

5mm allen head bolt.

 

Take it out and see if it's covered in swarf, which can sometimes affect the sensor's resolution....but when they're dead, they're dead and there's nothing you can other than walk to the dealer!

[Steve B 0]

Cheers for that, much easier as you say with the car jacked.

 

Ive done a quick check of resistance across pins 1 + 2, am getting 544ohms. Does anyone know if this is in tolerence of out...?

 

Im gonna scope it tommorow when i get the chance before taking it out, see if there is any signal present.

 

 

Thanks again i shall return the results when they are in!

[fla 9]

yeah thats about right, it should be anywhere between 500 & 700 ohms, although that is just a static test. If you've got an oscilloscope, wave some metal in front of it with 12v applied to the sensor and see if you get a reading. Better still if you can borrow one from someone to try, that'll rule it out one way or another.

[Stan 24v 0]

If it does turn out that you need a coil pack, I have one here mate ;)

[Steve B 0]

Excellent, cheers fella:

 

Jus hoping to get a conclusive result either way, should have some more news by tommorow evening all going well....

[Steve B 0]

Seem to have sorted the problem...

 

Had hte car on charge for the past two days via maintainer, also uplugged the crank sensor loom and took a resistance reading.

 

Was kinda hoping that the charge would sort it out, which it has.

 

Is there some kind of cut off for the ecu or coilpack that doesnt let it fire below a certain voltage?

 

The engine was cranking fine, but this is all i can logically think of to be honest...

 

Its on trickle full time now, so hopefully thats the end of it -

 

cheers for all the adivce and opinions guys, very helpful indeed. Nice one!

[dr_mat 0]

The ECU needs > 8v I think to maintain the car running, but let's face it, if the alternator is turning (which it was), it will be seeing an easy 14v constantly, so I doubt that's your fix..

[bcstudent 0]

I agree; I suspect, like my mate and his Corrado, you'll be seeing this problem again.