Another engine that won't start

[Keeper of The Kitten]

Ladies and gentlemen of the forum,

My poor little Kitten has been sat around for a while awaiting it's engine swap - now it's ready to happen, but ideally we need to start the engine to warm the oil and drain it. Less messy you see!

Well the car won't start. Not surprising really given how long it has been sat around.

What we do know is this:

The spark plugs are getting power and sparking happily.

The fuel rail is getting pressure.

But the injectors don't seem to be triggering.

...so what is the sage advice from forum members? I am thinking about crank sensors perhaps but who can give me some pointers? I really want to get on and swap the engines but this is sort of holding things up at the moment...

Thanks in advance!

__MDC__

[twoqu]

Hi!

Have you checked to see if there is voltage at the injectors and other sensors?

[Keeper of The Kitten]

The injector relay (?) is on the list to test - will know more soon!

Thanks, any more ideas?

__MDC__

[UrS4boy]

Bad cam position sensor (Hall sender) or back connection to same. Bad crank position sensor or connection to same.

At least for C4 UrS, unless the ECU gets a signal from the cam position sensor, it will NOT fire the fuel pump relay on start-up. Once the car is started, it runs off the crank position sensor. The cam sensor can actually fail while the motor is on (and you get a CEL ) and the motor will still run. However, you will be lucky to get is started again after the ignition is turned off, even for a second.

HTH

Dave F.

[porkkis]

It should't give spark neighter if the hall or crank sensors have failed.

Check the fuses first. The injectors are behind one as they are supplied constant 12v and ecu is triggering the earth side.

[Keeper of The Kitten]

Thanks guys I will get back to you when we have checked this out!

My first thought was also hall sensor but mechanic told me we were getting spark, for sure. So perhaps the fuses are the answer?

I will let you know how we get on!

__MDC__

[CP951]

Similar problem but I had on BMWs in past. Spark, fuel pressure, starter all ok but didnt start. Eventually traced to a large intake air leak from a disconnected / loosely fitted hose from the carbon canister. Hence when starting, air flows in but not via the MAF route. No MAF signal to ECU hence injectors won't inject or start.

[S2central.net]

Suggest to check the silly stuff like fuses and all electrical and earth connections round the engine. The earth straps on the rear of intake manifold are critical.

It will only spark if its getting signals from hall sensor.

An oscilloscope (or test light) on the injector connectors should see those triggering as long as the ECU is happily closing the earth paths.

Check fault codes - it might point to an important connection problem.

[Keeper of The Kitten]

Thanks guys! I'll let you know what's happening soon.

__MDC__

[Jon441cc]

Martin , have look @ fuse #32 (timing III ) that might be the problem

[Keeper of The Kitten]

Cheers Jon - I'm just off to the garage to see what we can do!

__MDC__

[Jon441cc]

Fingers crossed ....

[Keeper of The Kitten]

Right, well it looks like we are getting 12v at the injectors - did a bit of consultation with Martyn (VAG) and he thinks the hall sensor looks a fair bet, so we'll try that!

Hopefully get this old engine out asap, and the g/box, and get on with the replacement!

__MDC__

[S2central.net]

Getting 12V at the injectors is but part of the story. When cranking it, you wanna see switched earth on the other injector pins. Use a test LED or oscilloscope. Thats the only way to see that the ECU is trying to drive the injectors.

If you are getting sparks then I don't see how your hall sensor (G40) could be bad.

Is the pump actually pumping fuel to the rail ?

Fault codes will spot something stupid like open connections if something has been moved and forgotten.

Paul

[Keeper of The Kitten]

Rail is getting fuel pressure, that's no problem! ECU is the same one I've always had but will get the injector switching checked. Simon (mechanic) can check fault codes but nothing has been moved at all yet, it's all the same stuff that was in there when I bought the car!

Simon is pretty certain that it is the triggering of the injectors though, so if it isn't the sensor perhaps it is an ECU problem? It's just that I have been told the hall sensor is the one thing that is notorious for just working one day and then (clicks fingers) never again.

We'll get to the bottom of this!

__MDC__