Possible Ecu Problems

[Metal miki 2]

The day I got my GTI it broke down

 

It knocked out while I was driving and won't start again. I've changed the plugs leads distributor cap and rotar arm and Deffo have spark, I also have fuel getting to the rail. I had an auto spark check the alarm and he says it's grand so now I'm stuck.

 

Could the ecu have packed in? Anyone else had this problem?

[Anthony 1,003]

Unlikely in my experience - I don't think I've ever seen a faulty Jetronic ECU.

 

Jetronic is a pretty simple system and easy enough to diagnose.

 

Obvious question - is any fuel being injected?

 

(also, it's generally beneficial to keep everything relating to a given problem in a single topic, rather than having multiple different threads)

[Carbs4me 45]

you sure the spark is strong enough? mine was sparking and still wouldnt start, but it was due to a poor spark

 

I always suggest this, but is it not the ignition amp, as the same happened to me!

[welshpug 1,666]

If you get a decent consistent spark on cranking then you need to check the wire from the coil to the ecu, this will tell the ecu the engine is turning.

 

As Anthony said they are quite simple systems, a friend (who shall remain nameless, Eh Dan... ) spent ages swapping bits around for a few weeks and was getting quite frustrated with it so trailered it up to me.

I fairly quickly found that the three wires on the black plug to the Distributor signal lead had pulled out and were sat half an inch down in the rubber boot it really is often silly little faults that'll bring them to a halt.

Edited April 26, 2012 by welshpug

[Metal miki 2]

I've no idea what's up with it. I'm told there's pressure on the fuel rail so I'm only assuming its squirting into the cylinders.

 

I've only ever rebuilt A series and K series rover engines and messed about with Mitsubishi turbo engines so this thing is kinda strange to me lol. I'm far from mechanically minded but just get bogged in but this has me stomped.

 

When it comes to trouble shooting I'm useless but give me a bigger blower to bolt on or bigger injectors I'm grand.

[Anthony 1,003]

so I'm only assuming its squirting into the cylinders.

Assumption is the mother of all ****-ups.

 

Remove a spark plug - is it dry or wet and smelling of fuel? If you crank over with the plug removed, you'll normally get a noticeable whiff of petrol from the cylinder if fuel is being injected.

[welshpug 1,666]

pressure on the rail does not mean it will be injecting, simply that the fuel pump has primed.

 

you need to see if it actually is firing a signal to the injectors.

 

beaten to it by Anthony

 

 

a power probe and a multimeter is an invaluable tool for stuff like this, a probe can show that a signal is going to the injectors without you having to remove any parts, any decent auto sparky should be able to tell you what is up with it.

[Anthony 1,003]

any decent auto sparky

The key word there is "decent"

 

Most seemingly can give advice on where to tether a horse and the best place to buy a ten gallon hat, they're utterly hopeless at doing their actual job and quite often make things ten times worse...

[Metal miki 2]

The old plugs were wet so that would mean yes, injectors work lol

 

The auto spark hasn't a clue what the hell is wrong with it which really worries me as he's good at what he does.

[Metal miki 2]

Another thing I noticed, when I turn the key in my Scooby or my turbo coupe you hear the walbro buzz untill the pressure is up on the rail then cuts out, on the GTI I can hear a constant buzz that only stops if you turn the key back

[Tom Fenton 1,548]

For the sake of a few quid for a manifold gasket I like to remove the inlet and then crank it over to visibly see fuel being injected.

 

The signal for the injectors and ignition comes from the dizzy, so if you are getting fuel injected this means that the signal off to the ignition side is working. Thus the next thing to check are the bits that take this signal and make it into a spark, the ignition amp and the coil.

[kyepan 291]

or whip the whole rail off, still connected electrically and hydrualically, put four bottles over the injectors, and see if it's injecting.

[welshpug 1,666]

thinking back my 205 did something very much along these lines a few days after I bought it, the AFM + coolant temp sensor and several earths had died and it was chucking an immense amount of fuel in.

[pug_ham 245 3 Cars]

Can you hear the injectors ticking when you crank it over & have you tried a different tachymetric relay?

 

g

[Metal miki 2]

I've had the manifold off already to put a 4 pin relay in to boost the starter and don't fancy doin that again lol.

 

Once I get it home tomorrow I'll start and check all connections in the bay and see if anything looks tired.

 

 

[Carbs4me 45]

Did you put a new gasket on when you took the inlet manifold off? cause they tend to not reseal very well

Edited April 26, 2012 by Carbs4me

[Metal miki 2]

Na, I just cleaned the surfaces up and put a nice bead of high heat silicone instant gasket in. I know some people don't like it but it's great stuff

[Carbs4me 45]

id be carefull with that! if it dont seal properly you might end up fixing the current problem and that been the next

 

Try your horn too! sometimes when the ignition amp goes the horn stops working completely or sounds quite fibble!

[Carbs4me 45]

also any fuel contact with it might cause it to break the silcone up over a period of time

[Anthony 1,003]

Try your horn too! sometimes when the ignition amp goes the horn stops working completely or sounds quite fibble!

Errrr... the horn and ignition amp are completely unrelated

 

A decent RTV type sealant is fine for the manifold too - it's what I've used for many years.

[Carbs4me 45]

strange! the day before my ignition amp went my horn died! i changed the ignition amp it worked fine again. i thought they may have been related!

 

ahh i thought fuel and oil could break down silcone?

[Metal miki 2]

A decent RTV type sealant is fine for the manifold too - it's what I've used for many years.

 

Same here dude. I use it for nearly everything bar a head gasket lol

[steve@cornwall 100]

 

 

A decent RTV type sealant is fine for the manifold too - it's what I've used for many years.

 

I prefer it for inlets, more effective long term than some supplied gaskets, I find, for blocking those pesky extra waterways! Careful not to overdo it, especially at the top and foul the injectors, though..... especially if fitting the manifold complete with injectors and yo don't line it up properly first time!!!