2.1 DJ won't fire up after head rebuilds

[silverbullet]

Is you fuel pump working or getting 12v? How much petrol is in the tank and how old is it?

[ajsimmo]

Is you fuel pump working or getting 12v? How much petrol is in the tank and how old is it?

It seems so from his initial description, Ian.
"Injectors - removed and held them over a plastic pot. All are pulsing with conical jets during cranking."
This one has the hive mind pondering....

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[DJBuddy]

Pump definitely running! It primes on the ignition. Injectors pulsing as above.

The fuel level is low and it's old. Next step is to top up with a Jerry can but I won't get a chance until we're back from holiday now

[DJBuddy]

Ok, back on it now.

Replaced spark plugs.
Put 20l of E10 fuel in.
Adjusted the position of the chassis connections on the LH cylinder head.
Nothing...

Isolated one injector and spark plug. Set up my camera to film in slow mo. I could see the injector pulsing 4 times per cycle which surprised me as I assumed from the wiring diagram that this was a sequential injection system.
Found the VW workshop diagnostic manual for Digijet. This confirms that it's a batched injection system which means that injector order makes no difference whatsoever.

I went through the diagnostics procedure as best I could (some tests require the engine to be running) and it largely checked out. Coolant temp sensor value is good. Airflow meter checks out. Throttle switch is working. Grounding the centre pin of the dizzy plug triggers the ignition amp.

I hooked up my timing gun and confirmed that cyl 1 is pulsing at TDC when cranking.

The only time it shows any life is if I disable the pump and spray Easystart into the intake. It will fire immediately but cuts out after about half a second. If I keep cranking it does this repetitively every 2-3 seconds. I pulled out the tube from the idle valve so I could spray directly into the intake trunk so possibly it's because I'm bypassing the airflow sensor (the flap won't be moving because air is coming in behind it).

My gut is telling me that the ignition and timing is ok. It feels like it's something with the fuel. I'm running out of things to try...

[silverbullet]

Weak spark, I thinknthis has already been mentioned. Coil may have fallen over or more likely the TCI amplifier has failed or is failing.

Is the idle air valve buzzing when you switch the ignition on? Its often not loud so if thats gone then it might be failing to run because of inadequate air.

[DJBuddy]

Yeah I was concerned about weak spark as well, hence changing the plugs (as you know, v difficult to clean off they're fouled).
I did actually buy a new Lucas ignition amp but when it arrived I suspected to be counterfeit Chinese part. Tried it quickly, no difference so I'll return it.

Oh and yes the idle valve is buzzing.

So....
Just now, went out and tried some more Easystart in the intake, refitted the idle valve. Got my wife to crank at at the point of firing I plugged the fuel pump back in - she busy into life!

Very strange, I can't figure it out. It's a bit rough but idles. I'll let it cool down and then check the tappet settings.

[silverbullet]

This rings a bell. Engine that cranks with no fuel pump, but when not cranking the fuel pump works.
I can't remember the cause though. Faulty fuel pump relay?

[maxstu]

Test with another ECU.

[DJBuddy]

This rings a bell. Engine that cranks with no fuel pump, but when not cranking the fuel pump works.
I can't remember the cause though. Faulty fuel pump relay?

No, the fuel pump was running when cranking etc, it just felt like it was flooding. What I did was use Easystart and then plugged the connector back in during cranking just to prevent the initial flooding with fuel. Literally everything was checking out, so strange...

[DJBuddy]

Test with another ECU.

Possibly, but it's running now. I'll see how it goes.
Whatever was causing it to not start has to be attributed to the work I did. Everything was working fine before I stripped it. It's not impossible but would have been bad luck if an electronic module failed in the time it was laid up.

[maxstu]

My ECU failed without warning. Stopped for fuel. And that was it. Not controlling fuel injectors.

[silverbullet]

I have a failed DJ ecu which just continually sprays fuel in and floods the engine, I guess that the transistors that fire the injectors (actually they short them to earth to energize the coil and inject fuel) have failed in the closed state.

[DJBuddy]

Running sweet now, turns out it was the tappet adjustment.

After I refitted the heads, the process of turning the ending over by hand to set each cylinder to TDC caused the tappets to collapse. I tried my best to set the rockers but the slack in the tappets caused ALL of the adjustment screws to work themselves loose!
After running the engine long enough to build pressure back up in the tappets I set the rockers correctly and now it starts and runs beautifully.
Took for MOT on Friday. A total of 9 miles covered since the last one...

Thanks for help and suggestions everyone, it helped to eliminate a lot of potential errors.

[StevePotts]

I have a failed DJ ecu which just continually sprays fuel in and floods the engine, I guess that the transistors that fire the injectors (actually they short them to earth to energize the coil and inject fuel) have failed in the closed state.

Similar Issue : 2.1 DJ ‘overfuelling’
Hi.  Can anyone help me please?
I have a 2.1DJ that now refuses to start.  I’m fairly knowledgeable about thing mechanical until it comes to fuel injection systems which is where I think the problem lies.
It’s turning over but won’t fire.  Taking the plugs out they’re wet.  Very wet.  Dry them off and they spark as they should.  Taking the injectors out they spray continuously whilst the engine is being cranked (continuous spray, not pulsing).  I don’t think they should be doing this, but I’m not sure and I’d really appreciate someone confirming or denying it.  If that is wrong, then would I be correct in suspecting the ECU?  And if so, any recommendations for repair.
Many thanks in anticipation.

[Aidan]

Bentley manual doesn't make it clear it just shows conical spray pattern, but doesn't say if it pulses; I wouldn't be surprised if it was correct if continuous, when you start, there's a signal to ECU which says 'we are starting' and so ecu would throw fuel in, especially when coolant and air are cold, doesn't matter if rich so the engine starts, as soon as you release the key back to run position the idle control system takes over and runs the engine
So I would double check is the Air flow meter connected ?
Are the leads connected to the correct plugs ?
Does the idle control switch work correctly ?
Is the air bypass valve pipework all good, the one under does split

What has changed since engine last ran ?