fuel injectors

[casinoblue]

hey guys,

my mk2 16v is struggling to start after a head rebuild.

I think the problem lies in the fuel system. The main pump primes when turning on ignition. Have tried removing injector 1 and firing it into a jam jar, but i get one squirt when the ingition is turned on, but then nothing when turning over. surely the injector should be firing every rotation?

any ideas?

thanks,
james.

[Conker]

No, they only start to fire properly once the engine starts.

You can bridge the fuel pump relay to make them "live" (I used a bent bit of wire), and then gently lift the metering plate above the air filter to make them fire.  This is very dangerous though so take every precaution, and don't even attempt if you haven't got some kind of fire extinguisher - better safe than sorry.

Top tip for lifting the metering plate:  Stick a piece of masking tape to the top of it to form a handle.

[Conker]

Forgot to add...

1) Also remember that if you've only got one injector out and keep lifting the metering plate, you will be filling the other cylinders with fuel!!.

2) You need the ignition on while your doing this, but its bad for the coil to have the ignition on for too long, so be quick!

3) If you need new injectors, get some brass mercedes ones off ebay for about the same price as having them cleaned (I paid £17 each)

4) If you've had a head rebuild, I would suspect somethings amiss with that, not the fuel.  First, I would double check your static timing!!

[casinoblue]

thanks conker,

have triple checked the timing several times and all marks line up perfectly.

the engine turns over fine, just won't fire up. have spark and replaced dizzy, arm, and leads.

a bit stuck now

cheers for the info tho

[Conker]

Few ideas...

Have you checked your getting a spark at the plug (pull the plug and earth it against something safe and turn the engine over)??

Also, once my 16v needed a bump start after some repair work, despite having plenty of juice in the battery to turn the engine over. I presumed it was something to with priming the engine or something like that.

Oh, and apparently another good tip is to repeatedly (at least ten times) turn the key round to the first stop where the fuel pump primes but doesn't turn the engine over, as this makes sure your got loads of fuel pressure and no air locks.

Finally, I have been known to regularly forget to re-attach any/all of the vac pipes, which can make starting difficult. My most common culprit is the big rubber one on the back of the intake manifold.


Good luck!

[mattkh]

hey guys,my mk2 16v is struggling to start after a head rebuild.

Hi
Have you done a compression check.

[casinoblue]

haven't done a compression test yet no. have replaced all the top end gaskets, stem seals and re-lapped all the valves so all should be good on that front. it felt like there was compression when turning the engine by hand.

that will probably be the next check, once i've triple checked the simple stuff again.

thanks both for the replies and info