SCALA INJECTION WILL NOT START WITHOUT HELP!!

[mattg34]

Hello all. Im getting desperate to sort out the starting on my 89 scala injection! It will not start first thing no matter what the outside temperature. It will turn over fine and eventually fire after about ten or fifteen secs then run about 500 rpm and a little rough for about 30 secs then settle down to 1000rpm and run perfectly. The only way to start it a present is to apply lots of pedal to make it catch. My mk1 golf with the same engine fires up first time alll the time instantly so there is clearly a problem with the rocco.
The car has had the following work done
injectors removed and seals replaced
FITH injector working fine
new cambelt(timing set correctly)
new metering head in 2004
plugs changed in 2011
rotor arm cap and leads 2011
The co level has been set to 2%
The wiring to the avv and the wur has been checked for supply and seems ok
the wur and the aav have been cleaned out
The ribber o ring on the idle screw has also been re newed.(filter also clear)
the lift pump has been checked for operationn and seems to be working fine
New fuel pump relay
fusebox removed and cleaned out and all fuses replaced with new
relay contacts checked and cleaned

Once the car has started it runs very well and will start every time instantly uness it has been left for a while ie an hour or so wheich again it requires only a small amount of pedal to get it to fire.
I m ust add at this point that i have changed the tank and filler neck as these iteams had become rusty, the fuel filter has also been changed as this was full of crap and small amounts of rust. This starting fault had also occured before all this had been changed to.

My initial thoughts are loss of pressure in the system, timing adustment or maybe a fault with the adjustemnt on the plunger on the metering head????
I am running out of ideas and would welcome any advice you guys have, i am a vw audi mechanic myself but i always like to hear from the experts!!!
If anyone is willing to take a look or do a pressure test on the car i can pay them a few quid and plenty of tea and biscuits!!!

Many thanks guys :

[PeteGLi]

Have you checked all your vacuum hoses are ok and none have perished? The short one on the front of the inlet manifold tends to get very soft and perish.

Have you had your fuel system pressure checked - both cold and hot, and that none of the injectors are leaking?

If the pressure is dropping when the engine is not running, then this could cause the difficulty starting.

DX engine CO content should be 1% plus or minus 0.5%.

Timing depends on what fuel you are using - 98 or 95 RON. It is 6 degrees with 98 RON and 0 degrees with 95 RON.

Hope this helps.

[mattg34]

Hi pete thanks for getting back to me. I have checked the vacume pipes and have sprayed carb cleaner over the manifold arae to check for air leaks it all seems fine to be honest. Im also thinking like youself that it may be a fuel pressure issue but i don't have any testing equipment which is very annoying as i want to get this sorted asap!!. I will check the timing again this weekend and re check the co level also. Thanks again Pete, any more ideas throw them my way.

[PeteGLi]

The easiest check is whether the injectors are leaking, as you can do this without any special equipment. You just need to pull the injectors out of the head, and put them into a jar, get some fuel flowing through them and then when you stop the flow, see if any of them continue to drip.
If any of them do, then that injector needs replacing.

[mattg34]

I'll give that a go Pete, thanks again. I'm thinking the best place for injectors is gsf or euro, unless anyone knows me a cheaper place? I'll update any progress on here.

[bensspares]

my experience says that the engine is difficult to start when warm if the injectors are nfu...if they are leaking, by the morning (8 hrs or so) all the fuel has evaporated.this sounds more like a pressure problem, a symptom of this would be poor starting and misfiring on the road whilst opening the throtle. Check the gravity valve, pressure escaping will be evident when you release the petrol cap.

Euro car parts were the best btw, genuine bosch for a tad under £40 each..

[mattg34]

Cheers for the reply ben. I must say I've never noticed any pressure build up when taking the fuel cap off. I've had a modified BMW filler neck fitted to, but the fault occurred before this. Is the gravity value part of the main pump? If so do you know if they can be replaced without changing the whole pump! I'm assuming that if there is no pressure when taking off The cap then there isn't sufficient pressure in the system?

[bensspares]

If there is no pressure noise when removing the petrol cap then it is unlikly to be the gravity valve, this is nothing to do with the fuel pump btw.....

Is the main fuel pump (under neath by axel on driverside) making any noise, ie does it sound like its strugling or is it even running.are you totaly sure the lift pump in the tank is working,

this fault is either fuel presure related or its the cold start system its self,

the HAYNES bible states the reasons why engine wont start from cold, if you dont already have 1 I would strongly recomend that you purchase a haynes, its the reason i can guide you now and helped me gain all my knolege regarding many vw's....It will save you a fortune in the long run

Without sounding patronising, are you sure all the fuel lines are going to the correct componants, ie the flow and return to the warm up regulator and the cold start valve mounted in the intake manifold.

The symptoms you describe at the start of this topic shout fuel pressure problems realy loudly to me. its either 1 of the pumps or incorect mixture on cold start caused by either a faulty thermo time switch, faulty aux air device or the warm up regulator, haynes has all the test proceedures for all the injection componants.

I maybe wrong but it sounds seriously unlikly to be the injectors themselves, when its running, spray some easy start around the injector seals to see if the idol speed increases, ifso, the injectors are not airtight in the head and will be causing a weak mixture and may well be causing the difficult to start from cold issues.

I hope this helps you out, there is nothing worse than everytime you shut down the engine you wonder if it will start again.

[mattg34]

Thanks again Ben for getting back. I purchased a haynes manual the other day so will look into the testing part of the cold start system. I did test the WUR recently and cleaned it it was giving a 23 ohms reading which seems to be within spec. I presume the tts is working as the fith injector is powered off this if im not mistaken and its spraying fine from cold. The AVV has been cleaned up but im still not 100% sure this is working, should this make a noise when running(ie hissing sound?) am i right in thinking if this is not working it causes the mix to run rich?
Both the pumps seem to be buzzing away fine with no noise , although the one in my mk1 cabby seems much louder and this has no running faults at all!!

I think my first attempt this weekend will be to look at the injectors and test the AVV.

Many thanks again Ben and Pete for all the advice

[ianaudia4]

Quick way to check the AAV is to squeeze the pipe when the engine is running and hear for a change in engine note, if none it is not working correctly, simple.
You could also check the micro switch on the top of the throttle body is working, with the engine off you should hear a slight "click" when opening, a lot of these have been farted about with over the years, they were set at the factory and should have yellow or white paint on them i.e leave alone!

Another thing as well is to check the earth strap is fitted to the block, if not this can cause all sorts of weird problems, should connect from the coil to one of the rocker cover studs.

[DT1]

Haven't mentioned the accumulator, it's job is to keep pressure in the system.

They don't go very often, but it's not unknown.

An easy thing to check since you have a 'spare' on the golf.

[mattg34]

That more good advice many thanks guys ill get on it this weekend(other half allowing of course!!)

[bensspares]

The aav increases the idol speed to compensate for the exta drag of a cold engine, you should hear a hiss when its open and as Ianaudia4 states, with engine running when cold, pinch the hose and the revs should drop, when engine warm there should be no change in the engine revs when the hose is pinched.This does not effect the mixture as it is a throttle bypass valve only. Also check the hose for any damage as if this is drawing fresh air it will make the mixture weak and could be causing the cold start issues.

The wur is a valve operated by a bi metal strip in side the unit, when engine cold it allows aditional fuel into the system until the engine is warm enough not to require extra fuel.it is coltroled by temperature, these rarley fail. this is the only device that changes the mixture in the system.

The cold start valve (5th injector) only opporerates for a brief moment when starting the engine subject to coolant temperature and is controlled by the thermo time switch and the mico switch on the throtle valve.

Check all the air related hoses related to the injection system, if any are perished or allowing in fresh air the mixture will be lean and cause the poor cold start issues.

Pressure accumlitor, unlikly to be the cause but a good outsider for the fault.
to test if the system pressure is holding, switch on ignition to prime the system back to pressure.switch off, then with a cloth for catch the fuel, slacken and redo the main feed line from the fuel filter to the metering head. there will be a good squirt of fuel if the pressure is good. then prime the system again and leave for a few hours, then do the same test again, the fuel should squirt exactly the same.if not then you have the answer.

If everything was fine before you carried out the initial work then the fault lies in something youve not done on reasembley...It might just be a leaking air hose somewhere.

[mattg34]

Just a quick update. Unfortunately driving home to work on the scala at the weekend the bloody clutch cable pulled through the bulkhead in busy traffic As much as i love this car its starting to drive me mad!!! I have purchased a mk1 golf repair panal does anyone know if these are the best iteams to use or is there a specific scirocco one? looking at it it looks like i might have to cut holes in the golf one to accomodate the vacume hoses?

On the starting front i have removed the main pump and accumulator to check the operation and generally check it over(that was fun on my back two inches from my face!) Both iteams seem ok but im still waiting to try a second hand accumulator from Mark h on here just to rule it out. Before attacking the pump i left the car for a day and checked the pressure at the fuel filter as advised by Ben and found non at all!! Im am now led to think from the advice from you guys that the injectors could be at fault which is a shame as i could do without the £180 bill for new ones!!

Hopefully at some point this week i will get to check them properly. Out of interest does anyone know which pins you have to bridge on the fuel pump relay holder to power the pump foe the injector test?

Many thanks guys ;)

[PeteGLi]

....................I have purchased a mk1 golf repair panal does anyone know if these are the best iteams to use or is there a specific scirocco one?

There is a Scirocco specific one, but it is worse than usless. The golf one is the preferred choice.

.................... looking at it it looks like i might have to cut holes in the golf one to accomodate the vacume hoses?

Correct.

.................... Out of interest does anyone know which pins you have to bridge on the fuel pump relay holder to power the pump foe the injector test?

The two large ones !