DX Fueling and Starting Issues

[dneill101]

Hi,

Having a bit of an odd problem with my Scala in that the car is near impossible to start with the cold start injector connected, both cold and hot, but fires up immediately when it is disconnected even when cold? By disconnected I mean the 2 pin plug removed from the injector. I've read that it should be very hard to start with it disconnected? I have checked the mixture and set it by leaning it out until it starts to stumble and then turning it clockwise until it smooths out and checked with a colour tune kit. Timing is all correct and the car runs perfectly and returns good mpg so this suggests fueling is all good, its just odd that it wont start with the cold start injector connected. All I can think of is that when the injector is active it is throwing too much fuel into the manifold making it far too rich?

I've also noticed that the idle screw is all the way in so I can't bring the idle below about 950rpm, I've checked everywhere for air leaks by spraying carb cleaner etc and found nothing. I also cleaned out/checked everything when I had the head off. Is there anything else that could cause this?

Has anyone else had these issues?

Thanks
Dom

[BlackGTX]

may be the seals on the 5th injector need replacing

[dneill101]

may be the seals on the 5th injector need replacing

Did check and reseal the injector when I had it out, next time I'm home from uni I'll try and test the injector flow and go from there.

[BlackGTX]

warm up reg can also be a starting problem

[mark1gls]

The problem you have is the injectors are worn and leaking fuel into the cylinders when the car is switched off, that is why it starts better with the 5th injector unplugged, I ran for 18 months with a 5th injector till I fitted new injectors.

The fuel system is kept under pressure when you switch the engine off to help with starting.

Does your car start with the 5th injector plugged in and when you press the accelerator and runs lumpy as if it's flooded with petrol and runs fine once warm as the extra petrol is burnt off then I recon its the injectors.

You can remove them and check the amount of fuel coming out and check if they leak but it's not always easy pulling them out.
Guide in Haynes manual on getting them to spray and how much fuel comes out, spray pattern etc.

The 5th injector is should only work when the engine is cold, a sensor on the front of the head tells the injector to spray fuel in, its brown in cooler and has 2 wires coming from it, thermo time switch is its proper name.

Normal for the idle screw to be right in and idle speed should be 950-1000 rpm, I run mine at 1000 as it's a little smoother set up like that.

[dneill101]

Leaking injectors would make sense since I know it's recommended to replace the injectors after about 135k and they are on 150k now. It is possible to start it with the 5th injector connected but usually runs very lumpy and stalls after a few seconds. Getting the injectors out to test them shouldn't be an issue as I had them out not long ago so I'll do a spray test when I can and probably replace them anyway for peace of mind.

Thanks

[mark1gls]

Your problem sounds just like mine.
I'm on my third set now after 284,000 miles and 24 years of owning my 1988 Mk1 Golf Gti cabriolet.
There is 2 types of injectors, later type - air shroud type which have a cap on then end of the injector and an air hose going the the head between cylinders 3 and 4, or early type - non shrouded type with no cap on the end of the injector.

later type are now getting harder to get so the price has gone up.


Pull them out and test them, pull out the fuel pump relay and the relay below it, take the reply from below and get it to fit in the fuel pump relay socket in the fuse box, the fuel pump should run as soon as the ignition is turned on, lift the air flap in the metering head and fuel should spray out of the injectors, spray them into some jars then clean with a cloth and wait to see if any petrol drips out on to a bit of kitchen towel, it may take a few minutes.

[mark1gls]

Forgot to add, fuel injectors also have 2 types of thread, fine and course.

If the car starts ok with the 5th injector unplugged it and run without it. Don't leave it to long though, as you have messed with the mixture get the car to a garage to test the CO mixture and set it to 1.5%.

If you are changing the injectors for new very soon get the mixture set up after they are fitted.

Are you running on super unleaded?

[dneill101]

284,000 miles is impressive haha. Thanks for all the info that's very helpful, mine are the later type so I'll keep a look out for some new ones but in no great rush as I won't be using the car much for the next couple of months while at uni. I've been meaning to get the car down to the local garage to get the CO set correctly when I have a chance and yes I am running on super unleaded.

[mark1gls]

When you have an MOT they will hook the car up to test the mixture and usually give you a print out of the settings, if your MOT is soon might be worth seeing if they could adjust the CO for you?

You may need to use a friendly local garage to do this as expect some bigger companies like Halfords, Kwik fit etc may not want to do it.

[dneill101]

Had an MOT a few weeks ago and there wasn't an issue then but having fiddled with it since then it can't do any harm, I know the guy at the local garage so that shouldn't be an issue.

[mark1gls]

Not telling you "how to suck eggs"... be careful not the press down to much when adjusting the mixture screw or you will be pressing on the air flap and that will affect the reading.

Handy having a mate at a garage.