MK1 Golf GTi - 1.8 DX Engine - Cold Start Problem

Dear Members,

I would like to request for some help please.

I have a MK1 Golf GTi 1983, 1.8 DX Engine.

I have an issue with cold start. I need to crank it several times before I get it ticking, but it is extremely sluggish while the engine is cold. If I tap the accelerator, it has a delayed rev and when it crosses 2500 rpm approx it cuts out. When the engine is hot it runs really good and the accelerator is responsive as it should be. Also the car drives excellent when it's hot.

So far I have checked and confirmed the following:
- Cold start valve and thermo time switch ok
- WUR ok
- Timing ok
- throttle valve setting ok
- checked auxiliary air valve and also replaced, ok
- vaccum pipes ok
- new spark plugs
- HT cables ok
- coil ok

I noticed whenever the engine is cold and I lift slightly the fuel metering unit sensor plate, the engine runs a bit smoother, but if I lift too much the engine cuts out.

Also when the engine is cold and when pulling the throttle cable I hear a thumping sound at times as if the sensor plate is hitting against the rubber housing.

I don't know whether changing the fuel metering head will help. It is expensive and a gamble.

What puzzles me is that I have had the car for 7 years (off road) and when I first bought it, it was running fine. I have replaced the fuel lines and brake lines as they were leaking a couple of years back. It's only recently I connected the pipes up to get the car running again and I have this issue. I have not touched or amended any settings.

I am running out of ideas.

Appreciate your help and input.

Thanks.

Main Fuel pressure?

Ok, I will admit that my knowledge of CIS is very limited.
But I will tell you first hand from years of storing things for winter (about 4-5 months depending on weather), that fuel systems take a beating.

Fuel evaporates from things, it is it's nature.  When fuel evaporates it leaves behind a gooey, sticky residue that is more Lacquer and gummy, than one would think.

I have had to clean out many a Carburetor, Jets, bowls and such over the years to get thing running.  Sure they may start and run dodgy, but I have seen some of the lacquered skin break off and clog filters and carbs.

What with the tank lines swirlpots, accumulators, filters, pumps and CIS fuel distributors, the cavalcade of items that can get corrupted, yours isn't surprising at all.

Often I read "It was put away running great" but then again months years, is going to have an adverse effect on the fuel system.  Fuel goes bad and looses its effectiveness in weeks E-10 gas is worse yet as the alcohol evaporates quicker and dry rots things from the inside out.

Diesel is a little better on the long term, but can grow things in the tank and items like alge.

My 2 cycle guy recommends that you renew fuels after 2 weeks, and always add Stabil to it.  I don't know what Stabil does, but since I have started using it about 15 years ago, I haven't had the need to tear apart a carb, or fuel system on a Car, or a Leaf Blower/Chainsaw or what not since.

I would imagine that you need to carefully take things apart and use a safe type cleaner to remove the residue that your evaporating fuel has left behind, as the fuel that is flowing over the gooey stuff make it more gooey, and stickier as it is trying to clean the items,  MMO (Marvel Mystery Oil) helps as it cleans and ungooey's sticky items as well as slicking up the lacquered up items.

So it may be that some things just need careful cleaning to restore them to proper operation.   Just my 2 Cents of opinion, over years of Dual SU carbs and fuel lacquered things….

Thank you for your responses. I will get hold of a pressure gauge and check the system pressure.

Ref the fuel, I did put in fresh fuel, however, will check to see if there is any contamination which is restricting the fuel system.

Will provide updates as I find the solution to share with the community.

Thanks.

Hi there,
A quick update.
I disassembled and rebuilt the fuel distributor using a new gasket kit. Bought from eBay for £64. Cheaper than buying a second hand distributor.
I found some contamination (corrosion) but not enough to cause an issue. Anyway I have ruled this out.
Next step to check fuel delivery pressure.
Would a weak fuel pump cause cold start issue?? I mean when the engine is warm the engine works well.
Also where can a source a fuel pressure test kit for the K Jet system. VW quote a VAG tool but it's too expensive.
Thank you.

I made a gauge for about £35 last year as a good one was too expensive and the eBay cheap sets are a load of rubbish. I'll try and dig out the link to the one I made and post it up. Probably won't be until tomorrow afternoon though.

Decided to have a quick look now, here's the link.

The Bad Habit Rabbit - Volkswagen Rabbit Page - Fuel Pressure Gauge

Most important tip is that you get the fittings with the correct thread for the K-Jet connections. I got mine with a hose tail connection so a rubber hose could be fitted on. Second most important tip is that all the gauge connections are also the same thread. I got hose tail connections for that end as well. I can't find the links to the parts I bought now as it was about 18 months ago but it all came off eBay. I'll post ay links I might find.
Good luck, keep us posted.

I would re test the cold start circuit again
ive had a gti that did that from cold and it ended up being the cold start valve I'm sure
mind you ive also taken the complete cold start equipment off and ran it with out and it just ran lumpy from cold
its defo fuel related and I would say lack of fuel
is it running lean ??
hope you get it sorted

I have just had to replace my cold start valve and the only issue I had was actually getting the car to start when the engine was fully cold (left overnight). Once it had started it ran the same as when the cold start valve was good.
I agree that it's a fuel related issue. Possible even the sensor plate or FD plunger sticking when cold.

Hi Saulty & vwoldmad1,

Thanks is for your input.

I certainly will look into making my own fuel pressure test kit. There is a automotive hose manufacturer (Think Automotive) in Twickenham where I can get the pipe work made from to fit the system. They are quite good, I used them in the past for other things.

Ref the cold start valve, I read some literature that the cold start valve only operates upto 8 secs to assist the starting. I wouldn't expect the cold start injector to run until the engine is warm. From cold (park overnight), the engine starts after a few attempts and is very rough on idling, maybe around 400 rpm. I put my foot on pedal and it cuts off as there is too much air.

I didn't mess around with the fuel / air mixture as this is set correctly and I don't want to mess with it.

When I was servicing the fuel distributor, I tested the sensor plate and function of the distributor by blowing air into it and checking when I lift the sensor plate a little that there should be flow. This is the case.

I thought the fuel accumulator maintains the pressure in the system; not sure if this has any input.

I think the best bet for me is to first test the system pressure to see if I get the correct figures and then explore other options.

This K Jet system sounds like a simple system but is a nightmare to troubleshoot.

Bosch - K-Jet - Workshop Manual.pdf

Great literature to explain the function of the K Jet CIS

too much air not enough fuel
wish I could help more try not to keep throwing money at it until you know the part is defo broke
try to borrow and try
if the cold start operates for the short duration that can be ruled out
I have a mk1 gti cabby at mo and it starts first turn and the cold start isn't functioning at all runs a bit ruff 800rpm and warm up in 2to3 mins and runs good
I have had your prob in past and chased the problem all round the houses I feel your pain
your crack it I'm sure

aux air valve stuck open ??/

BoschMechanicalFuelInjection.pdf

This is some more simplified literature I found on the net ref the fuel system.

Hi vwoldmad1,

AAV is ok. When cold it is open and as the engine heats it should close to stop the extra airflow.

I also bought another one from eBay and installed it, didn't make a difference.

the flap in the metering head is clean and moves freely and postioned correctly
its doing my head in now lol
said before I had a met gold gti 15yrs ago did the same
push pedel from cold it would hesitate like mad until warm was ok until you touch the pedal
have you checked all your injectors

long shot but as you know a car will run better when warm using a leaner mixture
but if the injectors are spraying fuel correctly rule them out
looks like your on top of it process of elimination
keep going

check your injectors

Ok mate, will check the injectors as well.

The process of elimination is costing a lot of £££

I don't mind spending money on new parts, but the frustrating thing is that you are paying an arm & a leg for second hand rusty parts with no guarantee.

You may get the correct power on the WUR but that doesn’t mean it’s working correct.. take it off, check the gauze, clean with injector spray only, take off the back (may take force or an engineering screwdriver) this has got to be almost sparkling & clean. Has the 5th injector been mentioned to test as well? Easy enough to do, take it off, 2 bolts, put the injector in a jar of something clear, get someone to crank the engine & it should spray evenly for a few seconds.. if it does this then it’s ok. Perhaps get a tune as well to get your mixture right too.. hope you get it sorted.


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