K jet cold starting

Hey hope someone can help.   I have an 89 cab gti, amazing original condition but having sorted all the usual issues I’m left with a cold start issue.

the car starts on the first touch of the key, but If I dare touch the throttle it dies pretty much instantly.   It will reluctantly restart sometimes but it’s hard work and shakes a little kind of misfiring.  If I hold the throttle and persist, once oil reaches about 60 and thermostat opens, it’s fine.   Runs really well and will restart while warm/hot no problem.   If I start from cold and just leave it for a couple of mins and don’t touch the throttle. It will keep going and smooth out as I said , once temp increases.

in terms of background,  previous owner had the metering head reconditioned.  Under my ownership  it’s had a new tank and neck (tank seam had a leak) , fuel filter, leads and distributor cap/rotor, plugs, full set of new injectors, air filter, oil and filter change.

I purchased the parts and made up a gauge for testing fuel pressure.   I have 5 bar control pressure and following a refurb of the WUR it starts cold at 2 bar and climbs to 3.4 in two mins.  All as per spec.  The WUR refurb has improved the time it takes the car to stabilise when cold - it was previously taking 6 mins to get to 3.4 bar.

I’ve taken off the AAV and tested it,  I’ve taken out the 5th injector and tested that also,  both fine. Timing and co has been set.

Now totally out of ideas,  it’s fuel or air but don’t know where to go next.    Anyone help ?

My cab had this problem I ended up having a top end rebuild, head gasket, oil seals, valve stems seals head skimmed, injector seals etc and it solved it. Runs as it was new so not sure what cured it lol


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Are you using super unleaded?

I am yes

Has it done this as long as you've owned it? Might be with checking the volume from each injector is broadly the same. Also worth checking for vacuum leaks.

I've not had it long but the cold starting has been consistent throughout to varying degrees.  The fuel volume issue I guess is possible.  I discounted it as the metering head was reconditioned by a third party by the previous owner.  There are obviously different qualities of 'reconditioning' though and I doubt the garage that did the work knew what they were doing.   

Would fuel volume issue not also be evident on a warm engine though ?

And vacuum leaks…..I've traced every pipe and checked physically for any obvious splits or poor fitting.

Corin Morgan said

I've not had it long but the cold starting has been consistent throughout to varying degrees.  The fuel volume issue I guess is possible.  I discounted it as the metering head was reconditioned by a third party by the previous owner.  There are obviously different qualities of 'reconditioning' though and I doubt the garage that did the work knew what they were doing.   

Would fuel volume issue not also be evident on a warm engine though ?

I guess it depends how far out it is - I think cold engines are more susceptible to variations in air/fuel ratios.
You say you've had the CO checked, what is it at? When I rebuilt my car (inc metering head and engine etc etc) it took me a while to get it to run when cold. It would fire, but never idle, then it would idle, but behaved like yours, I had the mixture too low. When I got it to a garage to get it set properly we settled on about 1.5%.

I guess that's a possibility.  The co was set to 1.4 by a local specialist but that didn't solve the problem.  That was before I reconditioned the WUR and fixed the fuel pressure problem. Since then I've bought Gunson and checked it myself at 1.5 ish (gunson not super accurate ) but the cold start issue is pretty constant.  I could get it more rich I guess but it shouldn't need it , it certainly won't when hot as it's running fine once warm.   

I've always found they run better with the CO set at about 2.3% and gone by the colour of the plugs, Reading spark plugs | Tuning Spark Plugs (enginebasics.com).
You're not going to destroy the planet.

I've now set the Co to 2.1 according to a gunsons gas tester - may not be super accurate I know.    Seems much the same,  it starts first time and does idle well…until you touch the accelerator l then it immediately dies and won't restart.  

I know the principles of engines but if someone could explain what could be going on that would be great. The mixture must be right for a cold start as it starts and runs.  Pressing the accelerator will activate the throttle switch,  what happens when that switch is activated as I wonder if that could be key ?

The fuel volumes I still have not done,  need to research how to do that, but, I'm not convinced this is the issue.  If it was it wouldn't idle happily before the accelerator was pressed ?

put a seal kit in a metering head set the volume
screws to base setting from fully in to11/4 out
waiting for the weather to warm up to set the
volumes with injectors into catch bottles volumes
not correct but does start ok

Sorry, are you saying  this resolved a cold starting issue you had ?

in my view i am saying volumes would not cause cold
start issue

Then I've run out of ideas, can't think of anything else I haven't explored

I've tested the fuel volumes, that's all ok.   Anyone have any other ideas ?

Mk 2's, had a switch on the throttle valve that was from memory something to do with  cold accelaration enrichment, the 5th injector was opened for a fraction of a second when the engine temperature was low, it may be worth doing a bit of research on that.

You could start it from cold, give it some throttle so it cuts out then have a look at the plugs, that would give you an idea whether it's too little or too much fuel. I've always found if an engine stops then on restarting it coughs and splutters for a bit before running smoothly the problem is over fuelling.

Thanks for reply,  I had come to a similar conclusion so did some more research and discovered the thermotime switch had the two terminals reversed.  This meant the switch was open and supplied an earth path to the 5th injector all the time.  So I think when I pressed the throttle, that fired the csv and flooded it.  Now that's resolved I can throttle it and raise the revs…but…it's still lumpy and misfires a little then once warm enough it just settles and all is well.   

So I'm close but still not quite there.  I think it's still over fuelling, if it dies and I try and restart it's like the starter runs quicker like there is less compression which I assume is fuel in the cylinders acting as lubrication?   Whilst it's making that sound when cranking it will not start.   If I leave it for 5 mins, then it will start again - the fuel evaporates ?

Realise this post is a bit old now, but will throw in my 2 cents.

It's a long shot, but maybe this might help as I had this issue on my '93, even after replacing both fuel pumps, but one day 'accidentally' fixed it by ensuring the lifter pump had a good seal on the tank.

Oneday I filled the car's tank right to the top and noticed fuel leaking on the ground - it was coming out from where the in-take/lifter pump was seated at the top of the tank (under the rear seat). The rubber O ring/gasket wasn't sealing properly.

I tried adjusting the rubber O ring but it kept moving around, so I got frustrated and used some aviation gasket liquid sealant instead. Since then the car has had no issue starting.

I don't know why this helped, but it did.
 

Oneday I filled the car's tank right to the top and noticed fuel leaking on the ground - it was coming out from where the in-take/lifter pump was seated at the top of the tank (under the rear seat). The rubber O ring/gasket wasn't sealing properly.

I tried adjusting the rubber O ring but it kept moving around, so I got frustrated and used some aviation gasket liquid sealant instead. Since then the car has had no issue starting.

I don't know why this helped, but it did.

That is because the seal wasn't fully tight when compressed.
I have never used a sealant on the sender o-ring, but when I am playing with the tank, I make sure that the o-ring is clean of rust and usually clean it well with Alcohol or brake-kleen.

I then slather the o-ring with Vaseline, as well as the sender side and the Tank side.

I place a rag in the opening and clean the Seat of the tank, and make it shiny.  I also slather it and the Cleaned top of the sender to the tank with Vaseline prior to resealing it.

Before I drop the assembly into the tank, I will clean the float arm and spring as well as verifying that the wiper arm is clean as well as the Pot so I get good ground potential from it.  I take a string and tie the filter to the assembly as I have dropped that sucker in to the tank, and have to go through the process again…after I get it in, I cut the string and pull it out before I seal it.

The Vaseline will hold the seal in place on the sender, and as you tighten it in the cammed fingers it allows the sender cap to seat the o-ring and slide on it to allow you to fully tighten the sender to the tank.  I imagine that previous you weren't getting it fully tight.  The sealant acted as a lube to allow it to get tighter.

The Sender is on the low side of the tank, so when you top it off and over fill it will have fuel at the seal level.  Also the Fuel Pump Regulator will by-Pass all the Fuel the Fuel rail  won't will need back to the tank at 45psi.  This pressurizes the tank a wee bit to help with hot starts, and keeping residual pressure in the lines.

This is different on a CIS as the running pressures of the system is a tad higher.