Engine cuts out

Hi all,

Been slowly thralling through the forum searching for what could be causing my engine to cut out. It's similar to some problems I have read about. Anyway…

I got a 93 sportline so i understand the engine to be a digifant(?) I have owned the car for about 2 months and I do a 40 mile round trip every day in her. Not had any major problems to speak of other then this intermittent cutting out problem. The engine starts first time every time with no hesitation. I pull off and she drives flawlessly for the first few miles. The only problem is that on some rare days she will cut out as warming up. I think its normally as she is around 60-70 degrees on the mfa oil temp. She just cuts out and wont restart for about 2-3 minutes. its almost text book each time it happens. There was only one occasion when I down geared and she sprung back into life again and one other occasion when shortly after getting her going again she cut out within a minute. I never have any problems once she is warm. Matt at dub unit noticed my cold start (blue plug) was disconnected so we reconnected it but the car takes a VERY long time to start so I pulled it off again.

When I bought the car she fuel filler pipe was in a very sorry state so I changed it ASAP. I have also recently dropped a magnet into the tank to clean that up a bit. The pump lifter filter was not clogged up at all. Just a few small traces of rust. I will be changing the main under bonnet fuel filter this weekend to see if that helps but because of the cut out always happening at the same time I do not think this is the problem. My thoughts are that some sort of sender or maybe the WUR is up to no good at that particular stage of the engine warming up. Anyone got any ideas?
It dosnt happen EVERY time but when it does its always at the same stage of engine warm up which points to some shutting or sticking after warm up? Am I making any sense? Thanks for any help in advance guys, other then this little niggle I love my golf but would really like her puuuurfect!

The Warm-up-Regulator
This simple device is responsible for controlling the amount of fuel delivered to the engine during it's warm-up period. The pressure acting upon the top of the control plunger varies depending on the engine temperature and provides an effective method of enrichment.

The control pressure is tapped off from the primary pressure circuit in the metering head's lower chamber through a tiny restrictive hole which gives it the ability to differentiate between the two pressures. A flexible pipe then connects the control plunger gallery to the warm-up-regulator and returns back to the metering head to a connection next to the primary pressure regulator's transfer valve. This valve is in the circuit to close the fuel from the control circuit when the engine is off, avoiding the total loss of system pressure while the engine is stationary.

The internals of the warm-up-regulator are quite simple comprising an inlet and outlet port, a stainless steel shim, a bi-metalic heated strip and a spring.

The input to the warm-up-regulator flows into a small chamber in the top of the unit, its return is through a small drilling and back to the metering head. By controlling this return flow it will cause a change in pressure acting on the top of the control plunger. With a cold engine the flow must be fairly free giving it a lower pressure. This will allow a higher lift of the plunger which in turn will enrich the mixture under these conditions. The free flow is obtained by the internal bi-metalic strip exerting a downward pressure on the spring which decreases the pressure acting upon the shim, this lower force allows the fuel to flow almost uninterrupted.

As the bi-metalic strip is heated, by either it's heater element or natural heat soak from the engine, the downward pressure acting on the spring is gradually decreased, increasing the force of the spring, which in turn increases the control pressure.

Typical cold engine control pressure will be as low as 1.0 bar increasing over approx. 10 minutes to around 3.5 bar. Some warm-up-regulators have a vacuum connection that will sense a drop in vacuum and lower the control pressure during these acceleration periods.

The voltage supply to the regulator is from the fuel pump relay, because if the ignition was on without the engine running, all enrichment would be removed as the bi-metalic strip would be heated prematurely and the driver would not benefit from the cold engine enrichment.

The two pipes that connect to the warm-up-regulator have different sized 'banjo unions' to avoid them being connected incorrectly. The control pressures quoted are as an example only and reference should be made to the technical data as these pressures can be specific to the part number located on the unit's housing.
This unit will have a resistance value of approximately 20 to 26 Ohms.

NOTE :- it is important to disconnect the electrical connection to the unit before any pressure testing on the control circuit is performed as this will prematurely heat the bi-metalic strip and cold control pressures will not be available.


I would try a replacement of the above , this car should be running K-jet injection ?

The very late Cabrios had late MK11 GTI digipants and cats :dontknow:  

ECUs and lots of electricery sensors festooned everywhere around the engine all waiting to go wrong when they get old…..

Did they still have the blue 5th injector though :dontknow: perhaps its one of the last Kjets.
 :dontknow:
Can we have a picture

Unlikeley but not impossible you are running digi, check your log book for eng code or get it off the block.  Cab digi eng are basically a dx unit with pb EMS, so alot of dx parts are the same.  

I'm agreeing with Chudd about the WUR.  If it is digi and you need info, give me a shout as i've got to know these systems v well of late :wink:

Hey guys, thanks loads for the replies. On closer inspection I think the engine is not a digifant. Anywho… I am getting the problem much more frequently now. Happened thsi morning on the way to work. Its got to the point where I know exactly within 2/3 minutes when she will stall and I can pull over time exactly 2 minutes and she fires straight up again. Some times I then get a repeat performance a mile down the road. Also if I have enough speed down gearing can pop her back into life.

Chudd - Thanks loads for you very informative post. I Believe the WUR is where my problem lies. I am trying to get hold of a second hand one right now as they seem pretty expensive to buy new. Just one thought, does it matter that the blue cold start valve is disconnected and I have trouble starting if I connect it?

hi mate,

i had the exact same problem, i have a spare warm up reg, but it turned out to be the dizzy…

when the car wouldnt start after cutting out after 20 mins or so, the hall sender was giving out one spark and no sparks after that, so the engine would try and turn over but never actually crack…

i went through the following trying to sort it

fuel pump
accumulator
metering head
fuel filter
cleaned injectors
magnecor leads
oil pump
water pump
dizzy cap
rotor arm
new battery
redid the wiring
new fuel pump relay

all for it just to be the dizzy

good luck dude

grungeisdead said

hi mate,

i had the exact same problem, i have a spare warm up reg, but it turned out to be the dizzy…

when the car wouldnt start after cutting out after 20 mins or so, the hall sender was giving out one spark and no sparks after that, so the engine would try and turn over but never actually crack…

i went through the following trying to sort it

fuel pump
accumulator
metering head
fuel filter
cleaned injectors
magnecor leads
oil pump
water pump
dizzy cap
rotor arm
new battery
redid the wiring
new fuel pump relay

all for it just to be the dizzy

good luck dude

Nice one chief, I was thinking teh dizzy at one point but mine happens probably 5-10 minutes of driving from cold start not 20. I probably gonna get the WUR and ISV changed first (if i can find cheap enough ones) then will change the dizzy after. Already changed HT leads and plugs so I might as well. Thanks for the help anyway matey.

grungeisdead said

i have a spare warm up reg,

Wanna swing it my way for a nominal cash amount ?

Hi all just to resurrect this thread. I have sinced had the WUR replaced, when doing this Matt (dubunit) unplugged the ISV which seemed to make no change to the engine at all. I now have the cold start (blue plug) disconnect and the ISV disconnected. I have driven to work today and she hasn't stalled so will just have to wait and see what happens. It just seems funny that the cold start valve, when plugged in, makes the car a bit funny to start and that the ISV doesnt seem to help when connected or not. Something larger is at work here and I'm going to get to the bottom of it! I am just going to get some pics which may help someone diagnose my problem.

K got some pics:

Pics of the engine (the engine is a DX engine number)






Picture of the ISV and Cold Start Valve (behind) both currently disconnected



Does anything look a miss to anyone?



Also, any ideas what this is?

I have since found a bolt sitting innocently on my drivers side wishbone! My mate said it was off the inlet manifold, looks like this is the culprit (read anther post which had the same problem as me and this solved the issue). I'm going to try and ram this sucker back in and hope for the best! Wish me luck.