Engine stutter under heavy load

Well i had a nice few days and then today happened!
Went to a local meet yesterdAy and she drove well all day.

And then today - turn over but wont catch at all, not even a splitter. As if there’s no fuel! (Pulled a spakrplug and defo getting spark so reckon its fuelling again).

The only thing i did since yesterday was that i was fiddling with the thermoswitch on the coolant flange as she always struggled to start cold. I cant see how this would possibly effect the general fuelling system, unless someone can tell me otherwise…

Next stop: crack the nut on my brand new fuel filter and see if any fuel is actually getting up to the engine bay. Or any better ideas?

Thermo switch controls the 5th injector but as you said it should try and start eventually.

Did the spark plugs smell of fuel or look wet?

Can you hear the fuel pump running when cranking the engine over? Maybe try the No17 relay trick so the pump runs as soon as you turn on the ignition.

Plugs smelled slightly but not wet..

And yes the new pump runs with the new relay.  ALso tried pulling the relay and putting a jumper lead to make the pump run continuously- which it did. But still not a sniff.

Like theres no fuel getting to the engine at all… i wondering if taking it for a long run dislodged some old crude maybe?. But thought that would have made it run poorly at that moment.

Just cant see why it ran so well the last couple of days with the new pump and relay…?

I also pulled the 5th injector and sprayed a bit of QuickStart in there but no joy either

Well you know the pump runs, but is it pumping fuel?

You need to prove that next, because running them dry will destroy them very quickly, and you did have it running dry, albeit backwards!

So prove that the pump is moving fuel next.

Today I cracked off the feed to the fuel
Filter and turned it over - fuel!
So did the same on the other side of the filter - fuel there too.
I think therefore the pump is ok.
Next I pulled an injector and turned it over - no fuel.
So the issue seems to be after fuel filter and before the injectors - possibly the metering head? Can’t see why this has suddenly decided to play up but there you go.
Any tests I can perform on it?
Apparently the k-jet was rebuilt/refurb before my ownership so hoping it’s ok…
Thoughts?


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Further to my last post I’m thinking about the fiddling I was doing a few days with the thermoswitch. Everything was working up to that point…
1. The female plug on it looked very dodgy on the wires


This then got me suspicious about the state of other wiring.
This is where my knowledge ends as I noticed an engine component with a feed and return to the metering head along with a connector. It’s to the left of the dizzy oil filter. This too has an electrical connector.
Is it possible I’ve damaged this wiring and that effects the metering head?
It’s almost as if the fuel is there but the metering head doesn’t want to send it.
Hope that makes sense.


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Having checked Haynes I now know it’s the control pressure regulator. I’ve also tested it as per Haynes and I’m only getting 10v when I should be getting 11.5v. Could that be the issue?


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A lot to digest there, I'll tackle one at a time…

1. I would jump the fuel pump (have a search on here if you don't know how to do that), then you can run the pump without cranking the engine over. Pull the big rubber boot off the CIS unit, pull an injector, and carefully lift the air flap and you should get fuel from the injector.
2. You can get new plugs (Junior Timer is what they are called, not expensive) I'd re-wire that.
3. The thing you are talking about with the 2 fuel feeds is the Warm Up Regulator - it is a critical thing and can cause all manner of trouble! It is wired in series with the cold start (5th injector) and other bits managed by the thermo time switch. I'd say the voltage is low because of the dodgy wiring…

Some useful resources on here: https://www.vwgolfmk2.co.uk/clubforum/index.php?topic=114.0

If you really want to solve CIS problems you will need a fuel pressure test gauge. Link in my signature for how I built mine.

gregpank said

[mention]paceman [/mention] i turned the ignition on/off a dozen times to keep getting the pump to run to try and prime the system but no joy

I haven’t try crack off the line off to see if amy fuel is actually coming out of the pump. But before i do that, your comment about wiring - is it possible i got the wires the wrong way round? Would that make it pump ‘backwards’ (into the tank as opposed to pulling out of it). From memory it was brown wire on positive, red/yellow wire on negative.

Its a replacement tank so should be pretty clean and its a ‘81 tintop so no tank lifter pump.

Stick the relay up one slot

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Yes wiring does not look great so need sorting or it will fail.

Could be the plunger pin in the metering head has stuck, this controls the fuel to the injectors, as mentioned try starting the car with you lifting the flap underneath the rubber boot.

There is a few guides on here and the web to how the plunger should move.

[mention]paceman [/mention] [mention]mark1gls [/mention] thank you both!.
I jumped the pump after pulling an injector and lifting the circular air flap plate - and fuel! I noticed it was a bit mucky in there so first cleaned it with white spirit, then gave it a metal polish, including the air flap.
Success!
So i think it had got a little grubby and sticky and wouldn’t lift.
I’ve also ordered new junior timer plugs and corresponding wire for the thermo switch and 5th injector as they’re bound not to be helping. (Incidentally where do these two sets of cables meet each other?)
Next job is test those as she’s very rough warming up. Think the thermo switch may have packed up - not cheap! But thats for another day - im quitting while ahead
As ever, awesome forum support from you stalwarts - thanks again.
Lets just hope i dont need you again too soon!

The thermo time switch only tells the 5th injector to spray fuel in when cold and it's only a small spray of fuel for a mater of seconds.
You can test the 5th injector and thermo time switch by removing the 5th injector (2 Allen key bolts and go carefully with the gasket) and put the 5th injector into a jar, start the car from cold and you should see the 5th injector spray fuel.

When my injectors leaked and the car was difficult to start from cold andI had a lumpy idle I unplugged the 5th injector (unplugged the blue electrical connector) as it was adding in to much fuel and ran with the 5th injector for about 12 months before I replaced the main injectors.

Soooo…. Problems are back.
After sitting for a week after a decent drive, she wouldn’t start. Not evening a splutter.
1. I repeated the earlier test of pulling an injector, bridging the fuel relay for constant flow, pulling the big boot off the distributor and then lifting the plate - fuel comes out of injector fine, as before.
2. While I was there, I repeated this for the 5th injector. No fuel (although it’s quite warm today). I think as suspected my cold start system is, as the Germans would say, kaputt.
3. My suspicion was that on cold start, no fuel is being sent to the injectors at all. So I then reinserted both injectors, lifted the plate again for 5-10 seconds to fill all 4 cylinders with fuel vapour. Turned her over and bang, came to life!
4. Went for a decent drive. With the new fuel pump she pulls smoothly through all gears, no juddering. So I think I can rule out a dodgy new pump or relay.
5. Then parked her up for 20/30 mins and tried a warm restart.  Couple of splutters but started and ran fine.
6. I have also replaced the very dodgy junior timer plug on the thermoswitch. I haven’t replaced the one to the WUR yet as looks ok.
7. My suspicion is that if I leave her overnight to fully cool down, she won’t start.
To summarise, we have spark but no fuel on cold start.

What are my next steps, would you say? [mention]paceman [/mention] [mention]mark1gls [/mention]


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As per point 7 in my last post, just tried her after 24 hours cold and turns over but won’t catch at all. Defo think K-jet is keeping the plate closed for some reason…


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You need a fuel pressure test gauge, you can DIY one, check link in my signature. Sounds like. Your WUR isn't doing what it should and the control pressure is too high when cold. This pressure dictates how easily the plate and plunger can move. When cold the control pressure should be low allowing the plate to move more allowing more fuel. Only way to confirm is with a gauge.

Took a step back and had a ponder and went back to the fact that the problems started after i’d been poking around with the thermoswitch for the 5th injector and the junior timer plug on the WUR.

Id already replaced the thermotimer junior timer connector (still doesnt work so guess the actual unit is dead), but hadn’t done the same swap on the WUR junior timer.

So got my wife to try and start the car and i gave the WUR connector a good wiggle - and success!

I swapped the dodgy junior timer and she started again. Still a bit tough to start (as 5th injector doesnt work), but at least shes back to how she was!

Acid test is to leave it overnight and see if i can start her up tomorrow…