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This isn't even funny any more at this stage. Most of you will be familiar with the problem from vage but for those of you who aren't....

Basically the problem is this:

When the car is cold and you start it up it starts straight away and most of the time it idles fine, but touch the accelerator and it just starts to miss and cuts out. The odd time it won't even idle when you start it and just cuts out again. Try to start it straight away in either case and it won't start. Leave it for half an hour or so and it will start ok. Let it warm up for a few minutes before touching the accelerator and it will run fine.

When the engine cuts out and you are trying to start it it sounds like there's no compression so I did a compression check to see what the story was. Result, absoutely zero compression on 2 of the 4 cylinders, full compression on the other 2.

But now it gets really interesting, I knew if I left the car for a while it would probably start, so I left it for half an hour and did another compression test, and had full compression on all cylinders!

Sometimes the car starts and runs ok from cold. There was even a time back a few weeks ago when it was perfect for 4 days in a row.

Now when this first happened I suspected a mechanical issue with the tappets or something like that due to the fact that the compression was coming and going.

Then someone suggested that the reason for the loss of compression could be washdown due to overfuelling and/or a weak spark.

So at this stage I have been through everything I could think of that could be affecting the spark or fuelling.

I have swapped the following parts with ones that are known to be working:
Tappets
ECU
Tci-h unit (little unit that controls the spark at different revs, sits on top of the ecu)
Distributor
Knock Sensor
Coolant Temp Sensor
ISV
Fuel pressure regulator
Coil

And tested the following:
Airflow meter
Throttle position switches
Connections to all of the items mentioned in the above lists

The obvious things like plugs, leads, cap and rotor arm are all brand new.

The alternator is charging ok and the battery is good (I read somewhere that low voltage to the injector rail can cause overfuelling)

At this stage I'm thinking it's either a problem with the loom or else as fasteddie suggested on vage the pressure control valve in the oil pump could be stuck causing the pressure to be too high when the engine is cold, thus pumping the tappets up enough to open the valves and cause the loss of compression.

I'm going to do an oil pressure test then swap the pump over and do another oil pressure test to see what difference that makes.

If that doesn't work then the next job will be to swap the loom for another one.

Anyone got any other ideas? I'll consider anything at this stage to get the thing going.
 

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I don't think that bore wash is the problem, why would the compression return if the engine had not been turned over. I would remove and clean the oil pressure relief valve, or complete oil pump. It sounds as if the valves are not closeing, (tappets jacking up). I presume that they are hydraulic. Some engines before 1985 had shims, but I would think your's is hydraulic.

John
 

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Thanks Chris, about time this got sorted is right!

I swapped over the oil pumps today, both have the same part number.

There's still something not right though, the oil pressure is fluctuating from very low to very high.

Before I did any work on the car or even tried to start it today I attached the oil pressure tester and started it up. The pressure immediately went up to 210psi and then the car cut out. The car wouldn't start then but even turning it over on the starter made the pressure go up over 120psi.

I connected the tester to the jetta (1.6td) then just for an idea of what the pressure should be. Starting the jetta from stone cold the pressure was 75psi at idle rising to 90psi at about 2000rpm.

So at this stage I was thinking there was definitely something wrong with the golf so I pushed it into the garage and swapped over the pumps.

Started the car after changing the pump and the pressure gauge sat at zero for about 20 seconds and the car ran fine, but I was worried about the low pressure so I switched the engine off and restarted it, again the pressure shot up to 210 and the car cut out, exactly as it had done with the old pump!

So I left it for half an hour or so (to go and bash my head off a brick wall) and then came back and started it again. This time the pressure stayed very low when I started the car (about 15psi) and the engine ran ok. Then I tried gradually increasing the revs, as I did the pressure kept rising until it got just over 200psi and then the car started to run like shit again.

I dropped off the revs and let it warm up fully, when warm the pressure at idle was very low but revving the car still made the pressure increase way more than the jetta had when it was stone cold.

I added a tin of engine flush to the oil and drove the car for about 5miles so. I'm going to see how it behaves in the morning and take it from there.

So it would appear that the problem is being caused by high oil pressure, 200-210 psi seems to be the pressure at which the tappets are forced wide open and the valves are getting stuck open.

Question is what is causing it?

Any ideas?

At this stage I'm sick of messing around with it and since the problem now seems pretty certain to be within the engine itself I'm thinking just get another engine for it and have the problem sorted once and for all.
 

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Oil pressure should be 2 bar (29.5 psi) minimum at 2000 rpm at 80 degrees.

Your problem is the oil pressure relief valve. I'm sure this is in the oil pump but I never really looked. I have a pump at work and will be going in today (later, too many cans) and will have a close look and get back to you before this evening.

John
 

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Checked, and the oil pressure relief valve is in the pump, and it's sticking. You will have to get a new pump or strip the old one and clean the relief. On some pumps you can't get the plunger out, so a new pump is the only option. The pump you put in must have some rust or debris in the plunger.

John
 

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Did you prime the oil pump before you fitted it. If not it is possible, though unusual, that there was severe wear for that 20 seconds and then some debris got stuck in the relief valve plunger. If not I'm at a loss at this stage.

Poltergeist ?

John

 

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might be worth a look (prob not but...) what you discribed in some of you post geo, is a lot like what was wrong with mine today, try looking at the connections to, and inside, your air flow meter. thats what was causing mine to flood when accelerator was touched, and konk after turning over at 500rpm for a couple of seconds...

Best of luck what ever is up with it! (Mk4 calipers are working a treat!)
 

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Discussion Starter · #12 ·
I already checked the airflow meter Oisin and as far as I can tell it's working fine. The problem definitely seems to be to do with the oil pressure.

Good to hear the mk4 calipers are working ok, that mod is on the to do list for my car when I get this current problem sorted out
 

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Discussion Starter · #13 ·
Looks like the pump I fitted is a faulty unit.

It's not holding oil pressure now at low revs when the car is hot. I'll swap it for a secondhand one I have lying around and we'll see what happens.
 

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You should return it, and get a new one FOC. I hope thats the cause, because there's nothing left.

Best of luck man.

John
 

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Glad to hear it's back going again, you can change your Signature now!

So we'll see it all nice and shiney out at the Gandon next week end then
 

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QUOTE (Geo @ Jan 4 2006, 01:54 PM) <{POST_SNAPBACK}>Looks like it did the job. Car seems fine now.

The other pump was obviously a bad one.

You still sound like you're expecting something else to go wrong next ..
 

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Fair play George well done, hope it goes ok for you now at last!! Can I have a spin
 
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