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Disconnect fuel pump for R? Compression test

Kenny11

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Hey all,
on the R I've tried to find the fuse etc to disable the fuel pump before carrying out a compression test.

The problem I've had is blue smoke from the exhaust. I'm leaning towars valve stem seals due to symptoms and hoping it's not piston rings?.

Also...what's a common compression difference between all cylinders. I've heard this can be between 10-15/20%.

All input welcome and thanks in advanceA
 

Pedro

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Compression can vary due to cylinder wear & tear a healthy engine will give out 100% with no more than 10% between high & low readings the trick I've used in the past for below 100% is drop a teaspoon of engine oil in the plug hole & retest if the readings on the gauge are inaccurate
 

Kenny11

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Compression can vary due to cylinder wear & tear a healthy engine will give out 100% with no more than 10% between high & low readings the trick I've used in the past for below 100% is drop a teaspoon of engine oil in the plug hole & retest if the readings on the gauge are inaccurate
Thanks for the info Pedro.
On the latter part of the answer with the teaspoon of oil retest. If the compression value changes, is this a good or bad thing?
 

Pedro

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Sorry it was a Tablespoon added into the cylinder for a wet test so do this then crank the engine over maybe 5-6 times if pressure increases after adding oil then it could indicate the piston rings are worn but as you rightly said it may be valve seals or even carbon build up stopping the valves closing as this issues plagues all direct injection engines so a process of elimination I'm afraid but if you can get a camera into the inlet ports it will show if the valve chambers are clogged up
 

Kenny11

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Sorry it was a Tablespoon added into the cylinder for a wet test so do this then crank the engine over maybe 5-6 times if pressure increases after adding oil then it could indicate the piston rings are worn but as you rightly said it may be valve seals or even carbon build up stopping the valves closing as this issues plagues all direct injection engines so a process of elimination I'm afraid but if you can get a camera into the inlet ports it will show if the valve chambers are clogged up
Thank you for the advice as I'll try this if there is such a discrepancy.
Do you know how to disable the fuel pump by any chance?
 

Pedro

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You only have to uncouple the plug on the pump but make sure the fuel system is fully depressurized before removing the fuel line leave the car to stand for a few hours sometimes garages leave them overnight to let the system drain off
 

Kenny11

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You only have to uncouple the plug on the pump but make sure the fuel system is fully depressurized before removing the fuel line leave the car to stand for a few hours sometimes garages leave them overnight to let the system drain off
I take it then that a compression test can only be done with a warm engine if the fuel pump is operating. I always thought the rule of thumb was to do the compression tests with the fuel pump disabled and on a warm engine.

Just trying to figure out how to get the best/most vaild compression readings on the RCZ.


Also, just realised your nearby (Cheshire) Pedro 👍👍
 

Pedro

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The test can be done on a warm or cold engine depending on the issues if internal damage is suspected then you would obviously use a cold test if its piston rings or bores then a warm test is used as the internal parts would have expanded for adequate pressure readings obviously you will need to isolate the fuel system to get a dry chamber scenario easiest way is to pull the fuse or power supply whilst the engine is running to stall it then whip out the plugs & connect up the gauge but don't try to check one cylinder if the engine is still in a live state (connected up to the pump) as it will still fire & the reading will be dud
What is the mileage of the car & oil consumption?
Yep Oswestry is not far as the crow fly's :)
 

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The test can be done on a warm or cold engine depending on the issues if internal damage is suspected then you would obviously use a cold test if its piston rings or bores then a warm test is used as the internal parts would have expanded for adequate pressure readings obviously you will need to isolate the fuel system to get a dry chamber scenario easiest way is to pull the fuse or power supply whilst the engine is running to stall it then whip out the plugs & connect up the gauge but don't try to check one cylinder if the engine is still in a live state (connected up to the pump) as it will still fire & the reading will be dud
What is the mileage of the car & oil consumption?
Yep Oswestry is not far as the crow fly's :)
The R doesn't have a dedicated fuse to pull out. I may try the route you previously mentioned on the High Pressure Fuel Pump ( uncouple the plug on the pump but make sure the fuel system is fully depressurized) which would solely be on a cold engine (when turning it over) in this case.

I assume a leak down tester may be more suitable in this instance.

Its on 64k and the oil consumption is only evident when i did a 500 mile trip, I lost about 1/4 to 1/3 of oil.

My true belief the issue with my valve stem seals (VSS) rather than piston rings. For the following reasons:
  1. Blue/white puff of smoke on initial start up (for about 5-10 seconds) then disappears
  2. Car runs with no problems otherwise, pulls as it should with no misfires
  3. No constant plumes of smoke when driving. Only small traces of smoke if its been idling for a while (in traffic/drivethrough)
  4. The car had been sitting for some time before i bought it - 5/6 months (Ive read the VSS are a common problem on these, especially if they have been sitting for some time)
  5. Not sure what this means but - when sitting on an incline (to pull into a parking space), under this slight load blueish smoke does come out the exhaust.
Thoughts?

Hopefully catch up some time in the future if there are any local forum meets.

Ken
 

Pedro

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Yes you may be right the seals will can rock hard if the engine is left unused for a considerable amount of time also I have a suspicion that it could also be carbon build up around the valve seats which is preventing a proper seal (common on direct injection) either way the engine is a burning off a slight amount of oil the logic behind theses engines using oil is for very 1000 Klm they can burn up to a litre & some will use more tan others depending on the condition of the engine &the way its driven
As for Bluish smoke its normally a small amount of oil bypassing the valves on high or low acceleration being burnt off
 

RCZ-R

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Here is the result of a compression test I did on my R with about 100k on the clock.
 

Kenny11

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Here is the result of a compression test I did on my R with about 100k on the clock.
I did actually see this previously when I was searching through the forum..... Looks like your within 15% with those results

Great to see your R over the 100K mark. How long have you had it?

Have you carried out walnut blasting on the R? Needed to change the seals? Any maintenance recommendations?
 

RCZ-R

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I did actually see this previously when I was searching through the forum..... Looks like your within 15% with those results

Great to see your R over the 100K mark. How long have you had it?

Have you carried out walnut blasting on the R? Needed to change the seals? Any maintenance recommendations?

I had the R over the course of over 5 years and used it almost daily. Mostly for long hauls all around Europe and the country.

No, I did no walnut blasting on mine as it was not required. As I hardly ever used it for short trips or city driving there was no build up on the intake. But for the peace of mind I once did an italian tune up. And then weeks after that the intake was partially stripped down for taking pictures of intake's inside. There was only a minor amount of build up so we decided to not strip it down any further and not to clean it. It was all OK.
Over the years I also learnt that a rainy/drizzly day and a long autobahn drive at high speeds help to clean up the residue in the intake due to high air humidity. The engine always felt like new afterwards.

There were no other work on the engine required over the course of my ownership, except for those I listed in my thread. No valve seat gaskets. They were fine. I drove the car all the time so they had no chance to harden and go bad.

For maintenance I strongly recommend to change the engine oil more regularly than advised. If hard driven then cut the oil change schedule by half. And keep that oil level ALWAYS at max. If it drops by 3mm at the stick, fill it up. And do not use any racing oil, like 10w60. Just stick to what Pug recommends. And while talking about oil, don't forget to change the gearbox oil from time to time. It often get overlooked in the process but is as essential as the engine oil.
 
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