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Old 12-02-2016, 05:36 PM   #19
YarisVVTi2002
 
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Thanks Bluevitz-rs
I put new plugs but no improvement.
I have been pulling the EFI fuse recently before the compression test. I didn't at first. I have always held the throttle open for the test.

I have taken the rocker / valve cover off now.
First impressions are the timing chain is fairly slack but I doubt it's enough for it to jump off the cogs. It is a VVTi so I'm not sure how to check the correct chain slackness?
There is quite a lot of water under the rocker cover. The car has been outside unused in the cold for weeks.
Some photos of it:

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Old 12-06-2016, 06:56 AM   #20
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New update

Won't low compression be due to either a problem with the cylinder pistons rings or the inlet or exhaust valves ?

I've taken out the VVT oil control valve & solenoid and tested the resistance across the 2 pins - it was 7.1 Ohms, which is normal for this one according to online info. The piston in the valve slides back and forwards ok and the spring acts normally. I can't see any obvious problems with it. I've cleaned it and sprayed it with carb cleaner in case anything is sticking. I haven't opened up the cylinder at the left end of the forward camshaft which contains the VVT gears- I'm worried I might not get it back together again.

I took out the camshaft sensor as well (to the right of forward camshaft) and cleaned it, it had a resistance across the 2 pins of about 2k Ohms, which is normal for a Hall Effect sensor according to online info. Visually it looked ok. The rotor on the right end of the forward camshaft has 3 cylindrical tabs on it (magnets?), which I guess provide magnetic timing pulses to the camshaft sensor.

I have never had any OBD errors relating to the VVT oil control valves or system so far. As I understand it the VVT system adjusts the valve timing so that it holds more exhaust gas in the cylinders at higher revs to improve fuel economy. I'm assuming that at starting conditions the VVT system is not active unless it's stuck somehow?

I've turned the engine over for short periods with the rocker cover off. The tops of the valves seem to go up and down normally. The timing chain is normally tight but in some positions it is slightly slack (droops down in the middle as in photo).

Everything inside the cover is covered with slightly sticky baked on oil deposits, which I've cleaned off as much as possible. Part of the cam lobes (the short radius part) has a baked on yellow coating which indicates that they are not running in contact with the tops of the valves. Is this normal? Also the sides of the cam lobes had carbon deposits, so they must have been running hot to carbonise oil.

I'm starting to think that the oil supply to the top half of the engine has been insufficient? Perhaps there is a small inline oil filter for the VVT oil control valve? It's mentioned in the Lexus video but is it on a Yaris ?
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Old 12-07-2016, 12:48 AM   #21
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I think 3 bars is around 43 psi, that's pretty low, looks like it's been pretty hot under your valve cover. Wonder if you may have a head gasket leaking between two cylinders? or carbon build up on top of valves keeping them from sealing? With only 58,000 miles, it should just be getting broke in, but if it's ever been hot, aluminum heads tend to warp and crack.
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Old 12-07-2016, 01:02 AM   #22
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I just reread your last post again, I don't think a head gasket of carbon on valves would cause all 4 cylinders to have low compression, especially if all cylinders have about the same psi.
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Old 12-07-2016, 01:14 AM   #23
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It's either way -> missing spark or missing fuel !

58.000 driven Toyota engine just won't break up like that !
Theres no water to oil mix or oil to water mix and so head gasket is just fine ...
I would quickly put all together again and start from basics !
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Old 12-07-2016, 02:35 PM   #24
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Quote:
Originally Posted by KimmoKekki View Post
It's either way -> missing spark or missing fuel !

58.000 driven Toyota engine just won't break up like that !
Theres no water to oil mix or oil to water mix and so head gasket is just fine ...
I would quickly put all together again and start from basics !
+1
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Old 12-07-2016, 05:52 PM   #25
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No oil in water or water in oil that I can see. All cylinders have about the same compression, either low or normal. So it's unlikely it's the head gasket.
Currently, the car turns over fine but doesn't start no matter how much cranking is done. The cranking sometimes picks up speed and feels like it may start at some points but fades away after 15-30 secs of cranking.
I'm very sure there is a spark as I tested each HV lead with an inline spark tester.
I can smell petrol on the spark plugs after trying to start the car, so some fuel is getting through. Does the cranking rpm fading away indicate a drop in fuel pressure - fuel pump problems? Would fuel pump problems show up in the OBD test? There are no error codes today.
A test light on all the injector wires flash. So I guess the injectors should be ok, it's unlikely all 4 would go down at once.
The compression is about 5 bar today on all 4 cylinders. It's still not clear why it's so low.
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Old 12-07-2016, 09:50 PM   #26
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troubleshoot non-start Yaris voltage spark multimeter

I appreciate this thread as a guide to things to check with a non-starting motor.
I'd have a multimeter reading voltage while cranking. (Can use a plug into the accessory port.) Do these cars possibly have a minimum voltage level where spark and/or fuel is cut off? (Cranking voltage would be higher w/ plugs removed for visual spark check.)

Note: IC engines need fuel, spark AND fuel, spark and valves in correct sync.
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Old 12-08-2016, 12:23 AM   #27
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Engine turns over but doesn’t start on a Yaris VVTi

Compression testing gives you only information if there is huge difference in between cylinders !
Good way to test if you are guessing lack of fuel is test with brake cleaner spray or something similar highly flammable spray !
Take intake boot away from throttle body ..
Someone goes to ign key and starts crancking engine .. when it's cranking over you just start to spray cleaner into throttle body !
Engine will fire up immediately if you have fuel delivery probs !
It'll also stay running as long as you give it cleaner !
Of course you have to adjust spraying or engine will go too rich and die .....
This method works on all petrol and diesel engines !
That is the 1st thing to try when there is no clear vision what causes problems

P.S. Sorry for my really bad English ... i'm Finn and we do speak rally English 8)
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Old 12-09-2016, 11:00 AM   #28
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@ KimmoKekki
"It's either way -> missing spark or missing fuel"
I'm 100% getting a spark. In the UK we have spray's such as Cold Start which are very flammable to help starting. I've already tried this by spraying it in the air intake. There was no improvement in starting. I really doubt there is a big fuel supply problem, as I already established that the fuel pump is pumping lots of fuel into the injector manifold pipe and that the injectors are working. The plugs are also getting wet after turning the engine over. In case the engine was flooded, the car has been left for days and it still didn't start. Your English is fine :)
@ dogsridewith I hope this thread helps others. I'm convinced that the non-starting issue is not an ignition or fuel supply problem. It is also intermittent. I've tried starting it on a fully charged battery and when it's jump starting off a second battery in another car. All no difference.
I'm afraid that leaves compression / timing as the cause.
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Old 12-09-2016, 01:41 PM   #29
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Engine turns over but doesn’t start on a Yaris VVTi

I should read everything 4 times before answering :/
Did you check valve clearances when valve cover was away ??
Also did you check timing marks ?

Last edited by KimmoKekki; 12-09-2016 at 02:04 PM.
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Old 12-09-2016, 02:39 PM   #30
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No security light flashes after the doors are opened by the key fob. No other warning lights have come on.
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Old 12-09-2016, 03:00 PM   #31
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I've taken the Yaris to a local garage to get an opinion and they confirm that the ignition and fuel systems are OK. They think that the timing chain is stretched and have offered to fit a timing chain kit for about £600.
I'm not sure that this is the full story. Why would this stop the car starting and be intermittent? There is no suggestion that the timing chain has jumped a cog.
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Old 12-09-2016, 04:33 PM   #32
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With a stretched timing chain it should be shown symptoms earlier like running rough engine codes etc.

Yaris' are not known to stretch chains. I would get a second opinion
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Old 12-09-2016, 04:47 PM   #33
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I was thinking that same question ..
I read that 1st posting again couple of times and thinking about timing chain jumping ....
58K driven ...
Fuuuuuck ...
Your car must be fitted with O**L's timing chain in that case !
Can you remember when exactly it start to sound rough ?
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Old 12-12-2016, 08:56 AM   #34
YarisVVTi2002
 
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Does anyone whether a stretched timing chain can cause a car not to start and a drop in compression from 11 to 2 bar? And cause this effect intermittently, so that some days the compression is normal and it starts and other days it won't start and has low compression.
I can't see the point of spending £600 changing the timing chain if there is some other problem as well. May be it's safer to change the engine?
@ tmontague Opinions cost a lot of money I'm not sure what other test the garage could do, short of stripping down the engine?
@ KimmoKekki the car was running rough for months, from my original post, but not all the time.
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Old 12-12-2016, 09:54 AM   #35
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Can you take a picture of your timing marks on the cams so we can see it is correct. They should be lined up like mine here...
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Old 12-14-2016, 07:12 PM   #36
jra
 
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I would doubt if a loose timing chain would cause low compression or keep it from starting, unless it's jumped a cog on the sprockets. If your valve cover is still off see if the chain has any wear where the pins connect the links together and if the rollers are loose, but it should be good with no more miles than you have on it. If you have spark it should start on ether, so that leaves not getting spark at the right time. Maybe chain jumped cog? chain sprocket sheered key and turned on shaft? inconsistent cam or crank sensor, firing plugs, then not firing for two or three revelations? had that happen to my 2.7 Tocoma truck.
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