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Engine Diagnostic Required - Stuck Valve?


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Right. My TR6 of 15 years has never been particularly pampered as such. She'll get driven into the garage in September, turned off, and left as is. I'll start her at Xmas for 5 mins, and then expect to drive her out in April (which she has always done bar the occassional stuck clutch plate..............).

 

However, this time its been two years. I've started her every 6 months (which she does after 10-20 turns of the engine) but this last time she wasn't having any of it. After 5 mins of turning her over she eventually started BUT very roughly with a very high pitch "chirrup" through the exhaust (and audible through the engine) on each full turn, and sounded like she was only firing on 5 cyls. I put fresh petrol in and let her tick over up to operating temperature (during which the "chirrup" is hardly noticeable) but once I depress the pedal the noise comes back in full efftect.

 

Any ideas?

 

Jake

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Couple of starters - you don't say whether you have checked for a healthy spark at all plugs, nor whether there is a nice cone-shaped spray from all injectors. Have you?

 

I'd suggest you have plenty of checking to do before you assume a stuck valve...

 

Cheers,

John

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Hi Jake, in addition to John's comments above, we're assuming it's PI rather than carbed? For future reference, before laying up you need to add some stabiliser to the petrol, otherwise the fuel loses some of the more volatile ingredients and can cause corrosion, rusting and leave gummy deposits, and I think you'd be wise to invest in a set of "drier" plugs which replace the spark plugs (I think you can recycle these driers by warming in the oven to drive off any moisture. Prior to attempting to start the engine, remove the driers and crank engine (in bursts of 10-15 secs or so, giving the battery time to recover and starter to cool down) over until you start registering some good oil pressure then put clean and dry spark plugs in and give it a whirl.

 

http://www.enginewise.co.uk/acatalog/Dehydration_kits.html

 

I'll post a link for the fuel additive/inhibitor when I can find it.

Edited by jonlar
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Sorry, should have said, car is a 1971 USA car still on Strombergs.

 

Thanks for the tips, am going to give her another go tomorrow after a set of new plugs and some new fuel.

 

Jake

 

 

Hi Jake you may well need to clean the carbs out.

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Jake

First thing you need to do is a compression test; this will tell you immediately if you have a problem on one of the cylinders, rings or valves; are you sure the chirping isn’t a blown head gasket?

 

If you’re not inhibiting the engine in any way, 6 months between engine starts is way too long. Acidic by-products from the combustion process will eat into the bores, valves etc & I’m surprised it hasn’t seized up altogether between starts; the clutch plate is also likely to weld itself solid to the flywheel.

 

My motor seized solid many years ago whilst the car was waiting to be restored, since the restoration was completed 3 years ago, I start it every week & warm it through & always take it for a run out if it’s dry.

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By means of a squirting a cleaner through them or by stripping them down? Please say the former should suffice!

 

J

Jake if you have Strombergs dont use carb cleaner on them without taking the Diaphragms out from under the top covers first as cleaner will destroy them

Stuart.

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Jake if you have Strombergs dont use carb cleaner on them without taking the Diaphragms out from under the top covers first as cleaner will destroy them

Stuart.

 

Thank you for that tip, I could have made matters worse otherwise!

 

J

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Good news (well, for me!), I did a compression test (115, 127, 127, 130, 120, 117) so all ok there (apart from a slightly more than 10% variance.....) and changed the plugs , gave all the contacts a quick going over with a suede brush, and bingo! She's fine.

 

Ta for all the help and will treat her better from now on!

 

J

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