Author Topic: Check valves  (Read 1387 times)

philmas

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Check valves
« on: March 24, 2023, 22:10:14 »
Sorry if this has ben discussed many times before.…
I’ve had this « 5 cylinder » cold starting issue for as long as I own the car (over 30 years…), this happens  mainly when the car has sit in the garage for more  than 24hrs, and resolves after 5 or 10 min.
Until very recently, I was convinced that there was a faulty check valve somewhere.…
But when searching this forum, I understood that a leaking valve should lead to a difficult hot start…
Could  someone shine a light on this, and tell me if that points rather to an injector problem , or does it mean a valve gets « stuck  » or « sticky » in the closed position when cold?
Thanks for your precious knowledge (and help!)
« Last Edit: March 24, 2023, 22:25:50 by philmas »
Philippe from Paris
Euro '71 280SL manual 4sp

ja17

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Re: Check valves
« Reply #1 on: March 25, 2023, 04:25:29 »
I guess your saying it starts well but on 5 cylinders at first?  Could be a leaky injector, faulty IP check valve, or possibly one of the IP fittings not properly torqued.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

rwmastel

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Re: Check valves
« Reply #2 on: March 25, 2023, 05:21:06 »
30 years?!?!?  You should have come here sooner.  We've been online 20 years.

I would first determine if in fact (we should always work with facts) it is running on only 5 cylinders at start up.  It could just be running roughly on all 6.

Pull one spark plug wire, start it.  Put that back and pull the next and start it.  Proceed (even it it has to sit overnight) through all 6 to determine which cylinder is faulty, if any.  Of course when the faulty cylinder has its wire pulled, start up will sound "normal".

Then, work to determine if the fault on that cylinder is fuel, air, spark, or compression.

Let us know what you find!
Rodd

Did you search the forum before asking?
2017 C43 AMG
2006 Wrangler Rubicon
1966 230SL auto "Italian"

philmas

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Re: Check valves
« Reply #3 on: March 26, 2023, 19:39:49 »
Thanks for your help…
I guess this sounds like 5 cylinder running… I should inquire further to determine which is the faulty one.
How a spark issue could resolve by itself after 5 min…? More probably a fuel delivery problem…
Btw, I found  some sites that claim still having the valves on stock for about 200€ …probably fake news!
Philippe from Paris
Euro '71 280SL manual 4sp