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Old 07-04-2003, 12:06 AM
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Please Help!!! Hot Start Problem

I purchased my Mercedes 1979 450 slc last year from California. Odometar doesnt work and its read 140000 miles. I fixed everything on this car except Hot starting , door lock vakum leak and RPM decrease from 1000 to 500 every time when i shift from Park to Drive. Somebody did new tune-up on this car (distributor, spark plug wires). I put new spark plugs, injector cleaner and fuel accumulator but I have hot starting problem from day one. Engine always start right away when is cold even if I dont start a car for a few months but after i drive a car and engine is hot it takes me few long crankes to start. It helps a little if I accelerate. Also I did little experiment and I bypassed black valve size of golf ball that is conected to the air filter. After I bypassed this valve it was little bit easier to start when is hot. Also before I bypassed this valve engine was "dieseling"(continuing to run after shut off). After I bypassed this valve engine stops "dieseling". I read a lot of posts about hot starting problems and it seems nobody have an answer for this problem. I instaled new fuel accumulator and I checked fuel pressure regulator for leak(puling out vakum line). It was vakum there and no fuel leak. Mr Stevebfl give to me great idea to tee pressure gauge to fuel distributor and monitor pressure. I dont have pressure gauge so before I get one I wanted to check If any of you ever fixed this problem because it seems like a common problem. Thanks for all your help specially to Mr Stevebfl
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Old 07-04-2003, 12:10 AM
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Join Date: Jan 2003
Location: USA
Posts: 699
Dear BO79450SLC:

I read somewhere that some old Mercedes models (possible yours) has problem with vapor lock in its fuel lines, causing hard starting problem when hot. Try to search mercedesshop or about vapor lock problem and some remedies.

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Old 07-04-2003, 02:24 PM
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Thanks Eric

I read a lot of posts and mostly people have a same problem like I do but seems nobody ever fixed this problem. But thanks for reply.
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Old 07-04-2003, 03:56 PM
Super Moderator
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
My 380SL was getting harder and harder to start when warm. While I am still chasing its lumpy idle, when I replaced the injectors and injector seals, the hard starting went away.

I have heard that fuel injectors "leak down" causing hard starting.
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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Old 07-04-2003, 11:38 PM
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CTAYLOR thanks for reply

Is it any way to check injectors without replacing them??
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Old 07-21-2003, 07:30 PM
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Fuel pressure should remain in the system to aid restarting.

The check valve at the puel pump outlet fails, and allows loss of this system pressure. That is why it takes some time to re-start...because the system must rebuild pressure that the check valve failed to retain.

Mark Shinnick
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