1977 MERCEDES BENZ 450SL WON'T START

  • Tiny
  • monty747
  • 1977 Mercedes Benz 450sl

Engine Mechanical problem
1977 Mercedes Benz 450sl V8 Two Wheel Drive Automatic 132000 miles

Vehicle was stored, and started once a month. I missed a couple of months, now it trys, but won't start. I've changed the gas, new injectors, new spark plugs, new cold start valve, checked the fuel pump. Can't figure it out. It has spark, and seems to be getting gas. Any ideas?

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Thursday, June 24th, 2010 AT 10:26 PM

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  • Tiny
  • rasmataz
  • Member

Check the fuel pressure to rule out the fuel filter and fuel pump and also check if the injectors are pulsing

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Thursday, June 24th, 2010 AT 10:52 PM
  • Tiny
  • monty747
  • Member

I neglected to post that I had changed the fuel filter, checked out the fuel pump (it is pumping properly), and the injectors do pulse, at least the two that I checked do. Monty747

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Sunday, June 27th, 2010 AT 7:51 PM
  • Tiny
  • rasmataz
  • Member

It is pumping properly but what is the fuel pressure-EFI system don't like low fuel presssure that's not within specs.

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Sunday, June 27th, 2010 AT 8:47 PM
  • Tiny
  • monty747
  • Member

1977 450sl is mechanical fuel injection, not EFI

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Monday, June 28th, 2010 AT 4:58 PM
  • Tiny
  • ScottinSoCal
  • Member

Yes, and the injectors don't pulse (or at least they shouldn't). The Bosch K Jetronic system is a CIS setup - the injectors spray a constant stream of fuel when the fuel pressure goes high enough to open the spring-loaded valve in the injector.
If you've verified the fuel pump works, and you've replaced the fuel filter, I would next want to check the Warm Up Regulator (badly named, because it controls much more than just the warm up cycle) and the fuel distributor. The WUR sits at the front of the engine and establishes the control pressure during operation. Basically it's the gatekeeper for the gas. It has to work for the car to run. The fuel distributor is under the air filter housing and it looks like a post-modern spider. It does just what the name implies - it distributes the fuel. If bad gas got into it, that's enough to kill it. If the diaphragms on the WUR went bad, that's enough to kill it. Unfortunately testing either of these gets into advanced skills that I wouldn't recommend for the average shadetree mechanic. My best suggestion is to find a good local independent and take your car in.

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Friday, December 10th, 2010 AT 8:47 PM

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