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I have a 1990 300SL that takes a time to start when its

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I have a 1990...

I have a 1990 300SL that takes a long time to start when its cold. I have to press the foot feed down to prime it. once it starts it takes 5 minutes at idle to warm up then its runs fine. The mercedes mechanic said it needed a Cold Start Valve. $700 later. That did not fix it. Next they said it needed a Fuel Pressure Regulator. $500 later that did not fix it. Now they think its a vacuum leak and the need 6 hours of labor to take the manifold off to inspect it and no guarantee that will fix it. Where do I stop the bleeding. The car is very nice looking but has 150,000 miles. I paid $6000 for it and have put $2000 in it. When do I give up and sell it for salvage. Any ideas on what I should do?

Mechanic's Assistant: How many miles are on the vehicle? And when was it last serviced?

150,000 miles and seviced 200 miles ago

Mechanic's Assistant: Are you fixing your 300SL yourself? What have you tried so far?

Have you not read what I typed?

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

No just let me know please

Submitted: 8 months ago.Category: Mercedes
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Answered in 8 hours by:
11/14/2017
Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago
Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 6,082
Experience: 20 years Master Certified excellent fix rate and have access to factory wiring, and instructions.
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Hello, my name is***** and i will do my best to assist you.I am going over your story now and will reply back soon with some info,thanks!

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Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago

with your issue it sounds like it can be a simple temperature sensor.

there is a cold start temperature sensor that activates the cold start injector to add the extra fuel to help start the car. OR it can be the idle air valve that is allowing too much air at idle when cold.

have they mentioned anything about those?

Lou

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Customer reply replied 8 months ago
The put a new cold start valve in and did not help. They did say it might be a vacuum issue but would need to take the manifold out (6 hours labor) to see if thats the problem. Is the air idle valve easy to get to and inspect?
Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago

no you must have misread what I said,

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Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago

the cold start injector only injects based on coolant temperature, so if the temperature sensor has failed then the cold start injector would not be activated to inject.

i will try and get you some documents that would hopefully help

the info for the old cars is not as easy to obtain but I will try.

Lou

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Customer reply replied 8 months ago
Okay yes that is what they put in and did not help. Unless it was a bad one. But a diagnostic would tell them that would it not?
Customer reply replied 8 months ago
Is the temperature sensor easy to get to and I put it in myself?
Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago

well with a car this old there was limited fault codes and diagnostic pointers.

yes the temp sensor is easy to replace.

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Customer reply replied 8 months ago
Its not an expensive part so maybe I will attempt it and see if that helps. Where on the radiator is it located?
Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago

its located on the engine, i am trying to find the location, there is a 4 pin sensor up in the front and i think this one is in the rear of the engine. on the top , near the back of the cylinder head.

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Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago

ok the temp sensor is at the back of the engine on top, mounted on the cylinder head.

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Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago

its also possible that the ground is bad to the cold start valve so keep that in mind.

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Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago

also you will want to check the overvoltage protection relay to make sure the fuse is ok and there is no corrosion in the connection.

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Mercedes Mechanic: Lou P. master tech, Mercedes Technician replied 8 months ago

look on the top of your water pump / thermostat housing and those are temp sensors.

you are looking for the same as the smaller one near the top back of the engine.

Lou

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