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1966 250SE Coupe
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117 Posts
Most modern electronically fuel injected cars have a system that primes the fuel pump and pressurized the system, by briefly turning on the fuel pump, when you rotate the ignition key to the "on"/"run" position. Then, if no input is received from the distributor, or in some cases, engine oil pressure, or flywheel teeth movement, the pump immediately shuts off. This is to prevent the pump from running after a crash, and causing a fire. My suggestion would be to connect a volt meter to the pump, and check to see if you have system voltage during engine cranking.
 

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MB W123 230E, MB 200D, MB 350SL
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10 Posts
Discussion Starter · #6 ·
Most modern electronically fuel injected cars have a system that primes the fuel pump and pressurized the system, by briefly turning on the fuel pump, when you rotate the ignition key to the "on"/"run" position. Then, if no input is received from the distributor, or in some cases, engine oil pressure, or flywheel teeth movement, the pump immediately shuts off. This is to prevent the pump from running after a crash, and causing a fire. My suggestion would be to connect a volt meter to the pump, and check to see if you have system voltage during engine cranking.
Hey @austinado16 the thing that you've said is Right. When the engine cranks there's light coming from my test light so there's live feed going to my fuel pump. Very helpful 👌
Thanks again!
 

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1984 300D
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5,798 Posts
As in post 7.
If the fuel pump is working during cranking did the engine start?

This is generic to a lot of gasoline engines. If the Engine starts during cranking and you turn the key back and the engine dies that is a symptom of a bad ignition circuit resistor.
The reason is that during cranking the resistor is bypassed.

Note that high energy ignitions don't have the resistor. Your car is old enough it could have the resistor.
 
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