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ml320 2000 fuel pump diagnosis

10K views 15 replies 6 participants last post by  Witek_M 
#1 ·
I have a 2000 ml320 that I purchased new. It now has 240,000 miles. I have replace the fuel pump once before. I did it after I paid MB diagnostic cost to tell me the problem. This time The car sputtered a few times before dying and not starting again. The engine turns over but does not start. I borrowed a pressure gauge from local store and I do not get any pressure from fuel rail. I checked the fuse and it looks good. I tried the relay test where you remove the relay and jump the two wires. I did not get any fuel pressure. I purchased a new fuel pump. I am now not sure that I am getting power to the terminal on the fuel pump. I need help with procedure and testing of wires and old pump. The fuel pump is about 6 years old. It still looks good. I am not electrically tech friendly. Pictures and diagrams would help me greatly. Currently the old fuel pump is out and the new one is still in the box. I did connect the new one to the terminal and turned the key to the 2 position to see if it would run. It did not. :|
 
#6 ·
I have a radio shack digital multimeter and a new circuit tester. I am not too sure how to use the mulitmeter. It has DC, AC, DIODE, OHM, ohm of 200, 2k, 2m. I will try to do it tomorrow. I tried jumping the relay when the old pump was in. I am not sure I did it correctly. I have purchase two terminals male and I will make myself a jumper cable. If I get no current what could it be?
 
#8 ·
Remove the K3 relay and turn the key to pos. #2.

With a small piece of heavy gauge wire stripped at both ends or jumper wire with spade terminals attached (preferred), insert one end into slot 30 and the other into slot 87. The jumper wires must make contact with a silver dot in each slot.

Then test the GREEN wire at the fuel pump connector for 12v and test the BROWN wire for ground. Do not connect the fuel pump for this test.
 

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#14 ·
You meant black lead to brown wire?

With relay installed you should get 2 seconds pulse when key is first turned to position 2. Constant supply when cranking. Battery is discharged at 12.2 V.
 
#15 ·
yes, I meant the black lead to the brown wire. Battery if giving reading of under 12 volts. there was a pulse when the key was turned on to the two positon. I will remove the battery today and recharge it overnight. Is there a way to bench test the old pump? I was afraid to install the new one only to find out that the old was still good. New one is still in the box.
 
#16 ·
Bench testing fuel pump would involve submerging it in bucket full of gasoline, connecting positive to where green wire goes, negative to where brown wire goes and then checking fuel delivery rate and pressure.

Last words of a *******: Hold my beer.
 
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