Engine cranking but not starting?

Tiny
BLESSING EWOBOR
  • MEMBER
  • 2007 MERCEDES BENZ R350
  • V6
  • 2WD
  • AUTOMATIC
  • 235,487 MILES
The engine of the vehicle is cranking but not starting, the engine was scanned for diagnostics trouble code, but no code was available. It was observed that fuel is not supplied to the engine. I energies the fuel pump with external battery, the fuel pump was working. However, while cranking the engine power was not available at the fuel pump. If the fuel pump connector is disconnected and probed while cranking, it will display 10v, immediately it is connected no voltage will be available to the fuel pump any longer. Removing the connector to the fuel pump and supply eternal battery voltage, then crank the engine, the vehicle engine will start running.
What could be the problem?
Could I get a wire diagram for it?
All the fuses have been checked and confirmed okay.
Thank you
Monday, December 16th, 2024 AT 10:02 AM

7 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,149 POSTS
I have seen the MAF sensor failure and cut off the fuel pump for safety. If you unplug it and the engine starts, then you know that is the problem. Here is a video to show you how and I have included the sensor location in the diagrams below.

https://www.youtube.com/watch?v=lXLJbuAZ4CE&t

Here are the fuel pump wiring diagrams as requested. Check out the images (below). Let us know what you find.
Images (Click to make bigger)
Thumb
Thumb
Thumb
Thumb
Thumb
Was this
answer
helpful?
Yes
No
Tuesday, December 17th, 2024 AT 11:42 AM
Tiny
BLESSING EWOBOR
  • MEMBER
  • 754 POSTS
Thank you very much.
Was this
answer
helpful?
Yes
No
Tuesday, December 17th, 2024 AT 5:32 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,149 POSTS
You are welcome, please let us know what happens.
Was this
answer
helpful?
Yes
No
Wednesday, December 18th, 2024 AT 10:01 AM
Tiny
BLESSING EWOBOR
  • MEMBER
  • 754 POSTS
Yes, I will let you know.
Was this
answer
helpful?
Yes
No
Thursday, December 19th, 2024 AT 11:07 AM
Tiny
BLESSING EWOBOR
  • MEMBER
  • 754 POSTS
Hello,

The problem was the fuel pump fuse (fuse No 57), I used multimeter to test for continuity while testing the fuse initially and there was continuity. Pulling out the fuse later from the fuse box confirmed that the fuse has heat - up, the terminals even pulls into the fuse box. Replacing the fuse solved the problem, the engine has started and running fine. Does it mean that continuity is not a good way to test for fuse.
Was this
answer
helpful?
Yes
No
Saturday, December 21st, 2024 AT 2:25 PM
Tiny
BLESSING EWOBOR
  • MEMBER
  • 754 POSTS
The mistake that I did is that measure the continuity on the fuse without removing it.
Was this
answer
helpful?
Yes
No
Sunday, December 22nd, 2024 AT 8:31 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,149 POSTS
Usually that will work, it might have been a bad connection, did you remove the fuse and inspect it? Glad you could get it fixed, thanks for letting us know. Please use 2CarPros anytime we are here to help.
Was this
answer
helpful?
Yes
No
Monday, December 23rd, 2024 AT 1:09 PM

Please login or register to post a reply.

Related Engine Not Running Content

Car Cranking but Not Starting? Try This
VIDEO
Car Cranking but Not Starting? Try This
Instructional repair video
Engine Not Starting
GUIDE
Engine Not Starting
Over the past 20 years at 2CarPros we have identified the top problems that are easily fixed. This guide can save you a trip to the repair garage or calling a tow truck and...