ML350driver07

I have a 2007 ML350 (W164.186 / 272 engine). My fuel pump will not run when I start the truck. If I remove the fuel pump relay (F4 fuse block; Relay O) and jumper the fuel pump circuit (circuit 30 to circuit 87), the pump with run. With the key in the ON position, I am getting about 12.5V on one of the relay signal contacts (F4 fuse block, P5, pin 3, circuit 86) and about 3.5V on the other relay signal contact (F4 fuse block, P6, pin 4, circuit 85). I'm thinking the 3.5V is faulty or something in the signal circuit. Maybe the ECM isn't grounding properly. I've swapped relays and tested the current relay with 12V and it clicks and makes contact.

I'm referencing MB wiring diagram: 5415 2103mad (4Q 2007).

So far I have replaced the fuel pump and the main battery. Fuse 57 for the pump is good and the relay is good. The initial problem was losing power a couple time on a highway trip and once I shut the engine off it would not restart.

Can anyone help?

(Purchased in 2012 at 78,000 miles and have about 192,000 now)

Maj. Dundee

It is impossible to service these vehicles without the use of a . Codes must be read in the ECM and the rear SAM for starters.

Read actuation PDF.

Additionally, look at all the codes for the ECM. Open PDF and in the white search box type the word FUEL and hit ENTER repeatedly and it will give all the codes that relate to fuel.





Jump start the truck as you did before.

Turn eng. off and remove key, do not replace relay.

Check both contacts on fuse 57 for 12v in the Load Compartment Fuse Box.

Then check cir. 30 cavity in relay Ko for 12v making sure you touch relay contacts.

Maj. Dundee

How long does it take to check a fuse?

ML350driver07

Thanks for the info! Sorry for the delayed response. So, I followed your advice and got 0V at fuse 57 contacts and 0V at the outbound circuit 30 to the fuse and fuel pump and 12V at circuit 87 (inbound from cir. 30). I expect this is normal with the relay open.

Here are additional scenarios:
Key ON / Relay Installed - 0V cir. 30 outbound / 12V cir. 87 inbound / 12V cir. 85 signal / 12V cir. 86 signal
Key ON / Relay Removed - 0V cir. 30 outbound / 12V cir. 87 inbound / 3.5V cir. 85 signal / 12V cir. 86 signal
Key OFF / Relay Installed or Removed - 0V cir. 30 outbound / 12V cir. 87 inbound / 0V cir. 85 signal / 0V cir. 86 signal

Before I jumped the truck, I scanned it using an Innova 3100f scanner, I found 7 generic codes:
P0015 Exh Cam Position Timing - Over-retarded (Bank 1) - this one has been intermittent before my fuel pump issue
P0627 Fuel Pump Control Circuit / Open
P0174 System Too Lean (Bank 2)
P0463 Fuel Level Sensor A Circuit High Input
P0455 Evap Emission System Leak Detect (gross leak/no flow)
P0627 Fuel Pump Control Circuit / Open - Yes, twice
P0171 System Too Lean (Bank 1)

I cleared these codes. After jumping the truck I scanned again and only got one code:
P0627 Fuel Pump Control Circuit / Open - I didn't see this code in your PDF files.

So, other than the obvious "what next?", I rigged up a toggle switch between cir. 30 and cir 87 so I can now turn the pump on with the switch. However, is it safe for the truck to make it run in this configuration? Obviously driving it this way would eliminate the fuel shut off feature in the event of a crash.

Here are pics...


Circuit 30 outbound to Pump (0V)

Circuit 87 inbound from Circuit 30 (12V)

Circuit 85 (3.5V w/relay removed and 12V w/relay installed)

Circuit 86 (12V)

Remote toggle switch to turn pump on. I haven't left it on to start the truck and let it run but only momentarily on to build fuel pressure. Is it safe to run the truck this way?

Remote Toggle Switch

Remote Relay - this was the only way to test the contacts with the relay "installed".

Remote Relay

F4 Schematic Sheet 1

F4 Schematic Sheet 2

F4 Schematic Sheet 3

F4 Schematic Sheet 4

ML350driver07

Thanks for the info! Sorry for the delayed response. So, I followed your advice and got 0V at fuse 57 contacts and 0V at the outbound circuit 30 to the fuse and fuel pump and 12V at circuit 87 (inbound from cir. 30). I expect this is normal with the relay open.

Here are additional scenarios:
Key ON / Relay Installed - 0V cir. 30 outbound / 12V cir. 87 inbound / 12V cir. 85 signal / 12V cir. 86 signal
Key ON / Relay Removed - 0V cir. 30 outbound / 12V cir. 87 inbound / 3.5V cir. 85 signal / 12V cir. 86 signal
Key OFF / Relay Installed or Removed - 0V cir. 30 outbound / 12V cir. 87 inbound / 0V cir. 85 signal / 0V cir. 86 signal

Before I jumped the truck, I scanned it using an Innova 3100f scanner, I found 7 generic codes:
P0015 Ex Cam Position Timing - Overretarded (Bank 1) - this one has been intermittent before my fuel pump issue
P0627 Fuel Pump Control Circuit / Open
P0174 System Too Lean (Bank 2)
P0463 Fuel Level Sensor A Circuit High Input
P0455 Evap Emission System Leak Detect (gross leak/no flow)
P0627 Fuel Pump Control Circuit / Open - Yes, twice
P0171 System Too Lean (Bank 1)

I cleared these codes. After jumping the truck I scanned again and only got one code:
P0627 Fuel Pump Control Circuit / Open - I didn't see this code in your PDF files.

So, other than the obvious "what next?", I rigged up a toggle switch between cir. 30 and cir 87 to I can now turn the pump on with the switch. However, is it safe for the truck to make it run in this configuration? Obviously driving it this way would eliminate the fuel shut off feature in the event of a crash.

Note: I replied a few hours ago with the info above plus several photos. I haven't seen my post yet so I assume it is being reviewed by a moderator and may show up later.

Maj. Dundee

I interpreted the wiring diagram incorrectly. In all other relay diagrams M/B had cir. 30 as live at all times.

In this case it is cir. 87 that is live at all times. So in normal circumstances, cir. 30 & fuse 57 will not be activated until the veh. is cranked and started.

So, remove the kO relay and test cavities 85 & 86 while turning the key to start (helper required) Indicate which one sends a negative signal from the ECM and which one sends a 12v signal.

ML350driver07

Maj. Dundee

You must test 85 for a GROUND signal, not voltage.

ML350driver07

Maj. Dundee

What is the part number for your original relay?

Where did you get the replacement relay and what is the part #?

ML350driver07

Maj. Dundee

When you jump start the eng., do you bridge 30 & 87?

ML350driver07

Maj. Dundee

So if the truck runs when you bridge, and 85 is sending a ground signal, then there must be something wrong with the 86 wire.

Give me 1/2 hr.

Maj. Dundee

One other question. How did this problem occur, turned off eng. and the next morning it wouldn't start, or other?

ML350driver07

Maj. Dundee

OK go to the eng. compartment fuse box, locate and remove fuse 105. Clean both blades and reinsert. Then try and start eng. with everything in place.

ML350driver07

ML350driver07

Maj. Dundee

So what are you telling me? Was it the dirty blades on the fuse?

ML350driver07

Maj. Dundee

The problem is not the fuse, it's the contacts that the fuse goes into.

Roughing the fuse blades partially scratched the contacts enough to supply the proper voltage.

Vitls

Hello! Understand this is a really old thread but same problem as OP except the solution didn't work for me. I get 9.1v between 85 and 86 with key on engine off. And 14v key on engine on/running. Measured at ECM, same ~9v (swithced ground, testing to good positive).

is there a set of conditions that must be met before ECM will trigger switched ground? Im guessing one or more is not met before the engine is running giving me no switched ground to fire the fuel pump relay and thus no start.

2008 ML350 w164 272

thank you for any input!

Maj. Dundee

What is the problem you are having?

Do you own a scanner?

Vitls

Fuel pump does not turn on when turning key to ON/START. I'm able to jumper realay, get the pump on, start the car.

i have a MBII scanner that is able to scan ICS, R-SAM, etc. But did not see any codes that would be related if i didnt pull fueses/relays while looking for problem.