I just replaced engine wiring harness to my e220 1995 Mercedes and now I have no power to ignition and fuel pump

1. Check the fuel pump fuse: Locate your vehicle's fuse box (usually found under the dashboard or in the engine compartment) and check the fuel pump fuse. If it is blown, replace it with a fuse of the same amperage. If the fuse is fine, proceed to the next step.

2. Check the fuel pump relay: The relay controls the power supply to the fuel pump. You can typically find the fuel pump relay in the fuse box or a separate relay box. To test the relay, you can swap it with an identical relay (such as the horn relay) and see if the fuel pump starts working. If it does, the relay is the problem and needs to be replaced.

3. Inspect the wiring: Damaged or corroded wiring can cause a loss of power to the fuel pump. Check the wiring leading to the fuel pump for any visible damage, corrosion, or loose connections. Repair or replace any damaged wires and clean corroded connections.

4. Test the fuel pump for proper function: If you have access to a multimeter or test light, you can test the fuel pump terminals for power when the ignition is turned on. You should see a voltage for a few seconds as the pump primes. If there's no power at the terminals, the problem could be a faulty ignition switch, fuel pump control module, or a wiring issue.

5. Faulty fuel pump: If all the above steps show that power is reaching the fuel pump, but it is still not working, the pump itself might be faulty and need replacement.

The only way is to trace the wiring to hunt down that short. Just ck the wiring every few feet until u narrow it down to see where your losing your ignition power. Good luck

Diagnosing Mercedes Benz Misfire DTCs Auto Service World
Thanks

Description

*: ECM determines the start signal status by the signals of engine speed and battery voltage.
The ECM activates the fuel pump for several seconds after the ignition switch is turned ON to improve engine start ability. If the ECM receives a engine speed signal from the camshaft position sensor (PHASE), it knows that the engine is rotating, and causes the pump to operate. If the engine speed signal is not received when the ignition switch is ON, the engine stalls. The ECM stops pump operation and prevents battery discharging, thereby improving safety. The ECM does not directly drive the fuel pump. It controls the ON/OFF fuel pump relay, which in turn controls the fuel pump.

Component Function Check
1.CHECK FUEL PUMP FUNCTION
1. Turn ignition switch ON.
2. Pinch fuel feed hose (2) with two fingers.
1 : Air cleaner assembly


Fuel pressure pulsation should be felt on the fuel feed hose for 1 second after ignition switch is turned ON.
Is the inspection result normal? YES >> INSPECTION END
NO >> EC-466, "Diagnosis Procedure".
Diagnosis Procedure
1.CHECK FUEL PUMP POWER SUPPLY CIRCUIT-I
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector.
3. Turn ignition switch ON.
4. Check the voltage between ECM harness connector and ground.


Is the inspection result normal? YES >> GO TO 4.
NO >> GO TO 2.
2.CHECK FUEL PUMP POWER SUPPLY CIRCUIT-II
1. Turn ignition switch OFF.
2. Disconnect IDPDM E/R harness connector F10.
3. Check the continuity between IPDM E/R harness connector and ECM harness connector.

Is the inspection result normal? YES >> GO TO 3.
NO >> Repair open circuit or short to ground or short to power in harness or connectors.
3.CHECK CONDENSER-1 POWER SUPPLY CIRCUIT-I
1. Reconnect all harness connectors disconnected.
2. Disconnect condenser-1 harness connector.
3. Turn ignition switch ON.
4. Check the voltage between condenser-1 harness connector and ground.


Is the inspection result normal? YES >> GO TO 5.
NO >> GO TO 4.
4.CHECK 15A FUSE
1. Turn ignition switch OFF.
2. Disconnect 15A fuse (No. 32) from IPDM E/R.
3. Check 15A fuse.
Is the inspection result normal? YES >> GO TO 6.
NO >> Replace fuse.
5.CHECK CONDENSER-1 POWER SUPPLY CIRCUIT-II
1. Disconnect IPDM E/R harness connector E18.
2. Check the continuity between IPDM E/R harness connector and condenser-1 harness connector.

3. Also check harness for short to ground and short to power.
Is the inspection result normal? YES >> GO TO 13.
NO >> GO TO 7.
6.DETECT MALFUNCTIONING PART
Check the following.
??? Harness connectors E29, B10
??? IPDM E/R connector F10
??? Harness for open or short between IPDM E/R and condenser-I
>> Repair open circuit or short to power in harness or connectors.
7.CHECK CONDENSER GROUND CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect dropping resistor harness connector.
3. Check the continuity between condenser-I harness connector and ground.

4. Also check harness for short to ground and short to power.
Is the inspection result normal? YES >> GO TO 8.
NO >> Repair open circuit or short to power in harness or connectors.
8.CHECK CONDENSER-1
Refer to EC-469, "Component Inspection (Condenser-1)".
Is the inspection result normal? YES >> GO TO 9.
NO >> Replace condenser-1.
9.CHECK FUEL PUMP POWER SUPPLY CIRCUIT-III
1. Disconnect ???fuel level sensor unit and fuel pump??? harness connector.
2. Check the continuity between IPDM E/R harness connector and ???fuel level sensor unit and fuel pump??? and ground.

Is the inspection result normal? YES >> GO TO 11.
NO >> GO TO 10.
10.DETECT MALFUNCTIONING PART
Check the following.
??? Harness connector E29, B10
??? Harness for open or short between ???fuel level sensor unit and fuel pump??? and IPDM E/R
??? Harness for open or short between ???fuel level sensor unit and fuel pump??? and ground
>> Repair open circuit or short to power in harness or connectors.
11.CHECK FUEL PUMP GROUND CIRCUIT
1. Check the continuity between ???fuel level sensor unit and fuel pump??? and ground.

2. Also heck harness for short to power.
Is the inspection result normal? YES >> GO TO 12.
NO >> Repair open circuit or short to power in harness or connectors.
12.CHECK FUEL PUMP
Refer to EC-469, "Component Inspection (Fuel Pump)".
Is the inspection result normal? YES >> GO TO 13.
NO >> Replace fuel pump.
13.CHECK INTERMITTENT INCIDENT
Refer to GI-42, "Intermittent Incident".
Is the inspection result normal? YES >> Replace IPDM E/R.
NO >> Repair or replace harness or connectors.
Component Inspection (Fuel Pump)
1.CHECK FUEL PUMP
1. Turn ignition switch OFF.
2. Disconnect ???fuel level sensor unit and fuel pump??? harness connector.
3. Check resistance between ???fuel level sensor unit and fuel pump??? terminals as follows.


Is the inspection result normal? YES >> INSPECTION END
NO >> Replace ???fuel level sensor unit and fuel pump???.
Component Inspection (Condenser-1)
1.CHECK CONDENSER
1. Turn ignition switch OFF.
2. Disconnect condenser-1 harness connector.
3. Check resistance between condenser-1 terminals as follows.


Is the inspection result normal? YES >> INSPECTION END
NO >> Replace condenser-1.
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Here it is. Also The procedure
NOTE: The fuel pump relay is located in the engine compartment, attached to the relay bracket mounted on the front of the dash. Other than checking for loose connections the only service on the fuel pump relay is replacement.

PROCEDURE

1. Verify that the ignition switch is in the "OFF" position.
2. Disconnect the wiring harness plug.
3. Remove the fuel pump relay.
4. Install the new fuel pump relay.
5. Connect the wiring harness plug securely.

-Tim

Check the wiring between the fuel pump and the wiring harness, this sounds like a short or wire melting to something hot.

Listen for the fuel pumps to come on when you turn the car to on (not start) if you hear them its a spark issue normally. Suggest checking/replacing coil packs, engine wiring harnesses for degradation because of biodegradable wiring insulation.

Check valve in fuel system by pumps, or ignition system, or worse yet engine wiring harnesses shorting out due to breakdown in wiring insulation.

Fuel relays dont normally go bad fuel pumps and filters on the other hand do. Also check engine wiring harnesses for degradation as from 1993-1995 MB was forced to use biodegradable insulation on there wiring which fails due to the engine bay cooking it.

There is power at the fuel pump for aprox 3 seconds as soon as the ignition switch is turned on
then it does not get power again until the engine starts

so if you are checking the power at the pump you need to have someone else in the car to turn on the switch while you are looking at your meter , you have a relay under the hood under a plastic cover at the fire wall that controls the power to the pump .