advice e46 problems

jon1981

hi folks,

the car (05 e46 320cd) for the last 8 months has problems starting in the morning. i noticed that when i turn the key to the on position i hear a humming sound from the glove box which lasts about 30 seconds ... the car will start but IF i dont hear this humming sound i know the car will not start.

now the mechanic connected up the computer to it and it gave a low fuel pressure reading. they recommended changing the fuel pump and relay... im wondering could it just be the relay ?

any advice? if it was the pump surely it would have packed in by now as it has been happening for the last 8 months. any advice? i can change either myself, also if the pump is in the rear why do i hear the humming sound from the glove box area?

Hal1

The humming or usually a ticking sound could be a relay. I'd go with the cheaper option first. Try prime the fuel pump a few times before starting. Turn ignition on (not starting the engine) so the dash lights up and switch ignition off when the eml light goes out etc. I'd usually prime my car on a cold morning.

I reckon it is the fuel pump unfortunately, I don't think a relay would struggle on for so long if it was wearing out.

MacGyver

if you lift out the back seat you should hear if its the fuel pump under it when u turn on the ignition.

jon1981

MacGyver wrote: »

if you lift out the back seat you should hear if its the fuel pump under it when u turn on the ignition.

car finallly wouldnt start this morning, switch the fuel pump relay with the horn and bingo she worked. hopefully it was the relay and not the pump...annoys me the garage wanted to change the pump and would not try the relay first.

JohnCleary

There's 2 pumps on the 320d, low pressure in the tank and high pressure on the engine. Anyhow you seem to have found the source of your problem

jon1981

out of curiousity what does the other pump do? are they both fuel pumps? i know the fuel pump is under the rear driver side seat where is the other pump?

frank gooding

One is just to lift fuel from the tank. Low Pressure.

The one under the bonnet to send the fuel to the injectors at high pressure.

2 different jobs.

Myrddin

There is also a pre-supply fuel pump under the passenger seat on the underside of the car. This is very well documented as having a high failure rate. When you dont hear the hum, this is the pump not supplying diesel to the high pressure pump on the engine thus causing a non start.

I'd lay odds this pump is on the way out.

jon1981

EnterNow wrote: »

There is also a pre-supply fuel pump under the passenger seat on the underside of the car. This is very well documented as having a high failure rate. When you dont hear the hum, this is the pump not supplying diesel to the high pressure pump on the engine thus causing a non start.

I'd lay odds this pump is on the way out.

i hear the hum now since ive changed the relay, its early days but hopefully it was the relay and thats the end of the problem