BMW Fuel Pump Dying Characteristic

[wan520i]

To Sifus, Does anyone know how the fuel pump behave before it completely die? Will it "pretend" die, and become "alive" once a while before it finally gone? Another questions is, can we still start the engine if the fuel regulator faulty (FG)? will the FG stop fuel passing through it? Thanks for your inputs !!!

 

[goggomobil]

Depends what its going to die of.

 

[jarance]

yes, that is the symptom of a dying fuel pump.

It happen to me before.. Suspect it was faulty when I inject 12VDC directly to it and it did not buzz. Knock it a bit and it become alive. Die again when put it back into service after a couple of KM driving..

My advise.. change it before you get stranded on the road.

Fuel regulator is just only a spring activated device. It will released the excess pressure when the fuel pump is delivering the fuel to the fuel rail.
It is faulty, i.e. jammed shut that means that the pump pressure is always maintained at the fuel rail. Theorectically, the car should be able to start and go.
However, not good for the pump as it will overheat due to lack of petrol flow thru the pump. Flow of the petrol is restricted if the fuel regulator is jammed shut.

 

[wan520i]

Actually this happen to my car now:

1. Last 1 month or 2, after parked the car for 2 days, can't start the engine. Finally it start after keep cranking...cranking...cranking...

2. Last week, the engine couldn't start in town, after buying something from shop. Wait for about 25 mins, try to start, was OK.

3. Yesterday, stop the car to buy something in town, after 15 mins, couldn't start. Wait for 20 mins, the engine start-OK.

I suspect two components, either fuel pump or fuel pressure regulator..., your inputs please!!

Oh..another sympton is my car always need longer cranking to start since last year...

Thanks...

 

[chairoger]

Actually this happen to my car now:



Oh..another sympton is my car always need longer cranking to start since last year...

Thanks...

Cold start needs replacing? Distributor cap almost gone? Weak batteries? Quite possibly quite a few stuff

 

[pussy]

Wan520i

Actually this happen to my car now:

1. Last 1 month or 2, after parked the car for 2 days, can't start the engine. Finally it start after keep cranking...cranking...cranking...
- it's your FG or your injectors

2. Last week, the engine couldn't start in town, after buying something from shop. Wait for about 25 mins, try to start, was OK.
- it's either your FG or Ignition Switch or Crank Sensor

3. Yesterday, stop the car to buy something in town, after 15 mins, couldn't start. Wait for 20 mins, the engine start-OK.
- it's either your FG or Ignition Switch or Crank Sensor


I suspect two components, either fuel pump or fuel pressure regulator..., your inputs please!!

Oh..another sympton is my car always need longer cranking to start since last year... Crank Sensor

have fun checking, cos always this problem drives us up the wall..

cheers.

 

[wan520i]

BIG THANKS for Sifus inputs...

Latest update, performed fuel pressure test just now, attached a pressure gauge to inlet hose somewhere near thottle body.

Fuel pressure reading as below:
Idling: 2.8 bar.
Full load: 3.5 bar.
Engine off: pressure drop slowly (within 5-10 minutes) to ZERO after first & second test, maintaned at 2.5 & 3.0 bar for another tests.
Pinched the inlet hose after pressure gauge while idling: 5.5 bar.
(Forgot to pinch the hose before pressure gauge..aiyo..)

Mr.Pussy, how can I solve the injetors problem? by ultrasonic cleaning them? and may I know how to trouble shoot the Ignition switch? you mean wiring at ignition key there? Diagnosed by a Korean scanner revealed no fault code, will the Crank sensor fault code erased after each successful start?

chairoger, I don't thnk there is cold start valve & distributor cap inmy car, is M50B25tu. And I think there is no battery issue here as I can still do cranking..

Sifus, your inputs after this test please..Thanks.

 

[KL2DC]

On the wide spread N54 (335i) high pressure fuel pump failure cases, the symptoms include shuddering during idle, longer cranks and hesitation before limp mode. My friend got stranded in his brand new 335i in rush hour on a busy bridge, car had less than 2,000 miles. Nearly everyone I know who has a 335i is going through the same woes. Car goes out of commission for a minimum of 30 days. Only 30 fuel pumps goes into the US weekly, the backlog is in the hundreds. Boo to BMW and Siemens on this issue...

 

[jarance]

BIG THANKS for Sifus inputs...

Latest update, performed fuel pressure test just now, attached a pressure gauge to inlet hose somewhere near thottle body.

Fuel pressure reading as below:
Idling: 2.8 bar.
Full load: 3.5 bar.
Engine off: pressure drop slowly (within 5-10 minutes) to ZERO after first & second test, maintaned at 2.5 & 3.0 bar for another tests.
Pinched the inlet hose after pressure gauge while idling: 5.5 bar.
(Forgot to pinch the hose before pressure gauge..aiyo..)

Mr.Pussy, how can I solve the injetors problem? by ultrasonic cleaning them? and may I know how to trouble shoot the Ignition switch? you mean wiring at ignition key there? Diagnosed by a Korean scanner revealed no fault code, will the Crank sensor fault code erased after each successful start?

chairoger, I don't thnk there is cold start valve & distributor cap inmy car, is M50B25tu. And I think there is no battery issue here as I can still do cranking..

Sifus, your inputs after this test please..Thanks.

FYI, crank shaft sensor failure will disable the ignition and fuel pump circuit. This is the fail safe circuit incorporated in the ECU. That is why many people will misdiagnosed it as fuel pump failure because the fuel is not detected at the fuel rail.

Usually, I tap the 12VDC supply from the battery and connected it directly to the fuel pump to check the condition.

Idling: 2.8 bar and full throttle 3.5 bar. Have you try this test... check the fuel pressure @ 1000rpm, 2000rpm till 5000/6000 rpm.. (which ever is the highest rpm your engine can produce.) Find out the RPM when the pressure start to maintain at 3.5 bar. The pressure should be constant after a certain RPM.

BTW, it should be constant pressure regarless of the engine RPM.

You should also test the fuel pump without running the engine by jumpering terminal30 and 87 of the fuel pump relay as recommended by Bentley Handbook.

You mentioned that the presssure drop after 5 minutes. It should not dropped. If it does, that means that there the check valve at the fuel pump is faulty or small leak somewhere else.

Long cranking is usually due to faulty fuel pump (as in the check valve)

 

[wan520i]

Jarance,

So you are saying that it is also possible that my crank shaft sensor failure? but i diagnosed with a Korean scanner, there is no fault code. Will the fault code been erased after I managed to start the engine?

I didn't test the fuel pressure at certain rpm as you mentioned.

From the test result, can you say that the fuel regulator is failure or good condition? btw it does fluctuate according to engine load/idle. That is the main function of a Fuel pressure regulator right?

From the test, can you say that the non-return valve in fuel tank is failure? or where else can leaks? injectors? fuel pressure regulator?

And do you know where can I clean the injectors by ultrasonic cleaner?

 

[jarance]

Jarance,

So you are saying that it is also possible that my crank shaft sensor failure? but i diagnosed with a Korean scanner, there is no fault code. Will the fault code been erased after I managed to start the engine?

I didn't test the fuel pressure at certain rpm as you mentioned.

From the test result, can you say that the fuel regulator is failure or good condition? btw it does fluctuate according to engine load/idle. That is the main function of a Fuel pressure regulator right?

From the test, can you say that the non-return valve in fuel tank is failure? or where else can leaks? injectors? fuel pressure regulator?

And do you know where can I clean the injectors by ultrasonic cleaner?

Yes, crank shaft is one of th culprit.. My personal experience with crank shaft sensor failure is couple of time, the engine cannot start. One time on the highway, the engine lost power and I have to pull over to the R&R to check. After off the engine, it never start again until change the sensor.

Sometime a dirty sensor could also cause this problem. You have to remember that the location of the sensor is almost at the bottom of the engine. There is a possibilty that dirt or oil/mud might get caught between the magnetic pickup and the teeth of the crankshaft.

Try check the pressure with the engine not running by jumpering the fuel relay terminal 30 and 87. That way you eliminated the variable like faulty injectors and concentrate only on the fuel pump, regulator and check valve. The pressure must be constant during this test. The advantage about doing this test is the engine is off and you hear or detect any abnormal sound more easily.

There are a few shops around that does ultrasonic cleaning of injector. I have use one shop called "autokanak" in Gleamarie. They charged according to the number of injectors. This shop is very clean one and they a cute machine that you can install the injectors in it and it will do an auto test for the injectors. Tests like injectors spray pattern, volume check, cleaning, backflush, leak. If it fail the test, then they will dipped it a solvent and clean it with the ultrasonic cleaner.

 

[wiramod11]

well.. sorry to ask this question...

Basically i found out last mth.. everytime i stop by to pump petrol.. after finish my ride will had hard time to start the engine.

I found out that everytime when the fuel meter shows up that it near empty (thats when the light blink up) i can hear some noise "whheeeeww" whenever i press the acc. When stop to fill up petrol once done. I start to crank the car up.. and it can't start.. and i need to crank at least 2-3 times...

What is wrong.. is the fuel pump start to give way.? If change fuel pump do i need to calibrate the sensor as well..?? thanks.. my ride is yr 1999 M43 E36.

 

[jarance]

How many more kilometer when the low fuel light light up, did you drive before filling up? Usually there is about 10 litres left in the tank when the low light blink up.

 

[Iqlima]

Jarance,

So you are saying that it is also possible that my crank shaft sensor failure? but i diagnosed with a Korean scanner, there is no fault code. Will the fault code been erased after I managed to start the engine?

I didn't test the fuel pressure at certain rpm as you mentioned.

From the test result, can you say that the fuel regulator is failure or good condition? btw it does fluctuate according to engine load/idle. That is the main function of a Fuel pressure regulator right?

From the test, can you say that the non-return valve in fuel tank is failure? or where else can leaks? injectors? fuel pressure regulator?

And do you know where can I clean the injectors by ultrasonic cleaner?

Can you start the car when you short 11 and 14 in diagnostic socket with key in position 2 ?

 

[wiramod11]

How many more kilometer when the low fuel light light up, did you drive before filling up? Usually there is about 10 litres left in the tank when the low light blink up.

well.. i drove for around 20-30km when the low fuel light up... when ever the low fuel light up i can hear the sound "whhheeewww" whenever i press the acc. I try to fill up the fuel before the light up.. also same issue persists.. but without the annoy sound. Just that everytime i fill up petrol it was kinda hard to crank the engine... so does this a issue with fuel pump?

 

[jarance]

well.. i drove for around 20-30km when the low fuel light up... when ever the low fuel light up i can hear the sound "whhheeewww" whenever i press the acc. I try to fill up the fuel before the light up.. also same issue persists.. but without the annoy sound. Just that everytime i fill up petrol it was kinda hard to crank the engine... so does this a issue with fuel pump?

wira, hard to say about your problem. never ever encounter it before..

1. can you determine where the "whhhheeeeww" sound is coming from? Front or rear of the car?

2. When did you last change your sparks plugs, fuel filter?

3. Any smell of petrol when you fill to full tank?

 

[taabster]

Jarance, any idea how much is the injector cleaning charges like?

 

[jarance]

about RM50 per injector... lah

 

[Zoggee]

On the wide spread N54 (335i) high pressure fuel pump failure cases, the symptoms include shuddering during idle, longer cranks and hesitation before limp mode. My friend got stranded in his brand new 335i in rush hour on a busy bridge, car had less than 2,000 miles. Nearly everyone I know who has a 335i is going through the same woes. Car goes out of commission for a minimum of 30 days. Only 30 fuel pumps goes into the US weekly, the backlog is in the hundreds. Boo to BMW and Siemens on this issue...

Oh thats bad for BMW reputation. How are they gonna rectifies this problems?

 

[wan520i]

Can you start the car when you short 11 and 14 in diagnostic socket with key in position 2 ?

Iglima, i didn't try this, what can you tell about this test?

Thanks.