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bmwmilos

450 CDI shuts down intermittent, SAM??

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Posted (edited) · Report post

Greetings to all!

I have a problem and maybe someone had a similar experience before and can help.

A friend of mine bought a 2006 450 cdi and in a couple of days it shut down twice during driving,not being able to start for 2-3 minutes,then restarted and running ok again.

His neighbour hooked it to the tester and fault was P2000 ( related to crank sensor ). He replaced the sensor with BoSCH ( off course it was blocked and needed to be drilled ) however after a couple of days issue reoccurred. He brought it to me for diagnosing further. I hooked it to a tester and went for a drive and I was able to reproduce the problem. The car stopped with P1187 rail pressure code and had no pressure when trying to restart.

Edited by bmwmilos

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I read about SAM pin problem for fuel pump, I removed SAM from car,opened it up and found no obvious problems inside. I resoldered all of the pins and put everything back,went for a drive and it stopped again. I hooked a multimeter to fuel pump wire Teed a pressure gauge to low pressure supply. When started and during driving low pressure was about 2.5-2.8 bar, and voltage on fuel pump wire 13.5-13.7V. Then the car stopped and when trying to restart there was no voltage on fuel pump wire. I hooked the wire directly to battery but it still wouldn't start. After 2-3 minutes the voltage reappered during cranking and the car started.

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I did notice that the car does not stop when cold,but only after being driven for a while. When it stops for the first time,and after restart it takes maybe 3-5 kms to stop again. I was able to hear sometimes before stopping a relay click in SAM and noticed a drop in fuel pressure at the same time.

I also noticed that a few seconds before the engine dies if I am driving with throttle released the engine starts to judder ( as if I am playing with the throttle ) and the voltage on fuel pump also changes ( goes down then back a few times ). The tester is not fast enough to detect these changes,but I suspect that something causes the relay for the fuel pump, and also some relay for ECU to switch off.

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I suspect that the problem lies within SAM unit, maybe relays are bad or maybe there is some Darlington driver ( like ULN2003 ) that overheats and switches off. I will reopen the SAM unit and retest everything but I do not know what each relay does.

Does anyone have a CDI SAM pinout and relay list inside the unit? I would like to test if the power to the ECU also switches off when the issue occurs but I don't know which wires supply power to ECU.

Did anyone have a similar problem and how was  it solved ?

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You need to be looking on the high pressure side before you start on the low pressure side.

 

The low pressure side can easily be working correctly if you have a pressure sensing problems on the high pressure side.

 

I am assuming of course that you have checked / changed the fuel filter and that there are no leaks of any sort anywhere.

 

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The SAM has a row of pins that suffer from cold solder joints as you already know....you must remove solder from pins and re-solder them making sure you use a high temp soldering iron, not the old school slow lower temp kits.  The low pressure fuel pump wire is the second from one end. Check the plug, and it's wires inside it  as well as the soldering condition. IF it is a heat up this is usually the issue.   Have you checked your fuel filter condition and it's wiring? Wiring to the low pressure fuel pump in the tank? Grounds for it and the fuel filter/water separator?  You should be able to hear the low pressure tank pump run when you first turn the key on  and then it should turn off after building pressure. 

Now we are at the same place in diagnositics...as I have a no run situation also......it wants to start but only coughs.......so like you I am searching for high pressure issues.

Have you checked high pressure while cranking? It needs 120 to start.....I get 89....won't start. Rebuilding the high pressure pump is relatively easy, just keep everything in order and extremely clean. Also check the relief valve in each head of the pump for a weak or damaged coil spring which has slipped past it's perch and isn't holding the valve plug tight against the body. You can buy these valve at the dealership for around $30 each...buy 3...! If you get 120 then it's not your pump at this point.  BUT the working pressure is redicualously high, again sorry do ot remember exact number.... Now you must check resistance for the rail pressure sensor as to make sure it's not holding pressure or allowing some to leak back to the tank resulting in too low of pressure. Now go to rail pressure sensor and check it's readings, sorry don't remember off the top what they should be...   You can also check connection and wiring to the bottom of high pressure pump and both sensors on rail.....for damages.  Now we are at the same place...I'm about to swap out my rail and sensors for a known runner....fingers crossed.

Good luck and hope my problem helps you.

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1 hour ago, Mjolinor said:

You need to be looking on the high pressure side before you start on the low pressure side.

 

The low pressure side can easily be working correctly if you have a pressure sensing problems on the high pressure side.

 

I am assuming of course that you have checked / changed the fuel filter and that there are no leaks of any sort anywhere.

 

I forgot to write, fuel filter was the first thing to change, as well as filling the tank to max.

I do not understand your post,can you elaborate please what to look on high pressure side???

I wrote that low pressure fuel pump 12v supply goes missing, and it does not reappear for 2-3 minutes and during that time the car cranks but no start. The high pressure pump cannot produce pressure if the low pressure is missing.

P1187 is normal consequence, since ECU wants more pressure,but the pressure cannot be achieved due to low pressure pump stopping.

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The low pressure pump cycles as needed, doesn't run constantly unless required.

You can relay it also to help reduce the strain on the SAM, a good idea.
 

 

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I have resoldered the pins, even though there were no visible cracks or damaged pins or connector. I have connected a wire directly to red/black wire for the fuel feed pump and I used it for measuring pump voltage. When I determined that when the car shuts down the pump is not receiving power, i connected that wire directly to battery but the car still would not start.

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After 2-3 minutes of waiting when I try to start I see the voltage on fuel pump and the car starts immediately. So by my reasoning it cannot be only fuel pump relay/pin problem because if this was the case the car would start when I bypass fuel pump directly to battery. Something else is preventing the car from starting. 

 

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OK, here i go, with the stupid question....have you checked all grounding pins around each of these parts in the system..?  Could there be a bad wire going to the pump or the signal to the pump what is getting wiggled as you drive? 
I think I have been told at some point there is a relay in the SAM that is related to the fuel pump but it is a hard wired unit and difficult to replace....but I am by no means positive about this...?  It just rings a bell.....I think IZZY said something about it a while back.....and said it is a rare issue very rare.   Go over to Evilution and check the SAM information there, again you may need to become a member if you already are not one to get deep into the schematics...imho well worth the cost of their lowest donation requirement. They didn't get as many CDI's as we did so their knowledge isn't as good but their technical literature is far better imho when they have what you need. That is.   But this is your choice.  as you probably already know there is no chat there so you can't ask questions easily.  So we must use both sites as best we can.


Could you have a bad low pressure pump?  inside the tank ?

 

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Posted (edited) · Report post

Your logic is flawed.

 

Obviously the fuel pump circuit is working because the fuel pump runs when it is told to run.

 

Something is telling the ECU that the pump does not need to run. This can be a long list of things that you need to check. Running the fuel pump manually will not make the injectors inject. If the ECU is stopping the fuel pump it is probably also stopping the injectors along with all sorts of other things.

 

What do you think would happen for example, if the high pressure sensor was not reading correctly? The ECU would shut down the fuel pump and injectors in order to stop anything untoward causing damage.

 

If I had to guess, given that it takes a few minutes to start again, I would say your high pressure is too high. You need to read it real time with Star or Delphi. It may be just a faulty temperature sensor telling hte ECU that the engine is overheating.

 

 

Edited by Mjolinor
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This is exactly where i am.....replacing sensors or fuel rail to get those removed from problem and I have a STAR!  There is so many tests to do regarding this issue it's mind boggling!  

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When it runs do a injector leak down test and compare each injector with the rest, easy. so to speak.  That will at least knock those out of the problem?

 

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I did monitor the pressure in real time with Texa Axone. The demanded vs real pressure is almost the same,until I start to notice the voltage drop/relay click during driving, then real pressure goes slightly below demanded and the pressure regulators duty cycle goes to 80% or even higher. That would suggest fuel starvation and I was considering CP1 pump, I even have a Bosch repair kit ( I ordered two kits when I resealed the pump on my 450 cdi ), but I am puzzled by the fact that the low pressure pump switches off and does not restart for the next 2-3 minutes.

I guess I will remove the CP pump and open it up. I also have the orings for pressure regulator so I will also replace those,but the waiting time is still puzzling.

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I even tried the pressure sensor from my 450 but the problem remains. Maybe I will swap CP pump also for testing.

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Have you tested the wiring on the bottom of the high pressure pump yet?  

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Answer this question.  When you drive the car does it feel like it has no more power at full throttle than half or three quarters?  That is how mine would behave before I put seals in my high pressure pump.

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@Willysdo you mean the wires from additional element on CP pump or the wires from crank sensor? I did check all of those and there was no visible problems,not even cracked insulation.

@Nigel the engine feels full of power,running great with throttle fully available until I hear that click, then I sense a judder, even when going downhill with foot off throttle there is an engine judder ( and relay clicks in SAM )  about 10-20 seconds before the engine shuts down. When going downhill and this occurs it feels like I am giving small throttle input, that kind of judder. The engine shuts down not only in acceleration or constant speed,but also when going downhill with throttle released. This is why I don't think it's CP pump, since with throttle released there is no flow through injectors.

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6 hours ago, bmwmilos said:

do you mean the wires from additional element on CP pump or the wires from crank sensor?

Yes.....the additional wires dropping down from CP pump.

IF you can hear a definate 100% for sure click in the SAM, I suggest doing as much research at Evilution on relays in the SAM as something is telling me they have this information.  Also I remember this being discussed here before at some point, but they simply swapped out their SAM if memory serves me well....but don't count on it...lol.  It just rings a bell.  You have to have a STAR to teach in a different SAM  You just can't easily swap them out. The speedo and the ECU must be taught to speak with the new SAM...I have done all 3 in the past trying to sort out a different issue.

As for the low pressure from the CP pump.....when the pump gives up delivering the necessary pressure the rail pressure sensor see's the change and triggers the SAM relay to shut it down...No..??

I agree that there is many things that can trigger the SAM or ECU to shut the engine off, it's far too complicated of a car for it's own good imho...lol.

 

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I disassembled the CP pump and found practically nothing. All of the orings were ok, it seems they were replaced at some point. Plungers are bright and shiny,no signs of wear, one is slightly darker ( the one with solenoid on top ) but still mirror finished.

Only thing I found was that the fuel seal on shaft wore a groove inside the shaft, so I will polish that and I found locally a thinner seal so I will move it 2mm away from groove and it should be ok. There was no leak of fuel from pump. The one way valve springs are good and as far as I can test they hold, even the one way ball valve. So I will reassemble the pump with new seal set And then we will see.

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