Sprinter CDI Fuel Pressure?

Hi Guys
I am tyring to track down a suspected fuel problem with my 2002 208 CDI. Can anyone tell me what the pressure in the rail should be at idle?

Autodata suggests 1350 BAR operating pressure but is that RPM dependant?

Thanks
Glen.

groupbquattro said:

Hi Guys
I am tyring to track down a suspected fuel problem with my 2002 208 CDI. Can anyone tell me what the pressure in the rail should be at idle?

Autodata suggests 1350 BAR operating pressure but is that RPM dependant?

Thanks
Glen.

Click to expand...

At idle pressure should be anywhere from 150 (low,start up) up to 450bar.... CAUTION CAUTION, WARNING..... do not attempt to loosen a injector line while running EVER . That amount of pressure with seriously injure you or possibly kill you. The fuel rail pressure to the injectors can reach over 1500 bar (under load) .
I have never used nor heard of any fuel pressure gauges going that high... (and not leaking or exploding) .
Final question , what is the problem ???

Carl

Hi Carl
Thanks for the reply, i am really starting to scratch my had with this

It runs fine (sometimes) and others it just cuts out likes it has been switch off. Fuel Pressure Control Valve runs at around 18% most of the time but sometimes rises to about 24% usually before it fails. Fuel pressure is running around the 400 BAR mark but can rise to 600 ish, RPM dependant. (i am not fully convinced this is high enough though for a common rail system?) (I intend to check with another Sprinter at work in the new year to compare the specs)

There appears to be no pattern as to when it fails. Sometimes it wont run for more than a couple of minutes others it will do a 20 mile round trip.

Just before I bought it cheap from a friend the Merc Dealer repaired the engine wiring loom low down over the engine mount, replaced the fuel sensor on the front of the rail, the valve on the rear of the rail. This made no difference whatsoever. Predictably they then recommended 4 new injectors at £1600. This was when my mate gave up an sold it to me.

I have carried out a return leak off test on the vehicle which tested good, then removed the injectors for bench testing which also proved good.

I was watching live data the other day and it failed with the control valve at 18% and fuel pressure running at 350 BAR ish??

Do the sprinters have a LP fuel pump? I am assuming the one on the end of the CAM is the HP Pump?

Thanks,
Glen.

Glen: can you give me any codes in the CDI unit ??
And yes LP pumps are on Sprinters , up to 03 the pumps are just ubove the high pump (mechanical)
from 04 up they have electric lift pumps in the tank.
What year is yours


Carl

Hi Carl
The only code in is P0190 Bank 4/6 (Rail Pressure Sensor) The signal Voltage is too low.

I have just taken some data and uploaded it on the links below.

http://www.youtube.com/watch?v=LCvHV5Sa0r8

http://www.youtube.com/watch?v=yKWCOHTWd5U

All the time this data was being recorded the EDC light was on. The code P0190 would not clear as the live data shows 0 BAR Fuel Pressure. When I tried to clear the code the engine was interrupted for a split second.

The engine stalled on its own after around 20 minutes of idling then when I restarted it the fuel pressure started to register and the code would then clear. It stalled again about 5 minutes later and would not re start.

During the first run i couldn't help but notice that the injector readings were quite different, which i would have normally expected to be similar? On cranking in the second video they all read 0.0?

I checked the fuel pumps and they are both on the front of the engine, LP at the top and HP below. its a 2002. It was difficult to see but it looked a bit damp under the HP pump, couldn't say if it was oil or fuel though.

Thanks
Glen

Glen see if you can see low side fuel pressure . It should be apox. 3.5-4.5 bar under load.
Is the fuel filter new ???

Carl

Hi Carl
Thanks for all your advice so far.

The fuel filter is new and I cant see a LP measuring block in Texa Diagnostics, i am not sure if there is even a LP sensor to relay the signal? Do I have to do this manually?

With the way the engine cuts out its exactly like the key has been turned off, it does not seem to run out of fuel so to speak. I am also concerned at the lack of HP display (at 0 BAR) in Texa and how the injection values are dissimilar. Also the lack of any values at all on cranking seems strange?

Are the injectors supplied with a constant 90v ish of power and actuated via earth?

I cant help but feel this is electrically related, if the Wiring loom that the Merc Dealer initially repaired was damaged (and the repair wasn't just precautionary) could this have caused some damage the ECU maybe?

Thanks,
Glen.

If the filter is new and the rail PSI sensor is new and Pressure control valve is new , and you are still getting this code , you need to isolate which area the problem is in , low side or high side. If the van is a 2002 - 2003, there is a low side pressure sensor mounted to the lower front side of the intake manifold. But I am inclined to believe that there is a chance that there could be an issue with either air in the fuel system or High pressure pump issues. There is a specific test for the high pressure pump output, manually and electronically. The manual test is to remove the number 1 injector return line only (top of the injector),place a measuring vial on the injector return port, then unplug the fuel rail pressure control solenoid (valve), then crank the engine for 10 seconds and read the amount of fuel in the vial 40ml or less = poor HP pump performance , check for leaks or aeration , if none present and the low pressure system is OK then replace the HP pump. NOTE; make absolutely certain low pressure system is functioning as it should , for it will adversely effect the high pressure system.
And lastley , abrupt engine cutout can happen if fuel pressure fluctuates just slightly.
Another note: the engine has to crank faster than 250-300 RPM to obtain accurate testing
Carl

Thanks once again Carl,
Your suggestions make clear sense. I cant find a measuring block in my Diagnostic setup to check the LP side? I found a workshop manual on here somewhere that gave some useful spec on the LP & HP systems. I will look into checking the LP somehow.

I have previously carried out a leak off test on all four injectors (as you have explained for injector 1), and there was very very little being returned in the containers. I ran the engine for around 5 - 10 minutes at varing engine speeds and only returned 20ml into each container.


Thanks again,
Glen.

sprintguy said:

The manual test is to remove the number 1 injector return line only (top of the injector),place a measuring vial on the injector return port, then unplug the fuel rail pressure control solenoid (valve), then crank the engine for 10 seconds and read the amount of fuel in the vial 40ml or less

Click to expand...

I'm assuming here that unplugging the solenoid will keep the engine from starting just as unplugging the cam position sensor does? If so, the leak-off should be very little, like a couple mls. AFAIK, leak-off of more than a couple mls means the injector is bad.

Yeh unplugging the solenoid does prevent the engine from starting. Although I see your point, 40mls of leak off on cranking for 10 seconds or so does seem quite a lot but i think Carl is right with checking the LP and HP fuel pressure though.

The most i have seen is 450 BAR when running and the manual i found on here suggests up to 1600 BAR (which seems more like what i would expect from a common rail system) this may also explain some of the blue smoke which i think is poor atomisation of fuel as the engine consumes virtually no oil at all)

First step is to check the LP somehow!

By disabling the rail pressure sensor the rail doesn't buid pressure and the injectors do not open . all you are measuring is Fuel flow (volume) which is what the high pressure pump supplies (volume) so by removing just #1 leak off line and leaving all the others on you can measure the volume from the pump to #1 injector. By no means are you actually checking injector leak off but only pump volume to 1 injector (which happens to be closest to the pump line).
Now that you have mentioned the white smoke , the problem is indicative to not enough volume being supplied by the low system or the high pressure pump.
Remember that the rail is where the high pressure is created , not the actual pump itself (thats just high volume to the rail)

Carl
If I am wrong (which I hope I am not) please correct.

Hi Carl
Yet again that makes sense to me. When you say disconnecting the pressure sensor i assume you mean pressure valve.

The smoke is blue (ish) it's not white but I get your point. I haven't managed to go and see the LP set up on the vehicle yet however if there is a LP sensor then could i remove it and tap into the LP with my pressure gauge?

Thanks,
Glen

You should be able to tap into the LP side at the sensor (if applicable).

sprintguy said:

By disabling the rail pressure sensor the rail doesn't buid pressure and the injectors do not open . all you are measuring is Fuel flow (volume) which is what the high pressure pump supplies (volume) so by removing just #1 leak off line and leaving all the others on you can measure the volume from the pump to #1 injector. By no means are you actually checking injector leak off but only pump volume to 1 injector (which happens to be closest to the pump line).
Now that you have mentioned the white smoke , the problem is indicative to not enough volume being supplied by the low system or the high pressure pump.
Remember that the rail is where the high pressure is created , not the actual pump itself (thats just high volume to the rail)

Carl
If I am wrong (which I hope I am not) please correct.

Click to expand...

Under those conditions, you won't get anything out of the top of the injector, but if you don't pinch off the injector leak-off fuel return line, you'll get at least part of the fuel flow (returning to the tank after flowing out of the rail through the open fuel pressure control solenoid) from the high pressure pump coming out of that line.

Right guys,
I have removed the LP sensor (i think its the LP sensor?) and checked the fuel pressure. Results as follows:

3.2 BAR @ 750 RPM
3.6 BAR @ 1200 RPM
3.9 BAR @ 1600 RPM
4.0 BAR @ 2000 RPM Regulated above this RPM @ 4.0 BAR.

All these readings seem to be within the spec i have found, what do you think?

My conclusion based on the fact the HP sensor, the HP Control valve have been replaced. The injectors have been tested for excessive leak off both on and off the vehicle (Both ok). The HP is around 400 BAR and the LP readings are as above, i am strongly suspecting the HP pump!

Thoughts?

Thanks,
Glen.

Note: The fuel rail pressure solenoid is , in a de-energized state , normal closed (blocking of return ports on the rail) , it is held closed by a small spring.
Using a coil to produce a magnetic field aids in holding the pintal (ball end) in its proper location to adjust pressure generated in the rail ( at different loads).

Holly s#$% : I have totally miffed up that procedure ....... Talkinghorse43 : good call (and thanks for challenging) the procedure that I did describe SHOULD be as follows ...
unplug rail pressure sensor, disconnect leak off line at #1 injector , install an empty vial on #1 injector return port , COLLECT fuel from leak off line while cranking, and pour collected fuel into a vial and measure amount collected. 40ml or less = faulty HP pump greater than 40ml = fuel rail pressure solenoid.

I appologize , for the bum test info (never tested it that way before)
My bad

Carl

Right ok,

#1 injector leak off into its own container and then collect the fuel from the leak off pipe connected to #2,#3,#4 injectors and add the fuel together then measure.
(potentially some fuel could return to the tank via the normal leak off route from#2,#3,#4?)

I have previously done the leak off test connecting containers to each injectors return pipes. The rail valve was disconnected and there was virtually nothing being returned into the containers on cranking. This was why I re-connected the valve and run the engine and even then it took 5 - 10 minutes to put 20ml into each container.

I know this is not exactly the same as you described but unless i am not fully understanding, to me it does suggest low volume delivery?

(If needed i will do the test as described but i cant get hold of the containers for at least another week or so that's all)

Thanks,
Glen.

Hi Guys,
Could someone do me a favour?

Anyone with a 4 cyl CDI Sprinter with a Diagnostic / Code Reader check and post the Fuel Pressure reading for me?

I want to compare it to my MY2002 208 CDI.


Thanks
Glen.

Am having the same trubble with the same vehicle and was wondering if the regulator could be at fault. MINE IS NOT STARTING AT ALL, the fuel filter was empty of fuel when checked, i primed the filter input with an extenal fuel pump thinking that there may have been a leak, and if not maybe the electronics is sensing there was no fuel originally, failing to open the hp pump to pump hp fuel, but this did not work either. Can someone tell me what the resistance valves should be on the regulator so i can check.
It seems to me that the lp pump was not working either.
I removed the return lines off the injectors cranked and got nothing?
Am i on the right track?