CDI Fuel Pressure

[grayboots]

Hi,
Im still trying to fix my w210 e230cdi. Thanks to all of the advice im armed with the correct tools and have some codes and some way forward. The car now wont start which is good as previously ive bee trying to trace a fault thats not apparent.
Can anybody tell me the minimum fuel pressure i should see when cranking and at idle ?
My pc reports a fuel pressure of 100bar, when it was running i did see this at 350bar. This all seems really high but reading various posts ive seen pressures anywhere from 500bar to 1400bar.
Also can anybody tell me if there is a low pressure pump in the tank and if so what should the delivery pressure be to the filter ?

Any help appreciated

grayboots

 

[mersum1es]

Pressure at cranking sounds low, I cannot remember what value should be that ECU starts injection (it may vary according CDI 2/3 fuel system too) but I would say it should be around 250 bars when system is sound and solid. 350bar at idle sounds ok, it won't rise unless there is load on the engine. Your aux pump is front of the engine (no pump in tank).

Why fuel pressure is not high enough in crank? System may draw air from low pressure side (o-rings or pipes itself), injectors may leak too much to tank line, hp-pump may be worn, pressure regulator leaks or is jammed. I assume fuel filter is ok, hoses top of it ok, seal of filter cap ok.

 

[grayboots]

pretty sure im leak free. Got a kit from ebay on the way to do a leak off test. It would be nice to know that the injectors are all good. Hopefully it will start and idle !

 

[sc3992]

I hope you are leak free, the toilet isn't that far is it?

 

[Trickythemerc]

If memory serves me well I think a pressure sensor on the fuel rail failed on one of my cdi's causing it not start. The test for this was a squirt of easy start and it would run OK until you turned it off.

 

[mersum1es]

pretty sure im leak free. Got a kit from ebay on the way to do a leak off test. It would be nice to know that the injectors are all good. Hopefully it will start and idle !

You can only crank it too, better that way (it means that conditions are really no-start during the leak test).

If fuel pressure sensor is bad, you may unplug sensor, it should start in limp mode (plus CEL?) then if actual pressure is high enough.

 

[W210Virgin]

Try the crankshaft position sensor if you don't get codes read. It's a 15 min change at the top of the engine and won't report a fault. Cheap too at about £25+. Similarly the crank position sensor bit it's a bitch to get at!


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[grayboots]

Try the crankshaft position sensor if you don't get codes read. It's a 15 min change at the top of the engine and won't report a fault. Cheap too at about £25+. Similarly the crank position sensor bit it's a bitch to get at!


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Thanks for your comment, i did have a historic code for the cam sensor (signal not present) so i changed it, i also have a crank sensor ready to go on however i want to know exactly whats wrong first.
Im still convinced im lacking fuel pressure so im going to do a leak off test and if the injectors are all good im looking at the pump or regulator.
I cleared the codes and then rescanned the system after cranking it without it starting. Strangely it didnt think anything was wrong. This strongly points to a pressure problem in my humble opinion. A sensor fault or broken wire would surely generate a system fault.

I'll post again when ive a leak off result........

I will get there with this one !

g

 

[W210Virgin]

Certainly preserve with this. I had a similar issue in August last. I checked all the obvious, but had previously changed all the fuel lines. My immediate reaction was leak off. A check on this revealed one significantly leaking and 3 borderline leaking at the copper seal. In the end it was the camshaft sensor but obviously the leak off was a major contributor. Also, as a blessing in disguise, I was able to fix the potential black death before it started. It was a massive hassle at the time but worth it in the end I suppose. Fuel pressure should show up errors. From my research the fuel pumps are solid and don't give much bother. It seems like the cam and crank sensors are a bit troublesome. You might need a Star person involved.


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[W210Virgin]

And I meant persevere obviously☺


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[grayboots]

E320 update (if anyone is still interested !)
I did a leak off test, i found the "new" injector i had fitted was the worst of all. It had about 3x the quantity of the other 5 after a few minutes idilng. I was able to observe the fuel pressure and this remained at 350bar throughout the test. I concluded that the injector was a bit worn but probably not causing the problem.
I decided to change the injector copper washer, that turned into a nightmare very quickly. An hour or so steam cleaning and then a difficult extraction (reminds me of the dentist) only to find on re-fitting there were no threads for the injector clamp. I tried a helicoil....that pulled out. I ended tapping an m8 thread into the head that solved the problem maybe 2 hours later.
I restarted, left it running and was refitting the covers when it cut out. The original problem....
It appeared that when i went anywhere near the injector wires it would cut out. I split away the heatshrink for injector 3 to find the wires were fused together.
I re-scanned the CDI memory and this time it did report the short circuit. I did a temporary (permanent) bodge with some tape and now it all seems ok.
I cleared all the errors and today ive driven it around 150 miles.......maybe its fixed now.

g

 

[grayboots]

sorry, trying to get an image to display

 

[streethawk]

Sounds like a result if not a pita .well done

 

[BlackC55]

The rubber seal inside the injector connector often bulges from diesel contamination and can cause a non start.

 

[mersum1es]

That short circuit certainly makes engine cut...

Leak test result may change better/worse rapidly when temperature changes even slightly, keep eye on it.

 

[W210Virgin]

Good job. One for all 210 owners to keep an eye on. Sounds like you should do a bit of a job on the injectors too.