Hi guys

Renault Clio 2006 1.5 DCI 158000 miles
Engine code k9k766 (ROF)
It is defiantly a Delphi fuel system Auto Data says it is a 1400 bar system.

This vehicle has been to a few different garages and the customer is loosing faith and wants to take it to the dealer. I like a challenge and would like to restore the customers faith in us independents and gain a new customer and obviously fix the car LOL.

I am in the middle of building a data base of known good data and am really eager to become fluent in different common rail fuel systems. Any help is appreciated.

The vehicle chugged into the garage running very rough, knocking and leaving a cloud of white smoke behind it. I told the customer to turn the vehicle off quick as I feared internal engine damage wasn’t far off, if it hadn’t already happened.

I plugged the Modis in and retrieved code DF053 fuel rail pressure regulation function.

Initially I thought 1 or more of the injectors were dumping fuel into the cylinder uncontrolled and this may tie in with the fuel pressure discrepancy.

After looking through the data I noticed that the EGR position was high at 4.10v so I decided to investigate this as I really didn’t want to start the car up yet and this could explain some of my symptoms. Upon removal the EGR valve to my delight it was stuck just about fully open. I tried to clean and free it off but it clearly needs a new valve. I managed to close the valve and refitted with the plug left off so it couldn’t open and get stuck again to see if this was the cause of all my problems.

It started and idled 100 times better once the smoke had cleared.
But, when revved, the engine stumbles at 2500-3000rpm and then clears. Now I felt it was safe to do so I did a relative compression test.
I do not have known good figures but it seems ok.
RESULTS
Initial current draw was 600A settling down at 280A across all cylinders apart from 1 unidentified cylinder that was repetitively 2-8A lower than the rest. This hasn’t set alarm bells ringing just yet given the mileage of the vehicle.
I will confirm compressions with manual gauge.

On the test drive the car drove perfectly although when free revving the stutter is still present at 2500-3000rpm. Also under heavy acceleration code DF053 would be triggered. It appears I have at least 1 more problem.
First time code triggered.
Fuel pressure (setting) bar 1600 I assume this is desired?
Fuel pressure bar 1689 I assume this is actual?

Second time code triggered
Fuel pressure (setting) bar 1400
Fuel pressure bar 1249
There is definitely some fuel control issues, I have ordered an EGR valve that is coming tomorrow and would like some testing tip from you guys to accurately diagnose the fuelling issue.

I spent last night getting a test plan together to become familiar with this fuel system but I am sad to say I fell at just about every hurdle when testing started.

I read about the injectors aiding in dumping rail pressure so I scoped FRPS vs INJ current and found this very interesting (it draws a lovely picture too LOL)

Test 1 complete.
Test 2, pump max pressure and decay of leak back pressure. This didn’t go too well. I am hoping you guys can help me get ready for attack tomorrow.

I set the scope up, unplugged IMV and injectors but the car would only crank for 1 second with IMV disconnected. (this didn’t happen when I tried it on a mondeo)

Could I measure the resistance of IMV and insert a resistor of equal value to bypass this?
I powered the starter motor up manually with the IMV and injectors unplugged but rail pressure only reached 1.8v. I wondered what could have been controlling the rail pressure?

Should I start the engine and unplug the IMV and see if it can reach max pressure before it cuts out or would the injectors go into over drive and try dumping the pressure anyway.

After failing to complete this test I did a manual leakage test of the injectors and again I got some STRANGE results. At idle all injectors were leaking back very equal after a minute I raised the revs to 2500ish. All the bottles were filling up slightly faster but not excessive and still very equal. But the bottles started filling with smoke/vapour what looked like exhaust gasses.
Is this normal?
Should I be checking back leakage differently on these injectors due to there rail pressure dumping characteristics?

I realise these tests probably wont help me fix my particular problem but the more system knowledge the better I say.

If anybody has got any known good waveforms for this system including the pressure control side or info that would be fantastic.

Sorry guys I have just realised how long this post has got, I hope it doesn’t bore you too much lol.


Cheers
James