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Discussion Starter #1
Hi,

new to the forum would appreciate some help with a real odd problem I have with a dci 100 master. Vehicle came into use with non start in the mornings and poor running, did an injector leak back test, no 4 was leaking back before the others were even starting to fill, and number 2 wasnt far behind, 1 and 3 were matched perfectly. Changed 4 and 2, rechecked the leak back and they were all now well within tolerance and used gen renault parts, (cheaper than everyone else!!!) van now revved clean, no more misfire, roadtested and all ok. Went to start it up 2 hours later to recheck, bugger to start, and tottally flat when revved, pumped the primer and re reved all good. let it run to see if system had air in, turned off and retested 2 hours later same fault. Removed fuel filter and housing, fuel filter was old and quite badly blocked, change for new with seals. rechecked and guess what, same thing again!!!! rechecked fuel filter housing and did a vac test on to make sure its not leaking, seems fine.

Scanned using my snap on Modis, no fault codes apart from airflow meter (it doesn't have one, so no prob there).

Heres the thing, on live data the commom rail instantly sees 300 bar on start up, but the engine will be flat as a witches *** to rev, go to the engine bay pump the primer 3 times, or leave it to idle for 20 seconds and it will rev perfectly cleanly, and yet the live data is still showing 300 bar wether its revving flat or revving cleanly.

On the clear fuel line from the filter to the primer to the tank (the in line) after 10 seconds from shut down an air bubble will appear and continue to grow, so obviously air is getting in the system, but I have checked and double checked the filter housing, and the only place I can think its getting in (due to the way the air bubble travels towards the tank) is fowards of the filter housing ie pipe to the high pressure pump. This in itself is odd, and it has a spur off to nothing, next to the high pressure pump, could this be leaking?? I cant see it being the high pressure pump due to the live data readings when flat and when fine is the same, no other fault codes are stored, and the problem starting from cold HAS to indicate diesel leak back, and when I say problem I mean it takes 7/8 attempts to start.

Does the return system affect leak back on these systems, sory if that sounds stupid but it back feeds to the high pressure pump and then back to the tank so I would have thought the systems are seperate.

Please help me someone this van is starting to test my knowledge and patience!

Thanks in advance

Rich
 

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Discussion Starter #2
Please doesn't anyone have any ideas??? There must be someone on here really genned up on these DCi renault engines!!!
 

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depends on engine but the return goes back to the filter housing on any i have done then back to the tank so esentially maintains pressure once running

Does the 300bar vary at-all

Are you sure there is no airflow meter ?
 

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Fit a geuine renault fuel filter as aftermarket one's
pipe diameter being a fraction to small for a air tight
connection to fuel line. Remove fuel regulator plug
and check resistance across it's 2 pin's resistance
reading should be approx 5.3 ohms check for a 12v
at ignition on at this plug This 12v's travels through
regulator coil then to ecu switched earth to activate
regulator.Check fuel rail pressure sensor for a 5v feed at terminal 3 check terminal 2 at ignition on
should read 0.5 v terminal 1 earth. On fuel rail sensor
terminal 2 (centre one) back probe at cranking with multimeter and see what voltage your getting Hth
Regards Mickeybo
 

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Discussion Starter #5
Fit a geuine renault fuel filter as aftermarket one's
pipe diameter being a fraction to small for a air tight
connection to fuel line. Remove fuel regulator plug
and check resistance across it's 2 pin's resistance
reading should be approx 5.3 ohms check for a 12v
at ignition on at this plug This 12v's travels through
regulator coil then to ecu switched earth to activate
regulator.Check fuel rail pressure sensor for a 5v feed at terminal 3 check terminal 2 at ignition on
should read 0.5 v terminal 1 earth. On fuel rail sensor
terminal 2 (centre one) back probe at cranking with multimeter and see what voltage your getting Hth
Regards Mickeybo

I fitted a motaquip filter they are our main supplier, so I fill fit a renault genuine part and see if that helps. I will check the connections using the scope on my modis, do you have any idea what actual parts may be at fault.

FYI at idle, the fuel pressure does jump between 293 maybe up to 315 on live data, I thought that was acceptable, thats wether its flat or revving clean.

Is this right or not? What the hell can it be? I'm suspecting a mechanical fault as opposed to electrical, but the mechanical part at fault could be part of an electrical sensor.

I will try tommorow and come back with my findings.

Rich
 

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Discussion Starter #6
Is the fuel pressure regulator the small part on the return lines from the injectors with a plug with two pins?

Rich
 

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Discussion Starter #7
Hi,

Ive got this van coming back in this Friday and I'm going to fit a genuine renault fuel filter into the housing and test as per mickey suggested. Does anyone on here actually have an idea what part may be at fault. I have been told the injectors I have just changed are NOT coded, but is this the case they were numbered on top, but not hexdeciimal, ie they were all numbers, not letters and numbers. I am going to try and get hold of clip to see what that says, but I'm in real need of some help, hes a really good customer and I dont want to let him down.

If only BMW made vans, this would never happen :d

Rich
 
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