Hi guys,
Hopefully someone can help me with some diagnostic data, I hand scanned the Renault 2.2dci after a top end rebuild (head refurbish, all recon injectors, most stuff new) and no codes. I can't find any data to test anything and I can't get any live data from the scanner as it says 'mode not supported'. I didn't strip the engine, but did the rebuild, afik no electric connections are off but I can't rule anything out other than the engine internally seems fine & that it ran before stripdown okay (owner snapped an injector off in the head, prompting the top end rebuild and new set injectors).
The engine swings over on the starter fine and fires up with a little starter fluid in the intake till the fluid runs out - but won't run on it's own.
So far - primed the fuel system (electric fuel pump in tank) and tons of fuel will shoot out the supply to the HP pump. Fuel runs out the return line off the common rail and the rail appears to be full and dribbling out of the return but very slowly. So we have low pressure fuel.
There is absolutely no difference cranking with all the injector electric connections connected and disconnected, it's like the injectors are not firing at all.
I was starting to wonder if I'm getting high pressure in the rail, so I left the return line off the common rail off and cranked the engine, expecting to see a little jet of fuel out of the return line which appears to be a small bore drilling in the common rail. No squirting, in fact hardly any diesel coming out of the return line from the common rail. Either I'm missing something about it's operation (I'd have thought 200bar while cranking would have made a good little jet) or there is no high pressure, just priming pressure from the tank pump.
The HP pump makes a buzzing sound for a few seconds after the engine is off.
No lights on dash that shouldn't be, no immobliser flashing, no check engine light. It should just start, but it doesn't.
Any advice appreciated, I need to diagnose this fast. I have multimeter and a OBDII scanner + usual tools for a mechanic and really struggling to find any data. If it was a VW I could log in with vag-com and see what's going on with every sensor and perform output tests but I can't do that for the renault, don't even know if it is possible!
I really feel it's not injecting fuel, any diagnostics/tests/flow charts appreciated, starting with how do I know for sure if the Common Rail is getting pressure and if not why not etc.
Greg.
2.2dci won't start after rebuild, common rail pressure fail?
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greg123
- Posts: 50
- Joined: 26 Apr 2008, 00:14
2.2dci won't start after rebuild, common rail pressure fail?
Tdi VAG mechanic & vegoil converter
-
greg123
- Posts: 50
- Joined: 26 Apr 2008, 00:14
Discussion via citroen forum but resolution posted here as well:
Well I'm glad to say I found the resolution.
If anyone has a similar 'no start' after a cambelt or engine rebuild, this may prove of interest. This issue only applies to engines with the cam (cylinder) position sensor on the fuel pump rather than on the camshaft.
For those who are interested, on the 2.2dci/dti Renault/Vauxhall/Nissan engine with the Bosch CP3 common rail (CR system similar to many others) I tested the following and got these values, which turned out to be correct:
Crank sensor - 231 ohms (2 pin sensor)
Cam position sensor on fuel pump cover 10.16k ohms (2 out of the 3 pins)
With ignition on, centre pin on Pressure Sensor on the common rail gave 0.5v = 0 pressure, under cranking went up to 1.7v = approx 350bar
Injecor two pin connections gave 12v or more pulsed during cranking, 0v with ignition on.
All the above were correct and proved good rail pressure, sensors and pulses to the injectors. I did a leak off test to test if any of the injectors were leaking HP to leak off pipe, none were, just a very slow trickle/bubble after about 5 seconds of cranking out of the top of the injectors, as one would expect from new injectos (they leak out worse as they get older, one peeing out can empty the pressure of the CR and be enough to stop it starting).
So what on earth could it be I thought. I then went back to the cambelt timing, all spot on. BUT, the HP pump is gear driven 'on a 1:1 ratio with the crankshaft' according to the manual. The HP pump isn't sensitive to timing, it just has to spin, so shouldn't be an issue. But I dug out pictures of the timing end of the engine and it had a big cog on the HP pump and a small one on the crank, so evidently the HP pump turned at 1/2 crank speed. Now this wouldn't cause an issue, BUT on the renault dci the cam sensor is on the front of the HP pump sprocket cover, stupidly, rather than on the camshaft. So, I figured the manual was wrong about the 1:1 ratio and if you timed up the crank and camshafts perfectly, it's possible for the HP pump sprocket and thus cam timing signal to be 180 degrees out. There is no way in the manual or that I can see, without lifting the timing case cover, to check this. Normally it wouldn't be an issue as you would mark stuff up before removing belts, but this was a dismantled engine that I had to rebuild so I had no idea of a reference position and just timed the crank up.
Anyhow, I took off the timing belt, spun the crank 360 degrees and as I thought the HP pump moved round 180 degrees even though the crank was back to the same position. Refitted and tensioned the belt, spun it over on the spanner and re-check everything - the crank/cam timing just like before but now the HP pump is 180 degrees out from before and thus the cam timing signal (signals when no1 cylinder is coming up) is 180 degrees from what it was.
Turn the engine over on the starter for 5 seconds and it fires into a steady idle like it's been running a year, smooth as a baby.
Moral of this story is, if your common rail engine has the cylinder/cam sensor anywhere other than the camshaft (whcih can't get 180 degrees out) it's possible that if you have to rebuild a ripped down engine or lost your timing marks, you can put the cambelt on properly and lined up, but have the signal off of the 'cam' sensor 180 degrees out and get a no start with absolutely no codes/faults to see. The engine was merrily injecting the wrong cylinders! The second moral is never trust the manual. If I had believed it's 1:1 ratio (which didn't even make sense, you can't get a cam signal from a crank ratio as a crank spins twice for one revolution of a cam) or didn't think outside the box of the instructions for timing up the engine, I'd never have got this solved.
Hopefully this will be useful to someone else one day, who rebuilt an engine and timed it all up as per the book and £200 worth of sensors later still can't get it started, all because the crank needs spinning round 360 degrees and the belt putting back on again.
I wonder if only renault managed to put the cam sensor on the HP pump and invent this problem that didn't need to exist?
Drinks all round guys.
Greg.
Well I'm glad to say I found the resolution.
If anyone has a similar 'no start' after a cambelt or engine rebuild, this may prove of interest. This issue only applies to engines with the cam (cylinder) position sensor on the fuel pump rather than on the camshaft.
For those who are interested, on the 2.2dci/dti Renault/Vauxhall/Nissan engine with the Bosch CP3 common rail (CR system similar to many others) I tested the following and got these values, which turned out to be correct:
Crank sensor - 231 ohms (2 pin sensor)
Cam position sensor on fuel pump cover 10.16k ohms (2 out of the 3 pins)
With ignition on, centre pin on Pressure Sensor on the common rail gave 0.5v = 0 pressure, under cranking went up to 1.7v = approx 350bar
Injecor two pin connections gave 12v or more pulsed during cranking, 0v with ignition on.
All the above were correct and proved good rail pressure, sensors and pulses to the injectors. I did a leak off test to test if any of the injectors were leaking HP to leak off pipe, none were, just a very slow trickle/bubble after about 5 seconds of cranking out of the top of the injectors, as one would expect from new injectos (they leak out worse as they get older, one peeing out can empty the pressure of the CR and be enough to stop it starting).
So what on earth could it be I thought. I then went back to the cambelt timing, all spot on. BUT, the HP pump is gear driven 'on a 1:1 ratio with the crankshaft' according to the manual. The HP pump isn't sensitive to timing, it just has to spin, so shouldn't be an issue. But I dug out pictures of the timing end of the engine and it had a big cog on the HP pump and a small one on the crank, so evidently the HP pump turned at 1/2 crank speed. Now this wouldn't cause an issue, BUT on the renault dci the cam sensor is on the front of the HP pump sprocket cover, stupidly, rather than on the camshaft. So, I figured the manual was wrong about the 1:1 ratio and if you timed up the crank and camshafts perfectly, it's possible for the HP pump sprocket and thus cam timing signal to be 180 degrees out. There is no way in the manual or that I can see, without lifting the timing case cover, to check this. Normally it wouldn't be an issue as you would mark stuff up before removing belts, but this was a dismantled engine that I had to rebuild so I had no idea of a reference position and just timed the crank up.
Anyhow, I took off the timing belt, spun the crank 360 degrees and as I thought the HP pump moved round 180 degrees even though the crank was back to the same position. Refitted and tensioned the belt, spun it over on the spanner and re-check everything - the crank/cam timing just like before but now the HP pump is 180 degrees out from before and thus the cam timing signal (signals when no1 cylinder is coming up) is 180 degrees from what it was.
Turn the engine over on the starter for 5 seconds and it fires into a steady idle like it's been running a year, smooth as a baby.
Moral of this story is, if your common rail engine has the cylinder/cam sensor anywhere other than the camshaft (whcih can't get 180 degrees out) it's possible that if you have to rebuild a ripped down engine or lost your timing marks, you can put the cambelt on properly and lined up, but have the signal off of the 'cam' sensor 180 degrees out and get a no start with absolutely no codes/faults to see. The engine was merrily injecting the wrong cylinders! The second moral is never trust the manual. If I had believed it's 1:1 ratio (which didn't even make sense, you can't get a cam signal from a crank ratio as a crank spins twice for one revolution of a cam) or didn't think outside the box of the instructions for timing up the engine, I'd never have got this solved.
Hopefully this will be useful to someone else one day, who rebuilt an engine and timed it all up as per the book and £200 worth of sensors later still can't get it started, all because the crank needs spinning round 360 degrees and the belt putting back on again.
I wonder if only renault managed to put the cam sensor on the HP pump and invent this problem that didn't need to exist?
Drinks all round guys.
Greg.
Tdi VAG mechanic & vegoil converter