2008 Vauxhall Vivaro piezo injector currents

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2008 Vauxhall Vivaro piezo injector currents

Postby Valhalla » Wed May 22, 2013 11:31 pm

I have a Vivaro on the slab at the moment. The engine is the Renault derived F9Q_760, which appears to be running an EDC15C3 (or similar) controller for the engine. Problem symptoms are a light misfire when hot,, which become more significant when the engine is under load. As the engine diagnostics recognise the misfire, then a limp-home is set (causing the engine to shut down completely) which then happens more frequently.

I have measured the injector drive circuits at the harness point where it crosses over the top of the flywheel housing (this engine is difficult to access the wiring at the same time as run the engine, and the twisted-pair wires are tightly bound); what I am trying to see is if the injectors are truly faulty, or whether the problem is electrical. What I have discovered is that the load-factor in generating the misfire is associated to the point in the engine speed/load mapping where a 2nd pilot injection is switched-on. The injectors seem reasonably happy to run under a single pilot regime, but one or more of them is having difficulty when a second pilot is used. This would point to a needle control issue in one or more injectors, and that is where I am asking for any help that anyone can give me on this case;

The attached trace is of the currents for two injectors (one assumed "GOOD" is number 3 cyl, the other trace is under investigation), taken during a snaphot where the engine is accelerated from idle (vehicle at rest) up to circa 3000 rpm in order to generate some engine load to switch the second pilot injection on. If this test is done many times, the engine will eventually shut down with a misfire fault. The red trace shows a piezo current that seems to switch on and off quite cleanly. The blue trace shows a piezo that seems to switch on cleanly, but after the current is reversed to close the needle, the current appears to bounce around the zero current line for a number of cycles afterwards. Has anyone measured this on a piezo injector, and if so, was that injector faulty, or was the problem in the fuel spill rail?
Cyl3_Cyl4_snapshot_on_free_accel.psdata
Cyls 3 and 4 during loaded acceleration, twin pilot active
(955.44 KiB) Downloaded 403 times

My theory is that the injector/s that are faulty are OK when the needle is correctly seated prior to the next injection event (pilot to main), but when the needle and current are still oscillating, the switching back on of the injector drive stage is being upset. The fault codes for this problem (not necessarily correctly-interpreted by the controller, hence my use of the Pico toolset) are an intermittent P0301-9 (cyl1 misfire), with a recurrent P0200-C (injector circuit open) and a recurrent P2146-2 (Circuit A injector open). My experience is with Siemens SID204 in piezo control, but I have not seen any measures with a Bosch EDC15/EDC16/EDC17 unit on piezo injectors. The SID204 would certainly flag an error if the piezo stack was not stable when the current to "OPEN" was switched on.

As the engine has already had a new injector (on cyl.4 I think) about 2 years ago, the customer is wary of condemning this one again. I believe that both cyl.1 and cyl.4 injectors are not closing properly, based on my Pico traces. I have a similar trace to attach (if required) for Cyl.3 and Cyl.1 side-by-side - they show a similar result to the one that I have attached. I am extremely wary of disturbing these injectors, as they are notorious for seizing in-situ and requiring heavy-duty equipment (Pichler) to extract them - sometimes with dire consequences. I am treating cyl.1 as the injector over the flywheel (as per Renault convention) and cyl.4 as near the RH front wheel.
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Re: 2008 Vauxhall Vivaro piezo injector currents

Postby jez1342 » Thu May 23, 2013 5:19 am

have you checked the resistance of the injectors? from memory they should be around 180 Kohms.
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Re: 2008 Vauxhall Vivaro piezo injector currents

Postby Valhalla » Thu May 23, 2013 2:23 pm

Yep, the first thing I checked was the resistance with a DVM (Fluke) across each of the four twisted pairs as they arrived at the ECM. To be honest, this was the starting-point for checking the injectors themselves a bit further; the results that I got were inconclusive on the end two injectors (cyl.1 and cyl.4), as I could see a charge building-up from the DVM, eventually stabilising out to a halfway reasonable figure. Off the top of my head (most of the time!) I think that the centre two cylinders measured 230ohms (possibly 280ohms) but the outer two cylinders were much lower. If the meter probes were reversed, then the figures took several tens of seconds to restabilise.
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Re: 2008 Vauxhall Vivaro piezo injector currents

Postby Valhalla » Thu May 23, 2013 7:25 pm

jez1342 wrote: from memory they should be around 180 Kohms.

And indeed, you were absolutely bang-on the values here. Many apologies for quoting rubbish off the top of my head. I checked my notes again this afternoon, and the centre two injectors were each 178kohms, very similar to each other. The injector that I most suspect of being the misfire culprit (cyl.1) was 56kohms in my notes. I decided to recheck it this evening, after having run the engine through to normal temperature, and the probed resistance directly at the connector pins on the injector itself was 18kohms to 21kohms (climbing slowly). The other end of the engine (cyl.4) is yet to be rechecked. I'm still not happy with that one either, but getting to the injector unit is more of a pain (under the breather/separator units).

I ran a test on the electrical system for cylinder balance, using the Pico Automotive Diagnostics Beta software, but unfortunately it was struggling a bit with the signal off the battery (no problems on signal strength, but only occasionally reported the cylinder balance trace with "out of bounds" error messaging). I used the same setup on the battery with the normal oscilloscope function (AC coupled, auto ranging) and the signal was a bit noisy, but with a bit of low-pass filtering at 100Hz, quite readable. I have attached the trace that I took, which with filtering at low-pass 20Hz (to remove alternator phase swings) shows a clear pattern of three strong cylinders and one weak cylinder. This gives me some confidence that I only have one injector to deal with.

I ran a thermoscanner check across the back of the exhaust manifold, and there is some correlating evidence of strong cylinders at one end of the engine, but cyl.1 is down a bit on temperature at idle. The trouble here is that the end cylinders on a common manifold are always going to read a bit lower than the centre branches, so the temperature drop might not be the whole story. Hence a last Pico trace tomorrow (whilst the injector on cyl.1 soaks in Tunap 103) with a signal off the cyl.1 injector harness, to "time" the misfire information on the attached trace.
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Re: 2008 Vauxhall Vivaro piezo injector currents

Postby Valhalla » Wed May 29, 2013 9:54 pm

I didn't do the trace to identify the cylinder that was misfiring; something that I have done before with common-rail diesels is to touch the injector feed pipes with a finger whilst the engine is idling - problems with injector needle control often feel like a "buzz" through the pipe wall, rather than a defined pulse. The suspect cylinder on this Vivaro is buzzing something chronic, so I think that the Tunap Logic 103 is going to have to have one last spray before the injector comes out (some hope.... :roll: ).
I am going to try to find a way of measuring the injector pipe pulse objectively (I have got a clip-on tachometer probe from the 1980's that might yield a result), and if it works, I'll try and sell it to Pico :lol: Probably better than using a digit to decide whether an injector circuit is faulty or not. I'll dig out some of my old notes from work that I used to do on injection wave reflection, to see what instruments I used to use (it was a long time ago, when delivery "snubber" valves on injection distributor pumps were important to prevent premature cam lobe wear in the pumps)
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Re: 2008 Vauxhall Vivaro piezo injector currents

Postby aux_r » Thu May 30, 2013 6:52 pm

Hi, I agree with your first post, it seems a problem with piezo crystal in injector 4. In the attached file you can see a good piece injector working. If you get voltage versus current capture probably you see a voltage lost relative to the lost of the capacity of the crystal.
I think so, because the quantity of charge of provided to the crystal differs from the one of the discharge.

Regards
Attachments
Iny_piezo_bosch.psdata
(156.04 KiB) Downloaded 292 times
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Re: 2008 Vauxhall Vivaro piezo injector currents

Postby jez1342 » Thu May 30, 2013 8:25 pm

I normally check the resistances at the ecu end, once the anti-theft shieldy thing is removed.
like your capture via the alternator!!!!!
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Re: 2008 Vauxhall Vivaro piezo injector currents

Postby Valhalla » Thu May 30, 2013 10:47 pm

aux_r wrote:In the attached file you can see a good piece injector working.

Regards


Yes, that's a good trace, and illustrates the point you make about the charge on and off the piezo stack perfectly.

I still cannot budge this faulty injector - not helped by the puddle of water that reappeared on top of the engine earlier in the week - that is with the bonnet down, and nominally dry weather outdoors. It is clear that the vehicle design itself exacerbates a weakness in the engine, as the only way I can see water being channelled down onto the cam cover is via the heater intake on the bonnet. The puddle was 1/2" deep again yesterday.... :shock: I feel it is time to time to dust off the welder and make a special tool for the job a bit pronto!!

I threw the ECU shield anti-tamper fixings away on the first day I had the misfortune to work on this van. Not because they were in the way, but I wouldn't want to discourage any passing tea-leaves from removing it from the premises. :P
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Re: 2008 Vauxhall Vivaro piezo injector currents

Postby Valhalla » Tue Jun 11, 2013 10:59 pm

Special tool shifted the injector with no trouble at all. A lovely mix of tubes, plates, and bearings, mostly derived from old Rover 2000 scrap bits (possibly worth more than the van that I am working-on :roll: ). It took a few hours to get the tool correct, then a few minutes to pull the injector. The main advantage has been the continuous soaking with Tunap Logic 103; you can see where the fluid has penetrated right down to the injector washer face (albeit with an air-hammer to rattle the injector a day or two prior to the final pull).

Having got everything back together, I was initially a bit despondent. The misfire is still there on that cylinder. Accepting that I haven't coded the injector to the ECU yet (awaiting more kit) due to shortcomings in my general-purpose toolset, I thought that it would be a good idea to take another trace. Then the Pico software decided to play-up. So I have had to use (and re-set up the experiment) the last stable Pico software on my PC.

Attached trace shows just the single (previously faulty) injector now charging and discharging correctly, even under twin-pilot control. I have included the alternator charging ripple with a 20Hz low-pass filter (once again) on the same trace, just to make sure that the misfire really is on number 1 cylinder. Thank heavens it is.... This time, I had to run the engine at a fast idle to get a meaningful engine speed fluctuation, so all in in all, it appears that the injector will need to be trimmed for ECU control. That is despite the engine shuddering worse than before at idle (and at any other speed up to 2000rpm). I don't think there are any mechanical issues (I had a good look inside the cylinder whilst the old injector was out), so I'm a bit surprised. A major plus is that the fault code for the injector drive circuit has disappeared for good, even if the misfire code is a bit permanent.
Attachments
Post_inj1_replace_drive_current_vs_engine_speed_ripple.psdata
Older Pico Auto software used to overcome bug, setup slightly different to previous traces
(3.74 MiB) Downloaded 240 times
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Re: 2008 Vauxhall Vivaro piezo injector currents

Postby Robski » Tue Jun 11, 2013 11:11 pm

Are you the same Valhalla from a certain forum regarding a well moaned about scan tool (on there) ?

I ask because you seem to type in a totally different language on here, ie using bigger words :?
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