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Rops voltage at start up ?

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Mike Rosie
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Joined: 16 Nov 2005
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PostPosted: Sun Feb 02, 2014 22:25    Post subject: Rops voltage at start up ? Reply with quote

Trying to diagnose my non starting trooper and measured the voltage at the ecu for rops 0.6 volts
But not sure what the range the sensor is in input pressure and output volts ?
So cant equate this to pressure however measured my other trooper and it looked to get up to about 1 volt


The story is
Trooper started to take a bit longer to start but last time it did and ran ok.
Next day it won't start.
White wire trick done
fuel checked and it is there but not a great flow from outlet of head on crank even with separate supply run in.
I will need to compare the fuel flow with other trooper   (nrv fitted)
swapped cam shaft sensor from my other trooper
swapped orpcv from other trooper
measured crankshaft signal and it is there but cant quantify the size of the signal at the moment (where is crankshaft sensor)
Cranked with rocker cover off and no sign of oil from injectors.
brake lights ok and 12 volts on both red wires at ecu

Need to check that ropcv is actually getting a signal
Really need a tech 2 and considering a Chinese one.

Any thoughts ?
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PostPosted: Sun Feb 02, 2014 22:25    Post subject: Google Ads keep this community free to join!


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Gribble
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Location: Holset H221W

PostPosted: Mon Feb 03, 2014 12:19    Post subject: Reply with quote

Do you think you have cranked it long enough to build injection oil pressure ? take a few winds over to get there .

Sounds like fuel ,where did you put the separate supply to ? onto the mechanical lift pump I guess .

A cheaper way to do basic diag work is to plumb in a pressure gauge to the drain plug in the oil rail and see if the oil pressure is gettting up to 1.8 to 2.0 Mpa's and if it is start looking at the sensor signals.

The way to test and evaluate the sensor readings is covered in the manual under  6E  - 4JX1 driveabilty .

The chinese T2's are ok ,one of the local techs has brought one fo VX work.
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Mike Rosie
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PostPosted: Mon Feb 03, 2014 13:46    Post subject: Reply with quote

Gribble
I connected the temporary fuel to the suction of the filter and primed till I got fuel out of the back of the head.
Also tried filter unit from other trooper to see if that helped but no luck.
Must admit fuel flow seems weak comming out of the head but not sure just how much should come out on crank.
I did think it was fuel my self having had to repair both the fuel tanks on my troopers before due to corroded pipes.
But this one just dose not waunt to start.

Has anybody had problems with the fuel pump before ?
Any idea what the delivery fuel pressure is from the pump ?
If it is fuel should I not see oil squirting from injectors as they try to fire (assuming I have given it long enough) ?

Was thinking of getting another oil pipe and fitting a gauge to it to check oil pressure.

If your talking to the lad with the tech 2 could you please ask him if he remembers which outfit he dealt with
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Browndoff
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Location: Dublin 13, Ireland

PostPosted: Mon Feb 03, 2014 16:19    Post subject: Reply with quote

Firstly - well done! You seem to be trying things logically!

"should I not see oil squirting from injectors as they try to fire"      YES!! If the ORPS has signalled to the ECM that pressure in the Oil-Rail is adequate - then it WILL 'enable' the injectors - and you should, indeed, see the 'used' oil squirt out. So that must NOT be the case.

Since you must have had the Cam-Cover off to be able to see the Injectors squirt, or not squirt, then you can loosen the HP-Oil-Pipe a little and see if HP oil squirts out of THAT [it  would NOT be 'rhythmical' like the injectors]. If NOT - then you may NOT have the pressure required - which would imply that the ROPCV is STUCK closed. You would then have to remove and clean the valve - or replace, if damaged.

If the oil pressure seems strong, then the ORPS is NOT sending that vital signal back to the ECM - so try disconnecting the white ORPS-Wire and the zero-volts signal then received will fool the ECM into thinking that there's max pressure available - so it will enable the injectors! If it works THEN - that would indicate that you must replace the ORPS.

As for the fuel coming out of the back of the Head - ANY fuel available should allow it to fire - the 4JX1 does NOT depend on a particularly high fuel-pressure - so I doubt if fuel is still the problem!
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I've done some major repairs, including replacing half-shaft, replacing fuel-injectors etc.
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Gribble
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PostPosted: Mon Feb 03, 2014 18:30    Post subject: Reply with quote

Here's the site I buy stuff from  -  http://www.obd2tool.co.uk/wholesale/gm-tech2-gm-diagnostic-scanner-1762.html  

You need 2 other signals to the ECU at start up (cam and crank ) before it enables the injectors and even if you have these and cut the white wire if theres no actual oil pressure there the injectors wont fire
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Gribble
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PostPosted: Mon Feb 03, 2014 18:31    Post subject: Reply with quote

http://www.obd2tool.co.uk/wholesale/gm-tech2-gm-diagnostic-scanner-1762.html
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Mike Rosie
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PostPosted: Mon Feb 03, 2014 22:53    Post subject: Reply with quote

ok got a fluke scope meter home tonight and checked a few things.
Seeing nice pulse from crank and cam sensor.
can see the pulsed signal to orpcv
checked injector signal and no pulse so disconnected white wire and pulse to injector appeared
So looks like low oil pressure.
Measured orps voltage again and it only gets up to 0.7 volts other trooper goes to over 1.4 on start then settles to 0.9
I tried swapping orpcv before with no effect so suspect either air has got in due to low oil or cracked pickup (2 ltr extra has been added)
Or  its the oil pump which I find hard to believe.
I will try bleeding the oil rail and have another look at the orpcv

Is the orpcv a dump valve back to the sump given that when it sticks open they won't start.
And it controls the pressure this way.
I saw the pulsed signal to it on the scope on my running trooper and noticed that the oil pressure goes quite high on start up then settles to a lower level
It looks like a piloted valve and when energised the small pin is pushed in to the main valve and shuts the pilot so oil pressure is balanced across the main shuttle
and then the spring shuts it letting pressure build up.
Then when de energised the oil pressure behind the main shuttle escapes prom pilot and dp across valve opens it and drops oil pressure  in the rail.
The pulse width seemed to change with engine revs so suspect the ratio between on and off is variable to control the pressure
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Gribble
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PostPosted: Tue Feb 04, 2014 0:23    Post subject: Reply with quote

Thats a very,very good summary of whats going on in a 3.0 engine you must do a bit of hydraulic work do pm  me please we can swap info .Dither millamps come into the ropcv workings like any proportional control valve .
.
The ropcv does dump excess flow  to tank, opps sump as the hpop is a fixed displacement rotary piston pump and it goes to 0%  delivery to stop the engine hence the wont start thing when it sticks there , well it makes about 1.0 and a bit Mpa's which wont fire the injectors .


Wont help bleeding the oil rail as its a closed center  hydraulic system -  Wink
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crusader
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PostPosted: Tue Feb 04, 2014 7:43    Post subject: Reply with quote

Rare but I have had a pump failure.
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Browndoff
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PostPosted: Tue Feb 04, 2014 16:10    Post subject: Reply with quote

"have another look at the orpcv "            That's still the best option - while you HAVE shown that there's a SIGNAL to the solenoid on the ORPCV - you have not yet shown that there is ever an adequate PRESSURE in the Rail!

While the Cam-Cover is off, check to see if there's any leak from the Rail - e.g. from the O-Ring seal on the ORPS. Any such leak would defeat the best efforts of a perfectly-working HPOP and ROPCV - and mean that there was never enough pressure to fire the Injectors - without 'cheating' with the White-Wire-Trick!
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Mike Rosie
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PostPosted: Tue Feb 04, 2014 16:49    Post subject: Reply with quote

Yep that was going to be one of my next checks especially as I changed the injector copper washers a month ago.
But I must  admit last time I had the cover off I never saw any sign of a leak.
But it is difficult to check on your own.
Will have to get the wife out to turn it over while I give it a closer inspection.
I am also locating a spare HP oil pipe to mount a gauge on
What is the normal tickover oil pressure because on my other trooper I am measuring 0.9 volts tickover and 0.2 at zero pressure for both engines
so if say the tick over is normaly 20 bar for a voltage range of 0.7 volts then my duff trooper has a cranking signal of 0.7 volts which
would equate to 14 bar or 1.4 mpa
Which I believe is to low ?
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Red Robbo
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PostPosted: Tue Feb 04, 2014 17:11    Post subject: Reply with quote

Correct needs about 2.8 mpa to enable injectors (plus cam & crank signal)
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Browndoff
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PostPosted: Tue Feb 04, 2014 17:47    Post subject: Reply with quote

Tickover-pressure in the Oil-Rail is actually supposed to be TWICE what you thought - 40 Bar!
[img][/img]

BTW - "0.2 at zero pressure" - did you actually release the pressure from the Oil-Rail - or just measure with engine stopped? It's NOT necessarily the same thing! Moreover, when the ORPS-wire is disconnected - that means a zero-voltage signal to the ECM - that is interpreted by the ECM as MAXIMUM pressure in the Rail! That's why it then allows the injectors to fire - even though the REAL pressure might still be too low!

I think the rail-pressure is inversely proportional to the ORPS signal-voltage - though I DON'T think it's a linear relationship.
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Mike Rosie
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PostPosted: Tue Feb 04, 2014 18:21    Post subject: Reply with quote

20 bar was just a figure I used as an example really had no idea what it should be.
But at 40 bar that means I am just getting to 28 bar which is the minimum to fire the injectors or so I have been told
So given some inacuracy in my figures and engine differences I am probably just below the required pressure.
The voltage signal from the orps rises with rising oil pressure
I suspect the sensor pulls the ecu signal down towards zero volt rail so by disconnecting the wire it would go high.
Yes it was with zero pressure but to be honest I'll be surprised if that little valve is 100% leak tight
Non linear it may be I don't know but I have a spare and If I get a chance I will take it in to work and run it up on the test bench and see.

I am still hoping to find a leak in the system as I dont think or at least hope its not the pump
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TrooperDan
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PostPosted: Tue Feb 04, 2014 19:09    Post subject: Reply with quote

I use a modified HPOP pipe with a 5000psi guage on it. Even tho the gauge is suitable i always pull the main fuse  Laughing
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