# Techy diesel question



## 88927 (May 10, 2005)

Hi all
I wonder if any of you can point me in a direction close to getting this sorted???
Every so often, mostly when pulling away from a junction or going up a hill, we get (very intermittently) a kind of misfiring sensation from the engine. It cant classically misfire because it is diesel, but this is the feeling. It seems to do it more often when cold than up to temperature, but some inclines have produced the effect. At first I thought it was labouring in a gear or not able to make it's mind up which gear to be in, but I am now beginning to doubt that thought as it sometimes feels like a heavy stutter.
The power just seems to be fine but it is snatching as it goes, I know this is probably one of those things you need to experience to analyse, but I thought it was worth asking anyway, as I am suspicious of the dealers sharp intake of breath and a list of possible things it may be. Last time I mentioned it to a repair guy they said "oh they all do that sometimes". I looked in the mirror when I got home and didn't see any banana stains anywhere so I figured lets ask the experts.....
Looking forward to your replies and thanks in advance all.

Keith


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## richardjames (Feb 1, 2006)

Hi :lol: 
It could be a sticking valve - some REDEX in the fuel may fix same - just a guess
Richard


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## DABurleigh (May 9, 2005)

Keith,

Could be torque converter shudder. Check fluids.

If not that, has your engine got a manifold absolute pressure or mass air flow sensor?

Dave


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## Scotjimland (May 23, 2005)

Hi Keith
I'm not a diesel techy ..but my first thought was perhaps water in the fuel .. have you tried draining the fuel filter ? .. usually a small drain cock on the bottom of the filter, open until clean fuel runs out. This may explain why it's ok when hot. 
I'll ask our diesel guy at work tomorrow..


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## artona (Jan 19, 2006)

I remember years ago having a similar problem on a jaguar xj6. After loads of checks on different things I got it linked upto an auto-tune and it turned out to be an HT lead breaking down. Not suggesting this could be the problem Keith but it might be something other than fuel

stewart


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## Enodreven (Aug 29, 2005)

Hi, Keith

(1) Can you see the exhaust when this ?? missfire is taking place do you see any black smoke ??if you do then its proberbly worth :-

(2) If you haven't changed the fuel filter recently i would change it ? this will also cover the possiblity of water if any ? also check if there is a filter in the return line as some motors have these as well if you have change it

(3) Put one of the diesel injector cleaning addertives in the next time you re-fuel ?? you can get the large size from Halfords, read the instructions don't put to much in ?

(4) if that dosen't cure it and you are getting any black smoke ? you may need to get the diesel injectors cleaned or replaced ?? there are a number of small firms that specialise in servicing diesel injectors so it will be worth checking yellow pages etc ?

(5) It is worth occasionally driving at high revs for some distance this can help to clear the system, but be careful ?

hope these help

Brian


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## teemyob (Nov 22, 2005)

*Diesel Misfire*

Hello there,

I have been having numerous problems with my Merc 416 5 cylinder engine ONLY 8,500 Miles. I had a similar problem and initially thought it was linked to the sprintshift gearbox. However, I put some redex in the system as advised above and not only did it seem quieter but the dull momentary miss has gone.

Also whilst Im writing, I drained the old mineral oil, flushed the engine and re-filled with fully synthetic oil. I am amazed at how much less soot and smoke comes from the exhaust

Trev


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## Enodreven (Aug 29, 2005)

Hi, Teemyob

Another problem that has a similar effect on Mercedes is if the setup is anything like the car, and you use your left foot on the brake, you can get a similar problem/feeling. which is due to the electronics which link the throttle and braking systems on the Mercedes. 

It may not happen on the vans, but when the brake pedal is depressed even very slightly it disengages the throttle. So if you do use your left foot to hold the vehicle while waiting to see if it is clear to go and then press the throttle to move off if your timing is not perfect, the pressure on the brake pedal cuts the throttle ??? disconcerting ??? again it may not happen on the VANS but a lot of people have raised it and the answer is don't use the left foot on the brake ??

hope this makes sense


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## 88927 (May 10, 2005)

Thanks all for your replies, brilliant....
To answer some, I have put some injector cleaner stuff in the tank, didn't accurately measure the quantity though  , I guess this is the same as ReDex??
Torque converter shudder... now we are talking, that sounds just like the sort of expense I need :lol: :lol: , I had problems with the fluid levels when the power booster failed, for some reason the gearbox came out in sympathy and dropped its level, this I can check. MAF and MAP's?? Don't know is the answer but I will check, I think I see where you are going Dave.
Thanks Jim, should have been all checked when it had a major service, but who knows, although there is a warning light "water in fuel" and it doesn't light when running........
Could be right Stewart, thanks.
Hi Brian, haven't seen the exhaust when it does it, I'll need to remember to look next time, trouble is it usually does it while you are busy doing something else at the time :lol: , although there is virtually no smoke when it starts, even after two weeks idle??
I had thought of flooring it, like with a petrol to clear the carb, but didn't want to (actually was frightened to...) do this just in case..... I may try taking it out for a high speed spin to see (carefully).
Interesting point about the change of oil, Trev, I know different oils can make a difference so when it is due a change (about 10 gallons) I will get them to swap over to synthetic if it recommended for my old tractor engine. The Chevy 6.5 cannot be considered a modern engine, so I will need to check carefully before doing this.

I will let you all know what I find out but in the meantime, your replies are very welcome and I am grateful to you all.

Keith


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## teemyob (Nov 22, 2005)

*Thanks*



Enodreven said:


> Hi, Teemyob
> 
> Another problem that has a similar effect on Mercedes is if the setup is anything like the car, and you use your left foot on the brake, you can get a similar problem/feeling. which is due to the electronics which link the throttle and braking systems on the Mercedes.
> 
> ...


Hello there,

Thanks for that advice, I think you may have answered another problem I have with the van stalling if you take you foot off the brake and try to quickly pull away from a junction roundabout.

Trev


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## teemyob (Nov 22, 2005)

kands said:


> Interesting point about the change of oil, Trev, I know different oils can make a difference so when it is due a change (about 10 gallons) I will get them to swap over to synthetic if it recommended for my old tractor engine. The Chevy 6.5 cannot be considered a modern engine, so I will need to check carefully before doing this.
> 
> I will let you all know what I find out but in the meantime, your replies are very welcome and I am grateful to you all.
> 
> Keith


Gee Keith is that TEN US gallons or UK?

If so I think you need a wholesale supplier!

I bought my synthetic half price at Makro though I have seen cheaper in Spanish and French Supermarkets.

Trev


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## Pusser (May 9, 2005)

I know nuffink but using lateral thinking (I wish) it would appear to be fuel related whenever a large demand for fuel is required. So one would think a restriction in the fuels journey or a defect in that which is demanding the amount of fuel or an inability to use the fuel that has arrived. I haven't got a clue what I'm taling about but I just felt like being a clever for a few minutes.


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## 88927 (May 10, 2005)

Thanks for that Pusser, that is exactly my feeling about it mate, well put :lol: :lol: :lol: 

Keith


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## zaskar (Jun 6, 2005)

kands said:


> Hi all
> I wonder if any of you can point me in a direction close to getting this sorted???
> 
> 1/ Partiall blocked filter in the tank pickup
> ...


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## JockandRita (Jun 1, 2005)

Hi Keith,

Being a diesel, we can discount the HT lead, although on petrol engines, that could well be the case, as HT electrical problems are often mistaken for fuel starvation.

Most of it has already been said, but whatever you think, start cheap and work your way up.

Diesels love large volumes of air mixed with a fine atomised spray at the injectors to give the correct fuel to air ratio. The fuel and air filters would be my favourites at this stage, followed by injector removal and cleaning/servicing, (only if the additive didn't work).

It is unlikely that the fuel pump timing is out, unless it has been worked on recently. 

Another thing to think about is the quality of the fuel, ie, try refuelling at a different outlet to your regular one. It's not unknown for forecourt tanks to be contaminated due to excessive rainfall or seepage from a water source.

Whatever route you choose to go down, I hope you are successful.

Jock


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## 88927 (May 10, 2005)

Thanks zaskar and Jock
The RV was "fully" serviced in November (£1953 worth... ouch) so I am really hoping that ALL the filters were changed...
Your comment re the pump is an interesting one Jock, I spoke to the previous owner and he said it had a new fuel pump fitted about a year or so ago and he told me it cost him £1800 so whatever it was it was a big job. Now the RV has always had this stuttering occasionally, so I do wonder??? Is it possible for the pump timing to be diagnosed easily or is it a pump out job?
Another thing comes to mind, when giving it some pedal or the engine is under load, there is a tapping/spitting sort of sound, which I can only assume to be a manifold leaking?? This does not seem to be coincidental with the stuttering though, just when going uphill and it is holding a gear.
I am beginning to wonder if the two are connected?
Can anyone recommend a really good diesel mechanic in the Northants area who doesn't suck in volumes of air and tut :lol: :lol: ?

Appreciate all the advice guys

Keith


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## 91645 (May 1, 2005)

Hi Keith:
I experience the same "misfiring" (P30 diesel, 1996, 75000 kM) when accelerating in particular when on the cruise control. Other than that the engine runs fine. I have stopped to worry about this phenomenem. I thought for a while that it came from an additional filter I installed between the tank and the 12V lift pump because of an additional pressure drop over the filter. I will change the filter before the season starts and maybe it is over. I really do not know what it could be but it cannot be something serious. I change fuel and air filters regularly myself and check the fuel filter bowl for foreign matter and water ( I even do not have a water in fuel warning light). Since you have a new fuel injection pump I would not worry.
All the best
John


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## zaskar (Jun 6, 2005)

kands said:


> Is it possible for the pump timing to be diagnosed easily or is it a pump out job?....................
> ............................Can anyone recommend a really good diesel mechanic in the Northants area who doesn't suck in volumes of air and tut :lol: :lol: ?
> 
> Any faults on the pump should be recorded in the ECU memory and can be accessed via Tech 2 diagnostics.
> ...


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## olley (May 1, 2005)

Hi kands if the pump timing was out you would either be blowing out a lot of unburnt fuel (retarded) or an increase in engine noise "diesel knock" (advanced) either way there would be a loss of power, its much more likely to be filter trouble.

One of the previous posters said start cheap, good idea water trap, fuel filters ect. 
If that all fails then before you start spending big money take zaskers suggestion, the diagnostic's readout will not always tell you whats wrong, but its certainly worth doing.

Olley


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## DABurleigh (May 9, 2005)

kleinejohan,

Any chance your "problem" could be a "feature"? 

http://www.dieseltruckresource.com/dev/archive/index.php/t-39911.html

Dave


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## 91645 (May 1, 2005)

Hi Dave
Thanks for living with us. No I do not think that this is the root cause because my RV has not got an ABS system. I had a big stalling problem but that is a common problem with all 6.5l Chevrolet Diesel engines with an electronic fuel injection system: overheating of the FSD (fuel solenoid driver-this the black box bolted to the fuel injection pump). Matter was resolved by relocating the FSD to a cooler location away from the engine room.
John


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## Scotjimland (May 23, 2005)

Hi Keith 
I asked our HGV mechanic but without hearing or experiencing the fault he was reluctant to diagnose however he did advise having the injectors out and cleaned, infrequent use can lead to carbonising and sticking, he also said not to waste money on diesel cleaning additives which are good at keeping injectors clean but not much use once they are dirty..


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## 88927 (May 10, 2005)

kleinejohan you are my best friend in the whole world :lol: :lol: :lol: 
Your description is very accurate about accelerating with cruise control... The "misfire" does not happen all the time or even often and so when it does it makes you sit up and pay attention. And you say not to worry which is a comfort. Thank you for that......
Jim, thanks mate. Sounds sensible advice to me, I have now decided that it is not about to drop out of the chassis and will get it checked over (thanks zaskar) with the diagnostic tools and if required will have the injectors dropped out and serviced.
Hey at least we seem to be down to the little things being wrong now...

Thanks again all for all your help.

Keith

Ps I'll advise what I find with this problem as I suspect that it may be a common P30 fault...


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## Scotjimland (May 23, 2005)

More jobs for Peterboro... !! 8O 8O :lol: :lol: :wink:


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## johnsandywhite (May 9, 2005)

kands said:


> "fully" serviced in November (£1953 worth... ouch) so I am really hoping that ALL the filters were changed...
> Your comment re the pump is an interesting one Jock, I spoke to the previous owner and he said it had a new fuel pump fitted about a year or so ago and he told me it cost him £1800 so whatever it was it was a big job. Now the RV has always had this stuttering occasionally, so I do wonder??? Is it possible for the pump timing to be diagnosed easily or is it a pump out job?


 8O You certainly seem to like shelling out money Keith. I think you have too much confidence in the professional services done on RV's. Just my Honest Opinion. :roll:


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## 88927 (May 10, 2005)

And your answer is?

Keith


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## johnsandywhite (May 9, 2005)

kands said:


> And your answer is?
> 
> Keith


 8O My first RV the 1988 Coachmen. I took it for a 60,000 miles service although it had only done 23,000. I also had it MOT'd at the same time. I expected the 60,000 mile service to include everything. After the service and MOT. They said it had 12% wear on the rear brakes, 30% on the Front and negligable on the Park brake, Within 2 months I had a complete barke failure and within 4 months I had to replace the Rotors, Disc pads and brake pads on the Park brake. It didn't cost as much as you mentioned for the original service, but I also didn't get what I expected either. :roll: Professionals? Who are they? :roll:


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## Pusser (May 9, 2005)

kleinejohan said:


> Hi Dave
> Thanks for living with us. No I do not think that this is the root cause because my RV has not got an ABS system. I had a big stalling problem but that is a common problem with all 6.5l Chevrolet Diesel engines with an electronic fuel injection system: overheating of the FSD (fuel solenoid driver-this the black box bolted to the fuel injection pump). Matter was resolved by relocating the FSD to a cooler location away from the engine room.
> John


I thought that was what the problem was going to be. You beat me too it. :roll:


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## 88927 (May 10, 2005)

I see where you are coming from JSW, however my point is that if you are unable to do this work for yourself where do you go to get it done??? I don't like or enjoy shelling out money but if my options are limited then I have to pay someone else to do the work. I will always try to get a first class job done and in reality the cost is secondary to the workmanship I expect.
I have a very good friend who runs an MOT station and repair shop, unfortunately his roller shutter door is only 10 foot 6 inches high so the RV will not go in......
He has serviced all our motorhomes up till now but the RV is just too tall.

Just our luck :roll: :roll: 

Keith


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## Scotjimland (May 23, 2005)

johnsandywhite said:


> Professionals? Who are they? :roll:


They were CI5... Doyle and Bodie :wink:


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## johnsandywhite (May 9, 2005)

kands said:


> my point is that if you are unable to do this work for yourself where do you go to get it done??? I don't like or enjoy shelling out money but if my options are limited then I have to pay someone else to do the work. I will always try to get a first class job done and in reality the cost is secondary to the workmanship I expect.


  It is a problem I understand Keith. If I didn't have my son and friends to help me when the big jobs came around? I suppose I would be struggling with my screwdriver, pliers, string, silicone and Gaffa tape too. :lol:

8) Perhaps you could do the same thing as you are with your Awning? Have a weekend get together servicing and drink-up. :wink:


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## 91645 (May 1, 2005)

Keith:
Thanks for the flowers on top of that it was my birthday as well.
OK back to the "misfiring" of the diesel. I did a search on my "the diesel page" forum and what I think it could be is that maybe the diesel fuel injection pump is "off timing". I will ask the forum members whether my pump injection set-up is causing the misfire. I also checked some old data and found out that my pump in any case is not set correctly. According to my latest data the pump injects fuel at 9.4 to 9.5 degrees before top dead center. This is a little bit too early and this doesn't matter too much at idling speed but I feel that it becomes critical at higher revs : the injection window becomes too small. Also you said that the previous owner got a new injection pump. It would be of interest to know how the pump was adjusted for timing. Further give me your VIN of your P30 to check what your control system looks like and also to look into timing specs of your injection pump. Again do not worry this timing is for fine tuning only. I can hardly believe that there are almost no Tech II analysers in GB. I will check that with a Scottish member of the Diesel Page he drives a GMC or Chevy truck.
Regards
John


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## 88927 (May 10, 2005)

Hi John
Thanks for all your help, it is much appreciated.
I have PM'd my details to you.

Keith


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## damondunc (Feb 14, 2006)

*techy diesel question*

Hi folks,
I'm pretty new to motorhome facts,but here goes.One posibility no-one has mentioned is the turbo wastegate situated under the right hand front wing,with the engine off it should be free to move both ways,as its vacuum operated when the engine is running.these wastegates seize for a pastime some times closed giving an overboost situation,and sometimes partially open giving no boost at all.both of these faults may or may not bring the service engine soon light on.The fault has to occur three consecutive times to bring the light on permanently.(this is assuming that the RV is a P30 diesel turbo). Are all of the dash warning lights functioning ok,ie service engine soon,service throttle soon,check guages? even if a bulb is blown it can create a fault!
hope this helps Damondunc.


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## 88927 (May 10, 2005)

Hi damondunc
welcome to our site and long may you enjoy it.....

Thanks for your reply, I know the service engine soon and service throttle soon lights come on, when you first turn on the ignition, so the bulbs are defo ok.....
It is a 6.5 Chevy turbo diesel on a P30.
Sometimes when giving it some pedal I can hear the turbo whining, so I am guessing that it is spinning up ok, never thought of the waste gate though..... Is there a simple check for this or is that a dumb question??? Is this fed from the vacuum thingy that is bolted to the front firewall?
If so maybe I could check that it is working...

Looking forward to your reply

Keith


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## zaskar (Jun 6, 2005)

kands said:


> ............ Is there a simple check for this or is that a dumb question??? Is this fed from the vacuum thingy that is bolted to the front firewall?
> If so maybe I could check that it is working...
> 
> Looking forward to your reply
> ...


Hi Kands.
Yep, the check is simple. As Damondunc says, go under the front r/h wheel arch and look over and behind the front wheel.In front of you, you will see the turbo & wastegate. Without wishing to teach granny how to suck eggs!  , the wastegate actuator is the small vacume cyclinder on the end of the rod which comes off the side of the turbo.
What can happen ( and what happens on my p30 with annoying regularity :evil: ) is this.
Where the actuator rod connects to the turbo casing there is a small lever. Behind that lever is a rod which goes directly into the tubo casing and inside the casing mounted on this rod is a butterfly flap, similar to that found in a carburettor. The problem is the materials that the pivot rod is made from. Tt corrodes and jams in the tubo casing! This usually happens when the vehicle has been stood for some time tho' in my case it can take less than two weeks!!!!!!!!!!!
The fix is, whilst the turbo is COLD, smother it in WD40. Wait 1/2 hour and then very gently, try to move the actoator rod forwards & backwards.
The lever on the turbo should move through an arc of approximately 90 degrees. If finger pressure is not enough, carefully, AND I MEAN CAREFULLY!, use a pair of pliers on the lever. Be VERY carefull not to rush and be gentle, start with a small movement and slowly build it up to the full 90 degree swing. Once it's fully free (hopefully  ) dry off all the WD40 (remember WD40 is highly flammable and turbo's get a tiny bit warm! Then smother the pivot lever end in copper grease to keep the damp out.

Of course, all this rubish might not be neccessary cos it sounds like yours is free anyway 

p.s busted Turbo = 1k - 2k approx 8O 

p. s2. this used to be a common fault on the Fiats & Citreons, don't know what the later ones are like.


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## damondunc (Feb 14, 2006)

*techy diesel question*

Hi kands,
if the wastegate lever is free with the engine off,what should happen when the engine is running is:vacuum should be supplied to the capsule on the turbo pulling the rod and lever towards the front of the RV if the lever is still free to move you have either a vacuum leak or the vacuum capsule is perforated.quite easy to check, be careful though as the turbo gets hot pretty quickly. 
Damondunc.
ps the vacuum thingy on the firewall is a resevoir to supply vacuum to the heater controls.


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## 88927 (May 10, 2005)

Fantastic help guys, many thanks.
I will check this out later today and get back to you. Thanks for the warnings too, sometimes we can all do numpty things like put our hands on hot things :roll: :roll: 

I will check later but in the meantime thanks again...

Keith


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## 91645 (May 1, 2005)

Hi Keith
While it was time for a new diesel oil filter I decided to do a little test to find out whether my 12V lift pump was working properly and also to rule out this pump as a possible cause for the misfiring or stumbling. Since I had to prime the diesel fuel lines and fuel filter bowl I did this little test. For this purpose the engine should be idling. You need a small container also. I had this at hand anyhow because of the priming. While the engine runs you have to open the little valve near the thermostat and you have to lead the small black hose into the container. This little valve is there to drain water from the fuel bowl. 
If you open the little valve you can see a steady flow of diesel fuel ito the container. If the engine continues to run you know that your lift pump is working well, if the engine stops or stumbles you know that the lift pump need to be replaced. Well the engine continued to run well so the lift pump is working well. I also changed the electric control of this pump and now the engine starts much better the before. Problem here is that the lube oil pressure switch is a little bit too weak to start the lift pump (contacts alter too fast) . If you put a relay in between the pressure switch only has to switch the relay ( a few milliamps) and not the pump. If you are interested I can tell you how to do that. It really improved starting considerably.
Misfiring and stumbling under certain conditions is still a little bit a mystery : maybe it is a too heavy a load for the fuel solenoid driver. 
If I find more I will let you know.
John.


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