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Alan L's Avatar
 
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CIS fuel head

Folks , since we probably prefer not to go there, I am posting a pic of the inside of a 930 fuel head. Since I've pulled it apart.
It is not too different to the 911 head (CIS fuel distributer cleanout w/pics)
But I am none the wiser at the moment as to why the air plate is vibrating so bad at idle. I have raised the metering piston (the bit that sits on the air plate arm) just so you can see it. Supposedly there is supposed to be a small orifice in the head of this piston area to dampen the movement. But I can't find anything like that - other than a couple of decent holes in the head of the body leading into the top of the piston - which in fact I suspect connect to the WUR. There is a bit of scoring on the piston where it has been chattering in the metering chamber. There is also a light spring which sits on top - presumably to assist damping, or the balance on the plate arm.
I have partly assembled the springs/diaphragm so you can see how it goes together. On the top of the head, by each injector connection, you will find some small allen head screws. These seem to screw thru to the inside and set the spring tension - I'm guessing this is how you set all the springs up even.Well the mystery continues. I'm just hoping someone in CIS- land can point me to the cause of my problem, because it has got me stumped. But it really is too serious to try and operate the car like this.
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Alan
Old 11-29-2007, 05:57 PM
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WUR thingy

I am posting a pic of a bit I can't work out. It sits between the WUR and the fuel head inlet that controls the pressure on the metering piston. This apparatus does not appear in my CIS schematics, nor is it on my SC's. So, maybe it is unique to the 930. Because it sits in between the two bits that control the damping pressure I am suspicious if this may be the problem. If I knew what it was supposed to do I could check it. It has a tube out the base - but there was nothing hooked on the tube. Maybe it is supposed to have a vac line, and open some controller diaphragm inside under deceleration?
In which case I may have solved the problem.
The skinny line goes on to the fuel head directly on top of the metering piston, the fat line comes directly off the WUR. I am hopeful the problem is here - if only I knew what it was.
Alan
Old 11-29-2007, 07:33 PM
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My car does not have that piece. Almost looks like maybe an aftermarket fuel pressure regulator that someone added to help with faulty CIS.
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Old 11-30-2007, 02:37 AM
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Could that have been part of some Lambda enrichment device...cobbled togther? I have the Imagine Auto modded fuel head that closes the Lambda port on the fuel dizzy. FWIW, I don't remember mine looking like that when I removed it. it was much more of a Hobbs style frequency valve.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
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Last edited by sand_man; 11-30-2007 at 05:42 AM..
Old 11-30-2007, 05:32 AM
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Just out of curiosity, where was the vacuum nipple on that conister connected?

EDIT: I just read where you indicated that it wasn't connected.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
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Old 11-30-2007, 05:34 AM
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Then I wonder if this was some sort of full boost enrichement? My WUR has a vacuum port on the side that is connected to the throttle body Tee...it is designed to deliver more fuel at the upper end...obviously taking it's signal from vacuum/pressure at the throttle body. I wonder if this was an attempt at that?
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 11-30-2007, 05:39 AM
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It has a Bosch part No on it. And the tube at the bottom, I can suck and blow on. It feels like a diaphragm inside. The tube at the bottom is also threaded and adjustable - it is like a hollow bolt, with a slot in the end instead of head. There is a lock nut holding it in place against the cannister. I blew on the WUR end of the pipe and fuel came out the fuel head end - about a cannister worth. So it has to be a head of fuel sitting over an adjustable and pulsed diaphragm. But how and why?
It is of similar construction to all the other diaphragm regulators normally on the motor - ie looks like it supposed to be part of the original system. Held on by 2 of the screws the Fuel head/air flap body bolts on to. Over the back of motor below the fuel head.
Alan
Old 11-30-2007, 10:19 AM
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I've never seen that on a 930 before. Call Bosch with the part number and they can tell you what it is and what it belongs on. I would (almost) bet a paycheck that is not a 930 part. I wonder if your WUR is bad (or needs adjustment) and the PO cobbled another pressure regulator to make it run.
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--clutch-monkey
Old 11-30-2007, 12:14 PM
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Quote:
Originally Posted by Alan L View Post
It has a Bosch part No on it.
And you thought it would only confuse us if you posted it?
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Old 11-30-2007, 01:20 PM
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I admire your DIY spirit - dismantle a fuel head that has thingy's and springs and tubes you can blow on.
Old 11-30-2007, 03:01 PM
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Quote:
Originally Posted by DonE View Post
I admire your DIY spirit - dismantle a fuel head that has thingy's and springs and tubes you can blow on.
With the nearest Porsche dealer 300 miles away, and the number of Porsches in my locality able to be counted on one hand, (mine being the only 930 I know of) certain things become a necessity. But if you like doing these things, it keeps you out of other trouble. And is better than mowing the lawns - altho they still seem to need mowing.

At the risk of confusing you (Spuggy) the part No is 0 280 161 007. I will try e mailing Bosch - I would not expect much help in NZ.
I had to get it out again for the number - I was dumb enough not to write it down while I had it out.
I am suspecting possibly a problem with the WUR. I have the fuel head back together and have hooked a pressure gauge in line between the head and WUR. The plate still goes into its spasm mode - and when it does the pressure fluctuates like crazy too - so the pulses are sent right down to the WUR.
I am about to measure all the pressures. I did this on my SC a few years back, but memory fails me. To do the warm pressure the pumps must be on. I pulled the air plate switch to do that. But the injectors are screaming like mad. It seems to me I'll fill the engine up with fuel leaving it in this state for 20 minutes?
Alan
Old 11-30-2007, 05:43 PM
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Checked the WUR, and nothing wrong inside. Checked some fuel pressures - I did'nt leave the injectors screaming for 20 mins. I bypassed that system and hooked 12 V directly onto the WUR connections (from a battery). After 20 mins I turned the key on to see what the pumps could register. The pressures seem unusually high according to my info. Hopefully someone can confirm I have this right. But my cold pressure is 50 psi. I believe it should be 20-30. My warm pressure is 70 psi (should be 50). My system pressure is over 100 (my gauge only goes to 100). Should be 100 max. I have cut the warm press back to 60, but will have to take all the shims out to get to 50. Does this sound right - my injector opening pressures were around 50.
Alan
Old 11-30-2007, 07:40 PM
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Googled for "0 280 161". It's described as a "fuel damper" or "fuel dampner". Many hits.

0 280 161 015 = Porsche 944 part
0 280 161 006 = 1982-1988 BMW 528e M20

Bosch don't list that part for your car in their efi_techservice.pdf file though.

I'm not real clear where was fitted on your car - is this part #33 on this diagram?

http://www.pelicanparts.com/PartsLookup/HTML/911_USA_84_86_KATALOG/107-20-Frame3.htm

That's described as a "vacuum limiter", but it seems to go more or less where you described it, and look fairly similar...

All your pressures seem quite high. Bosch quote 2.1 + 1.1 bar opening pressure = 2.1-3.2 bar for my injectors. I make that a maximum opening pressure of 47 PSI, so yours are right at the top limit.

What do you mean "take the shims out to get to 50" for the WCP? The shims in the pressure regulator are to adjust SYSTEM pressure - you need to move the plug in the WUR to adjust WCP?
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Old 12-01-2007, 02:30 AM
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0 280 161 007 is Bosch fuel accumulator/pressure regulator that usually sits on Mercedes. Shouldn't be there on 930 CIS. That's something cobbled up. Remove it and try again. It seems that somebody was trying to make DIY fuel enrichment system using non-Porsche fuel parts. The nipple whould be connected to plenum and it should regulate the fuel pressure to 3 bar (or whatever it's made to)+plenum pressure.

I'm quite puzzled to what PO was trying to achieve by attaching it between WUR and fuel head? If there is no nipple attached to it, it will act like a 3 bar pressure limiter.

There is a big fuel accumulator on 930 CIS just besides fuel filter. It sits on drivers side of engine compartment. Is it there?
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Last edited by beepbeep; 12-01-2007 at 05:52 AM..
Old 12-01-2007, 05:34 AM
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Nr. 16 is OEM fuel accumulator. It's main purpose is to keep some pressure in system so it doesn't take a long time for fuel pumps to pressurize system to 7 bar before start. It's just an accumulator and is not there to adjust fuel pressure in any way. Amount of fuel injected by CIS depends by pressure differential between system pressure and control pressure (which is smart way to assure that amount of injected fuel won't change if fuel pumps loose their efficiency later on).

I guess PO tried to cobble up his own fuel enrichment device by attaching EFI pressure regulator in order to raise system pressure or decrease control pressure during boost or something.

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Last edited by beepbeep; 12-01-2007 at 05:45 AM..
Old 12-01-2007, 05:37 AM
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What year is the car? What WUR number do you currently have? I'm curious if you have the correct WUR for your year car. I realize that many CIS WURs are interchangable, even from different makes and models, but it might be another indication of what you're dealing with if this system has been tampered with...
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 12-01-2007, 05:41 AM
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P.S.

If I was in your place, I would remove Mercedes fuel regulator, re-assemble CIS fuel head very carefully and try to start the car.

It was very brave of you to dissassemble fuel head just like that. It's nothing I would try to do...I heard that CIS fuel heads aren't really DIY-friendly and kinda hard to put back in working order. I hold by thumbs for you!
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Old 12-01-2007, 05:56 AM
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Hardest thing on the CIS head is to reseal them.
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Old 12-01-2007, 10:01 AM
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Thanks for the info guys, I had come to the conclusion this extra part does not belong. The orientation of the union fittings is wrong. The WUR really neeed to be on the other side of the engine. They have rotated it 180 deg.
It had no vac hose hooked on it. So, I'm trying to figure if it is there for the enrichment purpose you talk of, or trying to get rid of this cursed air plate spasm.
I will try and dispense with it and see if we do better. But this will mean getting new fuel lines made up - which will take a while. There will be no union fittings close at hand.
I suspect the WUR is correct - altho I cannot find a part No on it now that it is back in car. Is it on the bottom? It does have the vac nipple going to the plenum chamber - and looks different to my SC one.
I dropped my system pressure by taking all the shims out (there were plenty).
Given it was off scale on my 100 psi gauge, this seemed logical. It seemed to have the effect of dropping the WUR pressures too - more into the range they should be in.
Relax Goran. I am no longer afraid of the fuel head - but there are a couple of tricks to putting it back together. I will post them here - as they are worth mentioning. Do not be afraid to pull it apart - but really most people will probably never have to unless you have a critically badly functioning fuel system. In which case for an hour or two investigation, it may well prove to be useful.
There is an O ring sealing the base of the unit to the air box. This is one of the potential vac leak areas that few probably check. You have to prise the head out of the air box. When I next pull my airbox out, I am going to rechamfer the entry for this unit. The O ring was cut to pieces. I discovered this 10 minutes before the shops closed for the w/end. Rushed into town and managed to get an O ring right on closing time. When I reinstalled mine, I ended up having to pull it off. Again, it has sliced the O ring. So, if you have a vac leak you cannot find - here is one potential spot that would be hard to find. I am going to rechamfer this hole.
I had no leaks after reassembly. The two halves are held together by many torquex? screws. I used the ratchet setting on my cordless drill to evenly tighten them down. I used no sealant. But I also noticed there are no filter screens in any of the inlet banjo fittings. I suspect this is a mistake and they have been removed. Any crap in the system will go straight to the injector, or worse, block one of the tiny metering slits. Good luck on cleaning them - they look about 2 thou wide. I intend to source some banjo screens. They can be fitted with the head in place later.
I had one issue that caused me to pull it apart again, apart from the fact the plate flutter still exists. It pissed fuel out to one cylinder. I could detect the cylinder, so when I lifted the two halves I knew which injector meter system I was looking for. I thought one of the ceramic caps must have dislodged off the spring when I put the two halves together. (Line it up perfectly - do not rotate it later , at all, to get the screws back in housing). But it had torn one of the elongated O rings around the metering slot - on the internal chamfer as you push the barrel back into the housing. It is impossible to see this - the diaphragm gets in the way. I had put one drop of oil shared between the 8 O rings to help it in (This head is made to do 8 cylinders - but for us Porschephiles they have not cut the slits on two of them. Make sure your orientation is right when you put the barrel back or you really will have fun - not sending fuel where it is needed and sending fuel where it is not wanted). I had torn one of the elongated O rings. Luckily I had a spare O ring of the right dimension, so hopefully back OK now. 2 nd time lucky. Other than that, it is not too difficult.
But this unit does function differently to the 911 and textbook CIS scheme. They rely on a constricting orifice between the WUR and the metering piston head for damping. This unit has no such orifice and is in direct full contact with the WUR. It does however have a light spring which sits on top of the metering piston - you can see it in my pic. It sits in the recess in the top of the piston.
I still have no idea why the plate vibrates so bad. It may be this extra piece - because it is a spring regulated diaphragm - so maybe it is setting an oscillation up. My other thought for this Sunday was to make up a clearance fit piece I could push into the union fitting for the WUR at the fuel head. I would drill a small hole in it, thus introducing a restrictor orifice like the CIS manuals normally show. If it did not work, I have destroyed nothing, and could simply remove it. It would not tell me the cause of the problem tho, but may fix it. It may have the effect of slightly slowing the airplate /piston response tho.
But I m struggling with this one.
Thanks for the thoughts. And the Google - saved me trying to deal with Bosch.
Alan
Old 12-01-2007, 10:59 AM
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Quote:
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.....


It was very brave of you to dissassemble fuel head just like that. It's nothing I would try to do...I heard that CIS fuel heads aren't really DIY-friendly and kinda hard to put back in working order. I hold by thumbs for you!
I consider myself pretty hard-core DIY, but I would have balked at this job. Good luck and keep us informed.

Last edited by DonE; 12-01-2007 at 03:41 PM..
Old 12-01-2007, 03:35 PM
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