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Fuel system pressures - It works now..



I've been busy this winter working on my 930 and I'm finally to the task of checking my fuel system.

Vehicle information:
1987 Porsche 930, 3.3 liter, K27, sport cams, Kokeln inter-cooler, B&B headers.

Items that I've completed thus far on the fuel system:

1) Changed fuel filter.
2) Cleaned fuel injectors (thanks to excellent posts on this forum).

Tonight I hooked up the CIS to my vehicle (empty engine bay) and my fuel "system pressure" is very low. I'm only seeing 2 bar max. on the gauge. My CIS pressure testing gauge is new. I am running both fuel pumps simultaneously by jumping terminals 87 and 30 at the fuel pump relays in the boot area. Both the "system pressure" and "control pressure" show 2 bar. All electrical connections to the intake manifold, WUR and CIS system are disconnected as well.

Battery voltage is 12.6 VDC.





YELLOW arrows indicate the connection locations at the fuel head and WUR for my CIS gauge connection. Can anyone onfirm that I'm connected correctly at the WUR? I simply installed the CIS gauge in-line from the fuel head to the WUR.

I'm afraid to re-shim the fuel regulator since this car was running ok this past spring. I'm curious if my pressure will increase if I had 14 VDC to the pumps as it would have when it's running. Does this matter??

My goal here is to check fuel pump delivery (volume), control pressure, system pressure and control pressure change with WUR connected, fuel injector flow (volume) while connected to the fuel distributor. I also plan to adjust my my AFR once I get the engine re-installed and running.

I'm planning on testing fuel pump delivery volume and pressure tonight to see if they are in spec. I need to purchase the correct M14 fitting to connect to my fuel delivery line. I'm not sure why my new CIS guage set didn't have this ftting. If the fuel pump volume and delivery are ok then I assume that I should then shim the regulator at the fuel head.

What troubles me is that this car was running fine this past season. The only fuel system related item I've changed is the fuel filter and I'm using an approved part # filter.

Are there any other fuel system related items that I should be checking?

3/23/2010:
I confirmed this evening that my fuel pumps are pumping adequate volume and I'm getting 7 bar pressure to the fuel head. I'm still only getting 2 bar pressure from the port on the top of the fuel head to my CIS pressure gauge though. Any suggestions on what to check next? Shall I go ahead and shim the fuel head regulator to increase my "system pressure"?

I can't believe that the pressure would've changed just because the fuel head sat on my bench dry for a couple of months? I've not read anything about needing to keep the fuel head fully charged with fuel while it's off of your engine. Any comments on this topic from anyone?

Latest update from 3/24/2010 ( Success )

I'm not really sure why the darn CIS pressures didn't check out yesterday. My morning started at 6 am and the pressures were both 2 bar as previsouly stated. I bled and bled that darn CIS system I guess until it had no choice but to work for me.

I must've bled it 15 times using various methods to ensure that any entrapped air was gone and nothing.. Then I shimmed the fuel head regulator to increase the pressure. Both the system and control pressure increased to the same level. I then changed the shims back to the original configuration and tried again. Finally the darn thing works and I'm not really sure why but here are the results..

Fuel pump pressure: 7 bar
Fuel pump delivery volume: 1618 cc ( 1 minute test duration)
System pressure: 6.7 bar
Control pressure "cold": 1.5 bar
Control pressure circuit delivery volume: 240 cc / 30 seconds...
- This started out as 15 cc / 30 seconds... OUCH...


Thank you all that respond,
HFR_Racer
__________________
Thank you,
HFR_Racer

'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.

Last edited by HFR_Racer; 03-24-2010 at 05:26 PM.. Reason: Added more information.
Old 03-22-2010, 06:50 PM
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Looks like you are measuring cold control pressure.

Cold starting (when engine is bone cold - left overnight) control pressure will be about 2bar.

If your fuel gauge has a lever then turn it to change from control to system pressure. The system pressure should be about 6 bar (ish).

If you could start your engine you would see control pressure go from 2bar (ish) up to around 3.7+/- bar (ish) as it warms up.

This is the difference between control pressure and system pressure because when measuring control pressure some fuel is returned to the tank.

Also I find it more convenient to just pull the green wire connector from the back of the fuel head than jump fuel pumps. Just my $0.02
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'85 930 - Black on Black
'95 993 Turbo - Silver

Last edited by Helmsy; 03-23-2010 at 03:02 AM..
Old 03-23-2010, 02:58 AM
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Control pressure and system pressure.

Helmsly:

Thank you for your response. I agree with your comments on how it's supposed to work, but I'm not getting the results that I expect. My control pressure is good at 2 bar but my system pressure isn't enough to open the fuel injectors (only 2 bar).

Maybe I'm not hooked up to my fuel head and WUR using the correct ports?


I'm going to attempt to measure my fuel pump pressure this evening. I hope that I'm getting good pump pressure.

3/23/2010: Fuel pump pressure is good at 7 bar.

I only have the manifold sitting in my engine compartment. No electrical hookups (only the fuel lines) and the CIS pressure gauge are connected.

I hope that someone can help me solve why both my control and system pressures are at 2 bar.

HFR_Racer

MORE INFORMATION ADDED TO ORIGINAL POSTING 3/23/2010 (EVENING)
__________________
Thank you,
HFR_Racer

'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.

Last edited by HFR_Racer; 03-23-2010 at 07:04 PM..
Old 03-23-2010, 02:19 PM
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Where in Indiana are you?
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Mark 1979 930 Euro ***GONE AND DON'T MISS IT AT ALL***

"Worrying about depreciation on your car and keeping mileage down is like not ****ing your girlfriend so her next boyfriend finds her more appealing"
--clutch-monkey
Old 03-23-2010, 03:51 PM
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Am I using the correct fuel head and WUR port?

I'm located in Lafayette...


Please chime in and let me know if I testing the "system pressure" and "control pressure" using the correct ports?

My CIS pressure gauge is connected between port #1 located on the top of the fuel head and port #2 of my WUR. Am I correctly connected? Or should I be using ports #3 and #4??



One other suggestion I've heard is to remove the Andial 7th injector from th equation. Any comments on whether it is ok to leave it in the test circuit?
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Thank you,
HFR_Racer

'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.

Last edited by HFR_Racer; 03-23-2010 at 06:17 PM..
Old 03-23-2010, 06:12 PM
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You have it wrong. Take line #2 off and connect one end of your gauge to it and the other to where that line connected to the WUR. Basically, put in series with line #2.
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Mark 1979 930 Euro ***GONE AND DON'T MISS IT AT ALL***

"Worrying about depreciation on your car and keeping mileage down is like not ****ing your girlfriend so her next boyfriend finds her more appealing"
--clutch-monkey
Old 03-23-2010, 06:18 PM
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And yes, lose the 7th injector while testing.
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Mark 1979 930 Euro ***GONE AND DON'T MISS IT AT ALL***

"Worrying about depreciation on your car and keeping mileage down is like not ****ing your girlfriend so her next boyfriend finds her more appealing"
--clutch-monkey
Old 03-23-2010, 06:19 PM
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Ok.. Then I'm hooked up correctly from my fuel head to my WUR. I've been hooked up in series to port #2 Basically from port #1 to #2.

When checking "system pressure" the valve on my CIS guage setup is turned off (blocking flow to the WUR. Basically, the 7th injector doens't matter because it's not in the circuit when testing the "system pressure"

Do you agree?

Thanks for the help thus far..
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Thank you,
HFR_Racer

'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.
Old 03-23-2010, 06:32 PM
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Disconnect hose #2 from the WUR and connect it to one end of your gauge. Connect the other hose on your gauge to where #2 was. Leave #1 out of it.
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Mark 1979 930 Euro ***GONE AND DON'T MISS IT AT ALL***

"Worrying about depreciation on your car and keeping mileage down is like not ****ing your girlfriend so her next boyfriend finds her more appealing"
--clutch-monkey
Old 03-23-2010, 06:40 PM
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Are you near Indy? I can help you if you're close.
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Mark 1979 930 Euro ***GONE AND DON'T MISS IT AT ALL***

"Worrying about depreciation on your car and keeping mileage down is like not ****ing your girlfriend so her next boyfriend finds her more appealing"
--clutch-monkey
Old 03-23-2010, 06:42 PM
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Thanks for the offer.. I'm an hour north of Indy and I taking tomorrow off of work to work on this project as well. If your up for the drive feel free to join in the fun.

Anyway.. I'm hooked up correctly. Yes, I'm hooked inline with port #2.

Let's move on the next question then. Any ideas on why my control pressure is low now but the car was running ok all of last season? I'm sure it didn't only have 2 bar of "control pressure" last year because that won't even open the fuel injectors.

Shall I adjust the regulator in the fuel head to increase my "control pressure" or am I likely looking for something else since the car ran last year?

I'm really reluctant to adjust the fuel head regulator.. Can you tell???
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Thank you,
HFR_Racer

'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.

Last edited by HFR_Racer; 03-23-2010 at 06:55 PM..
Old 03-23-2010, 06:50 PM
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Don't adjust control pressure. You are in the ballpark there at around 2 bar. You need to reference the temp/pressure chart to be sure but that is close. Your system pressure should be between 6 and 6.8 bar if I recall correctly. If you only have 2 bar system pressure then something happened since you last drove it or your gauge is wrong. If you are in series with #2 and you flip the valve on the gauge to system with no change I would suspect that the valve is faulty.
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Mark 1979 930 Euro ***GONE AND DON'T MISS IT AT ALL***

"Worrying about depreciation on your car and keeping mileage down is like not ****ing your girlfriend so her next boyfriend finds her more appealing"
--clutch-monkey
Old 03-23-2010, 06:57 PM
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I've checked the valve on my CIS setup and it's working correctly. I honestly believe that the gauge itself is ok as well since it's new and it accurately read the fuel pump pressure at 7 bar.


Could it be that air is trapped in the fuel head and I just haven't bled it out yet?
According to the "Bosch Fuel Injection & Engine Management" book you simply run the fuel pump for 10 seconds and shift the CIS pressure gauge valve back and forth a few times to clear the entrapped air from the CIS system. Is this correct or is another method preferred?

I noticed that the Haynes manual says to hold the CIS flap down for up to 5 seconds while the fuel pumps are running to bleed the CIS system. Maybe I've just got air in the system?

Also, I did tip the CIS unit slightly (30 degree angle) to clean off the old intake manifold gaskets from the intake surfaces. It's not a problem to tip the CIS unit slightly on it's side to clean off the old gaskets is it?
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Thank you,
HFR_Racer

'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.

Last edited by HFR_Racer; 03-23-2010 at 07:35 PM..
Old 03-23-2010, 07:08 PM
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I agree with Mark that you should remove the 7th injector and put your gage in the #2 spot.
With the valve open you should see ~20lb cold pressure, ~45lb warm pressure and ~90lb system pressure.
What is that black cap on the vent tube of the WUR? That tube needs to reference baseline air pressure.
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Old 03-23-2010, 07:32 PM
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Brian:

The black cap on my WUR is the factory vented cap. I've confirmed that it is open to atmosphere as it should be.

My only problem as of now if that my "system pressure" is not 90 psi. Could it be that I haven't correctly/fully purged the air form the CIS system? Or another reason?

I'm confident that I didn't suck up any dirt or debris into the CIS system when I stored it and when I hooked it up. Also, I labeled all of the hoses so I'm confident that I hooked the CIS back up to the vehicle correctly.

I'm going to try to purge the CIS system reall well tomorrow morning.

Any other Pelican's that would have comments on correctly purging a CIS system?
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Thank you,
HFR_Racer

'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.

Last edited by HFR_Racer; 03-23-2010 at 07:45 PM..
Old 03-23-2010, 07:41 PM
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The fuel system is an open loop back to the fuel tank. To purge you simply turn on the pumps and let the fuel travel through the gage lines for several minutes. Put a trickle charger on the battery if need be. You will be able to hear air going through the system just like purging your house water lines.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 03-23-2010, 07:49 PM
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Crap.. I was hoping that you weren't going to say it was that easy.. I've ran the pumps and the return circuit to the tank is working properly. I have heard the air bubbles moving back to the tank for a short period of time after I started the pumps. I've actually done this several times now with no increase in "system pressure".

Based on all that I've said in the above thread would you then agree that I need to adjust my fuel head regulator to increase the "system pressure"?

According to the Bosch CIS Injection book I'll need to add 2.7mm of additional shims to my fuel head regulator... Is that even possible

If the fuel head regulator adjustment doesn't increase the "system pressure" then what? Tear down the fuel head for re-build / inspection?

Do you have any other conceivable ideas as to why my "system pressure" suddenly is only 2 bar versus last summer. Isn't it odd that it suddenly falls off a cliff like that?

It just doesn't make any sense to me that the fuel pressure would change that drastically just because I left the CIS dry for a while. I didn't drop the darn thing.. Yet..
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Thank you,
HFR_Racer

'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.

Last edited by HFR_Racer; 03-23-2010 at 08:14 PM..
Old 03-23-2010, 07:57 PM
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I wouldn't add shims. If your pressure dropped that much you have a fault somewhere. Shims are just a band-aid in that case and may not even work; you might even do damage. Also, you said both pumps are running by jumping the relay in the boot. Are you sure both are actually running? Take one relay out at the fuse block and try running the pump with the relay still installed. Then move the relay to the other one and try again. Make sure both actually run.
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Mark 1979 930 Euro ***GONE AND DON'T MISS IT AT ALL***

"Worrying about depreciation on your car and keeping mileage down is like not ****ing your girlfriend so her next boyfriend finds her more appealing"
--clutch-monkey
Old 03-24-2010, 02:50 PM
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Success...... Finally......

Fuel injectors all spray nicely and basically the same volumes..

Injector #1: 4.3 oz / 30 seconds
Injector #2: 4.3 oz / 30 seconds
Injector #3: 4.2 oz / 30 seconds
Injector #4: 4.3 oz / 30 seconds
Injector #5: 4.3 oz / 30 seconds
Injector #6: 4.3 oz / 30 seconds





Additional note: The flap on my CIS actually hung up once during my testing today. When I freed it I heard a pretty good pop. It was mechanically hung up. Any ideas on what it can hang up on?
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Thank you,
HFR_Racer

'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.

Last edited by HFR_Racer; 03-24-2010 at 05:30 PM..
Old 03-24-2010, 05:27 PM
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My bet is somehow you are measuring it wrong with the gauge or have a fault (as suggested by Mark) so I wouldn't adjust shims or WUR.

Is your gauge on the pressure side of the WUR line? I presume some gauges if you cocked it shut and the gauge was on the wrong side it wouldn't read correctly. Try swapping the connections from your gauge hoses to the WUR.

All you need to do is undo #2 in your picture and put your gauge in between the #2 connection with the gauge on the side where the fuel is coming from and cock it shut and open a few times and then leave it shut.
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'85 930 - Black on Black
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Last edited by Helmsy; 03-25-2010 at 03:22 PM..
Old 03-25-2010, 03:18 PM
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