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HFR_Racer HFR_Racer is offline
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Join Date: Sep 2005
Location: Indiana
Posts: 546
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?

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,
Thank you,

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

Last edited by HFR_Racer; 03-24-2010 at 06:26 PM.. Reason: Added more information.
Old 03-22-2010, 07:50 PM
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