 FI Challenged Individual Checking Fuel Pressure, and a question re: fuel pressure regulator |
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| 76-914 |
 Mar 23 2009, 10:56 PM
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#1
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Repeat Offender & Resident Subaru Antagonist  Group: Members Posts: 13,876 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California 
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Trying to teach myself about FI. Bear with me! Does it matter where you check the fuel pump pressure i.e. before or after the pressure regulator? Secondly tell me if I got this right: 76 2.0 GC series engine; Fuel leaves the tank, flows thru fuel filter to pump where it is pumped to the passenger side fuel rail the over to the drivers side fuel rail. One branch on this fuel rail feeds the cold start valve while the other branch goes to the pressure regulator. If pressure exceeds appx 35psi then excess is bled off and routed back to the tank outlet/pump inlet junction??? Is this how it works???? Thirdly, does Pelican rent a gage? I took a water pressure gage (0-60lb) and checked pressure on outlet side of PRV. It pegged the gage so I'm thinking wrong gage/wrong side of PRV or pump is on steriods. Can ya hep me?
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| SLITS |
Mar 24 2009, 06:56 AM
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None  |
Tank .... fuel filter ..... pump .... passenger side rail ... across engine ... driver side rail (cold start valve tees off here) .... pressure regulator .... back across engine to tank return line.
Pressure should be measured at tap for cold start valve (after pump before pressure regulator). Pressure should be 29.4 lbs. At 35 lbs you might be over-riding the closure spring in the injector and causing it to leak fuel. |
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| type47 |
Mar 24 2009, 07:21 AM
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#3
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Viermeister Group: Members Posts: 4,254 Joined: 7-August 03 From: Vienna, VA Member No.: 994 Region Association: MidAtlantic Region |
QUOTE(SLITS @ Mar 24 2009, 05:56 AM)  Pressure should be measured at tap for cold start valve (after pump before pressure regulator). The fuel pump should supply more than the desired pressure for the system so I would guess you measured at the wrong place; the regulator adjusts for the right pressure. Look for the tap mentioned above. |
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| Bleyseng |
Mar 24 2009, 08:08 AM
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#4
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Aircooled Baby! Group: Members Posts: 13,037 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
or if its pegged it could be a pinched return hose. (IMG:style_emoticons/default/aktion035.gif)
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| SLITS |
Mar 24 2009, 10:53 AM
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#5
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
Sorry I didn't fully read the post .... You say you pegged a 60 lb guage. If you close off the return line by dead heading into a guage you will peg the friggen guage. You plugged the bleed off so the PRV doesn't really come into play.
Read pressure between the fuel pump and PRV anywhere you can tap in, but do not dead head the pump ... I don't know the max pressure on a D-Jet pump, but a CIS pump, dead headed will peg a 150 PSI guage. Hey Geoff ... you still rebuilding MPSs? |
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| underthetire |
Mar 24 2009, 11:19 AM
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#6
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914 Guru Group: Members Posts: 5,062 Joined: 7-October 08 From: Brentwood Member No.: 9,623 Region Association: Northern California |
If you are new to FI, i suggest you read all of this:
http://members.rennlist.com/pbanders/ It's for the D jet, which will be different, but it will show you the basics. This website solved all my original problems. Nother one is look at the megasquirt manual, lots of good basics in that one to. http://www.megamanual.com/mtabcon.htm |
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| McMark |
Mar 24 2009, 01:03 PM
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#7
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914 Freak! Group: Retired Admin Posts: 20,180 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
(IMG:style_emoticons/default/agree.gif) Check fuel pressure at the CSV port.
If fuel pressure is low there, but pegging the gauge at the outlet of the regulator, then likely your fuel hoses are hooked up backwards near the battery. |
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| 76-914 |
Mar 24 2009, 10:21 PM
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#8
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,876 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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 Hot Damn this is some good information. Dead head I have. Good info on fuel pressure. Yes I've read over rennlist but my mind is on overload and I forgot to source it when doing this. Once again I relied on my Haynes and got 35.7 psi there. I'll look for that test port or use the hose to the cold start valve and retest. You guys know your stuff! (IMG:style_emoticons/default/agree.gif) |
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| 76-914 |
Mar 24 2009, 10:43 PM
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#9
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,876 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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QUOTE(McMark @ Mar 24 2009, 12:03 PM) (IMG:style_emoticons/default/agree.gif) Check fuel pressure at the CSV port. If fuel pressure is low there, but pegging the gauge at the outlet of the regulator, then likely your fuel hoses are hooked up backwards near the battery. I don't think they are???? Before connecting either of them I kicked the pump on and assumed the one shooting petro was off the pump. This is the hose I connected to the right side rail. This is the part where I got stupid and dead headed. The only remaining original hose was left in place still connected to the pressure reg valve so I could test easily the fuel pressure. I will replace that hose and test with system intact. |
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| McMark |
Mar 25 2009, 11:22 AM
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#10
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914 Freak! Group: Retired Admin Posts: 20,180 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
QUOTE I kicked the pump on and assumed the one shooting petro was off the pump That's a good way to get it right. But getting it wrong isn't that uncommon, so gotta ask. (IMG:style_emoticons/default/wink.gif) |
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| 76-914 |
Mar 25 2009, 03:25 PM
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#11
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,876 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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(IMG:style_emoticons/default/headbang.gif) OK. Retested at "test port" and pressure was appx 31 on a 10yr old air gage so I'm guessing the pump is good and at some point I need to get a better gage and set the pressure correctly. I should mention this car was not running, 53,000 original and found that the pump relay not working. Jumped relay (#30 to #87) to complete pressure test. This is where I am getting confused. I don't have power to #86 so I wanted to trace it down. Looking at my Haynes (black&white flow chart on pg 181(which says it is for 75 model year-no listing for 76 here) I find J17 (pump relay) and follow #86 to the ECU where it connects to terminal 19. What color is this wire so I can find it outside of the ECU or relay board. Wouldn't I need to disconnect this wire to check for ground at terminal 85, anyway? Now, 2 questions about rennlist statement below. What controls the 1 1/2 second activation of the relay. If it turns off doesn't the pump stop? And secondly, I don't understand the last comment about switching the key on/off. how many times? Once, five times? What happens then? Or did they mean turn switch to off position before replacing ECU? And what is meant by "If no ground is available to wire 19 ............"? I thought #19 was a hot (12v) wire. Is 16/24 off the ECU the neg switch for this circuit.
NOTE: Relay is active for only about 1- 1 1/2 seconds after the ignition has been switched on. Check with voltmeter; relay is wired from ground through control unit. Do not connect terminal 85 to ground without first disconnecting wire 19 leading to the control unit, otherwise the control unit will be damaged. If no ground is available to wire 19 (switch ignition on and off), replace control unit. |
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| 76-914 |
Mar 25 2009, 03:29 PM
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#12
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,876 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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QUOTE(McMark @ Mar 25 2009, 10:22 AM) QUOTE I kicked the pump on and assumed the one shooting petro was off the pump That's a good way to get it right. But getting it wrong isn't that uncommon, so gotta ask. (IMG:style_emoticons/default/wink.gif) I agree, THX |
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