View previous topic :: View next topic |
Author |
Message |
Witty924
Joined: 05 Nov 2019 Posts: 17 Location: UNITED KINGDOM
|
Posted: Mon Apr 13, 2020 3:06 am Post subject: Fuel not getting to the injectors |
|
|
Hi everyone,
Happy Easter.
So I did the dreaded fuel system check today. My in talk fuel pump and outside fuel pump both seem to be working. Fuel is coming through to the fuel air mixture unit in the engine, however I’m not getting fuel to the injectors.
From what I have researched I believe that the injectors won’t work unless there is a set amount of pressure, so even though my fuel pumps are working it could be that I’m not getting enough fuel pressure to get the injectors working.
That said I could be wrong.
Has anyone had similar issues or found a separate issue why fuel won’t get to the injectors or come through the injectors?
Thank in advance for any advice. _________________ Witty924 - Porsche 924 2.0l NA 1984 |
|
Back to top |
|
|
dogleg5
Joined: 01 Apr 2020 Posts: 29 Location: No longer with us
|
Posted: Mon Apr 13, 2020 10:20 am Post subject: |
|
|
Did you remove the snorkel off the fuel distributor and lift up the plate? Or you could take the air cleaner off and reach in and push the plate up from the bottom. |
|
Back to top |
|
|
Witty924
Joined: 05 Nov 2019 Posts: 17 Location: UNITED KINGDOM
|
Posted: Tue Apr 14, 2020 9:42 am Post subject: |
|
|
Thanks Dogleg,
So that’s something I can try quickly for sure.
The outcome I guess is if fuel fires from the injectors when I do this I have a faulty fuel distributor/air mixer unit, right? _________________ Witty924 - Porsche 924 2.0l NA 1984 |
|
Back to top |
|
|
dogleg5
Joined: 01 Apr 2020 Posts: 29 Location: No longer with us
|
Posted: Tue Apr 14, 2020 9:51 am Post subject: |
|
|
No. If fuel comes out, all is good there. When you open the plate you're replicating air flow through the meter. The more you open it the more fuel you get. With it closed it'll block fuel to the injectors even though the fuel pump(s) is (are) running. |
|
Back to top |
|
|
Witty924
Joined: 05 Nov 2019 Posts: 17 Location: UNITED KINGDOM
|
Posted: Wed Apr 15, 2020 9:41 am Post subject: |
|
|
Sorry dogleg,
What I meant is the unit plate isn’t operating correctly with my intervention.
So I guess the common fault for the plate not working is a vacuum leak or is there a possibility or something else within the unit?
I just want to make sure I diagnose any potential failures within the fuel/air unit,
Thanks again _________________ Witty924 - Porsche 924 2.0l NA 1984 |
|
Back to top |
|
|
dogleg5
Joined: 01 Apr 2020 Posts: 29 Location: No longer with us
|
Posted: Wed Apr 15, 2020 9:59 am Post subject: |
|
|
Someone else will have to address the inner workings of the fuel distributor. I just bought my 924 and am just getting familiar with all of it. First off the plate should be free to move. It is weighted and there is some resistance. If it's coated with gunk (not uncommon) carb or brake cleaner will take care of that. Also, besides noise from your fuel pump there should be noise at the fuel distributor also. Plus disconnect the injectors from the lines as the injectors could be clogged as 2 of mine were. |
|
Back to top |
|
|
Ozzie
Joined: 12 Mar 2005 Posts: 4448 Location: Townsville, Qld. Australia
|
Posted: Thu Apr 16, 2020 10:57 am Post subject: |
|
|
Low fuel pressure will not allow spray from injectors but if both pumps are correct type then pressure should not be a problem
Likely a stuck valve that is supposed to move with the flap arm if it has sat awhile. _________________ Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance |
|
Back to top |
|
|
dogleg5
Joined: 01 Apr 2020 Posts: 29 Location: No longer with us
|
Posted: Thu Apr 16, 2020 11:08 am Post subject: |
|
|
Pressure would have to be pretty low for it to not spay something out the injectors unless they're clogged. |
|
Back to top |
|
|
Paul
Joined: 02 Nov 2002 Posts: 9491 Location: Southeast Wisconsin
|
Posted: Fri Apr 17, 2020 9:10 am Post subject: |
|
|
The injectors are closed until about 40-50 PSI. _________________ White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy. |
|
Back to top |
|
|
Witty924
Joined: 05 Nov 2019 Posts: 17 Location: UNITED KINGDOM
|
Posted: Sat Apr 18, 2020 8:20 am Post subject: |
|
|
Thanks all.
I’m going to run some final tests tomorrow and will circle back to you and let you know my results.
Appreciate the help.
_________________ Witty924 - Porsche 924 2.0l NA 1984 |
|
Back to top |
|
|
Witty924
Joined: 05 Nov 2019 Posts: 17 Location: UNITED KINGDOM
|
Posted: Fri Apr 24, 2020 1:00 am Post subject: |
|
|
Ok everyone, so it’s the fuel distributor and air mixture unit for sure.
I lifted the flap while someone turned over the engine and we have ingnition and start.
The problem is the car won’t start unless I left the flap manually so is the unit done or is there something else I can change to make it work properly?
I have cleaned it up so the plate inside is like new and everything is plugged in and clean as it should be should scratching my head on this now?
Thanks for advice in advance _________________ Witty924 - Porsche 924 2.0l NA 1984 |
|
Back to top |
|
|
dogleg5
Joined: 01 Apr 2020 Posts: 29 Location: No longer with us
|
Posted: Fri Apr 24, 2020 1:34 am Post subject: |
|
|
The only thing I can think of is you have an air leak. When the engine cranks and draws in air, the plate should open slightly and start feeding gas. If it does that when you open it manually it is either not drawing enough air (low compression, vacuum leak) or you are pushing it open farther than it would normally open by itself thus feeding it more gas which would indicate fuel pressure not high enough or sticking injectors. Are you opening the plate by pushing up through the air cleaner when you do this? And when you say it starts, it will actually run? What happens when you let go of the plate when it starts? Does it keep running or die? |
|
Back to top |
|
|
!tom
Joined: 28 Aug 2006 Posts: 1934 Location: Victoria, BC Canada
|
Posted: Fri Apr 24, 2020 3:20 am Post subject: |
|
|
Possibly the control pressure is wrong? _________________ 78 924 NA
5-lug |
|
Back to top |
|
|
dogleg5
Joined: 01 Apr 2020 Posts: 29 Location: No longer with us
|
Posted: Fri Apr 24, 2020 5:36 am Post subject: |
|
|
Could be. That can be adjusted with shims, but a pressure test needs to be done to see what's going on. Is it low pressure from the pumps or as you say, control pressure at the fuel distributor. If the car runs by manually opening the plate it could even be an adjustment of the plate adjusting screw. Could even have something to do with cold start. If there is too much pressure it will stop the plate from opening enough to send extra fuel. A manual would be helpful |
|
Back to top |
|
|
Witty924
Joined: 05 Nov 2019 Posts: 17 Location: UNITED KINGDOM
|
Posted: Sat Apr 25, 2020 5:07 am Post subject: |
|
|
Appreciate the thoughts on this gents.
So I raised it just a touch and the engine fires into life, however during the first minute or so I do have to touch slightly the plate through the air box (air box removed) to ensure the engine does stop running. After a minute of this the engine sorts itself and happily runs without me touching the plate.
However if I turn off the engine after 5 minutes let’s say and the engine is warm it still needs my intervention in the plate to fire up but once running it’s fine and continues.
It’s definitely on the start up that I have the issue. I don’t have a pressure test kit for the fuel but would this be the issue as once the engine starts all seems good.
I will go over all the vacuum pipes again tomorrow. I’m assuming you can hear air going through the main rubber air tube to the manifold unit due to the amount of air it’s sucking through, or shouldn’t you hear any sound of air at all?
Thanks again _________________ Witty924 - Porsche 924 2.0l NA 1984 |
|
Back to top |
|
|
|