Show full size 924Board.org
Discussion Forum of 924.org
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to 924.org924.org   Jump to PCA 924 Registry924 Registry

Fuel not getting to the injectors
Goto page 1, 2  Next
 
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions
View previous topic :: View next topic  
Author Message
Witty924  



Joined: 05 Nov 2019
Posts: 16
Location: UNITED KINGDOM

PostPosted: Mon Apr 13, 2020 3:06 am    Post subject: Fuel not getting to the injectors Reply with quote

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 Iím not getting fuel to the injectors.
From what I have researched I believe that the injectors wonít work unless there is a set amount of pressure, so even though my fuel pumps are working it could be that Iím 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 wonít 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
View user's profile Send private message Visit poster's website
dogleg5  



Joined: 01 Apr 2020
Posts: 29
Location: No longer with us

PostPosted: Mon Apr 13, 2020 10:20 am    Post subject: Reply with quote

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
View user's profile Send private message
Witty924  



Joined: 05 Nov 2019
Posts: 16
Location: UNITED KINGDOM

PostPosted: Tue Apr 14, 2020 9:42 am    Post subject: Reply with quote

Thanks Dogleg,
So thatís 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
View user's profile Send private message Visit poster's website
dogleg5  



Joined: 01 Apr 2020
Posts: 29
Location: No longer with us

PostPosted: Tue Apr 14, 2020 9:51 am    Post subject: Reply with quote

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
View user's profile Send private message
Witty924  



Joined: 05 Nov 2019
Posts: 16
Location: UNITED KINGDOM

PostPosted: Wed Apr 15, 2020 9:41 am    Post subject: Reply with quote

Sorry dogleg,
What I meant is the unit plate isnít 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
View user's profile Send private message Visit poster's website
dogleg5  



Joined: 01 Apr 2020
Posts: 29
Location: No longer with us

PostPosted: Wed Apr 15, 2020 9:59 am    Post subject: Reply with quote

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
View user's profile Send private message
Ozzie  



Joined: 12 Mar 2005
Posts: 4447
Location: Townsville, Qld. Australia

PostPosted: Thu Apr 16, 2020 10:57 am    Post subject: Reply with quote

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
View user's profile Send private message Send e-mail
dogleg5  



Joined: 01 Apr 2020
Posts: 29
Location: No longer with us

PostPosted: Thu Apr 16, 2020 11:08 am    Post subject: Reply with quote

Pressure would have to be pretty low for it to not spay something out the injectors unless they're clogged.
Back to top
View user's profile Send private message
Paul  



Joined: 02 Nov 2002
Posts: 9451
Location: Southeast Wisconsin

PostPosted: Fri Apr 17, 2020 9:10 am    Post subject: Reply with quote

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
View user's profile Send private message Send e-mail
Witty924  



Joined: 05 Nov 2019
Posts: 16
Location: UNITED KINGDOM

PostPosted: Sat Apr 18, 2020 8:20 am    Post subject: Reply with quote

Thanks all.

Iím 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
View user's profile Send private message Visit poster's website
Witty924  



Joined: 05 Nov 2019
Posts: 16
Location: UNITED KINGDOM

PostPosted: Fri Apr 24, 2020 1:00 am    Post subject: Reply with quote

Ok everyone, so itís 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 wonít 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
View user's profile Send private message Visit poster's website
dogleg5  



Joined: 01 Apr 2020
Posts: 29
Location: No longer with us

PostPosted: Fri Apr 24, 2020 1:34 am    Post subject: Reply with quote

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
View user's profile Send private message
!tom  



Joined: 28 Aug 2006
Posts: 1905
Location: Victoria, BC Canada

PostPosted: Fri Apr 24, 2020 3:20 am    Post subject: Reply with quote

Possibly the control pressure is wrong?
_________________
78 924 NA
5-lug
Back to top
View user's profile Send private message Visit poster's website
dogleg5  



Joined: 01 Apr 2020
Posts: 29
Location: No longer with us

PostPosted: Fri Apr 24, 2020 5:36 am    Post subject: Reply with quote

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
View user's profile Send private message
Witty924  



Joined: 05 Nov 2019
Posts: 16
Location: UNITED KINGDOM

PostPosted: Sat Apr 25, 2020 5:07 am    Post subject: Reply with quote

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 letís say and the engine is warm it still needs my intervention in the plate to fire up but once running itís fine and continues.

Itís definitely on the start up that I have the issue. I donít 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. Iím assuming you can hear air going through the main rubber air tube to the manifold unit due to the amount of air itís sucking through, or shouldnít you hear any sound of air at all?

Thanks again
_________________
Witty924 - Porsche 924 2.0l NA 1984
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions All times are GMT + 10 Hours
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group