Fuel Rail Pressure Sensor Vacuum Issue - Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum
Ford Focus Forum
HomeContact UsAbout UsGalleryDiscussion ForumsMarketplace


Go Back   Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum > Ford Focus Tech Discussions > General Technical Chat

General Technical Chat This section is for technical discussions relating to general maintenance, electrical issues, engine trouble, and recalls.

Search This Forum | Image Search | Advanced Search    
FocusFest FocusFanatics Merchandise

Reply




 
LinkBack Thread Tools Display Modes
Old 07-12-2015, 10:26 AM   #1
Focus Rookie
 
Join Date: Jul 2015
Fan#: 252201
Location: Basehor, KS
What I Drive: 2000 BLack Focus, ZETEC

Posts: 2
Points 8, Level 1
Points: 8, Level: 1 Points: 8, Level: 1 Points: 8, Level: 1
Level Up 15% Completed
Level up: 15% Level up: 15% Level up: 15%
Forum Activity 1%
Activity: 1% Activity: 1% Activity: 1%
FF Reputation: 1 Bamafan02 Good Standing Member
Buy-Sell-Trade Rating: (0)
Fuel Rail Pressure Sensor Vacuum Issue

I have a 2000 Focus, ZTEC engine that is having rough idle issues. After a month or so, I have nailed down the issue to the small vacuum line that runs from the intake manifold to the fuel rail pressure sensor. I removed the hose from the back of the intake, placed a plug on the nipple (intake manifold). Car runs great at all times, idle and when in gear. If I put the hose back on, it will idle okay, but when placed in reverse or any gear, barely runs (idles terribly, and will stall).

I removed the sensor and hose, could not find any obvious issues with the sensor or hose, replaced and have the same rough idle - put plug back on for now.

I replaced the two PCV hoses already months ago.

Any ideas - bad fuel pressure sensor possibly?

Any and all help is greatly appreciated.


Bamafan02 is offline  
    Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 07-12-2015, 03:28 PM   #2
Focus Fanatic
 
Join Date: Mar 2012
Fan#: 96610
Location: Fort Worth, TX
What I Drive: 00 wagon, 02 sedan both zetec atx

Posts: 8,237
Points 4,837, Level 44
Points: 4,837, Level: 44 Points: 4,837, Level: 44 Points: 4,837, Level: 44
Level Up 44% Completed
Level up: 44% Level up: 44% Level up: 44%
Forum Activity 89%
Activity: 89% Activity: 89% Activity: 89%
FF Reputation: 48 amc49 Great Standing Member
Buy-Sell-Trade Rating: (0)
You should be getting fuel out of the hose if a vacuum leak is there. That means sensor is bad, it has blown the diaphragm in it. You can vacuum test for it with a hand vacuum pump.
__________________
Originally Posted by amc49
I wouldn't hesitate to tear down the absolute latest in automotive technology to immediately understand half of it instantly and the other half in less than a half hour. ..LOL, that's me all right!
amc49 is online now  
    Reply With Quote Quick reply to this message
Old 07-12-2015, 05:39 PM   #3
Focus Rookie
 
Join Date: Jul 2015
Fan#: 252201
Location: Basehor, KS
What I Drive: 2000 BLack Focus, ZETEC

Posts: 2
Points 8, Level 1
Points: 8, Level: 1 Points: 8, Level: 1 Points: 8, Level: 1
Level Up 15% Completed
Level up: 15% Level up: 15% Level up: 15%
Forum Activity 1%
Activity: 1% Activity: 1% Activity: 1%
FF Reputation: 1 Bamafan02 Good Standing Member
Buy-Sell-Trade Rating: (0)
Thanks for the information - Ill test it and purchase a new one if needed!
Bamafan02 is offline  
    Reply With Quote Quick reply to this message
Old 07-12-2015, 06:02 PM   #4
Focus Fanatic
 
Marde's Avatar
 
Join Date: Jun 2013
Fan#: 115991
Location: Mesa, AZ
What I Drive: 2004 ZTW PZEV 2.3 ATX

Posts: 2,571
Points 4,224, Level 41
Points: 4,224, Level: 41 Points: 4,224, Level: 41 Points: 4,224, Level: 41
Level Up 37% Completed
Level up: 37% Level up: 37% Level up: 37%
Forum Activity 15%
Activity: 15% Activity: 15% Activity: 15%
FF Reputation: 31 Marde Great Standing Member
Buy-Sell-Trade Rating: (0)
Quote:
Originally Posted by Bamafan02 View Post
...If I put the hose back on, it will idle okay, but when placed in reverse or any gear, barely runs (idles terribly, and will stall)....
That is strange. Also, never seen someone do that + those results are very interesting.

With engine on, let's pretend your FRPS is telling the PCM pressure is 50psi; but when you disconnect that vac hose, the FRPS will tell the PCM that pressure is 40psi. You are now essentially "lying" to the PCM. The PCM does not know you disconnected the vac hose and it will not set a DTC (least not until you reach a low pressure threshold). I did some FRPS and manual fuel pressure test gauge tests last year which taught me enuf to comment about the 10psi difference I just described.

So, with the vac hose disconnected, the PCM, all engine sensors, just happens to run better by Luck... and is doing so with skewed air/fuel ratios at a minimum.

My guess is NO problem with your FRPS and problems lie elsewhere... but at the same time, the FRPS could be "slightly out of wack", just not bad enough yet to set a code.

My knee jerk reaction is to; replace fuel filter; run a bottle of some fuel injector/fuel system cleaner; have car scanned + test FRPS values to see what pressures it is reporting with and without the vac hose connected.

The FRPS is $100 or more. I would not replace it without some testing done first.


Quote:
Originally Posted by amc49 View Post
You should be getting fuel out of the hose if a vacuum leak is there. That means sensor is bad, it has blown the diaphragm in it...
Huh? OP never said he had fuel inside the vac hose; nor does a vac leak cause fuel to enter the vac hose. But yes, if fuel is inside there, the FRPS "diaphragm" or whatever is shot.
__________________
You've got to ask yourself one question: Do you feel lucky? -and could you really drive a Focus ATX Wagon?
Marde is online now  
    Reply With Quote Quick reply to this message
Old 07-13-2015, 09:07 PM   #5
Focus Fanatic
 
Join Date: Mar 2012
Fan#: 96610
Location: Fort Worth, TX
What I Drive: 00 wagon, 02 sedan both zetec atx

Posts: 8,237
Points 4,837, Level 44
Points: 4,837, Level: 44 Points: 4,837, Level: 44 Points: 4,837, Level: 44
Level Up 44% Completed
Level up: 44% Level up: 44% Level up: 44%
Forum Activity 89%
Activity: 89% Activity: 89% Activity: 89%
FF Reputation: 48 amc49 Great Standing Member
Buy-Sell-Trade Rating: (0)
There HAS to be a diaphragm in there for the vacuum hose to do anything. The diaphragm is opposite the pressure action of the sensor to detract or parallel to to add more and how it modifies it for load.
__________________
Originally Posted by amc49
I wouldn't hesitate to tear down the absolute latest in automotive technology to immediately understand half of it instantly and the other half in less than a half hour. ..LOL, that's me all right!
amc49 is online now  
    Reply With Quote Quick reply to this message
Old 07-13-2015, 11:10 PM   #6
Focus Fanatic
 
Marde's Avatar
 
Join Date: Jun 2013
Fan#: 115991
Location: Mesa, AZ
What I Drive: 2004 ZTW PZEV 2.3 ATX

Posts: 2,571
Points 4,224, Level 41
Points: 4,224, Level: 41 Points: 4,224, Level: 41 Points: 4,224, Level: 41
Level Up 37% Completed
Level up: 37% Level up: 37% Level up: 37%
Forum Activity 15%
Activity: 15% Activity: 15% Activity: 15%
FF Reputation: 31 Marde Great Standing Member
Buy-Sell-Trade Rating: (0)
Quote:
Originally Posted by Marde View Post
Huh? (@amc) OP never said he had fuel inside the vac hose; nor does a vac leak cause fuel to enter the vac hose. But yes, if fuel is inside there, the FRPS "diaphragm" or whatever is shot.
Quote:
Originally Posted by amc49 View Post
There HAS to be a diaphragm in there for the vacuum hose to do anything. The diaphragm is opposite the pressure action of the sensor to detract or parallel to to add more and how it modifies it for load.
amc give it a break man. I did not say, or mean to suggest that it did not have a diaphragm inside it because I used quotation marks. Yes, it does have a diaphragm or a diaphragm-like component inside it. Adding a description of how it works too...!?.. uhg.

If fuel in vac hose = FRPS is shot, broken, fried, done, kaput, in-op, defective, busted or... "whatever" is what I said; lightly suggesting it or the failure could be called anything and ID'ing the exact internal item that failed is optional.

__________________
You've got to ask yourself one question: Do you feel lucky? -and could you really drive a Focus ATX Wagon?
Marde is online now  
    Reply With Quote Quick reply to this message
Old 07-14-2015, 02:14 PM   #7
Focus Fanatic
 
Join Date: Mar 2012
Fan#: 96610
Location: Fort Worth, TX
What I Drive: 00 wagon, 02 sedan both zetec atx

Posts: 8,237
Points 4,837, Level 44
Points: 4,837, Level: 44 Points: 4,837, Level: 44 Points: 4,837, Level: 44
Level Up 44% Completed
Level up: 44% Level up: 44% Level up: 44%
Forum Activity 89%
Activity: 89% Activity: 89% Activity: 89%
FF Reputation: 48 amc49 Great Standing Member
Buy-Sell-Trade Rating: (0)
I'm not the one freaking out there.

Your response..............

'Huh? OP never said...'
'...nor does a vac leak cause fuel to enter...'

Uh, no............but technically not a vacuum leak, rather a fuel leak into vacuum. My bad there. I headed the OP off with the leaked fuel thing as proof it was OK.

Yet it seemed to draw you out...........as it has before.

I have NOT appointed myself as your or anybody else's personal tormentor. But I ask you to forgive me anyway.

We're all friends here, at least on my end. Love you dude, I always enjoy reading your posts.
__________________
Originally Posted by amc49
I wouldn't hesitate to tear down the absolute latest in automotive technology to immediately understand half of it instantly and the other half in less than a half hour. ..LOL, that's me all right!
amc49 is online now  
    Reply With Quote Quick reply to this message
Old 07-16-2015, 05:39 PM   #8
Focus Fanatic
 
Marde's Avatar
 
Join Date: Jun 2013
Fan#: 115991
Location: Mesa, AZ
What I Drive: 2004 ZTW PZEV 2.3 ATX

Posts: 2,571
Points 4,224, Level 41
Points: 4,224, Level: 41 Points: 4,224, Level: 41 Points: 4,224, Level: 41
Level Up 37% Completed
Level up: 37% Level up: 37% Level up: 37%
Forum Activity 15%
Activity: 15% Activity: 15% Activity: 15%
FF Reputation: 31 Marde Great Standing Member
Buy-Sell-Trade Rating: (0)
I did not freak out at all. You were wanting to argue or push that it HAS a diaphragm, and no-one said otherwise. I was just saying,... please stop directing that crap at me.

Yes, you and I are totally cool. You provide great help and should be praised for what you do... despite your spells of argumentative grumpiness-> which is sometimes very helpful and effective with some people. It is also kinda funny.

Peace.
__________________
You've got to ask yourself one question: Do you feel lucky? -and could you really drive a Focus ATX Wagon?
Marde is online now  
    Reply With Quote Quick reply to this message
Old 07-16-2015, 07:41 PM   #9
Focus Fanatic
 
Join Date: Mar 2012
Fan#: 96610
Location: Fort Worth, TX
What I Drive: 00 wagon, 02 sedan both zetec atx

Posts: 8,237
Points 4,837, Level 44
Points: 4,837, Level: 44 Points: 4,837, Level: 44 Points: 4,837, Level: 44
Level Up 44% Completed
Level up: 44% Level up: 44% Level up: 44%
Forum Activity 89%
Activity: 89% Activity: 89% Activity: 89%
FF Reputation: 48 amc49 Great Standing Member
Buy-Sell-Trade Rating: (0)
I can indeed be an ass at times I'll give you that. My personal problem among many others.
amc49 is online now  
    Reply With Quote Quick reply to this message
Old 07-17-2015, 12:38 AM   #10
C2H5OH
 
iminhell's Avatar
 
Join Date: Jun 2006
Fan#: 36222
Location: Darwin, MN
What I Drive: 2000 ZX3 & 2010 BMW 135i

Posts: 11,513
Points 21,317, Level 91
Points: 21,317, Level: 91 Points: 21,317, Level: 91 Points: 21,317, Level: 91
Level Up 94% Completed
Level up: 94% Level up: 94% Level up: 94%
Forum Activity 26%
Activity: 26% Activity: 26% Activity: 26%
FF Reputation: 53 iminhell Excellent Standing Member
Buy-Sell-Trade Rating: (4)
I'm just glad I shouldn't get anyone preggers here ...



The Fuel Rail Pressure Sensor is of the Delta variation. That is to say,
Fuel Rail Pressure = Manifold Pressure + Base Fuel Pressure

Vacuum in this case is considered Negative Pressure. Roughly speaking 20 inches of vacuum at idle would take a base pressure of 40 to about 39psi. Or if you run the car W/O the vacuum reference it would be at 40psi all the time (vs only at WOT).

Now typically 1 psi of fuel pressure is negligible and you'll never see a difference. But in this case it seems that the pressure is borderline to begin with and the loss of just a pound is making a noticeable difference. This to me points to a weak fuel pump or some other restriction in the fuel system.
I am not saying the pump is bad.
I am simply saying that the fuel system should be investigated further. Simple things first. And don't use any pour in cleaners, they simply don't work.


It's not uncommon for the tips of injectors to become gunked up from oil vapors from the PCV/EGR. It's quite simple to remove the rail/injectors and check. And if you're careful and clean you shouldn't need to replace anything.
Replacing the fuel filter is simple enough.
Etc.



Or it might just be that the vacuum line leaks. That would be the simplest answer/fix. And if that's the case you can use any vacuum line that fits (3/16" IIRC). And I'll also mention that the internal size of the line can have some effect on how responsive the engine is. A smaller diameter line will react faster than a larger. I only mention that because I've seen people use large line and reduce it then complain nothing was fixed.
__________________
13 years, 124,000 members and still no sponsored racing.
*your ad here*
*and here*......................................................................................................... *there's a wide open area here too*
*still space available*
iminhell is offline  
    Reply With Quote Quick reply to this message
Reply
Gear in this thread - Powered by O'Reilly Auto Parts

Bookmarks & Social Networks

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
What I Drive
Year, color, and model of your car. Example: 2003 Pitch Black ZX3
Name
Your real name.
City
State
Country
Insurance
Please select your insurance company (Optional)

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 08:25 PM.


Copyright 2002-2015 FocusFanatics.com. All Rights Reserved : Privacy Policy : Advertise Information

Focus Fanatics Ford Focus Forum offers many fun ways for you to engage with other Ford Focus Owners from across the world. Whether it be about the aftermarket performance modifications, technical how-to's, European tuned suspension or awesome fuel economy similar to the Mazda CX-3, Audi S3, Mazda MX-5 Miata and Acura TLX. You can find all Ford Focus, Focus ST and Focus RS related information here. Join our Ford Focus discussion forums and chat with local Focus enthusiasts in your area. If you own other makes have a look at Challenger Hellcat Forum, Charger Hellcat Forum, Cadillac ATS-V Forum, Cadillac ATS Forum, Cadillac CTS-V Forum, Lexus RC-F Forum, Lexus GS-F Forum, Mercedes GLA Forum, Mercedes GLE Forum, Civic Type-R Forum and Volvo XC90 Forum.




 

Search Engine Optimization by vBSEO 3.6.1