Go Back   Ford Truck Enthusiasts Forums > Performance, Engines & Troubleshooting > Ford V6 > 3.8 & 4.2L V6
Sign in using an external account
Register Forgot Password?


Lowish Fuel Pressure

Reply
 
 
 
 
LinkBack Thread Tools Search this Thread
  #1  
Old 03-17-2015, 04:03 PM
Enterprise Blue Enterprise Blue is offline
New User
 
Join Date: Jul 2012
Posts: 6
Enterprise Blue is starting off with a positive reputation.
Lowish Fuel Pressure

Hi all. I have a 2002 4.2 with 158,000 miles. It has a engine stalling (throttle has no effect, although it will idle roughly) for short periods of time symptom, regardless of load with a random frequency (once a trip to the coast or twice between stop lights, no way to predict). I've done some stuff and many tests but always twisting my evaluations is that my fuel pump pressure tests seem borderline.

I believe my specification is 28-50 psi, I get 28 at idle and a surge just above 30 when accelerating (hand working the throttle in the garage). I get 40 when I pull the vacuum line off the fuel pressure regulator (should be 40-50). I get a steady decrease in pressure as I pump the regulator vacuum up with a hand pump. I get a proportional increase in pressure when I pinch the fuel return line. Five minutes after I've shut down the engine my pressure, oddly, climbs from 28 to as high as 34 psi. One other thing I noticed, although my Haynes manual says nothing about it, is I get just 10 psi when I turn the ignition on (but it starts easily).

My question is about this particular test, not the entire problem . . . that would be a longer discussion. Should I eliminate considering the fuel supply issues since the test is within specifications? Or should I address fuel pump/regulator issues since it is borderline?

I wasn't getting any codes for most of the time period I've had this drive-ability issue but lately, maybe because I spend so much time idling doing tests and scans, I'm either generating or getting a preliminary result P1131 and or P1151, which may be related, along with so many things, to low fuel pressure.

Thanks for any insight you may have to offer.

Last edited by Enterprise Blue; 03-17-2015 at 04:06 PM. Reason: spelling
Reply With Quote
  #2  
Old 03-21-2015, 08:24 PM
Enterprise Blue Enterprise Blue is offline
New User
 
Join Date: Jul 2012
Posts: 6
Enterprise Blue is starting off with a positive reputation.
Well, giving up waiting for a response. In my document searches I found 20 psi as a minimum which triggered a trouble code on another 2002 Ford which does have a fuel pressure monitor (mine doesn't). Making many assumptions I'm thinking 28 psi, even though the minimum, is not too much to overcome with fuel trim and all.

When my engine stalls the MAF values go very low (cfm). I did one test drive with the MAF sensor disconnected and had no stalling. Since I've no related codes and the low value snaps in and snaps back to normal I'll investigate the wiring before I buy a sensor. Tested it previously but since it is intermittent I suppose I need to probe and wiggle or something.

Not thinking fuel system any more though.
Reply With Quote
Old 03-21-2015, 08:24 PM
 
 
 
Reply


Similar Threads
Thread Thread Starter Forum Replies Last Post
Starts once then won't restart unless WOT Cptn Rich 1987 - 1996 F150 & Larger F-Series Trucks 7 12-23-2014 01:34 AM
Help to confirm my bad fuel pump diagnosis chrisjb Super Duty & Heavy Duty 2 03-22-2014 07:06 PM
P0171 and P0174 + fuel pressure JR_F350 1987 - 1996 F150 & Larger F-Series Trucks 10 07-14-2012 07:07 PM
1992 F150 5.8 - miss under load when warmed up benwantland 1987 - 1996 F150 & Larger F-Series Trucks 2 11-05-2009 06:07 AM
hard-starting, rough idle, stalling eyancey Ford Inline Six, 200, 250, 4.9L / 300 23 09-17-2009 07:43 PM


Go Back   Ford Truck Enthusiasts Forums > Performance, Engines & Troubleshooting > Ford V6 > 3.8 & 4.2L V6

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump


Participate In The Forums

Create new posts and participate in discussions. It's free!

Sign Up »


All times are GMT -5. The time now is 08:10 AM.


Powered by vBulletin® Version 3.8.7 AC1
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Advertising - Terms of Use - Privacy Statement - Terms of Service - Jobs
This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford® is a registered trademark of the Ford Motor Company.

vbulletin Admin Backup