Low Fuel Pressure Reading/ Hard Start/ Rough Idle - Ford Truck Enthusiasts Forums

Notices

Low Fuel Pressure Reading/ Hard Start/ Rough Idle

Reply

 
 
 
  #1  
Old 12-30-2017, 10:37 PM
hltnmtthw
hltnmtthw is offline
New User
Thread Starter
Join Date: Dec 2017
Posts: 3
hltnmtthw is starting off with a positive reputation.
Low Fuel Pressure Reading/ Hard Start/ Rough Idle

I apologize for the long winded post, I just want to give an accurate dipiction to allow for clarity of the situation.

I acquired a 95 F150 4.9L XL from a lady who kept her husbands truck after he passed. The truck has, "supposedly" been run occasionally over approximately a 10 yr period. I am an amateur mechanic and I'm only doing the work myself because I can't afford to have it looked at, and I also think the experience I'm gaining is invaluable.

I am currently experiencing a lot of difficulty starting the truck (3 - 5 tries), which only works if I finagle the gas pedal. Once it catches it has an extremely rough idle and usually dies once I am able to get out of the truck and walk to the engine bay, which has made it very hard to get any KOER readings (Unless the code reader is attached and running, in which case it runs "well enough"). At one point it ran well enough to drive around my neighborhood a few times, ran like **** and shifted hard into 2nd (no noise, but you could feel it). The codes I got are for an insufficient EVP (replaced the solenoid after the code), 172 Ox lean, and 538 Insufficient Throttle Response (I did mash the petal during testing).

I got a fuel pressure tester today and it only goes up to about 28 PSI (KOEO, KOER).

Pertaining to the fuel system I have replaced the rear fuel pump assembly and tank (Spectra)(midship tank is still original, not functioning), the FPR (GP Sorensen), the fuel filter (twice, now motorcraft), the fuel pump & ECM Relay (Standard).

Ignition Components Replaced - Spark Plugs, Spark Plug Wires, Distributor cap and Rotor (Duralast), ICM (Delphi), Ignition Coil (Arts/Wells)

Emissions - (Vac Reservoir intact), Vac Lines (Silicon, Amazon), EGR (Duralast), EVP (Duralast), EVR (Arts/Wells),PCV Valve (Duralast), O2 Sensor

Intake/Throttle - Air Filters, Map Sensor (Duralast), ACT (Duralast), TPS (Duralast), TBI Gasket, (Cleaned IAC)

Etc. - Coolant Temp. Sensor (Duralast), Battery (Duralast),
 
Reply With Quote
  #2  
Old 12-31-2017, 08:55 AM
timbersteel's Avatar
timbersteel
timbersteel is online now
Postmaster
Join Date: Mar 2005
Location: Mexico, Missouri
Posts: 3,881
timbersteel has a good reputation on FTE.timbersteel has a good reputation on FTE.
The 4.9, 300, needs minimum of 40psi of fuel pressure to run, and that's a maybe. Ideally it needs to be between 45-50 running.

I would start by rechecking the fuel pressure and be sure the gauge isn't screwed up.

Edit: I hope you kept ALL the original Motorcraft parts. I've got new over-the-counter parts that are JUNK. Hell, most of the ignition components I have are 22-25 years old and are better quality than so-called MSD quality components.
​​​​​​
 
Reply With Quote
  #3  
Old 12-31-2017, 09:22 AM
wallen7
wallen7 is offline
Freshman User
Join Date: Nov 2017
Posts: 25
wallen7 is starting off with a positive reputation.
Fuel pressure at the rail needs to be 50 - 60 running and if I remember correctly closer to the 60 mark is normal on the 4.9l, the v8 engines run 40 - 45.
 
Reply With Quote
  #4  
Old 12-31-2017, 09:32 AM
timbersteel's Avatar
timbersteel
timbersteel is online now
Postmaster
Join Date: Mar 2005
Location: Mexico, Missouri
Posts: 3,881
timbersteel has a good reputation on FTE.timbersteel has a good reputation on FTE.
Originally Posted by wallen7 View Post
Fuel pressure at the rail needs to be 50 - 60 running and if I remember correctly closer to the 60 mark is normal on the 4.9l, the v8 engines run 40 - 45.
50-60 would be static reading

Running would be 45-55.

V8 run 30-32 running
40-45 psi static.
 
Reply With Quote
  #5  
Old 12-31-2017, 11:50 AM
hltnmtthw
hltnmtthw is offline
New User
Thread Starter
Join Date: Dec 2017
Posts: 3
hltnmtthw is starting off with a positive reputation.
Timbersteel,

I did that reading last night and I left the gauge attached to check for a slow leak. Will do another test today, the fuel pressure tester is new, but its innova which Im not too fond of. I plan to check and clean the injectors, but I'm thinking that the Fuel Pump I replaced might a possible culprit.

I have dual tanks and initially neither tank would function and when I removed the rear tank it was full of rust, had bad seals and the entire fuel pump assembly was falling apart. I haven't taken off the midship tank yet and I'm wondering if I need both tanks sealed and properly functioning to achieve the desired fuel pressure.

Unfortunately in a bit of a youthful learning curve, I have not kept all the motorcraft parts, and I'm starting to realize that I OTC parts are mostly crap. Although each piece replaced makes the truck seem stronger, it never addressed the core issue, which I now know revolves around the fuel pressure.
 
Reply With Quote
  #6  
Old 12-31-2017, 04:28 PM
hltnmtthw
hltnmtthw is offline
New User
Thread Starter
Join Date: Dec 2017
Posts: 3
hltnmtthw is starting off with a positive reputation.
Small update, pulled the fuel injectors, used the truck battery to apply 12 v. 5 functional w/ good spray pattern, 1 unresponsive.
 
Reply With Quote
  #7  
Old 01-01-2018, 05:33 PM
codejunkie's Avatar
codejunkie
codejunkie is offline
Senior User
Join Date: Jul 2005
Posts: 101
codejunkie is starting off with a positive reputation.
Fuel Pump Rear Tank

When the Machine Shop finished rebuilding my 89 the pump he put in the new (38gal) rear tank was from a Chevy. He handed me both pumps, the Chevy one was significantly heavier and he said it was far superior to the original in-tank F150 pump. I also got matched injectors for the fuel. He did a lot of things that I would not have thought of. This machine shop also builds engines for a place out west that we call the "Salt Flats", and he has a lot of photos on the wall of builds he made for out there.

He was pleased with the fuel system after doing all of his ideas for me. That was a long time ago (not really, but it seems so) and the truck starts like a champ even after being left in the snow for a month this winter. Oh, yes, he also told me to never tap-dance on the foot pedal while starting the engine.

Best of luck with your fuel problem.
 
Reply With Quote
 
 
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
mitchntx
6.0L Power Stroke Diesel
10
01-01-2012 11:48 AM
BieselDiesel
1994.5 - 1997 7.3L Power Stroke Diesel
27
08-07-2011 04:26 PM
BRay09
1987 - 1996 F150 & Larger F-Series Trucks
10
10-28-2010 12:15 PM


Thread Tools
Search this Thread
Quick Reply: Low Fuel Pressure Reading/ Hard Start/ Rough Idle


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.