Hey Happy New Year from Mississippi!
Hey I've looked thru all the posts about fuel pressure but still have a question. I buttoned up the '96 of my son n law's truck from the Great Broken Glow Plug Fiasco job & when I went to start it I had my fuel pressure gauge hose screwed into the FPR schrader valve port so I could see it. I spun the engine over 3 or 4 times by the starter relay until I saw my gauge move & then went to start it with the key. Fired right up & stumbled a time or two then leveled out. Guage reading was a little over 50 @ idle. cool. Later it dropped to below 40 & yet later below 10. Truck runs great & starts ever time. I re-did the fuel bowl & installed a Dorman fuel pump. Mostly because of the warranty. I was stopping the multitude of leaks that have been there for years. Anyway my Handy Genuine Ford Powerstroke Service manual calls for 3-10 PSI low side & 40 on the high side. Are these readings sposed to be taken @ Idle or with the engine reved some? My wife says gauge will rise - once almost to 50- If I rev it up. I know the Duck Feet need attention because the truck will run outta fuel @ 1/4 tank. It MIGHT be sucking some air!
Thanks!
Andy

 

At the schrader valve, at idle, it should be 40 or better. If it is dropping down to 10 something is suspect. How long did you let it idle? Did it go back up?

 

Oh I've let it idle a good bit, drove it twice. It's sposed to be below freezing tonight so I just moved it into the shop for the night. No anti freeze yet. Stll less than 10 PSI on the gauge. Gonne try a new gauge tomorrow.
This truck has NEVER had no care. Son n law said as a kid he remembers his dad puting a Drop Light under the hood at night so it would start the next morning! No evidence of fuel in the lube oil as of yet so I don't think a blown o-ring is the cause. Like I said truck runs great & has decent power. Nothing like my Duramax but runs good. I may be sucking air or have a Duckfoot piece clogging a line. The truck has a Laundry list of things it needed. Repaired the A/C 1st, then changed the water pump & started on glow plugs. Three disassembled themselves stuck in the head. That was an adveneture! Then repair all the fuel leaks. New pump, re-seal the filter housing. Stripped the heater, WIF, Vacuum sender outta it. The WTS light in the dash has stopped working now but glow plug relay is still working. Man them glow plugs stay energized WAY too long to suit me!
Thaks!
Andy

 

OK today I got to see about it a little more. I bottle fed the fuel pump right outta the jug into the pump, no change. I looked at the regulator spring & plunger but looks normal. Am I missing something here? The bowl vent vents to the return line AFTER the regulator plunger & spring assy right? I can't see where I could loose any pressure at besides catstrophic O-Rring failure around an injector but I don't think that's an issue.

 

I went through something similar on my wife’s 2wd, ended up being fuel pressure regulator on the bowl, they clog and don’t maintain pressure. Had a bunch of junk in the bowl as well, got that sorted and found out the 2nd stage in the mechanical pump had failed.

got frustrated with it after trying to clean everything up, then finding out the new pump I had put on 6 months before had shot craps. put efuel on it. No more problems. 65-66 psi no matter what with efuel.

 

Thanks! yeah this truck aint never had no care. I pulled the whole fuel system because of leaks, changed fuel pump, gutted furl filter, re-sealed everthing with kits from Diesel O-Rings. What bugs me is when I started it I had 52 psi & just watched it fall & fall. Oh Well at least the pump I bought has a Lifetime Warranty, it's gonna get used!
OK I'm gonna research E-Fuel!

 

yea that’s about the same thing that happened to me, thought I had it for a second and then it dropped like a rock.

the efuel that’s on my wife’s truck now I built myself years ago for my 4wd, since it’s down for engine rebuild I robbed it off my chassis and put on hers. I’m just gonna get a Marty’s kit for mine when I get the engine back together.

 

https://www.ford-trucks.com/forums/1...-to-clean.html

If they are not clean, pump overheats and dies

 

Yeah I've had that all apart & cleaned- Gonna go pull it off again just for %%$##@ just got offa phone with parts house - Closest new pump in California take a week to get here- and they On Fire! Just my luck...

 

that’s exactly what happened to mine, fuel pump started to weep, changed it out with new mechanical pump, lasted a few 100 miles and lost fuel pressure.

 

OK another question- The fuel line that comes from the bottom of the fuel bowl- I think this line runs the Vaccum Switch- Am I correct? Since the FPR is under positive pressure this line must be isolated from the rest of the FPR. Since I have a week of downtime I'm fixin to disassemble the FPR & get the bed ready to remove.
Thanks

 

Bottom of bowl feeds the high pressure inlet side of the pump on bottom

vac switch is in high side since the injectors can suck the fuel out of the bowl

 

No not the line on the bottom that goes to the high side of the pump, this line comes out from bottom of filter can on left side & pokes up into bottom of FPR assy.

 

OK I found a color flow diagram of the fuel system, which of course the site won't let me post here- It appears the fuel line that pokes into the bottom of the regulator re-circulates fuel BACK into the filter thru a wire mesh filter inside the regulator. This area had the vacuum switch in it. The diagram calls this the Fuel Strainer & is down stream from the FPR & is low pressure. There are two orifices, one .035" where the screen assy is where the filter puges air from the housing & a .020" orifice, both connected to the return circuit, down stream from the check ball. It would appear that the filter housing constantly purges fuel / air into the return circuit thru the .035" orifice & the FPR re-circulates fuel to the filter assy thru the Fuel Strainer & only time FPR returns fuel into the fuel return circuit is when psi there overcomes the psi from the filter .035" orifice & disloges the check ball & retruns thru the .020" orifice. Even if there was no regulator the fuel flow would have to back up against the .020' orifice & make SOME pressure. Oh yeah let me say that while I was bottle feeding the pump from a FULL 5 gal can it ran for less that 5 min or so & there is only a couple gallons of fuel left in the can. Thats a LOT of fuel being returned! It did not go into the crankcase area by looking at the dipstick. I see no other option but to conclude that the HP section of the new pump has failed. Now, the local IH dealer has an OEM one for ONLY $280 + Tax...I found an OEM one on Ebay up in Nashville for $165 2 yr warranty...I have also partialy dislodged the screen on the orifice assy & have to repair / replace that, after having removed / installed the FPR 20 times...I think I'm gonna go OEM & start over before I start hot rodding & spending a gazzillion $$$ on this truck that won't see 1000 miles a year use.
Thanks

 

I would add that ALL the fuel that returns to the tank does so thru them two Itty Bitty Orifices...
Oh yeah I called my handy Navistar Dealer- where I worked for a Looong time- and inquired as to the price of the screen assy & nice kid said "Owww, they proud that little puppy"...I asked how proud & he said "$278.33 + tax." ...For a $25 internet part...I said "You Ever Heard The Term "Pricing Yourself Outta Business?"