Need confirmed spec for fuel pressure -SOLVED ! !! ! ! ('95 4.0 ohv)

[EB4X]

Hey gang,
My Chilton manual states engine running should be: 35-45 PSI ...online search is all over the map...
For those who own a FORD SHOP MANUAL could you see what it states for my '95 4.0 ohv ? ....is Chilton correct? ....want to make sure, Chilton's have been off on some things...
I'm getting 29 -30 psi during "running test" ---Symptoms are light hesitation/ surging accelerating from 20 mph to 40 mph range.... occasional dying at stops. No more CIL's ...replaced a few parts which made vehicle's overall running condition better --- IAC /EGR valve / fuel regulator - filter / Cam sensor-sychronizer -- had code come up for that.
Thanks.
EDIT / SOLVED! : >> So being the Explorer isn't my daily / on budget / and frustrated with time spent testing / ruling out this...that / parts thrown at it etc.. it was put on the back burner again.... UNTIL I found this site doing more research...and WELLA ! ...it WAS the cause of my last gremlin I couldn't figure out ( P.S. Wasn't getting any more CODES !) ...and that gremlin was hesitation and surging when accelerating in the 20 - 40 mph (2nd to 3rd gear) range --most noticeably and frequently....not happening cruising down the freeway at steady speed.
The problem: Bad or subpar o2 sensor (bank 2 upstream in this case) ...and THIS WAS NOT TRIGGERING A CODE / CIL NADA NOTHING ZILCH ON MY OBD1 !!!!
I have this site / article to thank for figuring this one out (did have bad cam synch / code which combined gave me hideous surging):
SITE: Will an O2 Sensor Cause Surging?

Particular paragraph from that article:
"“Normally, your computer will throw a check-engine light and an O2 sensor failure code when the sensor gets bad enough to surge. But this isn't always the case; sometimes, the O2 sensor can trick the computer into thinking that everything's fine. One quick way to diagnose O2 sensor surge is to unplug the O2 sensor's wiring harness. When you do that, the computer will default to a standby program called "open-loop mode," where it completely ignores O2 sensor input and uses its best guess from other sensors. You can expect a check-engine light and a loss of power, but the primary thing you're looking for here is a reduction or elimination of surging. If it goes away when you unplug the O2 sensor, then odds are good that you've found your problem.”
DID I MENTION I'M NOW ECSTATIC AND DON'T HATE MY EXPLORER ANY MORE ??!

 

[C420sailor]

Returnless is 65+/-8psi. Yours isn’t returnless though, so ignore any search results up in that range. Wish I could help more but I only have a 2000 manual.

 

[poker4me007]

Here's a video I made of mine a year ago 97 4.0 ohv., mine runs about 29psi also.
My Haynes manual says 30 to 45psi, vacuum detached 40 to 50psi
Start at the 5min. mark.

 

[EB4X]

mine runs about 29psi also.
My Haynes manual says 30 to 45psi, vacuum detached 40 to 50psi

So mines fine then... going by my Chilton with 35 being lowest acceptable and getting 29/30 I figured I'd solved the last gremlin... sub par fuel pump operation.... now I'm stumped.... no codes.... vacuum test came out negative...........

 

[CDW6212R]

The 30psi level when running is at the bottom level of what is okay, 32psi I'd call better. What do you show with it running without the FPR vacuum line connected? That I recall being a bit above 35psi, maybe 37psi or so for my older Fords.

You might also run a second test to compare test gauges, they can vary some.

 

[EB4X]

What do you show with it running without the FPR vacuum line connected? That I recall being a bit above 35psi, maybe 37psi or so for my older Fords.

That one I got 39 .... even though I had installed a new regulator recently went ahead with that test... got 38 with engine off test on 4th key turn

 

[CDW6212R]

That will be fine for any throttle settings but off the gas completely. I had one car that I ended up with injector issues(old gas), and I first thought it might be the fuel pump. The pressure was right at 30-31psi the two times I checked it. But the miss I had got worse fast, and checking codes pointed to three or four cylinders. So I did the injectors and it was fine then. So the low 30's should be enough I think.

How old are the plugs, and wires? If old enough, it wouldn't be bad to do those soon.

 

[EB4X]

The plugs and wires are newer ...only have maybe 2K use on them. I'm leaning away from ignition / spark being there's no missing/sputtering/jerking involved, just a smooth surge scenario of accelerating and then slightly dropping and then continuing acceleration (surging)...almost like a trans slipping but not. If I'm heavy on the gas from a stop instead of light-foot acceleration, it accelerates perfect... no hesitation/surge.
I also performed a TPS test that appeared to eliminate that as a possibility - all three voltage applications checked out and manually turning throttle body hooked up to voltmeter illustrated normal behavior.
Take tylenol and coffee before reading following--I didn't want to muddy the waters with too much info before/ and assumed some was no longer relevant but here goes: One OTHER symptom is that after first minute of warming up in morning there is a slight surging / pulsating idle ---putting in gear / load stops that --and it will not do that the rest of the day (now that engine's warmed up) The weird thing there is I just replaced the EGR thinking that was my issue on both symptoms based on a random 411 code popping up - and ruling out IAC issues (being it's new AC Delco unit / with new gasket) and it appeared to fix both issues at first -idle did not pulsate / it didn't surge at first - ran great for about 10 minutes but then slight surge reappeared --so just a fluke, but that 411 code went away. BUT THEN with my new EGR I got on two occasions (only two....not coming back on CIL) code 332 (same as obd2 code PO401) "Exhaust EGR Flow Insufficient"-- this only came up after installing NEW EGR.... but has not returned....so chance my new EGR was sticking ...(?) ....
I'm wondering if my old OBD1 system isn't picking things up right away and now based on 332 code and for a mere $10 pop in a new DPFE sensor based on this:

Code P0401-Exhaust EGR Flow Insufficient

www.samarins.com

The weird thing (of a few) is that the surging is HALF as bad as it was before, especially noticeable after the EGR replacement--and as mentioned on strong acceleration; getting on freeway etc it does NOT surge at all anymore. And it doesn't die occasionally from a "quick acceleration" from a stop like it was semi routinely. So all I can extrapolate is that it had compound factors/issues and I've resolved most of them.
I'll update if CIL comes back on and results for when I pop in new DPFE .

 

[CDW6212R]

That sounds reasonable, that it may be a couple of things. I would include thinking a replaced part may also be a new or duplicate issue, like an IAC that is not perfect. It's been ages since people posted big troubles with an IAC, but new ones have turned out to be bad or similar to an old one. So maybe swapping a certain old part back in may narrow down some symptoms.

A miss code pointing at a cylinder can be a clue to a bad plug, but not having that, other items are more likely. I'd drive it hard, and check under the hood often, checking connectors and wires regularly. I had a bad miss about two weeks ago, and under the hood I pressed the coil pack connectors in, and made it smooth out. I couldn't tell that anything was disturbed, but it is a worry now about wiring connections for my 98 truck. You want to make it do something that you can track down. Watching closely for it is key, you keep doing that and I bet you find something soon.

 

[410Fortune]

36-42 psi is spec for the 91-97 trucks
30 psi is a little low.... might start chugging and missing with only 30 psi at the rail

 

[EB4X]

36-42 psi is spec for the 91-97 trucks
30 psi is a little low.... might start chugging and missing with only 30 psi at the rail

Thanks 410!

 

[EB4X]

Here's a guy with same symptoms in a tundra (I know...that's like a curse word...wont happen again) where it ended up being the fuel pump:

Surging during light to moderate acceleration

Today my truck really started surging at light to moderate throttle. Truck has 227,000 miles on it. It has been "serviced" at the local Toyota dealer...

www.tundras.com

DPFE replacement on it's way....if that doesn't resolve it looks like fuel pump replacement...and yes, I'm safely cutting access panel with nibbler...no comments allowed on that.

 

[CDW6212R]

Here's a guy with same symptoms in a tundra (I know...that's like a curse word...wont happen again) where it ended up being the fuel pump:

Surging during light to moderate acceleration

Today my truck really started surging at light to moderate throttle. Truck has 227,000 miles on it. It has been "serviced" at the local Toyota dealer...

www.tundras.com

DPFE replacement on it's way....if that doesn't resolve it looks like fuel pump replacement...and yes, I'm safely cutting access panel with nibbler...no comments allowed on that.

That's too slow, just use a sawzall and make a deep vertical cut.

 

[EB4X]

That's too slow, just use a sawzall and make a deep vertical cut.

True... although limited a sawzall can create some 'small' sparks...
END RESULT TO COME:
Being quality name brand pumps are made overseas now and my Ranger had connector issues a year after installing pump I'm all in on this idea. Plus to keep costs down I'm going with just the pump itself....so if down the road the float arm starts misbehaving it wont be a nightmare job.
I know not all agree.

 

[CDW6212R]

I was kidding of course, I knew the tank is right below the floor there.

I think you will need to open it up more to uncover the whole assembly. It has to come almost straight up for a bit.

 

[EB4X]

That's just a pic I got from some guy with a 96 that did it.... "to come" .... yeah seeing how / where everything sits I'll make my square go back another inch but not so much in the front as his.

 

[CDW6212R]

The couple of pictures I've seen before opened it up along the vertical surface a bit. I hadn't considered it myself, or I would first see how the assembly comes out to know what space is needed above it.

 

[poker4me007]

DPFE replacement on it's way....if that doesn't resolve it looks like fuel pump replacement...and yes, I'm safely cutting access panel with nibbler...no comments allowed on that.

Let us know when you fix the problem, and what it was.

 

[410Fortune]

one of my favorite modifications to my BII = fuel tank access door.
Before that I dropped the tank like 6 times
In 88 the BII had two pumps, one boost pump in the tank and high pressure pump on the frame. That system was problematic! the boost pump failed at least 3 times...........Over the years I went from 2.9L to 4.0 to now 5.0 and the fuel system/pump has changed more times then that. I now run a single Walbro pump in the tank with a *******ized 89 BII sending unit.........really handy to just remove the cargo mat, 4 sheet metal screws, pry up on the silicon and BAM I am at the fuel tank. If my pump goes out on the trail, its a 20 minute fix, not a off road tow home

I would still only install a Bosch, Carter or Walbro pump I have had too many cheap pumps fail on me and my customers over the years to install anything else. (nothing sucks worse then being stranded because a new fuel pump FAILED!)

SCREW YOU Airtex wells, brute power, spectra premium, and all the other cheapo parts store brands we pay a premium for!!!! Not worth the box they come in! I mean seriously the failure rate on these cheap pumps is STUNNING. When you work on enough rigs for enough cheap skates you will learn, its just not worth saving a few bucks...get the good stuff. /Rant

 

[CDW6212R]

Ditto, in the best conditions you can R&R a fuel pump in a couple of hours. But most times it's much longer because the fuel line fittings don't want to let go, or the mounting bolts(captured nuts) want to strip etc.

I'm on the fence about an access hole, because the pump shouldn't need work very often. Yet they do, so I'm also considering a pair of pumps for my blown project truck. With two identical pumps side by side if they will fit okay, one can run continuously, while the other is a WOT boosting pump. With relays they can be switched at any time, so a failure would not leave you stranded. But that is more complicated for sure, thus no OEM would ever do that.