no pressure (more gremlins)

2000 sport, 4.0, 4wd, greyish silver in color..

so last week i changed my oil.. (fram ph16, shell 15-30 oil, just as i always have) then this last friday on my way to work, i pulled off the highway and stopped for cigarettes..
i was cruising for about 18 miles with the cruise set to 65, so the trip only takes around ten minutes and its fully warmed up..
as i idled for a sec outside the store, my check guages light came on and i had no oil pressure.. hmm, damn gremlins again.
so i tap the gas pedal a sec and the pressure goes back up to 20, then dips to ten, holds for a sec and then drops to nothing, light comes on.. so i tap the gas again to make sure theres some oil on the valve train and shut it off.. pop the hood, check the oil, all ok.. no burning smell, no leaks, filters tight, pan drain plug is in place..

ive read only a very limited number of posts regarding this issue here.. i checked the pressure sending unit electrical connection and its ok.. ill pick up a mechanical pressure guage monday... my question is does anyone know what values i should have if i use a dmm and back probe the pressure sender, so i can eliminate that as the cause. im not one to just throw parts at something..

if the sensor values reflect the inst cluster, and the mechanical gauge, ill go deeper, pull the pan check the pump clean oil passages, but if if ind all is well ill move on to see if my inct cluster isnt to blame or a bare ground causing a false low pressure sig..

any suggestions?

skid_j2x said:

fram

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Problem found.

/thread.

skid_j2x said:

so last week i changed my oil.. (fram ph16, shell 15-30 oil, just as i always have)

any suggestions?

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get rid of the Fram, install a Mopar, Mobil 1 or K&N. filter.

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X2 on the shitty fram filter...

GO with a Wic or NAPA filter......(BTW, NAPA filters are made by wix)

so fram's is nfg then?

I used Fram on mine up through 120K miles.. then the oil pressure dropped. As soon as I changed the Filter brand the oil pressure came back to normal and stablized.

I don't know if there was a change in Fram's filter design over the years or what... what I do know is the dry starts discontinued as well. My assumption is the anti-drain back valve on the Fram doesn't work well with the 4.0L.

I used Fram filters on every vehicle since I was 16... but not after this experience.

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Whatever filter you get, use the Ford Mustang 5.0 filter. It's much larger and filters better.

bchulet: was the pressure loss at idle? thats when i lose my pressure..

skid_j2x said:

bchulet: was the pressure loss at idle? thats when i lose my pressure..

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Chances are it is the fram filter bleeding oil pressure out the anti-drainback valve. Change it first. If the pressure is still low (13 pis at hot idle is Jeep spec minimum) then check with a mechanical gauge or change out the sender next. If the pressure is still low, switch to 15W40 (Shell Rotella T is a good choice for the 4.0) or a good 20W50 to get the hot oil idle pressure back up over 13 psi. I run the old API SL grade 20W50 Havoline right now, with a quart of Lucas oil additive to keep my hot oil idle pressure up to at least 25 psi, just in case the gauge is biased and reading higher than the real pressure. Mine has 254,000 miles on it.

Slo-Sho said:

Whatever filter you get, use the Ford Mustang 5.0 filter. It's much larger and filters better.

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What year Mustang 5.0 filter will fit?

bgred2 said:

What year Mustang 5.0 filter will fit?

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to the best of my knowledge, every 302CID/5.0l mustang uses the same filter:

Motorcraft FL-1A
Fram PH8A
Purolater L30001
Mobil 1 M1-301

Yeah what he said, I happen to like the Purolator PureOne flavor.

Or the K & N HP-3001.

skid_j2x said:

bchulet: was the pressure loss at idle? thats when i lose my pressure..

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Pressure loss was at idle, more at freeway speed... however, I was experiencing dry starts with the Fram filter way before I experienced pressure loss.. and subsequently, hasn't occured since I changed to Mobil 1 or K&N.

I run both, interchanging between service intervals... if you compare them side by side, they both have similar constructions, port size, flow, etc. It's my understanding the filter element is made from different material.

But everyone has a preference, and not all Fram's are considered inferior... I ran Fram HP1 on my Hemi car that had over 650 HP with a high volume pump... it idled at 60psi. But keep in mind it got changed frequently and didn't have an anti-drainback valve.

Like most have recommended, change out the filter first... and see if that improves things -- then take it from there, maybe swap out the oil sending unit located beneath the oil filter housing.

Something to be aware of ... I've experienced the opposite using Mobil 1 and K&N oil filters... the pressure is actually on the high side at speed. My next oil change I'm going back to a Mopar filter to see of it falls back in the middle of the range as specified in the FSM.

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bchulett said:

My next oil change I'm going back to a Mopar filter to see of it falls back in the middle of the range as specified in the FSM.

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I have read some oil filter test reviews and I know that some Mopar filters are actually Fram extra guard filters and are a horrible design. I think it was the severe duty one that is the Fram.
Not all Frams are terrible. IIRC the tough guard was rated actually quite well. I gotta try and find that comparison page...
You can't go wrong with the Napa or if you go the Ford route a motorcraft filter.
I hope this helps

how many miles?

well, i pulled the pressure switch and installed a mech gauge.. drove it like i normally do.. then after about 20 miles or so, and running just over 210 on the thermostat.. i checked the oil press.. 15 psi on the mech gauge.. so i changed the pressure switch..
i misspoke when i originated this post.. i am running shell rotella 15w-40 not 10 40 ordered a pressure switch from napa (44.50, my cost) and the dash gauge reads 15 psi.. problem solved.. closer inspection of the old switch revealed deterioration of the seal between the threaded end and the plastic electrical conector.. maybe the cause of the pressure loss, maybe not.. it wasnt leaking oil..

skid_j2x said:

well, i pulled the pressure switch and installed a mech gauge.. drove it like i normally do.. then after about 20 miles or so, and running just over 210 on the thermostat.. i checked the oil press.. 15 psi on the mech gauge.. so i changed the pressure switch..
i misspoke when i originated this post.. i am running shell rotella 15w-40 not 10 40 ordered a pressure switch from napa (44.50, my cost) and the dash gauge reads 15 psi.. problem solved.. closer inspection of the old switch revealed deterioration of the seal between the threaded end and the plastic electrical conector.. maybe the cause of the pressure loss, maybe not.. it wasnt leaking oil..

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Great, But I would still junk the fram filter, and seriously consider moving to an API SL only (not SM!) grade of a 20W50 in the summer if your down to 15 psi hot idle pressure, just for insurance. Shell Rotell T 15W40 is not what it use to be.

skid_j2x said:

well, i pulled the pressure switch and installed a mech gauge.. drove it like i normally do.. then after about 20 miles or so, and running just over 210 on the thermostat.. i checked the oil press.. 15 psi on the mech gauge.. so i changed the pressure switch..
i misspoke when i originated this post.. i am running shell rotella 15w-40 not 10 40 ordered a pressure switch from napa (44.50, my cost) and the dash gauge reads 15 psi.. problem solved.. closer inspection of the old switch revealed deterioration of the seal between the threaded end and the plastic electrical conector.. maybe the cause of the pressure loss, maybe not.. it wasnt leaking oil..

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Glad to hear you're narrowing down the problem, I've suspected my sending unit may be a contributing factor, however 15 psi at idle appears low to me considering what my 4.0L has performed at since new.

Mine has always idled at 30-40 psi... constant. In other words it has never dropped below 30 psi since 1991 when I pulled off the dealer lot. And since new I always ran 20-50 Valvoline Racing oil and Fram Extra Guard filter until it hit about 120K miles. That's about the time I noticed a significant drop in pressure at speed, so I replaced the Fram with a Mobil 1 filter and Mobil 1 15-50 Synthetic oil and the pressure increased 10 psi across the range.

The good news is the pressure increased -- although to the high side -- the bad news is the damn thing leaks now. But I don't know if that's due to the oil & fliter combo... or the oil filter housing o-rings (seals) are shot... or the rear main is shot... or the valve cover gasket is shot... or the sending unit is leaking -- or all the above.

FYI... my oil filter housing started leaking between 40-50K miles... it was repaired under my 5/70K factory extended warranty. I thought the rear main was leaking, the dealer found the housing seals went bad -- which could be my current problem.

I would still ditch your Fram filter for a K&N or Mobil 1 filter; and your oil to 15-50 at your next maintenance interval as suggested... I bet your pressure increases to 30 psi at idle.

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