Oil Pressure issue with 1991 Allante
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Cadillac Allante Forum Discussion, Oil Pressure issue with 1991 Allante in Past Cadillac Vehicle Discussion; Hey Here is the situation. Ii'm hoping someone may have a solution. I have a 1991 Allante. It has the ...
  1. #1
    FLBill is offline Cadillac Owners Member
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    Oil Pressure issue with 1991 Allante

    Hey

    Here is the situation. Ii'm hoping someone may have a solution. I have a 1991 Allante. It has the 4.5 V8 Cadillac engine. It has an oil pressure problem ONLY immediately following an oil change. I do the oil change at a local garage.

    Oil and filter are changed every 3000 miles
    Have always used 30 w Rotella since I got it in June, 2009 with 67,000 on the clock
    The Allante currently has 130, 000 miles on it
    This issue has been occurring consistantly since the 90,000 mile mark.
    At oil change interval,.....
    car goes up on rack.
    oil is drained
    car is lowered
    oil poured into the new AC Delco oil filter
    oil filter is screwed onto engine
    6 qts of Rotella 30 w oil is filled into engine
    Start up
    engine oil light illuminates immediately
    No engine oil pressure noted on gauge
    After a few seconds you can hear valves lifters begin to rattle. (collapse)
    Repeated attempts result in the same scenario.
    Push car out of garage bay, and allow the car to sit for at least 4 hours.
    Attempt start : result is oil pressure and everything OK.

    I have tried every thing I can think of ...., 20/50 oil, 10 /40 oil, doing the change as quickly as possible. No variation makes a difference.

    The engine does not leak any oil. Between oil changes, there is NEVER an oil pressure issue. Oil pressure on gauge is always at the center or better. At idle, never get an oil pressure light. If the car sits unused in my gagrage for a week, at start up after sitting, there is immediate oil pressure.
    The car runs great; I have no issues with it other than this annoying one.

    This has occurred at EVERY oil change since 90,000 miles

    Any ideas??

    Bill

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  3. #2
    carnut is offline Cadillac Owners Master
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    Re: Oil Pressure issue with 1991 Allante

    The oil filter adapter has a bypass valve within it. Could be sticking shut? What I find odd is the oil pressure sender seeing no oil pressure should turn off the fuel pump. I dont think the adapter is specific to the Allante, any 4.5 part should work. Personally, I would use a multigrade oil all the time. Thinner oil flows quicker cold. I used Rotella in mine but 15/40 and I changed mine at 6 months or 5000 miles. 3000 is too early if you drive 10 to 12k a year. IMO

  4. #3
    FLBill is offline Cadillac Owners Member
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    Re: Oil Pressure issue with 1991 Allante

    Hi

    Hi Carnut. Thanks for the reply. Yes, I drive the '91 about 20 K a year. I just prefer the straight 30 weight in Rotella. The owner's manual does list it a a viable weight oil considering the region of the USA I reside... South east (Florida) .

    Don't know about the fuel pump and oil pressure sending unit dependency. I do know that they are tied together in that circuit, but it is bypassed by another cirtcuit during starting.

    I think somewhere along the way the concept about a lack of oil pressure in the sending unit wouild not allow the fuel pump circuit to continue to be energized, (thus effectively killing the engine before damage is done) was floated out there, but in reality is not the actual principle in place.

    So much of my issue with oil pressure is inconsistant. I am wondering if there is not an internal seal or something that may have become dislodged or a seal which may have become degraded or otherwise compromised. I would also think that I can not be the only person with this issue with these symptoms.

    Bill

  5. #4
    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
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    Re: Oil Pressure issue with 1991 Allante

    This sounds like a priming problem to me...a leaking check valve in the pump or a leaking seal at the pickup tube...

    As far as the oil pressure vs fuel pump thing... I know the engine will run without the sending unit even connected, and I've never witnessed low oil pressure shut the fuel pump off on any engine of this series (4.1, 4.5, or 4.9). I've only read it on these forums. I'm thinking it's misinformation.

  6. #5
    nbaum is offline Cadillac Owners Member
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    Re: Oil Pressure issue with 1991 Allante

    On my 92 Allante I had some oil pressure issues because of a lost oil gallery plug. I'am not suggesting you have that problem but my engine kept running with almost no oil pressure. I believe the connection between oil pressure and the fuel pump shut off was not on the 92's perhaps not on the 91's as well.

  7. #6
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    There is no relation between oil pressure and fuel pump operation... This comes up all the time on forums.

  8. #7
    kiwigram is offline Cadillac Owners Member
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    Re: Oil Pressure issue with 1991 Allante

    I wish to state that there is a connection. You will find the description in the Service Manual on page; 6E-C2-3 under the heading; Oil Pressure Switch. I feel that Rotella oil is too harsh for these engines. It is a diesel engine oil and as such has a high detergent action which is not the best for gas engines. I would suggest staying with the engine manufacturers recommendation of 10w - 30. I had similar problems with my '90 and after changing out the oil filter head with no change, I dropped the oil pan thinking that the oil pump relief valve had stuck, i found that the O-Ring between the pump and the block had broken allowing the oil pressure to dissipate at idle. I don't think this is the problem here, but I don't have any other suggestions.

  9. #8
    MoistCabbage's Avatar
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    So the fuel pump won't run with no oil pressure.....

    There's no oil pressure when the engine is off, the fuel pump needs to run for the engine to start... I see a problem.

    Unplug the oil pressure switch with the engine running. You'll get a warning light/message, and the engine will continue to run.

    Your thoughts on "diesel oil" being too "harsh" for a gasoline engine are incorrect.

    High detergent levels? Have you seen the detergent levels of synthetic oils,

  10. #9
    kiwigram is offline Cadillac Owners Member
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    Re: Oil Pressure issue with 1991 Allante

    " When the key is first turned ON….., the ECM will turn the fuel pump relay on for 2 seconds. This builds up the fuel pressure for cranking." What's the problem? :-)

    "The oil pressure switch acts as a back-up to the relay to turn on the fuel pump as soon as oil pressure reaches about 28 kPa (4psi)."

  11. #10
    FLBill is offline Cadillac Owners Member
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    Re: Oil Pressure issue with 1991 Allante

    Hi

    I have used nothing but Rotella, straight 30w in all of the vehicles I have owned and have not had an issue. The vehicles include :

    1975 Ford F-100 with 302 V8 (Drove it to 175 K and sold it . It ran great.
    1976 Ford F-100 with 300 6 (drove it to 170K and sold it. No problems.
    1979 Ford F-150 with 302 V8 (Drove it to 175 K and sold it . No problems.
    1983 Eldorado with 4.1 (it went 245K with me ) and I sold it. It ran great.
    1985 Eldorado conv. with the 4.1 ( I drove it 268K) and sold it. It also ran great.

    (the key to the Caddy 4.1 was regular oil changes and strict close monitoring of coolant levels.)

    I was advised right after I first started driving to use 30w oil. It has always been listed in the owner's manuals as a viable oil to use for the vehicles I have owned. I have used Rotella and continue to use it now primarily for the reason that it continues to have the zinc additive. Other oils do not. This zinc is critical for upper engine lubrication in particuilar. Since I have only had used vehicles, the type of oil used prior to my ownership has not been a concern of mine. Initiating at my ownership, I verify that 30w is applicable and use 30 w Rotella. I have never heard of any oil, even Rotella being labled as "harsh". Kind of sounds defeating of its' purpose to me.
    Anyway, anyone have any other ideas regarding my Caddy, lack of oil pressure AFTER an oil change issue?

    Bill

  12. #11
    MoistCabbage's Avatar
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    Have you tried using the CORRECT viscosity for your engine? 10W-30?

    Has anyone popped a valve cover off and check if something is preventing the oil from getting to the pan quickly? Does sustained high RPM cause an oil pressure drop?

    ----------

    Quote Originally Posted by kiwigram
    " When the key is first turned ON….., the ECM will turn the fuel pump relay on for 2 seconds. This builds up the fuel pressure for cranking." What's the problem? :-)

    "The oil pressure switch acts as a back-up to the relay to turn on the fuel pump as soon as oil pressure reaches about 28 kPa (4psi)."
    That's referring to turning the pump ON, not turning it OFF if low oil pressure is detected (post #2).

  13. #12
    FLBill is offline Cadillac Owners Member
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    Re: Oil Pressure issue with 1991 Allante

    Hey

    No need to remove a valve cover to inspect. The oil is getting to the oil pan (no obstruction). Have verified this by both a visual during the fill stage and immediately following the fill, as observed on the dipstick. I am using the CORRECT viscosity oil as recommended by the owner's
    manual. I live in South Florida and going by the chart in the owner's manual 30w is an appropriate viscosity oil to use (SAE 30 w for use where
    temps are ranging from +4 degrees to over 100 degrees) As stated, I also have tried various (multi grade) weights of oil. Oil pressure is always at the middle of the gauge. At idle, after warm up, it drops to one line below the center of the gauge. This issue is a real puzzle for sure.

    Bill

  14. #13
    MoistCabbage's Avatar
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    Well, it sounds like the pump is somehow losing it's prime when the oil is drained. I'm not too familiar with the 4.X pump design.

  15. #14
    FLBill is offline Cadillac Owners Member
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    Re: Oil Pressure issue with 1991 Allante

    Hey

    Thanks MC ....That is exactly what it sounds like to me. I too am unfamilioar with the working/ arrangement of the inside of the 4.x series. I agree, it seems as if the pump is losing its' prime, but I wonder why it does not lose prime between periods of time of non use. Do you think it might be getting air locked during the change and the oil does not go up into the oil pump or whatever, as I guess it would typically do, but does so over an extended wait ? I am still at a loss for a reason for this odd issue and why no one else had experienced it. Thanks for the replies !

    Bill

    Bill

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