Oil pressure drop to zero 79 ranchero

Discussion in 'General Ranchero Help' started by Shawn, Dec 2, 2018.

  1. Shawn

    Shawn In First Gear

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    When you start the car the oil pressure goes to its normal position once I put it in gear it drops to zero ive checked the oil and its at the safe/ correct oil level this started happening yesterday it also back fired two times on top of that it also turns off and restarts by its self randomly with out messing with the key ive rebuilt the carb spark plugs and wires I have no idea how to fix it can anybody help me out ? Not even my local shop can pin point the issue
     
  2. aquartlow

    aquartlow In Maximum Overdrive

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    Check the fusible links at the starter solenoid and/or the accessory stud(if you have GT style gauges), also have a look at the fuse box, could also be an ignition switch issue but that requires a bit more work to get at. Hope this helps.

    I realize this response was directed more toward the electrical issues and not exactly the oil pressure gauge reading, although the gauge is electrically powered thus the reason to check the fusible links.
     
    Last edited: Dec 2, 2018
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  3. ForistellFord

    ForistellFord In Maximum Overdrive GOLD MEMBER

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    Spot on, really. With the myriad of electrical oddities mentioned, that must be sorted before we begin talk of bad mains or a dying oil pump.
     
  4. Shawn

    Shawn In First Gear

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    Thanks ill look into and let you guys know if it worked
     
  5. LSChero

    LSChero In Maximum Overdrive PLATINUM MEMBER

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    Check and clean all your battery connections and grounds at engine and firewall..Shine up connections at starter solenoid.Make sure battery is fully charged with good cables and alternator is putting out 13.5-14.5 volts running.Then go from there..Welcome to site!
     
  6. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

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    I'd put my money on a worn ignition electrical switch, as I had the same problem in my '89 Bronco (not the same switch part number but the same basic design), but going ahead and checking all your connections underhood, on the right fender well is sound advice anyway, as our rigs are up to 40 or more years old, and they likely will have corrosion or loose connections. Fuse links can be checked with a 12 volt test light, poked in at the switch side of the connection, and the wiring wiggled, looking for a blinking or no light.
     
  7. plumcolr

    plumcolr In Maximum Overdrive SILVER MEMBER

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    i'd look at the ground straps, either battery lead or engine to chassis, and their attachment points first.
     
  8. burninbush

    burninbush In Maximum Overdrive

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    I'll take a shot at this ... beginning by saying that every car should have a mechanical oil pressure gauge, one that doesn't depend on any electricity to tell you your pressure. You can add one with a T-connector to the existing oil sender.

    Assuming it still has pressure, then that won't disappear instantly, so the problem must be electrical. Do you have a dash readout of pressure, or just a light that comes on to say 'no pressure'? If that's the case then the problem is likely the sender unit. Ground the wire leading to the sender, and watch the dash gauge for an effect. If you have a gauge that reads pressure, then it might be the sender, same test for it.

    Car starting itself must be the ignition switch, the one down the column, It might just need adjustment.

    It's also possible you have a connector problem feeding the instrument cluster, a large maybe 14-pin connector that feeds electricity to all the gauges and lights on the cluster. Remove the dash to get to it.

    Start with a real pressure gauge, they aren't very expensive. If it really doesn't have pressure then you'll want to talk to somebody about a rebuild.
     
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  9. cbolt

    cbolt In Overdrive SILVER MEMBER

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    You should be able to hook up a mechanical direct pressure gauge without even installing it, just to see what you actually have oil pressure wise once you put the car in gear. Cheap and easy place to start.

    I'm on the "your problem sounds electrical" bandwagon and could be as simple as a loose positive battery cable or as complicated as a chafed wire somewhere behind the dash. Good luck and let us know what you find.
     
  10. colnago

    colnago In Third Gear

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    Was the backfire through the carb, or through the exhaust? Is it still doing it?

    Joseph
     
  11. Gregory Cummings

    Gregory Cummings In Second Gear

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    what can you tell if the backfire is from the carb or exhaust. I had a backfire sounded like the exhaust backfire. Soon after my valve lifters or some thing in there started ticking and sometimes tapping. Funny thing is it doesnt do it all the time. Also very interesting, my 79 351/400M 2V rattles in the engine only in cold damp weather (figure that one out). she loves the summer but hates the winter i guess.
     
  12. colnago

    colnago In Third Gear

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    If it's through the carbs, your intake valves aren't closing, or you have burnt intake valves. Or your dizzy is WAY advanced (but if that were the case, you'd probably be pinging/pinking). Some carbs can be damaged by a backfire through the carb (but that's about all I know on that score).

    If it's through the exhaust, then there's gas igniting in the exhaust side. Late timing (real late), burnt exhaust valves (not usual), lean mixture leading to HOT exhaust manifolds), etc.

    Joseph
     
  13. Dan the ranchero man

    Dan the ranchero man MODERATOR Staff Member

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    I would look at electrical first before messing with the engine at all. The suggestion given at the beginning of this post will most likely help you find your trouble. Backfiring (in this case) sounds like your ignition is cutting out and then restarting. That will cause a backfire for sure. once that is handled "then" I would see how the car runs. If you still have engine issues then move on to diagnosing engine issues.
     
  14. colnago

    colnago In Third Gear

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    Dan,

    What would cause the ignition to cut in and out? I've not seen that before.

    Joseph
     
  15. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

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    Since it likely still has its Duraspark ignition, a weak coil (caused by shorting in the windings when it heats up during charging), a weak pickup coil in the dizzy (caused by a weak magnet) or a worn dizzy bushing and/or shaft, (which causes the reluctor on the shaft to sometimes not be the proper distance from the pole piece in the pickup coil) can cause the ignition to cut out and back in, but usually, the ignition just quits, stopping the engine.
     
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  16. Dan the ranchero man

    Dan the ranchero man MODERATOR Staff Member

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    All the things Andy said plus Bad grounds (to the engine) faulty ignition switch (internally broken) Duraspark box breaking down. On the box those will just shut the engine off after running a few minutes. Then any number of things can happen after.
    1) engine restarts after a few min
    2)engine starts right up but dies again after about 10 min
    3)engine engine will false start pop & sputter through carb or exhaust but after sitting a while (10 min or so) will restart.
     
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  17. Garbageman

    Garbageman In Overdrive

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    I owned a 71 that would run fine, then every once in a while would shut off while driving down the road. A few seconds it would restart, sometimes backfiring. It took a long time to determine that the coil had a hairline crack it. Once I replaced the damaged coil never had another issue.
     
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  18. plumcolr

    plumcolr In Maximum Overdrive SILVER MEMBER

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    Ditto on the coil. Also the dizzy cap. Look for crack or carbon track on the inside.
     
  19. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

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    Carbon tracking will only cause cross-firing, not necessarily backfiring (depends on where the piston is in the four cycles if it misfires to cause a backfire), but should always be inspected and cleaned every 10K anyway.
     
  20. 1979 RANCHERO GT

    1979 RANCHERO GT In Overdrive

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    Back to your original post. My 79 started the same thing with it's oil pressure gauge. A new sender from Ford fixed the oreilly sender problem. Part number E4ZZ-9278-A motorcraft number SW-1547-B.
     
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