My truck ('89 4X4 302 5spd) had been sitting in a parking lot for about 1/2 hour. I started it up and began to drive, when the "engine" light came on and the oil pressure guage took a nose dive. After about 5 seconds, the light went off and the pressure guage went back to normal. The engine is strong and doesn't burn any oil. Any thoughts on the cause?

 

DEpete,
If you haven't already, double check your oil level. I have seen something like this, but only on mechanical gauges, but never dropping that low. If the level is low, it could be that oil was sloshing in the pan, away from the oil pump pickup.

Keep in mind that the factory gauge is a glorified idiot light, that only warns when oil pressure is below ~4.5PSI. That's why I went to the trouble to install a 3-gauge panel in my '97 F150. Which by the way, I get >30PSI at Idle, and at 1500rpm, ~65PSI. Cold, >2000rpm yields ~95PSI.

It's also possible that your oil pump pickup tube has come loose and is sucking air. If you're oil level is OK, I'd watch it VERY closely, and possibly install a REAL gauge.

Let us know how it pans out.

Tony

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97 F150, 5.4l, E4OD, Towing Package, and every option except leather seats

 

Any bad sounds when the "gauge" was down? If your oil pressure really dropped that low, below the oil pressure switch turn on point, for any real length of time, usually hear something. Like something bad, a screech, loud clatter, etc. The crankshaft won't be supported on an oil film if pressure drops way low, and you will hear something uncomfortable out of it. If oil level is OK, next step is usually to hook up a real mechanical gauge temporarily in place of the oil pressure switch, and see if its really low pressure at idle or not. It could be something simple like the switch, or the wiring to it (connector on the switch is a good possibility).

 

I hate to be the bearer of possible bad news, but this is one of the classic signs in a Ford of main bearings (commonly referred to as "front mains" or "rear mains"). Most often, in the 302/351 the rears were the first to go. You can continue to drive it for a while, but this is a fairly serious problem, does not fix itself, and can be disastrous if you are driving and the pressure drops, then does not come back. Bite the bullet and go ahead and get'em done, you ought to be good for a long time after it's done(assuming you aren't in need of a complete rebuild because the rings are worn, valves are ok, etc.)

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My credentials? Yeah, they're right over there....

framed and hanging on the shade tree.

 

Thanks for all of the suggestions.

GranPa- No bad noise when it happened. I suppose that it could be a number of things. This isn't my everyday ride, but I do use it for long distance trips on occassion, so I'll keep a close eye on everything. If anything more comes of it I'll let you all konw. Thanks again to all.

 

For those who have replaced the "idiot light/gauge" with a real gauge set..... Did you simply replace the sender unit that triggers the light with another unit that measures and reports variable pressures? Could this new sender be used with the existing gauge set?

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2000 F-150 XLT Sport, Silver 4-door Supercab StyleSide
Short Bed (Only way to fit in the garage)
17" Sport Wheels with BFG tires, 3.55 R, 4.6l V8, Auto (First one in 20 years)
In-Dash Single CD Player, 60/40 Split bench dark graphite

Mods So Far
K&N Filter, Gatorback Spray-In Bedliner, Llumar ProShield Window Tint
WMS Velocity Tube, Black Westin Step Bars

Future Plans
Superchip, Upgraded Speakers/Stereo
FlowMaster Exhaust




[This message has been edited by Y2kXLTSport (edited 10-23-2000).]

 

DE PETE

I had the exact same thing happen on my brand new 2001 super crew with a 5.4. Mine would do it every once in awhile. Took it to the dealer and it turned out to be the oil pressure sender.

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2001 supercrew, 5.4,4x4,lariat,classIII trailer tow, bright red ,westin steps, access cover

 

Turned out to be the oil pressure sending switch. Easy (and cheap) fix!