F150 dry start

my 1990 4.9L engine has developed a dry start. After 5 seconds or so, the engine sounds great. Oil pressure is normal at first, then the gauge drops past low after about 5 minutes, but the engine still sounds and operates good. What's the deal? Oil pump or screen, bearings, any easy way to fix it before it dies? Slight leak from oil pan, looks like it is rusting from the inside, as after cleaning it the oil just appears from the driver's side of the pan, like sweat. Oil change doesn't help, turns black after a few days. Tried lucas oil treatment, no help there, either. Would like to drive it again. Any ideas?

test the oil pressure with an external guage to make sure the guage and/or sending unit aren't bad. If either is bad replace the bad equipment. if both test out ok, then you have a leak somewhere for sure, possibly something wrong with the oil pump. For the black oil try an oil system flush.

After checking gauge and sending unit,Does the pressure drop further when you give it gas? If so sounds like main bearings. Did this start all of a sudden or has pressure been dropping over a period of time, When was you last oil change (Bad Filter)? Does the car have high mileage? change viscosity to a heavier oil. If it's high mileage and you flush the system you can look for some smoke after flushing.

ervinj

ervinj

No, the pressure increases for a time when I give it gas,to about 2000 rpms. When I let off the gas to coast at any speed the pressure drops again to below L. Just started all of a sudden a few months ago when it was cold out and I heard squealing from the right side of the engine. The thermostat was stuck and I had no heat, replaced it and heat was good again. Last oil and filter change was about 90 days ago. Haven't driven but 500 miles since. Truck has over 100,000 miles, heard that flushing with engine flush might damage seals and worsen the condition. What should I use for flush? I heard that running trans fluid would be safe, sounds weird to me. What grade oil would you suggest to thicken the viscosity?

Bill

test the oil pressure with an external guage to make sure the guage and/or sending unit aren't bad. If either is bad replace the bad equipment. if both test out ok, then you have a leak somewhere for sure, possibly something wrong with the oil pump. For the black oil try an oil system flush.

Hi Garland

What flush would you suggest trying? I heard it could do more damage to the seals? Could a bad gauge or sending unit be contributing to the dry start?

Bill