Losing Oil Pressure 93 3.0

makonkey · Nov 23, 2014

I am trying to help out an elderly friend who can not afford to have his truck fixed. It is not in the best shape, but he needs something to drive. His truck has been losing oil pressure while he is driving at times. Since he did not remember the last time he changed the oil I did that for him and swapped out oil filters. He is still having the problem. I am able to do anything needed to get the engine running right, however, the money I spend will be my own so I would like to fix the engine without doing a full rebuild. I am not very familiar with these engines so I am not sure where to start.

From what I have found so far the oil pump is driven by the distributor gears. I am not sure if a failure here would cause temporary oil pressure loss or if it would always have no oil pressure.

The oil pump screen could have obstruction but I would need to drop the oil pan to determine. I am not sure how to test the oil pump itself!

The other issue is if the bearings are damaged from lack of oil.

Anything that I should look at before digging into the engine. I have decided not to remove anything yet so I can do any recommended checks first. I think the best course of action is for me to pull the engine and go over everything while giving it a good cleaning. I just want to make sure I am taking care of the problem for him if I do.

bucko · Nov 24, 2014

How do you know it's loosing oil pressure? I have to remember that these earlier Ford Rangers actually did have an oil pressure sender that varied the gauge in the cluster...the later (95 and later?) had a simple "yes" pressure, or "no" pressure, meaning the gauge would show at the middle, and never fluxuate.

Is there a way you can actually test for oil pressure, using another gauge that would screw into the same hole as the stock sendor? You may just have a faulty sendor.

makonkey · Nov 24, 2014

An actual oil pressure gauge is a good idea. He did tell me that he can hear the tapping etc you would usually associate with oil pressure loss. I have not driven it myself to experience it first hand as I do not want to risk causing more damage than there may already be.

RonD · Nov 24, 2014

Yes, oil pump is driven by the Cam syncro shaft, it is in the old distributor hole, same setup as distributor-camshaft turns gear on Cam Syncro shaft, which turns oil pump shaft and syncro shaft which has CPS(cam position sensor) at the top.
Cam syncro shaft/housing is a know failure point on the 3.0l, the bushing wear out and cause a loud squealing.
Total failure would stop oil pump.
CEL(check engine light) would come on if that happened since CPS would no longer be working(shaft isn't spinning with engine).
You could remove top of CPS and with coil unplugged, crank engine and see if shaft is turning.
Another test for oil pump would be to remove cam syncro housing and use a drill to manually spin oil pump, with key on gauge should popup to just below 1/2 when oil pressure at the sender goes above 6psi.
Yes, in the mid-80's Ford changed to an oil pressure switch, below 5.5psi switch is off and gauge shows 0, at 6psi and up switch closes and gauge shows just below 1/2.

Since you have been told about "tapping" from valve train the oil pressure is low, for sure.
If funds are limited I would suspect oil filter issue, probably a cheaper one was used and is now limiting flow, dirty or just not made well.
You could unplug coil, remove oil filter and put a bucket under filter housing, then crank engine and see how much oil is pumped out into the bucket

makonkey · Nov 24, 2014

I have already changed the oil and oil filter. This year model had an actual distributor rather tHan a cam sensor. Are those gears for the oil pump prone to failure?

RonD · Nov 24, 2014

Oops, lol, engine wouldn't start if distributor shaft wasn't turning, so oil pump shaft should be turning, never heard of distributor shaft oil pump shaft linkage breaking.
Drive gear on distributor shaft does have a "shear pin" but distributor wouldn't turn if that was the issue, so no start.

Oil pressure comes from bearings and oil passages.
Oil pump provides oil flow but not pressure.
Oil pressure means there is too much oil for the bearings and passages to use/pass, so back pressure builds up in the main passage after the oil filter, where the sender is located, and that is what we see as oil pressure.
Bearings wear over time and oil pressure goes down a bit, that is normal, more oil can flow out the worn bearings so less back pressure.

If oil pump flow was reduced then yes oil pressure would go down, or if oil filter wasn't passing the flow oil pressure would go down.
Oil pumps also have a high pressure valve, "ball and spring", that will open if there is any back pressure from filter or system, these can fail which will lower oil flow since valve is open.

I would pull distributor(check oil pump drive) and pull oil filter then check the flow from pump using a drill

Rearanger · Nov 24, 2014

If your friend thinks tappet noise is low oil pressure does noise go away when rpm is increased? Does oil light work when ignition on but not on run? Does the oil light flicker on idle?

How many miles on this engine? I assume if financial difficulty he did not keep up maintenance?

Mechanical pressure gauge hooked up to oil sender port would be best way to know what oil pressure was at any rpm.

Trying to turn oil pump shaft from removed distributor with drill is not easy.

makonkey · Nov 24, 2014

I ordered an oil gauge today. The oil pressure gauge is stable at idle. Going of memory he told me there is only 130,000 miles on the engine/truck.

He had been unable to drive the truck for sometime I believe a year or longer until he had the transmission fixed. It is hard to get great information from him I believe he is extremly embarresed about not being able to take car of his truck better.

The more I think about this the more I feel I am going to pull the engine and replace all gaskets and clean everthing. I just do not want to miss something and have it continue to have issues after I am done.

Rearanger · Nov 25, 2014

makonkey said:
The more I think about this the more I feel I am going to pull the engine and replace all gaskets and clean everthing. I just do not want to miss something and have it continue to have issues after I am done.

That's very generous but replacing gaskets will only slow/stop oil loss, not low pressure not caused by low oil.

makonkey · Nov 25, 2014

I was thinking clean and inspect parts. I plan to look at the main and cam bearings. Without knowing the condition of the bearings it is hard to tell how much it will take to repair. If it was my car I would replace the oil pump just because I was there. I just do not want to keep adding just because items to my bill. I did find a rebuild kit for around 350, that is more than I want to spend. I honestly hope to find a partially obstructed pickup screen. The cost of a full gasket kit is not to much more than just oil pan and valve covers so I plan to do everything regardless with the engine out.
If you were doing this job what would be the minimum you would recommend. I do not mind doing a little extra labor I would just prefer not to throw money at it, especially knowing it may not be well taken care of in the future.

Rearanger · Nov 25, 2014

makonkey said:
If you were doing this job what would be the minimum you would recommend.

I would not do anything until I understood what the oil pressure was. If you find low pressure what do you pinpoint as the problem - bearing wear, pump? Pickup screen is easy to clean, I believe OP can be removed from oil pan removal.

Given the owners financial position it may be best to just put used engine in it.

Angie · Nov 25, 2014

i have to ask, what really makes you think the motor needs to be pulled and all this done to it?

a bit of ticking is pretty normal on a motor with over 100K on it. putting a pressure gauge will be good to know what is going on, but please tell me what the gauge should be saying at idle say 700 rpm??

you might be trying to pull fly crap from pepper here and there are no real problems at all....

makonkey · Nov 25, 2014

My oil pressure gauge came today so I will install it tomorrow night and see what is really going on.

I know that the oil pan can be dropped without removing the engine. I have found in the past that it does not take me much more work to remove the engine. Then with engine on a stand I can do better/easier work.

I have considered a used engine. But think I would prefer to trust my work on the engine over a used one. Unless I find damage to bearings. If the bearings look okay should I pick up some plasti-gauge to determine wear?

Is there a way to test the pump to see if it is failing, or should I just plan to replace it?

Rearanger · Nov 25, 2014

makonkey said:
Is there a way to test the pump to see if it is failing, or should I just plan to replace it?

Oil pumps need to be tested for flow, there is no way to bench test the oil pump. Pumps create flow, resistance to flow creates pressure. If you're getting good pressure you can assume there is enough flow to overcome internal leakage.

If you're in that far just replace the pump.

makonkey · Nov 27, 2014

I started pulling the engine last night. I could not figure out an easy way to add the actual oil pressure gauge. EVERYTHING in the engine compartment is covered in oil and mud. I have only the engine to transmission and the engine mount bolts left to remove and I will have it out. I spent a lot more time than I expected last night. When I went to remove the flex-plate to torque converter bolts I had trouble getting to them. I ended up running my socket with a long extension up beside the engine so I could use my impact to remove them. I did not notice on the last nut until it was rounded off that my socket cracked. That let me spend another hour or so using a craftsman rounded nut extractor to get the nut off.

I decided not to worry about testing the oil pressure, I will just replace the oil pump and clean the screen. Still not sure about bearings until I see them.

Losing Oil Pressure 93 3.0

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