Oil Pressure Testing

How-to's and repair secrets for your 4WD can be found here. Have a question? Ask it in here!
Post Reply
User avatar
tabercro
Newbie
Posts: 12
Joined: Mon Mar 29, 2021 7:38 am
My tercel:: 1985 SR5 4WD
Location: Portland, ME

Oil Pressure Testing

Post by tabercro »

Hi All,

My 1985 Tercel seems to make a fair amount of lifter noise upon start up. It quiets down after it warms up. But I've noticed that even after it comes up to temp, that if I rev it a bit I get a bit of noise for just a second. I just recently changed the oil and the gear oil and noticed that my oil pressure light stays on for a split second at start up. I don't ever remember that before, but this car is fairly new to me and perhaps I'm just paying attention differently.

Is there any easy way to definitively test the oil pressure? If I use a mechanical kit, where is the best place to test it?

Am I barking up the wrong tree?

Thanks for your help.
-Tom
-------------------------
1985 Tercel SR5 4WD
1992 Volvo 740
1999 Volvo V70 R AWD
1986 Vixen 21TD
User avatar
dlb
Highest Ranking Member
Posts: 6826
Joined: Mon Jul 06, 2009 9:03 pm
My tercel:: none currently, 7 previous
Location: bc, canada

Re: Oil Pressure Testing

Post by dlb »

To check the oil pressure, you have to remove the oil pressure sender from the side of the block (that is what sends the signal to the oil light on the dash) and hook up a mechanical gauge, which are cheap enough at any auto store.

The only tricky part is finding the correct adapter. When I tested the oil pressure on my ae95 long ago, the kit that came with the gauge I bought didn't have the right adapter. I had a hell of a time figuring out what I needed. Oh I just found it in one of my old posts:

1/8" x 28 BSPT male to 1/8" NPT female adapter

If the kit you buy doesn't have the right size, that should be what you need.
User avatar
Petros
Highest Ranking Member
Posts: 11720
Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Oil Pressure Testing

Post by Petros »

it is a simple matter to rig an inexpensive gauge to the oil sender port, as DLB noted. the sender is behind the alternator on the side of the engine block, you have to remove the alternator to get access to it.

I do not think the lifter noise is related to oil pressure since the cam shaft is lubricated by splash from several "wells" in the head under the cam shaft, unrelated to oil pressure. Check your valve clearance first, that is more likely the cause of the noise.

these engines do not really have lifters, but rather rocker arms riding directly on the cam shaft. Check your clearance between the cam lobe and rocker arm pad, I have found it works better to set the clearance when it is warmed up. as I recall it is 0.016" intake valves, and 0.018" exhaust (but check the FSM for correct specs and procedure). it does not have to be off my much to be noisy. it is not difficult to check the valve clearances.

It is normal for the engine to get more quite as it warms up, the metal parts expand and clearances bet better, as designed by the factory. adding a sticky oil additive like STP may help, gives the parts better cold start protection for older engines. There is not much that can be done to make the oil light go off faster after start up, it takes a few seconds for the oil pump to pressurize the oil galleys, it typically has the light go off at only 7 or 8 psi, which is too low to safely run the engine anyway. it is just a "on/off" switch, and cold oil usually will pressurize it fairly quickly.

I once had a beater Toyota pick up I bought for $600. it had the 20R engine, ran well but my oil lite would flicker on between shifts, and at idle after warm up. so I added a gauge. on cold start up it came up to 20 PSi, but after it warmed up it dropped down to idling at about 7-8psi, hence the light flickering on. It would only rev to abotu 10 to 12 psi after it was warm, way too low. the bearings were completely worn out and it had very little oil pressure (likely from running with very dirty oil thanks to the previous owner's neglect). I eventually got another engine from a wrecking yard and rebuilt it and swapped it out after the original engine threw a rod though the side of the block. so low oil pressure is a serious matter.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
User avatar
tabercro
Newbie
Posts: 12
Joined: Mon Mar 29, 2021 7:38 am
My tercel:: 1985 SR5 4WD
Location: Portland, ME

Re: Oil Pressure Testing

Post by tabercro »

Thanks for the information! I'll definitely test the oil pressure soon.

Rocker arm noise aside, my Tercel hasn't been running very well since i replaced the timing belt this summer. I'm pretty sure I didn't somehow jump a tooth, but it's not outside the realm of possibility. It could also very well be fixing some of the emissions stuff like the PCV valve that were shot.

How well would this engine run if I were off a tooth?

Thanks.
-Tom
-------------------------
1985 Tercel SR5 4WD
1992 Volvo 740
1999 Volvo V70 R AWD
1986 Vixen 21TD
User avatar
dlb
Highest Ranking Member
Posts: 6826
Joined: Mon Jul 06, 2009 9:03 pm
My tercel:: none currently, 7 previous
Location: bc, canada

Re: Oil Pressure Testing

Post by dlb »

tabercro wrote: Wed Oct 13, 2021 6:53 am
How well would this engine run if I were off a tooth?
Do you have a timing light? That's critical for accurately timing the ignition. It will tell you if the timing is correct, and if you are off a tooth.
User avatar
Petros
Highest Ranking Member
Posts: 11720
Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Oil Pressure Testing

Post by Petros »

you have to pull off the timing belt cover to see if it is off a tooth. it will usually run fine, I once got a car that ran okay, but got really bad fuel economy. after checking everything else, I checked the cam timing. off by 2 teeth.

I do not think the spark timing will tell you that if it is off anyway. it is good to check the spark timing while you are at it, but you need to check the timing marks on the front cam sprocket to know if the belt was off. than check the spark timing.

I do not think either issue would make any difference in valve noise.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
User avatar
dlb
Highest Ranking Member
Posts: 6826
Joined: Mon Jul 06, 2009 9:03 pm
My tercel:: none currently, 7 previous
Location: bc, canada

Re: Oil Pressure Testing

Post by dlb »

Petros wrote: Wed Oct 13, 2021 3:56 pm
I do not think the spark timing will tell you that if it is off anyway.
If the timing is off by a tooth, won't the spark timing be impossible to set correctly? The distributor would be pushed as far as it can go in one direction but the timing mark will still be way off.

Which also leads me to ask, is it possible you put the timing belt on correctly but put the distributor in a tooth off? I would definitely remove the timing belt cover and check the marks like Petros suggested, but if the marks line up correctly I would put a timing light on it and confirm the distributor is not a tooth off.
User avatar
tabercro
Newbie
Posts: 12
Joined: Mon Mar 29, 2021 7:38 am
My tercel:: 1985 SR5 4WD
Location: Portland, ME

Re: Oil Pressure Testing

Post by tabercro »

I'll pop the top cover and check to make sure my timing belt is correct before I pull out the timing light. My mileage seems to be okay, although I have no reference point since I haven't really driven the car much yet. It seems to me it is around 27 mpg.

Thanks for the help.
-Tom
-------------------------
1985 Tercel SR5 4WD
1992 Volvo 740
1999 Volvo V70 R AWD
1986 Vixen 21TD
User avatar
Petros
Highest Ranking Member
Posts: 11720
Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Oil Pressure Testing

Post by Petros »

dlb wrote: Wed Oct 13, 2021 5:19 pm If the timing is off by a tooth, won't the spark timing be impossible to set correctly? The distributor would be pushed as far as it can go in one direction but the timing mark will still be way off.
maybe, but usually as I recall, the cam timing off a tooth is not enough to prevent correct spark timing. but if the distributor gear is off a tooth it will. one tooth off the distributor gear moves it far more than one tooth off the cam sprocket. of course you can also have the cam timing off, AND the distributor gear timing off at the same time. neither will affect the oil pressure of course.

that is why it is important to verify the cam belt is installed so the cam timing is correct first, than to check the spark timing. changing one will affect the other, so doing it in the correct sequence is important.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
Post Reply