4.3 TBI low oil pressure.

[00S104.3]

I have been noticing when I drive my '89 Blazer that the oil pressure (according to the gauge) seems to slowly get lower the longer I drive it. When I first start it up it is between 1/2 and 3/4 of the way up on the gauge. It stays there until I stop then it's a little bit lower like just under 1/2 way on the gauge. I drive some more or hop on the highway and it will stay at around 1/2 way up on the gauge while cruising and then when I stop it goes almost to the bottom and a couple of times it goes so far down that the "check gauges" light comes on. I recently had the truck in the shop because it was running bad and idling like crap. I had the ecm, o2 sensor, coolant temprature sensor replaced and also a new radiator since the old one had a crack in it. Before the truck was in the shop I was having the same issue with oil pressure and I replaced the oil pressure switch. I'm hoping it is not a bad oil pump.

Sorry for the long post but is there anything else I should try checking? Any help is appreciated.

[spideyjected]

How many miles on the engine? I'd get a manual gauge and hook it up to double check.

[00S104.3]

The truck has a little over 109,000 miles.

[spideyjected]

Hmmm, maybe the screen on the pump is dirty? I'd be inclined to say the pan's gotta come off.

[00S104.3]

Hmmm, maybe the screen on the pump is dirty? I'd be inclined to say the pan's gotta come off.


Noooo! I really pray that's not the case. :crossfing

['94 Big Blaze]

lol same problem here...

no oil pressure when idle but when you give it some gas it goes up...then when you stop it goes back down...either way the pans gotta come off

[00S104.3]

lol same problem here...

no oil pressure when idle but when you give it some gas it goes up...then when you stop it goes back down...either way the pans gotta come off


So, have you removed your oil pan? Or have you found out what needed fixed?

['94 Big Blaze]

So, have you removed your oil pan? Or have you found out what needed fixed?
Yup unbolted motor mounts and lifted engine, drained oil and then took out the screen,pickup,and pump.

The screen was really gunky soo i figures while i was doing i might as well do it right soo i replaced, oil pump,pickup, and a new screen. took about 2 hours and she was back on the road and running great.

[spideyjected]

00S104.3, is yours a 4X4 or not? 4X's are EXTRA fun!!!

[00S104.3]

00S104.3, is yours a 4X4 or not? 4X's are EXTRA fun!!!


Of course mine is a 4x4 so I'm in for a treat or out a lot of money if I have a shop handle it. I was always under the impression that the oil pump does not create the oil pressure it just pumps the oil throughout the engine. I may try some type of motor flush or seafoam in the crankcase to loosen up the sludge and maybe clean out the oil pan and see what happens.

[00S104.3]

I went to Vatozone and got a can of Seafoam and some oil and a new oil filter. I added a little over a half a can of the seafoam into the crankcase and started it up and let it run at idle for about 20-30 minutes. I was keeping an eye on the oil pressure gauge and it was up about 3/4 of the way on the gauge and went down to just under 1/2 on the gauge. It never got any lower than that. Then I got another surprise when I went to remove the oil drain plug it looked like it wasn't in correctly. It came out fine and the threads appeared to be ok but it wasn't sitting flush against the oil pan like it should. I let the oil drain until there was nothing at all coming out and then put the drain plug back in. It threaded in fine with just my fingers but it is not flush against the pan. I tightened it a little bit with a wrench and changed the filter and added the new oil. There is a slight drip from the drain plug but it's not really bad. I ran the engine after the oil change and the oil pressure was sitting at 1/2 way up on the gauge. I doubt the seafoam cured the problem but it was worth a try. I'll drive it some more and see what happens.

[00S104.3]

Well, I've driven my blazer a couple of times since using the Seafoam and the oil pressure is a little better. It still gets pretty low but not below 20 psi while stopped anymore. I don't know if it's because of the Seafoam or the cooler weather we have had the past couple of days. I'll keep an eye on it for now and hope for the best.

[spideyjected]

I really hope it works for ya!

[Jay-Sliver]

Try adding ATF (Automatic Transmission Oil) to your engine oil...about a liter (or a quart). The ATF will help clean and break up the sludge. Putting ATF in your oil will not hurt the engine at all. With the engine oil flush stuff, you arn't sapposed to drive the vehicle with the crap in it, where with the ATF, its ok.
G'luck.
Jay

[00S104.3]

I really hope it works for ya!

I got my fingers and toes crossed.:D


Try adding ATF (Automatic Transmission Oil) to your engine oil...about a liter (or a quart). The ATF will help clean and break up the sludge. Putting ATF in your oil will not hurt the engine at all. With the engine oil flush stuff, you arn't sapposed to drive the vehicle with the crap in it, where with the ATF, its ok.
G'luck.
Jay


I've heard of people using ATF in the oil but I'm a bit leary of trying it.

I am not driving with the Seafoam in the crankcase, I just added it to the oil and ran the motor at idle for a while and then drained the oil and filled it with new oil along with a new filter.

Thanks for the suggestion.

[Tink]

I sure hope that worked... it may be that you had some sludge in the passages that the seafoam cleaned out. I know on our fullsize, the oil drain back hole in the passenger's side head was plugged, causing low oil pressure.

[Hammer Head]

How many miles were on the oil? It could have just broken down & thinned out more once the engine warmed up..?

[00S104.3]

How many miles were on the oil? It could have just broken down & thinned out more once the engine warmed up..?

Actually the oil wasn't that old. I changed it about 3-4 weeks prior while I was putting a new starter on it. The oil pressure was still acting funny so that's when I decided to try some type of engine flush. So far the oil pressure hasn't dropped to zero at idle like it had been before using the Seafoam.

[00S104.3]

I'm bringing back my old thread instead of starting a new one.


My blazer died:( I thought I had the low oil pressure issue fixed well enough but I think the oil pump finally gave out. The oil pressure has been sitting at around 17-18 psi at idle (engine warm) and around 40-42 psi while cruising.

Last night on my way home from work I stopped at a light and the oil pressure went down to about 18 psi and then all of a sudden the engine died. When I turn the key on all of the other gauges move up but the oil pressure gauge doesn't move at all. The engine turns over so I don't think it seized. I had to have it towed home.

I'm not sure what I'll do yet. If the motor has to come out to change the oil pump then I may try to find a newer 4.3 with less mileage and drop it in or just replace the oil pump and hope for the best.

[spideyjected]

If the oil pressure drops too far there is a switch that shuts down the engine. Should just have to pull the engine mount bolts and raise the engine to get the pan off on a 2 wheel drive.

[00S104.3]

If the oil pressure drops too far there is a switch that shuts down the engine. Should just have to pull the engine mount bolts and raise the engine to get the pan off on a 2 wheel drive.


Mine is 4wd.

[BigTruckDrivah]

Did the engine start to "knock", or make any noise before it quit? Low oil pressure isnt always the oil pump, you could have some worn out main bearings causing low oil pressure. You could have a bad oil sending unit also. ATF does work really good in the crank case if you want to clean up a gummed up engine, FYI. I have used it many times in my daily beater, 96 ford aspire, lol, due to a sticky lifter. Ran ATF a few times right before oil change now shes like a sewing machine.

[spideyjected]

Does ot say anythwere how many miles the engine has on it? It would be easiest to switch out the sending unit and stuff first. I'm assuming the engine didn't make any wierd noises, but the bearings could be worn.

[00S104.3]

No noises that I could hear but I did have the radio on. I was just sitting at the light and the oil pressure gauge dropped to "0" and the engine shut off. I replaced the oil pressure sending unit a few months ago when I first noticed low oil pressure so it should be fine. The motor has 110,xxx miles.

[BigTruckDrivah]

Well, you did say it was idleing like crap. And oil pressure is gonna drop when the engine is trying to die, are you sure you dont have some other problem? What year truck is this and is it auto? Is it the one in your sig?

[spideyjected]

Hmmm. Still have your old Sending unit?

[00S104.3]

Well, you did say it was idleing like crap. And oil pressure is gonna drop when the engine is trying to die, are you sure you dont have some other problem? What year truck is this and is it auto? Is it the one in your sig?

It was idling normal (the same as it has been since i've owned it) I'm not 100% sure it's the oil pump I still have to check everything out when I have time. I may have some other problem.

It's not the truck in my sig. It's a 1989 S-10 Blazer 4.3l TBI 4x4 automatic.
http://i37.tinypic.com/24xf8cp.jpg

I bought it last October and I have been slowly fixing it up. Here is a list of things (engine wise) I have replaced...

ecm
oil pressure sending unit
o2 sensor
coolant temprature sensor
water pump
radiator
thermostat
starter
ignition coil
cap and rotor
plugs and plug wires
remote oil filter lines



Hmmm. Still have your old Sending unit?

The old sending unit was cracked and I threw it out.

[00S104.3]

This truck is beginning to wear on my patience.:mad:

I pulled a couple of the plug wires off of the plugs and used an old plug in the wire to check for spark when I crank the engine over, and I saw nothing.

I pulled the cap off and turned the engine over just to see if the rotor was turning, and it is.

I then pulled out the ignition coil and tested it with a multimeter according to my haynes manual. I'm not sure if I was doing it right or not but nomatter what I did I got no reading at all. It just stayed on zeros.:confused: I went ahead and got a new ignition coil and installed it and it still won't start nor is there any spark.

(I did notice that when I'm cranking the engine over the oil pressure gauge will start to go up.)

That is pretty much where I left off for today since it's dark outside now.

I plan to check out the ignition module next but I'm open to any and all suggestions on what else I should look at.

[spideyjected]

Test the new coil. Then make sure the coil is getting voltage.

[00S104.3]

It's alive!! :D


I pulled the new coil and tested it and I still could get no reading. I'm sure it's just me, Maybe I'm doing it wrong. I put the coil back in and then pulled out the ignition module and tested it according to the manual and still got nothing.:confused: I got a new ignition module and installed it and the engine fired right up. It seems like it's running better with the new ignition components.

I feel like a dumbass for assuming the worst, but it's a learning experience that will help in the future.

Thanks to all who helped. I appreciate it a lot.

[stealth]

Of course mine is a 4x4 so I'm in for a treat or out a lot of money if I have a shop handle it. I was always under the impression that the oil pump does not create the oil pressure it just pumps the oil throughout the engine.

You are correct, all the oil pump does is push the oil thru. It's the things like the bearings and such that create the pressure.

[BigTruckDrivah]

yup yup

[The Steel Cabbage]

I tried the Seafoam for the same issue your having and it didn't work. If anything, I think it made it worse! It seems to have loosened up sludge from other various places and centralized them at the screen.

I suppose that's a good thing if you want all of the blockages to centralize at the screen prior to installing a new one, but if you're not installing one right away, all it'll do is hurt your oil pressure even more (it did for me).

If it was any newer I'd say it was something else, but for a 20 year old truck, I'd be inclined to say it's about time for a new screen. The oil additives are good for cold starts, stabilizing oil etc, but for an actual blockage of metal shavings and sludge, you've gotta take the pan off. (probably tired of hearing that, aren't you?)