Saber

iTrader: (2)

So i did a search and found out that since my oil pressure gauge was reading low that i should change the sending unit. Well today i did that, When i started the car up it read 30psi but quickly jumped down to 15 psi. After driving awhile it goes down to zero and will only jump up to 15psi when i am accelerating. The connector didnt seem dirty or anything when i changed the unit. The previous sensor just stopped working im assuming since my oil pressure gauge always read zero and never moved. There is No Knocking or ticking noises coming from the engine bay just the normal sound of a belt so in my search i never found out what to do after changing the sending unit, What should i do next?

Car is a 91 rs 305 TBI and it has about 90k on it. And since this problem started the car has been driven just about 3000 miles.

Ward

iTrader: (1)

Well, I would be inclinded to think that a brand new sending unit is working properly. However, the passage to it could be clogged with gunk. I'm not sure if TBI engines have the little brass pipe thing that the sending unit mounts to, but that could also be clogged.

Saber

iTrader: (2)

When i took out the old sending unit it was pretty dirty and gunky on the end. How would i get this hole cleaned out? It was a pain in the *** to get the old unit out because of the location. ANy other suggestions on what to do next? Im going to buy a mechanical gauge tomorrow but where would i hook that up to. I just wanna see if maybe the gauge is bad.

Ward

iTrader: (1)

Well, I would probably do it when you change the oil. I would get a bottle of engine flush, the stuff you add to your oil before changing it. Maybe try running some of the engine flush stuff down the sender hole, along with a pipecleaner or small bottle brush. You cold also try blowing compressed air down it, but I'd keep the pressure low.

NEWMAN1786

Im currently in the same boat but i have a zz4 tpi now im losing hp i hope im not ruining my engine maybe my valves need to be adjusted i do hear a little tapping what engine oil shoul i be using maybe thats the problem im sure that5w30 stuff shouldnt be in there and oil does get thinner when its hot

bjankuski

Remove the electric gauge and put in a temporary mechanical gauge to verify what your actual pressure is. I doubt the oil passage is plugged since you get a reading at start-up that drops after then engine warms up. If the pressure is really that low you need to find out why (bad pump worn engine or ???).

Saber

iTrader: (2)

Reaaally old thread lol. Ive got a 350 now, long story short, the 305 was clogged, and do i mean clogged, i ripped the valve covers off and man, was there gunk everywhere, i was getting oil from 1 rocker and that was it, the others were clogged up completly, it spun a bearing shortly after i flushed the engine out and unclogged it. The gauge works fine now and the sendign unit does also(its on the new engine).

In response to the question asked by Newman, i use 10w30 oil in my car, when my gauge was bouncing around i had a clogged oil system, im assuming you mean your loosing oil pressure and not HP? think of it this way, in the crank, when bearings are going they wiggle around creating a bigger hole somewhere in the crank, it takes less pressure to push something through a bigger hole right? That is along the lines of how my mechanic explained it to me when i took it to him after it siezed up on me. I know its probably overly simplified but i get the picture. And i can hear a Clicking when i open my hood, thats the valves and a clicking sound is normal.

BASSETT IROC 85

iTrader: (2)

I agree with bjankuski time to find out what is realy going on.

Saber

iTrader: (2)

i have a new motor now, lol and no oil pressure problems. Problem solved i guess lol.

NEWMAN1786

lol i still need help

89RsPower!

newman describe your problem in detail, and as far as I know gm recommends 5w30 for zz4's

evans87

I have the same problem with my 87 IROC 305 tpi. I have also replaced the oil pressure switch (looks like a bell and is by the firewall) but the problem was not corrected. I do have a little smoke on start up but it goes away after a few seconds. I have no strange noises comming from under hood. It is always serviced and has the proper level of oil. The car has roughly 67k on it and it is driven only a few times in the summer months. I would love to have the problem corrected and welcome any thoughts

NEWMAN1786

when i start the car up it runs at about 30 psi and when it gets warm it drops to zero i can hear minor lifter tapping and now my engine feels like it has loss hp but im currently getting my transmission rebuilt so ill be ablt to say more later on this week when the trani goes back in

89RsPower!

to both of you I recommend removing the oil pressure switches and installing a known good mechanical gauge and take a reading of your oil pressure and let us know what you find and we'll go from there.

servo2055chevy

How do you remove the valve covers?? is there any special precedure or tricks to do that??? And I can see from the oil filler hole in the valve covers that my heads have alot of gunk in there... same with the PCV valve hole. how do i flush that sh*t out??

305sbc

iTrader: (3)

Valve-covers: normally four bolts or nuts. Use a 10mm socket and medium extension.

The best way to clean the gunk out is to remove the heads and get them reconditioned, then reinstall them. If you try to clean or flush them while on the engine you are liable to have bad results that will end up needing a complete engine rebuild.
IF you are set against pulling the heads for cleaning and you still want to do it, then you can pull the oil pan and oil-pump and clean out most of the gunk with the heads still on the engine. This will give you a chance to clean out the pan, the oil pick-up, inspect and re-seal your pump, inspect your bearings, and run a cleaning rod through the passage that goes up to your oil pressure sender.

I think I left out the descriptions on photobucket, but here are some pictures of a similar job, where the owner had a leaking oil pan and wanted the oil pressure to be a little more solid in his work truck.
http://s702.photobucket.com/albums/w...ild/?start=all