fastblacktalon25

Okay guys, here's the history...

Bought an auto 93 RX with a blown motor. Knew a guy that did RX's, and he hooked me up with a motor, only it was a standard. Then, he brought me a new motor...also a standard. Decided this was a sign to just convert the damn thing. Got everything needed, and finished the conversion Saturday .

First thing noticed was a blown air pump...sparks and smoke every time it pulled in, so it's disconnected now . Know I can't pass smog wihtout it, but it's the least of my troubles. Car starts and idles, though a little rough. HOwever, as soon as the thing warms up, it loses all pressure, drops from 60 PSI to about 15. I read 55 is standard, so I don't wanna risk driving after all that work and money. Also, I've read that it could be the sending unit. However, I'm not getting any kind of MIL or any codes, which concerns me since I know it should be on...no air pump connected, and no oil level sensor either.

Any ideas or leads? I've dumped enough time, money and resources. Always liked the cars and loved my 89, but really learning to hate them!

SLOASFK

iTrader: (5)

what's a MIL? you mean a CEL?

Manuals and Autos have the same motor, only the flywheel is different.

The stock oil pressure sending unit is notorious for giving low readings due to dirty contacts. Clean the sending unit's contacts, it's located just under the oil filter pedestal. Also, do you notice an oil pressure increase when you rev the motor? The oil pump is mechanically driven by a chain that spins at the same rate as the e-shaft (functionally similar to a timing chain). The oil pressure should increase when you rev the motor.

Because oil is thicker when it's cold, your oil pressure will be higher when the engine is first started vs when it's completely warm. This combined with dirty contacts on the sending unit is probably what's causing your "problem".

Also, did your friend build the motor or is it a Mazda reman? Most Mazda remans are known to come with a shitload of grease clogging the oil pump.

When you say there's no "oil level sensor", you must be wrong because if there wasn't, your car would drain oil as fast as you can pour it in. The oil level sensor is on the oposite side of the oil pan as the drain plug, and it's about the same size.

Disconnecting the airpump wouldn't cause the ECU to throw a code, and if the oil level sensor is disconnected, it'd cause the low oil buzzer and light to come on, but not the CEL.


Sounds to me like you've bitten off more than you could chew with this "project". I reccomend you read up for a while. Everything a newbie needs to know is stickied at the top of this section. I don't mean to sound like a dick, but I am.

dhays

iTrader: (1)

Warmed up and at idle, my oil pressure drops down to about 20. Should be about 60 at 3000 rpm I believe.

I have a faulty stock sending unit. It occasionally reads very low, or even zero. I have an aftermarket oil pressure gauge that reads accurately. When I stop putting money in the car in other areas, I'll order up a sending unit from Ray and install it when I change the oil. I don't know if a bad sending unit would give you a code. I have seen none with mine.

I recall seeing a way to test the sending unit in the FSM. I'd try that first and see what it tells you. I've heard of trying to clean the sending unit contacts but haven't actually tried it. If you are pulling the sending unit to test it, then you sure can't lose anything by trying to clean it.

fastblacktalon25

Well, pardon me for not taking the advice. On the 3rd gens, the auto and manual engives are not the same, and it's more than just a flywheel versus a torque converter. The 3rd irons are completely different, which is why you can't mount a manual trans on an auto. You can get away with mounting an auto trans on a manual motor though...
I have done a lot of reading, though I'm sure not enough, granted. That is how I managed to reqire the loom and set up for the manual pedals and any other differences. Great write-up.
There really is no oil sensor. The hole in the pan where it bolts up has been covered with a plate instead. Whoever he got the motor from, I doubt it was a Mazda reman. It was a used one with a single turbo setup (hence the reason I had to do the rewire).
And yes, the oil pressure increases when it is revved, due to the timing chain under the front cover. However, that is not enough assurance for me to take the thing joyriding around.
Lastly, MIL - Malfunction Indicator Lamp. That's what it's referred to in the shop manual, service manual, and is pretty standard for automobile manufacturers. Is not quite sure what CEL is though...

SLOASFK

iTrader: (5)

There's probably more than 100 people on this forum who would vehemently disagree with you.
https://www.rx7club.com/showpost.php...5&postcount=16
https://www.rx7club.com/showpost.php...38&postcount=4

Think about this...How could it be possible for a manual transmission to bolt up to an "auto rear iron" but not possible for an auto transmission to bolt up to a "manual rear iron"? They are cast steel, if they fit they fit.

Though they may have "different" rear irons in the sense that the auto may have a thinner iron from a cosmo or something, the bell housing bolt pattern is the same.

Like I suggested, clean the contacts on the oil pressure sending unit. It's located underneith the oil filter pedestal.

CEL is Check Engine Light. It's pretty standard among people who actually drive motor vehicles.

hades

iTrader: (4)

is there any chance it could be the oil pressure regulators? I have the same issue, I have driven the car since oct. with the issue and its never had any problems. It just that in the back of my mind I wonder if the pressure regulators got stuck open or close (not knowing how the operate) the pressure could drop dramatically.

I have searched for oil pressure regulator operation, and low oil pressure, but I haven't found a good post to clarify anything.

Next oil change I will try to clean the sending unit or maybe just install an
aftermarket gauge to play it safe.

fastblacktalon25

I see no real reason to argue over this point. However, I doubt that you have more experience in this department, considering I have done it.

Thank you for the input - from everyone. I will clean the contacts. Now that I think about it, they both looked pretty gunked up. One of those things I meant to clean before dropping the thing in, and then forgetting with everything else. I will also look into teh oil pressure regulators and see what I can dig up.

mdpalmer

iTrader: (24)

Sorry if someone already chimed in, but I didn't bother to read the whole thread Pressure should be around 60 psi @ 3k rpm when motor's warm. My idle pressure is around 10-15 psi when motor's warm.

fastblacktalon25

Cleaned up the oil sender as people offered (and I figured). OIl pressure had some noticeable increase...stays around 60psi with more consistency, but dips every once in a while . I will clean the contacts a little better with electrical contact cleaner on the loom and maybe even some emery paper on the sender. However, something tells me I will probably end up changing out the oil sender just to be sure. Thanks for the input guys.

j9fd3s

iTrader: (3)

old news, but the oil pressure sender just goes right to the guage, ecu doesnt see it at all, hence no mil/cel

oil level sensor is like that too.