Fire85GSLSE

iTrader: (29)

Ok, need the S5 gods out there to tell me what is the deal with this.
****** For those of you who don't know, don't reply!*********


Car is a 90 S5 Vert NA Auto a friend bought trying to get into rotaries.
Well he got screwed on this car from the last owner telling him it just needed a fuel pump so he bought it.

The car runs very poor and has no power.

I looked up the OMP test proceedure (D-17) thinking that it had something to do with it. Checking resistance between B1 and SM1/SM3 I got 26 ohms on both (16-31 is the range). So I moved on to B2 and SM2/SM4 I got 28 on one and 1.26 on the other.
Ok so the FSM says to replace the OPM. So I go get a S5 cover I had with an OMP on it and check those values the same way and they all tested fine, within spec.

So before I plan to swap out the OMP I wanted to check the voltage of B1 and B2 on the harness side of that plug. The FSM says you should have 12v on both B1 and B2. I got 10.2v on them both. The FSM says if no 12v then repair or replace the harness. (Ouch, that is a big job and will not be able to do it for him this semester.

So my question is Can I check some where on the ECU itself to see if it is giving the right voltage or is there another way to test the wiring harness before we even think about replacing this one?

Fire85GSLSE

iTrader: (29)

Anyone know anyone in B'ham that could do this work? His car is in my drive way but he might tow it home.

vaughnc

Well if the OMP is bad, the car will run in "Limp Mode" which prevents the car from revving. Before you spend allot of money though, if you can warm up the car then do a compression test on the engine. The hand-held compression testers used in Piston cars won't work, they're way off in measuring a rotary's compression. Best bet is to have the local Mazda dealership do the test (you'll get 6 compression numbers, one for each rotor face).

Now that might not be the most "time friendly or convienient" advice, but it's the cheapest and most sure fire way of knowing the engine's good. Just have a buddy tow it (or rent a u-haul toe dollie) to Mazda, warm up the engine, and have them do the test.

If the car has good hot-compression (after it warms up) on all 6 faces, then you've got a good deal. Like you said, it's a matter of either fixing the OMP or the OMP wiring harness. I'd go for a pull-a-part / salvage OMP first before dumping money into a new one (assuming you're not in a rush).

Also hit-up someone on the Tenessee rx-7/rotary club and they'd probably be more than happy to help.

Fire85GSLSE

iTrader: (29)

vaughnc, thanks for the help but that did not answer the question I was asking.
The car has good compression on all 3 rotor faces and on both rotors. Did that first thing. Also the fuel pump has been replaced with a new one (he did that before he brought the car to me).
I don't take nothing to Mazda as they are lost and tell you things that are not ture. I do have a crewcab diesel truck and a 18ft flat bed truck but again not gonna take it to Mazda unless the owner wants to.
As for the OMP, it is bad and is causing it to go into limp mode. I have tested it (see 1st thread) and also have plugged up a good one (tested it also) and still runs the same.
My problem (see 1st thread) is that the harness side of the plug reads 10volts when in fact the FSM (Factory service manual) states it should have 12v.
So what I need to know is can I test this circuit at the ECU or anywhere else on the car to see if I can get 12v or is there any relay that might cause this to get pulled down from 12 to 10 volts.

Fire85GSLSE

iTrader: (29)

Well, Mike if your on here it is not looking to good. Let me know what you want to do with the car. She is ready to be towed home or what not.


Anyone........

BlueTII

Have you bothered to pull the engine error codes? There is a how-to on our website. If the OMP is bad it will throw a code. Typically is the OMP is bad it also takes out out the driver in he ECU, which means both should be replaced.

Fire85GSLSE

iTrader: (29)

No I have not but I will try to find it and do it.
I really wish I could tell him exactly what was wrong and what it would take to fix it.

totpkg

Swap out the ECU ... quick and easy

Fire85GSLSE

iTrader: (29)

Don't want to swap it out with other things wrong. Would hate to loose two ECU's ....... think about it.

Boost Lee

iTrader: (3)

Did you get a 10V reading with the car running or just with the key in the on position?

Fire85GSLSE

iTrader: (29)

10v with the key "just On" like the factory FSm states to do.
Then I walked over to my 91 TII and did the same thing and got 11.8 with the key just on.

The car will run sometimes and sometimes not. When it does it is very poor, smokes on and off and has no power.

I am gonna try to pull some codes today on it and see what it reads.

Fire85GSLSE

iTrader: (29)

get this, I grounded the green connector to get the code from the ecu. Well nothing..... no flashes from the check engine light at all.

I also tightened all connections on the battery and try to start the car and it will not start.
Called the owner and he told me the check engine light was flashing off and on when he first got the car about 3 months ago. Now the car has not been driven since he got it due to it having no power.

I am thinking it has a harness issue somewhere since somtimes it starts/sometimes it dont, and since it was giving him the codes before with out grounding the green connector.

Any ideas????

I know the OPM is bad on resistance, but when I just plugged in the one I have it ran the same. So with the harness only giving 10v's instead of 12's I am thinking the harness is grounding somewhere/ is bad/ or the ecu is shot.

Wait....... I wonder if the stupid *** that rebuilt the car and used S4 body parts on this S5 used the s4 ECU also.
NEED ATO CHECK THE ECU NUMBER....... be right back.............................................. .................................................. .......................

Fire85GSLSE

iTrader: (29)

ECU is a 353 so I think it is correct.

OK, so if I tell him to get a ECU, harness, and an OMP does he have to use the 353 or would any S5 ecu work? I ask this because he has a S5 Automatic Vert.
Thanks for the pm's and replies.

NZConvertible

The 12V the FSM calls for is battery voltage that comes straight from the main relay. It has nothing to do with the ECU or grounds. First check the voltage at the battery and recharge it if it's low. If it's okay check for battery voltage at the main relay (ignition on). If that's okay check the wiring resistance between the main relay and the OMP plug.

Fire85GSLSE

iTrader: (29)

Sounds good. Might just swap that battery with my red top from my TII.
That way I will know the battery is strong and see what those readings are again.

That will also allow the ECU to reset and maybe my extra OPM that tested good will fix his problem although I hear that if the OPM goes out most of the time it takes the ECU with it.
Thanks

NZConvertible

Measure the battery voltage before going to the hassle of swapping batteries. Similarly resetting the ECU is easiest done by pulling the BTN fuse, pressing on the brake pedal for a few seconds and reinstalling the fuse.

RotaryResurrection

iTrader: (8)

Swap the ecu and omp at the same time, trust me. They generally fail together...rather the OMP kills the ecu, as Chris said above. I have both parts, if you need...

RRTEC

iTrader: (13)

Chad check your PM's.

RRTEC

iTrader: (13)

I read that sometimes if you plug a new OMP in without changing the ECU the computer will pop the OMP (opposite of normal where the OMP blows the ECU) so check the new one and make sure that it is still good after pluggin it back in.

THe omp's motor acts like a resistor (kinda) so if the motor gets shot an incorrect voltage will be fed back to the ECU burning that bad boy out.

Good luck Chad, I really think that if you swap both out at the same time you should be good. And you can move another car out of the yard..lol

Fire85GSLSE

iTrader: (29)

Check pm

Fire85GSLSE

iTrader: (29)

Well after looking over the wiring diagramof that circuit I decided to pull the Battery, the ECU and unhook the OMP. I plugged in my OMP, my S5 ECU, and then installed a good battery. I tested the voltage of that circuit before I try to start it and it read 11.8v so I was happy. I tried to start it but it was flooded bad. I did the MMO deflooding proceedure and hooked it all back up. I hit the ket and she ran, then shut off. I hit the key again and she ran and kept running. After the tons of smoke (Called dispatch to let them know incase someone called 911) I felt froggy and took it for a spin. Holy crap batman the verts are slllllloooooowwww as crap, but this one is running and running good!

Just got off the phone with the owner who just went back to AL this morning to tell him the news. He will be back this weekend coming up to take her her home and one less rotary in my drive way which makes the wife happy.
Now to get back to my repu!

Thanks for all the help everyone! I am sure Mike will thank you also once he gets on here.

RRTEC

iTrader: (13)

Why do you think I HAVE TO turbo mine...