...how long did it take you to replace the damn thing? I'm trying to estimate how much time I have to spend on replacing the OMP on my S5 vert.

If only these rotary babies would stop breaking down once in a while...

D

 

if you have a replacement it shouldnt take more than an hour or two. just be carefull not to snap the clear oil lines since they are pretty brittle. otherwise its a straitforward unbolt the old one-bolt on the one one affair.


as long as you have a 6" extension its not to hard to get at, dont have to pull anything else. take the 4 lines off before you unbolt the whole thing.

 

Hmmm...2 hours only? Wow, from the manual I got the impression that it takes more than that. Anybody out there with a different experience?

 

I am currently replacing the seals on my S4, and if i am correct i belive the S5 has the electric OMP. But it only took me about 2 hours to get it off because i pulled off the air pump air box and a few other things in the way. Otherwise it was pretty easy. If you dont have access to a lift lift up the front and unbolt the bottom shrouding (easy to do with a speed wrench) and the bolts you cant easily get to on top can be reached w/ a universal and extension on the bottom. oh yeah and you will have to drain your radiator to remove both of your hoses. I got my O ring and gasket from mazdatrix today and when i get back to school on monday i should be able to get it back together in less than 3 hours.

-brendan

 

You could always run premix.

 

Thats true and probrably more reliable if you can keep your oiling fairly accurate but i just hate the idea of premix and plus the cost of putting all that oil in

 

Maybe an hour at the most to replace an MOP... they are very easy to get to from under the car.

 

Question: How do I get rid of the ECU warning if I want to run pre-mix (without taking out the OMP and blocking it off) so the car wouldn't limp?

 

it will limp if you unplug the OMP you have to leave the OMP bolted up and electricaly connected. no one has figured out a way to fool the ecu into thinking its there another way. what you can do is get a block off plate, yank the worm gear out of the omp that sticks into the engine and bolt the plate back inbetween the omp and the engine. thats as good as it gets unless you go to stand alone EMS.

 

Hmmm...so if I leave the broken OMP in, reset the codes, and then run pre-mix, the ECU should still recognise the problem (and thus go into limp again) right?

I'm confused.

 

if it is throwing a code and putting it into limp mode right now, yes, it will do so even if you rin premix. the ecu MUST think that there is a FUNCTIONAL OMP on the car in order to run properly. the way it knows it is functioning is through the electrical sensors pluged into that go to the harness. S5 omps are notoriously flacky (as in they will fail, not even throw an error code, and then your engine will sieze in a matter of miles) so i say your best bet is to fix it enough to not put the car into limp mode and then just run premix. its not worth gambling your engine on a dicey OMP.

 

not entirely correct. my electrical omp died on me. i got a replacement and zip tied it to the side of my engine bay and plugged it in. the ecu sees it and is fine with it. it doesn't have to be bolted up to the engine. running premix now.

 

In therory, there should be a way to bypass the computer error, by measuring the coil resistance of each of the 4 stepping soleniods in the S5 MOP, and putting that resistance (and probably also the inductance) on the Black/Orange, Black/Blue, Black/LtGreen and Black/Red stepper motor leads.

So if the soleniods rest at 20 ohms then a 20 ohm 5 watt resistor on each pump wire should be fine to bypass that stepping motor/soleniod.

The only other trick required would be to make the ECU think that the voltage of the position sensor is changing.

The best bet for this would be to try a 1 ohm resistor, but because the ECU wants to see a change in voltage, you may have to build RPM shunt.

This would require either tapping off the RPM feed wire through a diode and resistors to the sensor leads. I have not personally tried this, but in worst case you might have to actually build a mirror circuit. In simplest case, a 3 amp diode and a 6 ohm resistor in series and a 4.7K ohm resistor "T"d into the wire between the diode and the resistor, other lead to 12volts.

Now mind you I have not personally done this, but simply suspect that it would work based on the electrical schematics and ECU schematics.

 

wow i looked around for quite some time trying to find a way to do something like this. icemark, have you actually seen instructions or heard of someone doing this that maybe would have a diagram of what you just described to work off of? i would love to be able to do something like this.

 

nah, its just from looking at the schematics and the specs on the MOP.

I have not tried it. I do not have a S5 OMP to test it out with. If someone wants to send me a broken or working S5 OMP, I'll build the circuit and test it, then send it and the MOP back for testing in a S5.

 

you would be able to build it with a broken omp? maybe i'll see about pulling off my broken one and putting on a block off plate since my working one isn't actually bolted to the engine .

edit: know where to get a block off piece for the omp?