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s5 omp welded open?

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Old 10-04-09, 02:08 PM
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Black 91 gxl
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Exclamation s5 omp welded open?

so i just bought a 91 gxl with a new rebuild and the guy said that the shop who he had rebuild the engine told him he should either "have the omp welded open" or remove it and run premix. at the time he didn't really know **** and they told him welding it open was easier so that's what he did.

so what i'm wondering is could this be reversed? if not should i just block it off and run premix, or is it possibly worth replacing the omp? should i expect to pass tailpipe sniffers at emissions?
Old 10-04-09, 02:23 PM
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It most likely can not be reversed. Remove the OMP and see if there has been any welding. Quite possibly, they just pulled the plug and cranked it open manually.

I was under the impression that if the OMP failed or was disconnected, the stock ECU would go into limp mode.


Does the paperwork from the rebuild indicate anything?
Old 10-04-09, 02:29 PM
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nope, paperwork doesn't say anything. can you elaborate on your explanation of what they did? i'm very knowledgeable about cars but new to rotaries and very new to omp systems.
Old 10-04-09, 04:53 PM
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Is the check engine light on? I would think welding it open would throw the code...
Old 10-04-09, 05:48 PM
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nope, no cel, car runs awesome.
Old 10-04-09, 07:28 PM
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Do you know if it’s getting oil? If it’s working what’s the problem? Idk if it will pass, as long as the charcoal, air pump and cats are on you should make it, you can run it a little lean too, and then change it back later.
Old 10-04-09, 07:36 PM
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well it definitely smells like it's getting plenty of oil.
Old 10-05-09, 05:16 AM
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assuming the dumbass did welded it
check to see how the oil injectors are plugged at the rotor housing.... a mirror or a finger, or a mirror with a finger would work. if your finger wont fit, use one instead of two, pinky instead of middle. if you feel weld there, just get a new engine.

check where the omp is - dumbass might have welded that too, then you need a front cover

your s5 emop is probably sitting somewhere in the engine bay so it is dry stepping, so it might fail soon


how about if you take some pictures of the engine bay so we can actually see what was done?
Old 10-05-09, 02:54 PM
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just realized today that there is no CEL because either the CEL bulb has been removed, burnt out, or somehow disabled. it doesn't turn on with the keys in the on position with the other hazard lights.

where exactly is the omp supposed to be located?
Old 10-05-09, 03:26 PM
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alright, well i found it. the fsm diagrams didn't really show that the air pump was in the way. from what i can tell it looks fine. all the lines are connected and look like they have oil in them.
Old 10-05-09, 03:26 PM
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facing the cabin, from the front of the car: the OMP is on the bottom left of the front cover.
Old 10-05-09, 03:30 PM
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alright, so now i'm wondering this. i know buying a mop block off kit is cheap, but from what i've read, i have to buy something like this http://www.digitaltuning.com/index.p...age=1&ecu=S5NA to do it? because if you remove it and just keep it plugged in somewhere in the engine bay it can short the ecu, and if you completely remove it, the car will go into limp mode correct? are there any cheaper solutions?
Old 10-05-09, 03:33 PM
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on the passanger side of the engine under the airpump. if it's welded it wont have wires running to it. look for two big white plugs near the intake manifolds they should be tied together. see where they go to.

you'll need that chip to go premix.
Old 10-05-09, 05:48 PM
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you can run premix and block off the omp. Just keeping it pluged in keeps the ecu thinking its getting oil. It wound short out the ECU. While your messing wit ht ii would check the voltaged wit the fm of the omp and the ecu omp wires.... just to be safe
Old 10-05-09, 06:57 PM
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Originally Posted by Ryan123
It wound short out the ECU. While your messing wit ht ii would check the voltaged wit the fm of the omp and the ecu omp wires.... just to be safe
not to be a douche, but could you repeat that in english please? i guess it's always 5 o'clock somewhere
Old 10-10-09, 03:17 PM
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Yea sorry about that lol typing on your phone during school can get messy.

It Will not short out the ECU(having the omp plugged in, off to the side while running premix).I would check the voltage from the ECU to the pump, and run the omp inspection and match the following results with the fms.
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