Eternal_Gamer

iTrader: (10)

Sup guys? I got a problem with the MOP(Metering Oil Pump) Control System. The car is a 1991 Mazda Rx-7 Turbo. I am getting a bad hesitation when I try to accelerate past 2000rpm or 10mph in each gear. It just bucks really bad when I try to advance anymore. I am getting MIL codes: 26, 27. I am using the factory service manual for troubleshooting reference. BTW, I did have MIL code 51, which is Fuel Resistor Relay. I replaced the fuel resistor relay and the code never came back. Next is the MIL Codes 26 & 27. I tested the MOP Stepping Motor Resistance at terminal +B1 and terminals SM1-SM3 = continuity. I did however get 24 ohms if i checked terminal +B1 and terminals SM2-SM4. The same thing for the other way around. If it was out of spec, the next step according to the book was to "replace metering oil pump". Luckily, I had a spare metering oil pump on a blown motor i have. The resistance on that stepping motor was reading 25-26 ohms on terminals +B1 and terminals SM1-SM3. Terminals +B2 and terminals SM2-SM4 also read 25-26 ohms. So I replaced the component which took an hour because I had to move the fan assembly for ease too. I fired the car up and took it for a spin. As soon as I accelerated to about 2000-2500rpm, the MIL came back on. I get the car home and check for MIL codes. Sure enough, it is No. 26 & 27, AGAIN! I check the resistance of the MOP stepping motor and it now reads like the defective MOP I just ****** replaced. So now I am screwed with 2 blown MOP's. I take a look at the troubleshooting again and flip the page and see that it says not to change the Metering Oil Pump until you do a electrical component inspection. So I messed up. So, the next step was to test Harness terminal voltage at terminals +B1 and B2 and I got 12v+, so thats good. The next step is to check Harness and connector continuity. terminal SM1 on MOP stepping motor and terminal 3S on control unit reads 0.03 ohms. The rest is the same on the rest which is SM2 and 3T, SM3 and 3U, SM4 and 3V. The book then says repair or replace harness. So I'm guessing my harness is screwed now. I tried the next step anyways which is testing the Control Unit terminal voltage. I test for 12v on ecu's terminals 3S, 3T, 3U, and 3V. They all put out 11.4v except 3s which put out 0v. So is my ecu and harness screwed now? Let me know what you think and get back to me. I really need to get my car back up and running, because its my DD for the moment since my 87 t2 still needs the new tranny. If both the ecu and harness are fucked, I'll probably go standalone ecu. but that is my last resort. Any help will be greatly appreciated.

SpeedOfLife

iTrader: (16)

disclaimer: I'm not experienced in this area, but could something near the OMP be causing it to break quickly, get in its way?

Eternal_Gamer

iTrader: (10)

I don't know what your trying to say. If your asking a question, then I can't answer it, because I can't figure it out myself.

SureShot

Your testing is very through, but there are some up front basic things the manual assumes at this point.

One is the ECU ground. It must be clean shinny bright metal-to-metal contact.

A common problem can also be the cheesy clip-on ground from the top of the bell housing to the firewall. Same thing - it must be clean shinny bright solid contact.

The hesitation can also be a bad spot in the sweep of resistance values from the TPS.

Some other up front voltage tests:
Engine running, headlights & heater fan on high (to load the alternator):
Alternator post to alternator frame = 14-14.5 volts (verifies the alternator output)
Alternator post to battery (+) = 0 volts (verifies the primary + wire)
Alternator frame to battery (-) = 0 volts (verifies the primary ground)
Back probe one of the solenoids near the oil filler to battery (+) = 0 volts on one of the wires (verifies the main relay & fuse connections)
Turn off the motor, but leave the lights on.
Battery (+) to battery (-) = ~12.5 volts and holds steady. (verifies battery)

SpeedOfLife

iTrader: (16)

Sorry, at first I was trying to figure out if the OMP is electrically powered or mechanically. Since I haven't searched for the answer I should just stay out of this.

Eternal_Gamer

iTrader: (10)

thanks. i jus got home. I will try these tests in a bit. I also called the guy at corksport and he told me to check all my grounds and says that my ecu can'tbe blown. so ill let you know how it goes.

Eternal_Gamer

iTrader: (10)

Ok, I tried all the tests, but I still get that hesitation. The hesitation is not at any specific rpm, its whenever I give it some throttle or my engine speed is pretty high for that specific gear. 1st gear I shifted at a little bit over 4000rpm and no hesitation. 2nd gear it hesitated at about 2800rpm, 3rd gear at 2300rpm. Im starting to think its my fuel pump. I am using the stock s4 t2 fuel pump with 155k on it. Since putting that in, I've been doing some good runs in 2 weeks with the mods in my sig but only at 10psi, but I think I am making more than the safe limit which is 250. Last year I put out 209rwhp at 10psi on a 110deg F day and I was running 12v straight from the battery and the fuel pump I had couldn't even send enough fuel to hold idle. Now I put on the HKS Racing Suction Kit, HKS TMIC, and tuned the F-Con for more fuel. It feels much faster at 8psi now than 10psi back then. Its very noticeable too. But since I put in the stock s4 t2 pump 2 weeks ago, I had turned the boost up for 10psi. So, I'm thinking I have to at least be putting out 220-225rwhp which should be near the safe limit, correct? Well, let me know what you guys think;

Eternal_Gamer

iTrader: (10)

id like to add that I did find a ground loose and fell off after i barely touched it. Is this ground shorting enough to fry an ecu?

SpeedOfLife

iTrader: (16)

^^ anything can happen

have you already tried things out after you secured the ground?

Eternal_Gamer

iTrader: (10)

yes, i have tried things out, but its the same.

micah

If you are getting codes 26/27, I highly doubt its your TPS, Fuel pump, or any other device OTHER than your ECU, Harness, or OMP (whether it be the position sensor or the stepper motor).

If you find out the ECU is dead, it wouldn't be the first time I've heard of an OMP dying and taking the ECU with it.

If it were me, I'd pull the ECU and find a known good one. Then measure the continuity of the engine harness ALL THE WAY to the OMP.. Then measure the OMP to see if its in-spec. Once I know ALL of those factors, put it all together again and fire her up. But right now there are too many variables that would make me afraid to put it back together without knowing.

Eternal_Gamer

iTrader: (10)

Did you read all my posts? I did a lot of tests already, including the ones you mentioned. When checking the continuity of harness, I got 0.03 ohms on all all terminals. The only one I failed was the ECU voltage at terminals 3S, 3T, 3U, 3V which is at 11.4v except 3S puts out 0v. The metering oil pump is out of spec of course. When I put a in-spec metering oil pump in and fired it up, it blew the metering oil pump and it became out of spec. So according to the tests by the FSM, I have concluded its the ecu, but I don't know what could cause it to blow. But the MOP failing and taking the ecu with it, does sound reasonable, but I just want to make sure if it is.

micah

Yeah, I just reiterated for posterity.... Yeah, thats it.

Sorry man. I know its gotta be frustrating. I'll shut up now.

RotaryResurrection

iTrader: (8)

It seems the OMP kills the ecu about 50% of the time when it goes out. So that even if you replace the bad OMP with a known good one later, you will continue to get the code because the control circuit inside the ecu was damaged.

Eternal_Gamer

iTrader: (10)

Thank you RotaryResurrection! I was looking for that kinda answer. I knew that the ecu had to be bad after my tests. I really just wanted to make sure what took it out. I wanted to make sure that the OMP is something that can take the ecu out and is something that is pretty common. My instructor advised me to check all my solenoids and stuff to see what went out and took out the ecu. I got code 51L Fuel Pump Resistor Relay and codes 26,27: OMP. I replaced the fuel pump resistor relay and the code never came back. The OMP however was replaced and it blew again. The resistance get reversed to the terminals straight across. So its out of spec. Well, thanks for the info. I will replace the ecu and OMP at the same so nothing gets blown. And if they both still get blown, then I will let you guys know. but hopefully that should do it.

RotaryResurrection

iTrader: (8)

The new OMP should not be bad, and should not be harmed by the ecu even if the ecu is bad. The only way to know is to try another known working ecu. The omp can kill the ecu, but not the other way around in my experience. If you are still getting the code with a known good omp, then it is because the control section in the ecu is bad, thus the ecu continues to report a connectivity issue...just because your wires on the outside are carrying good signal does not mean the board and components inside the ecu are as well...which is probably the problem.

Given the rarity of s5 turbo ecu's I would first pop in a cheap and easy to find s5 NA ecu and drive it out of boost to see if the code returns. If not then you can set to looking for a high dollar s5 t2 ecu. The NA ecu will operate the turbo engine with no issues provided you stay at very low/no boost.

SureShot

Handy with electronics?
Replace the three darlingtons that drive the MOP.

Eternal_Gamer

iTrader: (10)

Well, I checked the resistances on the bad OMP's terminals +B1 and SM1-SM3 and it is supposed to be within 15-35 ohms. It would read numbers out of spec. I tried the same for the opposite side terminals +B1 and SM2-SM4 and its out of spec. but if I change it around like +B1 and SM2-SM4 or +B2 and SM1-SM3, it would read 24ohms. I checked a spare OMP I had and it was in spec before I put it in. After I threw it in, and drove it, it hesitated and pulled the MIL codes 26,27 again. I check the resistances and its reading like the first bad OMP. I will try the NA ECU later tonight though.

Sorry for the lack of terminology, but whats the three darlingtons?

SpeedOfLife

iTrader: (16)

Are you hesitant to run premix instead of running the stock OMP? Because this would be another reason to do so.

RotaryResurrection

iTrader: (8)

Why? That is irrelevant to this discussion. On the s5 stock ecu, there's no way to remove the OMP, electrically. Even if you run dedicated premix you have to leave it plugged into the harness or the ecu will throw codes and keep the car from running properly. So...since he already has the codes and limp mode...the premix debate is moot. Whether or not he runs premix, he still has a bad omp/codes/limp mode to fix before the car will run.

Eternal_Gamer

iTrader: (10)

Sorry to say this but your questions and suggestions aren't helping me answer the questions I am asking. Just like Rotary Resurrection stated that it is impossible to remove the OMP from an S5 with the stock ECU. I am getting limp mode as it is because I am getting the malfunction codes. If I went premix, it would be the same. This is why I haven't done premix.

Did you read my last reply? What do you think about that situation with the good OMP malfunctioning after pluggin it up?

SpeedOfLife

iTrader: (16)

Chill out, I didn't realize it wasn't that easy on S5's to remove the OMP and have it work right.

I thought I was suggesting a feasible option, but now I know it isn't.

SureShot

Darlington: A cascaded transistor in one package. They look like a common 3 leg NPN transistor. They are commonly used to control power switching for stepper motors like the OMP and for the injectors.
Your local Radio Shack propably has them in stock.

micah

Do you happen to know the part number or value of those?

Eternal_Gamer

iTrader: (10)

the harness from the stepping motor to the engine harness was bad. I swapped in a new one and its fixed now. thanks for all the help.