OMC Cobra 5.0L EFI Spudder

[Ocean 22]

Re: OMC Cobra 5.0L EFI Spudder

I have the same engine, and i was having the exact problem with my engine. I was finally able to fix it last weekend. The problem was in the wiring that goes to the distributor from the main engine harness. I checked the connector that connects the distributor to the main harness, and found that there was a purple wire with black stripe that had cracked insulation, and it was rubbing next to the ground wire that is next to it on the harness. I checked that ground wire, and it was not getting a proper ground. The ground wire does not have any insulation on it. on my engine it is just a bare wire. You can check that wire for a ground by using a test light connected to the battery positive. I removed the tape on part of the harness and spliced a new wire to that ground, and connected straight to an engine ground. I attached it to the bolt that holds the starter solenoid to the engine bracket. I took the boat out yesterday, and now it gets up on plane and revs up to 4500 rpm at WOT. Check this out before you spend thousands at a shop.
I hope this helps. Let us know what happens.

 

[Ocean 22]

Re: OMC Cobra 5.0L EFI Spudder

CHECK THIS OUT I FOUND IT ON ANOTHER POST.
Disclaimer: never worked on an OMC/Ford 302 EFI engine, all of this comes from general Ford 302 SEFI experience, which I know this system is based on. If any of this data is wrong, I apologise. Also, please be aware this stuff assumes that there is a supply of known clean fuel, clean fuel filters, and good ignition parts in place. It also assumes that there are no other obvious problems such as the busted exhaust flapper thing mentioned above. Check that stuff before poking and prodding at the EFI junk, since more often than not, its not going to be the problem.

When checking the timing on a typical injected Ford motor, there is a connector that must be unplugged to set the base timing. Usually its right next to the distributor in the harness going to the TFI module. If these use a remote mounted TFI ignition module (looks to be the case judging by the pic of the distributor) it will be near the TFI module. Connector is a small black thing with two wires on it. Unplug it, and set the base timing to factory specs. Timing marks are stamped into the balancer, may need to wire brush them to find it. Do not use the groove on the balancer, its unrelated to setting the timing. Also be sure you're on the BTDC side of zero, or it will run real bad. TIming is set to the flat edge of the timing pointer. You should also hear a difference in the idle with this plugged in vs unplugged. It can be connected with the engine running without breaking anything. If you watch it with a timing light, you'll see the timing marks move with the connector in place.


The EFI system also has a total of 3 temperature sensors. The coolant temperature sensor is a two wire affair for the ECM. Looking at these exploded diagrams, its front port side of the lower manifold, item 69. There is the temperature guage sensor, single wire thing, front stbd corner of the lower intake, item 25. There is an air temperature sensor two wire thing on the lower manifold behind #5 injector, item 28. Not sure which of these OMC uses for their low power mode, but if you're unplugging the wrong one, it might cause problems. Most likely its going to be the coolant temp sensor though. The two ECM sensors are easy to test with a voltmeter, charts for expected value relative to temperature can be found here:

http://fordfuelinjection.com/?p=10

Key on, engine doesn't need to be running to check this but it won't hurt. Values will drift as it warms up though. WOuldn't be a terrible idea to check it engine cold and engine hot to see if you get sane values.

If they're using a MAP sensor, the vacuum line must be connected. I don't see one in the diagrams anywhere, but its a flat black thing, about the size of a deck of cards with one connector and one vacuum line. This determines engine load. With no vacuum, they typically run horribly rich.

TPS should also be checked. Its mounted to the top of the throttle body and has 3 wires. If its using typical Ford wiring on the sensor, meter from ground to the green wire. You should see about 1v with the throttle closed, and it should smoothly increase to about 5v WOT, with key on and engine not running. Idle voltage is OK anywhere from .8v - 1.2v but its normally roundabout .9-1.0.

Fuel pressure at idle with the vac line on the fuel pressure regulator (item 60) is 30-35 psi, no vacuum is 40-45 psi. At WOT, I'd expect to see 30-35 but 29 isn't going to cause any problems.

Injectors are usually not an issue, and if one is bad you'll usually feel a dead miss, or have a rich running condition that can be tracked to one cylinder. Assuming these are typical Bosch injectors used on all other Fords of that era, they're cheap and easy to get at parts stores. Need to know which color the top of the injector is to size it properly, but you don't have to pay OMC prices for one.

Is there an engine diagnostic connector on this thing anywhere? If its of the typical Ford type, you can pull codes with a test lamp and a jumper wire. Not sure if the codes may be tweaked per OMC spec, but it surely looks like a regular old Ford EEC IV brain to me, probably with an altered program but there isn't anything special about that computer.They're quite durable, and almost never the source of problems on an EFI Ford.
__________________
1993 Rinker FiestaVee 300
twin 5.7L/Bravo
newly appointed with Bravo III lower units

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

I have the same engine, and i was having the exact problem with my engine. I was finally able to fix it last weekend. The problem was in the wiring that goes to the distributor from the main engine harness. I checked the connector that connects the distributor to the main harness, and found that there was a purple wire with black stripe that had cracked insulation, and it was rubbing next to the ground wire that is next to it on the harness. I checked that ground wire, and it was not getting a proper ground. The ground wire does not have any insulation on it. on my engine it is just a bare wire. You can check that wire for a ground by using a test light connected to the battery positive. I removed the tape on part of the harness and spliced a new wire to that ground, and connected straight to an engine ground. I attached it to the bolt that holds the starter solenoid to the engine bracket. I took the boat out yesterday, and now it gets up on plane and revs up to 4500 rpm at WOT. Check this out before you spend thousands at a shop.
I hope this helps. Let us know what happens.

Sure glad you found a fix....
I'll do some digging around the wiring harness' to see if there is anything similar going on.

Thx for the report !

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

Well, I checked the wiring, and located the same harness, my wires were all intact and looked fine. I measured the bare wire to ground, and it measured ~ 8 ohms. So I clipped on a redundant wire to ground and it lowered it to about 3 ohms. But, I still have the problem when reving past 2500 rpm.

I think I'm going to pull it out of the water and do some testing in the driveway. I want to figure out the trim sensor and wiring anyway....

Thx - Dan

 

[Ocean 22]

Re: OMC Cobra 5.0L EFI Spudder

Update:
I took the boat out this weekend, and it was running great, however later in the day the i was running at WOT, and the rpms went down to 2700 rpm. it started spuderring and would not rev up any higher in gear, but in neutral it would rev up to 4700 rpm with no problem.

I HAVE STARTED TO THINK THAT THIS ENGINE HAS SOME MAJOR PROBLEM WITH THE COMPUTER.

when i took the boat back home and i ran it in the driveway it would rwev up in gear. I am getting tired of constantly trying to get this engine to run correctly. Let me know if you have found a Fix?

 

[180shabah]

Re: OMC Cobra 5.0L EFI Spudder

Revving the crap out of your engine with no load is diagnostically irrelevent (it'll do 4700 on two cylinders) and can lead to some very costly damage.

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

I didn't have a chance to pull it out this weekend....
Mine will spudder in neutral as soon as I hit anything greater than 2500 rpm.
I gonna pull it this week and see what I can see.
If I strike out, then its off to the dealer : (

 

[Ocean 22]

Re: OMC Cobra 5.0L EFI Spudder

have you been able to find the cause of the problem? please share your findings. Thank you

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

I pulled the boat yesterday, I'll be messing around today and through out the weekend. Haven't found anything yet.
Will chime back in w/ any discovery

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

Okay so I located the wiring and connector for the trim sensor, and it pretty much is measuring open. So I tried placing a few different resistors in place of it where the guage read between 1/2 way and full down. (typical running position) It was a 50 ohm resistor.

Ran it up, and it still starts cutting out after 2500 rpm.
So my guess is that the trim sensor is not feeding the ECC.

I did notice that the arm on the trim sensor barely moves in the full down position, there is still about 4/5 travel left in the arm. seems like there is something missing like a doughnut or a bracket or something that makes for full travel of the sensor. I can put the trim up just a little bit, and it doesn't touch anything at all???

So back to the drawing board on the trouble shooting : ( >

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

Did some more testing today w/ a neighbor who happens to be a mechanic and better versed in code checking.

The code that we were seeing during test were 11, and 12.
11 = System pass
12 = RPM over range limit.

We un-plugged the battery to clear all codes, powered back up, and read just the 11 (system pass)
Ran it at idle for a few minutes, re-read codes and got 11 again.
Took it into failure mode, read codes and got the 12 back.

So, the system is sensing a rev limit of sorts, but doesn't point to the culpret that is causing the failure.

He suggested after looking at the wiring diagram, that it could be the knock sensor, or know sensor amplifier. We searched around the block for the sensor and the wiring, but couldn't find the sucker. must be burried in a crevas on the manifold or something.

Anyone have any idea where it might be located?
Once I locate it, then there are a few tests I can run on it.

He has a scanner at work that he's going to bring home tomorrow to see if we can find something. Plus one of the guys he works with is has a lot of experience with boats, so he's gonna ask him some questions too.

Thx - Dan

 

[Ocean 22]

Re: OMC Cobra 5.0L EFI Spudder

The knock sensor is located on the rigth side of the engine behind the head. you have to look near the fuel resevoir. It is somewhat hidden, however the wiring for the module is also in that area. good luck let us know how you go about testing the nock sensor and the module.

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

The knock sensor is located on the rigth side of the engine behind the head. you have to look near the fuel resevoir. It is somewhat hidden, however the wiring for the module is also in that area. good luck let us know how you go about testing the nock sensor and the module.

Okay - I'll check that out - Thx !
Figured it was burried / hidden somewhere....

 

[gadget73]

Re: OMC Cobra 5.0L EFI Spudder

Code 12 is idle rpm out of range. Has someone messed with the "idle screw" on the throttle body? Thats not an idle screw, its a throttle stop screw. It should be set just in far enough so that the plate doesn't quite bottom. Idle speed control is done with the idle control motor on the side of the throttle body.

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

Code 12 is idle rpm out of range. Has someone messed with the "idle screw" on the throttle body? Thats not an idle screw, its a throttle stop screw. It should be set just in far enough so that the plate doesn't quite bottom. Idle speed control is done with the idle control motor on the side of the throttle body.

Thanks, but according to the list, code 12 is:
RPM outside Self Test upper band limit.

I have not messed w/ the idle screw. It idles fine, and runs smooth all the way up to 2500 rpm, both under load or in neutral.

It's definately getting Rev Limited by the controller, but whats causing it is the mystery.

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

Well, I can see the wiring harness, but I can't see the K.S. nore can I reach my hand in far enough to follow the wires to the sensor.
Looks like I'm SOL on this one.

Now I need to decide where to take it to get fixed.
Or, I may just put it back in the water and at least use it for putting around the lake.
So, a whole summer goes by, no skiing, wake boarding, tubing...
Woah is me, guess I'll have to spend more time around the pool, or on the golf course......:redface:

 

[gadget73]

Re: OMC Cobra 5.0L EFI Spudder

Thanks, but according to the list, code 12 is:
RPM outside Self Test upper band limit.

I have not messed w/ the idle screw. It idles fine, and runs smooth all the way up to 2500 rpm, both under load or in neutral.

It's definately getting Rev Limited by the controller, but whats causing it is the mystery.

well, on a standard Ford setup, code 12 refers to the idle speed, basically it means the idle is too high. Should be 600-700 rpm. If its above that, I'd bet thats the issue. Most often thats caused by someone messing with the screw, usually to work around a bad idle control motor which is the root of the problem. If your idle is where it belongs, thats likely not your issue.

Mind you I have no direct experience with the OMC specific implementation of this computer system, but I've worked on a whole lot of EFI Ford products that use the same engine controls. OMC may have tweaked the programming some, so its very possible those codes mean something slightly different. I have to suspect if that comes from the engine running test though, that its not any different from the standard Ford meaning. During the engine run test, the throttle is left in the idle position, so it can't mean a WOT rev limit.

As for the knock sensor, does it actually have one? Lots of Fords did not, but if you did have one, it should be on the starboard side of the block, just forward of the bellhouse cover and above the starter. Its probably tucked down there right where the exhaust pipe comes down, so its likely not real visible.

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

Thanks for the info, it really idles fine and has never been an issue.
Thus, I never had the need to adjust the screw.
After reading some things on the Ford forums, I know that not all models have the KS. But it is shown on the wiring diagram in the manual that I have.
It may not be there...I can't see back there anyway, but I'll give another try in the location that you suggested.

Thx - Dan

 

[Danno5.0]

Re: OMC Cobra 5.0L EFI Spudder

Might have made some headway today.....
I found the Knock Sensor where Ocean 22 said it was.
Just couldn't see it until I opened up the rear compartment for the Bimini Cover:

There it was in plain sight, and I could even reach it well enough to inspect the wiring and the connector. I confirmed the wires w/ the manual....
I decided to clean the connector and contacts, as log as i had it apart..
A friend told me how to do a static test on the KC:
I have a meter w/ Frequency on it, so I probed the wire from the KC to the amplifier w/ a saftey pin. Turned the ingition on and observed the meter while I created my own knock w/ a mallot and a long socket extension.
Banged it a few times and observerd the freq jump up and down.....
Next, I monitored it with the engine running, and as I increased the throttle, the freq increased along with it.
Much to my suprise, I could take it all the way up to 3500 rpm w/ no spudder.
Ran it up a few times to find out that now it starts to spudder when I exceed 3500 rpm. Could this be becuase I'm in neutral or no load??
I tried the same in gear, and it did rev limit at 3500 rpm...

Not sure if the ECC know that its not under load and decides to rev limit the engine. Seems logical to me....
Might have to put er back in the water tomorrow and give it a try under load.

Crossing my fingers

 

[gadget73]

Re: OMC Cobra 5.0L EFI Spudder

A rev limiter in neutral wouldn't surprise me. That would actually be a good idea. Outboard motors have done this for years, but with a somewhat more basic system that just doesn't let you push the throttle very far when not in gear.