Tricky919

Kr1276, i had the same problem with one of mine on my old boat....

Island Hopper

Alli,
The information for the sensors is in the PCM 555 manual #33. It lists allot of the sensors, and what the resistance readings should be. The regular 496HO service manual is probably the weekest manual, Merc. has put out to date, especially regarding the smatcraft system. I guess that is why they have an additional one. I just checked again, 10.1 + or - 2% ohms is what is stated in the manual. When I checked my old one it read .9 ohms, and a new one fixed the problem. So I think you are on the right track.

docmanrich37

Had problem like that end up being a bad low drive oil sensor.replaced the oil jug with new sensor and since then no buzzer except the rev limiter.operator error.

Island Hopper

Any Luck?

Alli-Runner

Island Hopper,
You the man, for now! Swapped the IAC this morning and no problems running on the hose. Will lake test it on Saturday. Thanks for the help and will update this weekend. Appreciate the help!

Island Hopper

Sounds good, let us know after you run it.

Alli-Runner

The IAC fixed the problem. Thanks Island Hopper!

Island Hopper

Glad it worked out.

Baddogg

sounds like you know something about 496 mags. heres my issue. twin 496 28ft pantera port has a pop at low rpm. ddt shows nothing , pop seems to go away after 12-1500rpm. shows both motors running within 50 rpm at w.o.t. problem is a sob any ideas???every test imaginable done to no avail compression.leakdown. how about injector problem???

Raylar

Badddog:

On the 496's we have seen some weak injectors that for some reason have a weak operation at idle up to about 1500rpm, then the fuel pressure increases enough to overcome the sticky or weak injector and the motor seems to smooth out, only to start popping again below 1500rpm. First thing to check is fuel pressure. Put a fuel pressure guage on the schraeder valve on the injector fuel rail, disconnect and plug the small rubber vacume line that runs from on top of the intake manifold down to the cool fuel pump system Turn the key on and read fuel pressure, it should be at least 39 to 40 psi. Start the motor and the fuel pressure should be a minimum of 42 to 43 psi. If the pressure is moderatly lower it could be a bad regulator on the cool fuel system cooler. The lower fuel pressure will not generally set a code on the scanner, but the engine just won't run right. If the pressure checks ok, you should probably suspect a bad or weak injector. With the scan tool you can actually fire each injector seperatly and listen for the injector operation with the engine not running, but the key on. The only other item we have encountered with a slight miss at lower rpms has been a bad crankshaft position sensor or sometimes a bad IAC motor, however these usually set codes for themselves on the scanner. Hope these findings help in your search.
Raylar