496 HO engine trouble - calling Ray@raylar
#13
Registered
![Default](/forums/images/icons/icon1.gif)
I agree with BBB, could be a fuel contamination issue.
It is not that unusual to find cam and crank faults in the fault code history even when both are fine. I am assuming these are not active faults which would trigger a steady audio alarm. Check the resistance according to specs below.
Camshaft Sensor - A to B 24.04 mohms and B to C 24.05 mohms
Crankshaft Sensor - A to B 23.2 mohms and B to C 23.21 mohms
What is the 5 volt sensor circuit doing when the problem occurs? Is it maintaining 4.9 to 5 volts?
I have also seen secondary voltage leaks near the ECM cause "phantom" problems on the 496. You have ignition coils directly below the ECM. The Electro Magnetic Interferance (EMI) from a 40,000 volt discharge (spark jumping to ground) within a few inches of the ECM will cause the engine to stumble. Sounds unlikely, but I learned that hard way that it can happen.
Dave
It is not that unusual to find cam and crank faults in the fault code history even when both are fine. I am assuming these are not active faults which would trigger a steady audio alarm. Check the resistance according to specs below.
Camshaft Sensor - A to B 24.04 mohms and B to C 24.05 mohms
Crankshaft Sensor - A to B 23.2 mohms and B to C 23.21 mohms
What is the 5 volt sensor circuit doing when the problem occurs? Is it maintaining 4.9 to 5 volts?
I have also seen secondary voltage leaks near the ECM cause "phantom" problems on the 496. You have ignition coils directly below the ECM. The Electro Magnetic Interferance (EMI) from a 40,000 volt discharge (spark jumping to ground) within a few inches of the ECM will cause the engine to stumble. Sounds unlikely, but I learned that hard way that it can happen.
Dave
#14
Registered
Thread Starter
Join Date: Feb 2001
Location: Stuttgart, Germany
Posts: 38
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
Thanks very much for the information so far!
Here is todays update:
- no water and no dirt in the water seperator....
- no dirt or debris on the screen of the inlet of the booster pump.....
- no fault codes when engine is at idle
- fault codes of cam and crankshaft sensor when under load, but these fault codes do not stay in the memory when engine is shut off and then is restarted
- all injectors tested ok
- fuel pressure stable at idle and under load, no fluctuation
- Batterie and ground connection of engine checked out ok twice...
- meassuring the resistance of the sensors produced strange readings..about 9 kohms
Ordered both crankshaft and camshaft sensors to replace the current ones. If that doesnt cure the problem I will tear this electronically overengineered piece of s*** out of my boat and put in something simple with a carb and a mechanical fuel pump! Any 540s on sale?
-
Here is todays update:
- no water and no dirt in the water seperator....
- no dirt or debris on the screen of the inlet of the booster pump.....
- no fault codes when engine is at idle
- fault codes of cam and crankshaft sensor when under load, but these fault codes do not stay in the memory when engine is shut off and then is restarted
- all injectors tested ok
- fuel pressure stable at idle and under load, no fluctuation
- Batterie and ground connection of engine checked out ok twice...
- meassuring the resistance of the sensors produced strange readings..about 9 kohms
Ordered both crankshaft and camshaft sensors to replace the current ones. If that doesnt cure the problem I will tear this electronically overengineered piece of s*** out of my boat and put in something simple with a carb and a mechanical fuel pump! Any 540s on sale?
-
Last edited by Preuni; 06-03-2005 at 01:09 PM.
#16
Charter Member # 90
![](https://www.offshoreonly.com/forums/images/icons/charter_member_star.gif)
![Default](/forums/images/icons/icon1.gif)
I didnt read all these post but I had a similiar problem. I unplugged the knock sensor and WOW!!!! There was the problem and it ran like a spotted ape!!! I replaced the old one with a new one after that weekend and it was still fine. Bad Knock sensor!!!
-Shoe
-Shoe
Thread
Thread Starter
Forum
Replies
Last Post
pachanga
General Boating Discussion
16
10-13-2008 12:40 PM