Hi All,
Firstly may I introduce myself. I am a new first time boater who has bought a "project" boat to get ship shape over the winter ready for some fun off the South coast of the UK next season. I am enjoying finding out about my new intended hobby and the challenge of repairing the boat is part of the enjoyment (some may say I am a glutton for punishment!). Although new to boating, I have worked as a development engineer for 20 years in the automotive field and so I have some knowledge of the systems involved although I recognise that there are differences.
The boat itself is a 2000 Bayliner Capri 2050CZ which it would be fair to say has probably been a bit neglected for the past few years. My wife is cleaning, polishing and renovating generally and it is up to me to get the thing going again. I bought it from a distant friend of a friend as a non-runner and have only sketchy information on what has gone before...
The problem is that the engine will start and run for a few seconds only before dying. It will restart immediately and do exactly the same thing again. If I try to keep it going by giving it some throttle then it can be kept going a little longer by revving it wildly but it will still die out as soon as the revs are dropped. The system is the Mercruiser MEFI3 throttle body injection. The engine has done 207 hours, with 69 of those at <1000rpm. It appears to have plenty of compression as it is hard work for the starter to crank over. I have borrowed a diagnostic tool and there is a Code 33 MAP sensor fault recorded. I can clear this and it will recur on the next run. I have unplugged the ECU connectors and confirmed the power, signal and ground wires to the MAP sensor as OK. I have confirmed that the 5V and ground are present at the MAP sensor connector with the ECU connected. However, if the MAP sensor is disconnected and the ECU is allowed to drop into its rpm based limp home strategy, the engine will start and run continuously without problem! Obviously it will then flag a Code 34 MAP sensor error, but this does not matter. This to me suggests that the fuel delivery side of things is working fine (pump and FPR). Under these circumstances the engine sounds sweet and there is no excessive smoke.
Given the above symptoms I thought that I would take a punt with a new MAP sensor, however, it has not solved the problem (£80 down the drain :-( ) . I have also pulled the MAP sensor out of the manifold, connected a Mityvac vacuum gauge and hand pump to it and monitored the ECU live data (engine off) whilst I vacced the sensor down. The ECU reported vacuum and that on the gauge were pretty well in agreement with each other, which suggests that both the sensor and the ECU input signal conditioning is working fine.
I then connected the vacuum gauge to the inlet manifold with the engine running and found that I was getting a reading of no more than 15" Hg at a fast idle. I wonder if anyone could comment on whether that is acceptable? I did wonder if there was an inlet manifold leak?
There is something else which I think is worth saying. At some time in the past the stock Mercruiser flame arrester has been replaced by a K&N one. However there are no hose connection barbs on the K&N for the hoses removed from the MC one. This has created a few doubts in my mind as to whether the vacuum / venting has been plumbed up right. I could really do with some advice in this respect, particularly from anyone with a similar system. At the moment the hoses are as follows:
- The port side rocker cover vent pipe is just flapping loose.
- The starboard side rocker cover vent pipe is connected to a (vacuum?) spigot in the middle of the aft side of the throttle housing, between the fuel inlet and fuel pressure sensor.
- The diaphragm rupture hose from the reference port of the fuel pressure regulator is connected to the vent port on the side of the distributor. I am pretty sure that this is both wrong and dangerous, but would like your opinions please?
Obviously I need to get any external factors such as venting and vacuum sorted before investigating the engine further and potentially getting the spanners out on it.
Apologies for a long rambling post, particularly as a first one, but I wanted to get all of the information over.
Any ideas anyone?
MAZ4477
Firstly may I introduce myself. I am a new first time boater who has bought a "project" boat to get ship shape over the winter ready for some fun off the South coast of the UK next season. I am enjoying finding out about my new intended hobby and the challenge of repairing the boat is part of the enjoyment (some may say I am a glutton for punishment!). Although new to boating, I have worked as a development engineer for 20 years in the automotive field and so I have some knowledge of the systems involved although I recognise that there are differences.
The boat itself is a 2000 Bayliner Capri 2050CZ which it would be fair to say has probably been a bit neglected for the past few years. My wife is cleaning, polishing and renovating generally and it is up to me to get the thing going again. I bought it from a distant friend of a friend as a non-runner and have only sketchy information on what has gone before...
The problem is that the engine will start and run for a few seconds only before dying. It will restart immediately and do exactly the same thing again. If I try to keep it going by giving it some throttle then it can be kept going a little longer by revving it wildly but it will still die out as soon as the revs are dropped. The system is the Mercruiser MEFI3 throttle body injection. The engine has done 207 hours, with 69 of those at <1000rpm. It appears to have plenty of compression as it is hard work for the starter to crank over. I have borrowed a diagnostic tool and there is a Code 33 MAP sensor fault recorded. I can clear this and it will recur on the next run. I have unplugged the ECU connectors and confirmed the power, signal and ground wires to the MAP sensor as OK. I have confirmed that the 5V and ground are present at the MAP sensor connector with the ECU connected. However, if the MAP sensor is disconnected and the ECU is allowed to drop into its rpm based limp home strategy, the engine will start and run continuously without problem! Obviously it will then flag a Code 34 MAP sensor error, but this does not matter. This to me suggests that the fuel delivery side of things is working fine (pump and FPR). Under these circumstances the engine sounds sweet and there is no excessive smoke.
Given the above symptoms I thought that I would take a punt with a new MAP sensor, however, it has not solved the problem (£80 down the drain :-( ) . I have also pulled the MAP sensor out of the manifold, connected a Mityvac vacuum gauge and hand pump to it and monitored the ECU live data (engine off) whilst I vacced the sensor down. The ECU reported vacuum and that on the gauge were pretty well in agreement with each other, which suggests that both the sensor and the ECU input signal conditioning is working fine.
I then connected the vacuum gauge to the inlet manifold with the engine running and found that I was getting a reading of no more than 15" Hg at a fast idle. I wonder if anyone could comment on whether that is acceptable? I did wonder if there was an inlet manifold leak?
There is something else which I think is worth saying. At some time in the past the stock Mercruiser flame arrester has been replaced by a K&N one. However there are no hose connection barbs on the K&N for the hoses removed from the MC one. This has created a few doubts in my mind as to whether the vacuum / venting has been plumbed up right. I could really do with some advice in this respect, particularly from anyone with a similar system. At the moment the hoses are as follows:
- The port side rocker cover vent pipe is just flapping loose.
- The starboard side rocker cover vent pipe is connected to a (vacuum?) spigot in the middle of the aft side of the throttle housing, between the fuel inlet and fuel pressure sensor.
- The diaphragm rupture hose from the reference port of the fuel pressure regulator is connected to the vent port on the side of the distributor. I am pretty sure that this is both wrong and dangerous, but would like your opinions please?
Obviously I need to get any external factors such as venting and vacuum sorted before investigating the engine further and potentially getting the spanners out on it.
Apologies for a long rambling post, particularly as a first one, but I wanted to get all of the information over.
Any ideas anyone?
MAZ4477
