Hi guys,
I have been reading this forum for quite a while now, and have always loved all the tips and knowledge you shared. Thank you!
This beeing said, here goes my first post
I wrench quite a lot on outboards and love the challenge, so I bought a Tohatsu/Mercury 30 hp 4 stroke, which the previous owner said just needed servicing. Turned out there is something wrong with the fuel injection/ECM.
The symptoms:
-Typically starts fine, idles great
-P.o. said it runs fine under load, could'nt test that myself so far
-After sitting a couple of minutes it sometimes (maybe 1 out of 20 times) does'nt start back up
-If I unplug the high pressure pump it starts right up with the pump diconnected
-If I then plug the HP Pump back in it continues to run fine
The P.o told me, that the motor once had a fault with the fuel pump driver, so he powered the HP pump externally. He said this eliminated the problem.
The HP pump has a connector with two connections. One is connected to an earth, and the other is connected to the starter relay. The former ground cable is just cut and isolated. When the motor is running it reads 0.2V (strange, should have continuity I think?).
Here are my findings:
-Fuel pressure is adequate (48 PSI). As soon as you crank the engine it builds in a matter of seconds. Also in the no start condition
-Spark is adequate, even in the no start condition
-Injector resistance is within spec.
-Injector pulses are abesent in a no Start condition (tested with noid light). When the motor runs, all three injectors fire. As soon as I unplug the HP pump, the pulses work again.
-If I connect my voltmeter to the injector connector, I read 7.2V in a no start, and about 16V in a run scenario.
So, the problem is, that the injectors don't get enough Voltage in a no start condition. From what I saw in the Service manual, the HP pump and the injectors get their power from the same ECM outlet. I wonder if I could fix the Problem, by just hotwiring the Injectors (the power side).
But it still puzzles me, that it will restart with the HP pump diconnected.
I'm sure there are many people on this board that know a lot more than me about troubleshooting this system, please feel free to share your knowledge.
I appreciate all the help I can get
Thanks in advance!
I have been reading this forum for quite a while now, and have always loved all the tips and knowledge you shared. Thank you!
This beeing said, here goes my first post
I wrench quite a lot on outboards and love the challenge, so I bought a Tohatsu/Mercury 30 hp 4 stroke, which the previous owner said just needed servicing. Turned out there is something wrong with the fuel injection/ECM.
The symptoms:
-Typically starts fine, idles great
-P.o. said it runs fine under load, could'nt test that myself so far
-After sitting a couple of minutes it sometimes (maybe 1 out of 20 times) does'nt start back up
-If I unplug the high pressure pump it starts right up with the pump diconnected
-If I then plug the HP Pump back in it continues to run fine
The P.o told me, that the motor once had a fault with the fuel pump driver, so he powered the HP pump externally. He said this eliminated the problem.
The HP pump has a connector with two connections. One is connected to an earth, and the other is connected to the starter relay. The former ground cable is just cut and isolated. When the motor is running it reads 0.2V (strange, should have continuity I think?).
Here are my findings:
-Fuel pressure is adequate (48 PSI). As soon as you crank the engine it builds in a matter of seconds. Also in the no start condition
-Spark is adequate, even in the no start condition
-Injector resistance is within spec.
-Injector pulses are abesent in a no Start condition (tested with noid light). When the motor runs, all three injectors fire. As soon as I unplug the HP pump, the pulses work again.
-If I connect my voltmeter to the injector connector, I read 7.2V in a no start, and about 16V in a run scenario.
So, the problem is, that the injectors don't get enough Voltage in a no start condition. From what I saw in the Service manual, the HP pump and the injectors get their power from the same ECM outlet. I wonder if I could fix the Problem, by just hotwiring the Injectors (the power side).
But it still puzzles me, that it will restart with the HP pump diconnected.
I'm sure there are many people on this board that know a lot more than me about troubleshooting this system, please feel free to share your knowledge.
I appreciate all the help I can get
Thanks in advance!