Merc 4.3LX not starting

[ctak]

Went out on Sat. with my 18' Bayliner, 4.3LX and docked to hit the head. When I came back the motor wouldn't start. It would turn over rev. for a second and then die. Had to use the kicker to get home. After bringing it home did some testing. Fist pulled the fuel filter off and changed it. Checked the inline filter by the carburator and there wasn't one there. I cleaned some of the contacts to the electric fuel pump to see if that was the problem. No help. I looked at the manual and it said when the key is turned on you should hear the electric fuel pump running. I turned the key and not a sound. Then I looked down by the starter solenoid where the positive wire to the electric fuel pump terminated, next to it was the main 12 volt red wire. I took a wrench and jumped them to see if the fuel pump would run. It ran as I could hear the clicking. Fired it up again and it ran this time for about 20 seconds and then died. Tried cranking it and wouldn't turn over.<br />I took it to a local shop and they looked at it and said it needed a new fuel pump and a complete tune for about $650. <br />I was thinking it was just a problem with power getting to the fuel pump. Maybe a solenoid or something. Can anyone give me some insight.

 

[12Footer]

Re: Merc 4.3LX not starting

I almost hate to say this, but those are the symptoms of a bad fuel pump. To confirm this, take a test light,and clip it between the fuel pump lead and engine ground. Turn the key to ign on, and see if it lights. If it lights, fuel pump. If it don't, YOUR theory is correct, being a bad connection.

 

[ctak]

Re: Merc 4.3LX not starting

Does the ignition just need to be turned on or turned over and cranking? I turned the key to the on position and put the probe on the connector. No light. I went to the starter slave solenoid and had 12v on one side and nothing on the other. Then went to the inputs(small wires) and did not have any voltage there either. The inputs for the starter slave solenoid lead back to a terminal block and shift interupter switch then back to the distributor and to the Ignition amplifier on the ground side (black) while the positive voltage wire (yellow/red) leads to the plug in connector and ignition switch. I guess I need to test the solenoid. Does this require 12v at the inputs? Or could it be the Ignition amplifier?<br /><br />Any help would be appreciated.

 

[12Footer]

Re: Merc 4.3LX not starting

Your reading on the solenoid are normal,Colin. You need to put the tester on the wire going to the fuel pump only,and the ground clip to ship's ground. Turn the key to ignition on only (no need to start).<br />If the engine truns over when you actually do try to start it, the solenoid is fine.<br />If the engine will not trun over with the starter, it is a low battery, or corroded connector,or solenoid (internal if it "clicks").

 

[DeepBlue69]

Re: Merc 4.3LX not starting

I had the same problem, engine run's for a few seconds and shuts off. It is the oil pressure sender next to the oil filter on 4.3 leter engines, pulled both wires off sender, install a jumper wire between wires, engine should run. Note: Must sense oil pressure to keep running after started. Try putting a twelve volt test light on choak before and after putting on jumper cable. After start cycle power comes from altenater to keep it running. Note: There are three oil senders on engine. Write Back if you need further information.

 

[ctak]

Re: Merc 4.3LX not starting

Thanks to Deep and 12. I think that has fixed the problem. I checked the Oil pressure switch down by the filter and the connectors were corroded. I took the sensor off and cleaned the terminals and connectors the best I could. I then jumpered the two wires and turned the ignition key to on, the pump started humming. I then reinstalled the oil pressure switch and hooked up the wires and she turned right over. I let her run for about 25 minutes varying the throttle between 700 - 2000 rpms. Seemed to run fine. I'll take a chance on the water in the next day or two. I just wanted to say thanks for all the help. This board is a great help and resource for boaters everywhere. Wish I had found it earlier. Keep up the great work..<br /><br />

 

[ctak]

Re: Merc 4.3LX not starting

A quick question for Deep. What do you mean by putting a 12 volt test light on the choke before and after the jumper? Is this to see if there is voltage at the jumper? I didn't quite understand.