rpengr wrote:
I don't know if you are right about the alternator running the fuel pump... I will let someone else answer that. If that is the case, then there must also be a pre-start circuit to run the pump, because it is not uncommon to have a dry carb after sitting for a long period.
I have had two experiences that contradict the alternator theory:
-- I have had a bad alternator, and the engine kept starting and running fine until the battery got low.
-- I have started the engine after having a completely dry carb (because of rebuilding it). I just crank for about 3 sec, then turn the key off, then key back on, wait a few seconds, then crank again (and pump the throttle). After 3-5 tries it started right up. I did it that way because I am thinking that the pump runs for a few seconds each time you turn the key on. I'm not sure though.
You could have a bad pump that is somewhat shorted, therefore causing the low voltage? Or it could be a problem somewhere else in the circuit? Why don't you check voltage at the pump while you have someone else turn the key off and on.
Yeah, I was kinda going out on a limb with my dry carb theory, not knowing boats much. But what you say makes sense...
I don't believe the pump itself is the problem, as it runs fine when I remove the fp relay and hardwire the power to the fp. I'd post the schematic that I have, which i am sure represents the wiring I have on my boat, but I'm thinking Seloc wouldn't like that
![Confused :?](./images/smilies/icon_confused.gif)
It shows the wiring going from the back of the alternator 'Indicator Light' terminal to the relay coil positive.
Does anyone know how much voltage is required to excite the fp relay? I'm half tempted to just rewire this lead to the ignition switch, but I don't want to bypass any safety measures or have fuel pumping out the top of the carb if I forget to turn the key off!
What gets me is that the power going INTO the alternator shows 12v or better... that's why my theory of the alternator needing to spin up came into play. However it makes sense that the fp would get it's power from the battery to start with...
Something rpengr said just clicked... looks like there is a line from the starter solenoid to the fuel pump relay coil positive as well? maybe that connection is bad, and it's not switching the fp on while cranking... therefore no initial start? Once the engine is running and the starter is no longer cranking, that circuit is disabled and the voltage from the alternator takes over? I'm going to go check that line from the starter.
Thanks again, fingers crossed!