Volvo Penta 1993 434A 4.3 V6 Fuel System electrical circuit driving me crazy

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[FONT=&quot]I have a 1994 Tiara that has twin Volvo Penta 4.3 V6's model 434A. Over the last couple weeks my starboard motor would die on me while running on plane, warmed up and running about 3200rpm's. I would restart it and then it would run fine for a while and then do the same thing. I would restart it again and then it would run the rest of the day 4-5hrs without problem. This happened several times and then one day died and did not start like it was out of fuel. When the key switch was turned on I could not hear the pump running but I could with the port motor. I purchased a new fuel pump relay thinking that was the problem but still no luck. I then found the inline resistor. I removed the resistor and plugged the two terminals together and the pump started running when the key switch was turned on just like the port motor does. So I started the motor but went to shut it off and the motor would not shut off. The only way to get it to stop was to unplug the wires where the resistor went. I purchased a shop manual to understand the wiring diagram for this motor but I'm still confused. What I would like to know how this electrical fuel pump circuit works. What the resistor actually does, is it giving power to the relay when ignition switch is turned on or is it taking power from the alternator. I know once the alternator is creating power this sends power to the fuel pump relay which sends power to the fuel pump. Sorry for the long dissertation but hopefully somebody can help me out. I have many hours trying to figure out what's going on, both hands on and reading these great forums.

P.S. I also changed fuel/water separator's also[/FONT]
 

TLubas

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Aug 6, 2017
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Was this issue ressolved? if so can you please let me know what was the cause. your problem sounds similar to ours and we are losing our minds trying to figure it out
 

Dave-R

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Mar 18, 2008
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Not sure what you mean by resistor. When the starter is engaged the power supply comes from the starter to the fuel pump. When the engine starts, the fuel pump power supply is from the alternator. There is a inline diode that keeps each power supply from back feeding the other. If your alternator is failing, this could be one of your problems. Maybe someone could post an electrical diagram for you to see. Dave-R
 
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