Volvo 4.3L fuel issue... electric fuel pump question.

[RandyJ]

In all of my years I've never had to deal with it before but I thought once the ignition switch is turned on that the fuel pump had constant voltage to it. I used a noid light to figure out that mine is getting voltage only while cranking the engine. When the key switch is released the power to the fuel pump stops. Is this correct, what it is supposed to be doing? What should I be looking for? I'm assuming I may have corrosion in a terminal or a bad key switch since this boat was under water last year (it sunk). As is this boat will crank and run great for a short distance then it only runs if I pump the throttle... if I don't pump the throttle it acts like it ran out gas.

 

[skydiveD30571]

Re: Volvo 4.3L fuel issue... electric fuel pump question.

Once you stop cranking the engine (once it catches), the fuel pump is then powered by the alternator. There is a diode in the wiring from the alternator to the pump, and when faulty will cause that.

However, pumping the throttle shouldn't make a difference if the fuel pump is off. What kind of 4.3 are we talking here? Carb? EFI? What's the full model number?

 

[RandyJ]

Re: Volvo 4.3L fuel issue... electric fuel pump question.

It has the volvo carburetor. I don't have the full model number but I'll get it. I can tell you it's a 1993 model. Since the boat has been sunk I pretty much suspect corroded terminals/connections somewhere. Hoping to get a chance to tinker with it some tomorrow. If I could figure out which relay is the fuel pump relay that would probably help. There are two mounted on a bracket with the reset button thingy. They look exactly alike and I know one has to be for the fuel pump. When I checked continuity with yellow/red or black wire the results were essentially the same and pretty confusing (this is how I normally identify wires).

 

[skydiveD30571]

Re: Volvo 4.3L fuel issue... electric fuel pump question.

With a full model number we can point you to the service manual which will have wiring diagrams for the charging and fuel systems. The fuel pump relay is energized both by the ignition switch while cranking, and alternator while running. If the relay was bad, the pump wouldn't run at all.

 

[RandyJ]

Re: Volvo 4.3L fuel issue... electric fuel pump question.

I've got the manual but it doesn't tell me much... doesn't tell me how the system works. Looks like I need to find the output from the alternator and check to see if it is putting out to the relay while the motor is running... if not then hunt for the diode.

 

[Don S]

Re: Volvo 4.3L fuel issue... electric fuel pump question.

We still need to know what model you have to help you.

 

[RandyJ]

Re: Volvo 4.3L fuel issue... electric fuel pump question.

We still need to know what model you have to help you.

yep... I'll try to crawl up on the boat soon. Just had major dental work and not supposed to be getting my blood pressure up.... all drugged up at the moment on pain pills. I may have that number somewhere in a file or on old posts.

 

[Don S]

Re: Volvo 4.3L fuel issue... electric fuel pump question.

I just looked back in some of your older threads, looks like you have a 430B

You don't have any diodes in your system, and there is no description of how it worked. Volvo didn't do that till later.

The fuel pump relay 28 gets power from the brown wire from the alternator that activates the relay so the pump gets power from the 30 terminal of the relay.

I put some color in the wiring so it's a little easier to visualize.

View attachment 7732808 AQ205-434 Hi Res 26.pdf

 

[RandyJ]

Re: Volvo 4.3L fuel issue... electric fuel pump question.

Thanks Don. Since this boat has been sunk it has been one electrical or carburetor problem after another and I expect more problems. Corroded terminals/connections seems to be the recurring issues. I've already replaced ignition parts, spark plugs, coil, and had to clean terminals on trim relay. When I am better recuperated from dental work I hope to make time to thoroughly go through every electrical connection & component. It's a heck of a very nice well maintained boat. Not sure if I want to keep it or sell it... I'm down to only 18 boats in my yard now. I've been told there's a 12 step program for people like me.....

 

[RandyJ]

Re: Volvo 4.3L fuel issue... electric fuel pump question.

I think we got the fuel pump issue resolved. I found some corrosion on terminals of the relays... took the family out two days in a row with no fuel problem. The issue now I'm thinking... is either carburetor or timing. Doesn't want to run good with a heavy load, simply not enough power like it had before. The only way to get it started at any time is with full throttle. When running at WOT I can back off just a little and it will speed up for a little while then slowly go back down 200-300 rpm. Top cruising rpm seems to be 4200 at best. Running just under 4,000 rpm most of the time at WOT. Temp tops right at 150, oil pressure seems good at around 50 psi. As mentioned earlier, new distributor cap & rotor button, new points & condenser, new (used) coil. Surely I got the timing right... we also put a new water separator fuel filter on recently. It will start kinda okay but does take longer to start than it should, and at WOT when it shouldn't.