4.3 GL Fuel Pump Issue

[jharvey1984]

Hi. I am new to boating and iboats. I recently purchased my first boat (98 four winns) with a volvo 4.3 gl carbureted (engine number 432BPBYC) engine and sx drive. The last time I took it out I could not get it to start on the trailer. Discovered the fuel pump is not working. I jumped the pump directly from the battery and it works fine so pump is OK. I replaced the relay and checked the breaker... still no luck. From searching on the forums I have learned that power to the pump is provided from the starter during starting and the alternator during normal run. My question is what should I do next? Should I jump the pump to get it started and then unjump it to see if it continues to run? If so then that would narrow it down to the starter, right? If not then would that give me any useful information? Thanks in advance for any advice.
Jimmy

 

[Bt Doctur]

Re: 4.3 GL Fuel Pump Issue

May be a pressure switch just above the oil filter, may have the oil presure sender with it.

 

[Don S]

Re: 4.3 GL Fuel Pump Issue

From searching on the forums I have learned that power to the pump is provided from the starter during starting

May be a pressure switch just above the oil filter

Volvo's DO NOT use an oil pressure switch, or power from the starter solenoid to operate the fuel pump when starting.
If you head up to the adults only sticky, you can download the OEM service manuals for the BY model fuel system and electrical systems that explains how it works.
The power to operate the pump comes from the start relay, which powers the fuel pump relay through a diode.
Sounds like you have a wiring problem or an open diode. Manual 7797452 showing the wiring diagram in section 10

 

[jharvey1984]

Re: 4.3 GL Fuel Pump Issue

Thanks guys for the quick response. I D/Led the manual took a look at the diagrams. The diode you are talking about is the one with the orange wire on one side and the yellow red on the other, right? Where is this diode located along the wire? Where is the start relay physically located? I assume that checking the start relay would be the easiest thing to check first.

 

[bruceb58]

Re: 4.3 GL Fuel Pump Issue

This is what I would do.

Pour some gas in the carb and get it started that way. If the engine stays running becuase the fuel pump is on, you need to determine why the fuel pump doesn't operate during cranking. Pull the relay and measure the pin at the fuel pump relay while cranking to see if you get voltage.

If the engine won't stay running, bypass the fuel pump relay to keep the fuel pump running and the engine running and measure the voltage of the L2 terminal of the alternator. You need to have the fuel pump relay plugged in during this step to put a load on this terminal.

I really doubt the diode wil be bad unless you had a short circuit at the fuel pump relay that blew the diode out before blowing a fuse/breaker.

 

[JOEC.]

Re: 4.3 GL Fuel Pump Issue

I had this problem last year with my 4.3. the diode is located IN the alternator. replaced the alternator and been working ever since.

 

[bruceb58]

Re: 4.3 GL Fuel Pump Issue

There is a discreet diode in the harness. Not sure what you talking about with your alternator. The L2 terminal comes straight off the regulator. The L2 terminal is normally connected to an indicator light and will sink current when the alternator is not charging. An internal diode would prevent this from occuring.

I have no doubt that replacing your alternator solved your problem. It was the regulator that failed though.

 

[JOEC.]

Re: 4.3 GL Fuel Pump Issue

I'm at work now (no manual to refer back to) but if I remember correctly the fuel pump is powered by the ignition during starting, only when cranking not in the key on in run position, and when the engine starts the fuel pump gets it's power from the alternator. Maybe different years are different. Mine has the high pressure pump on it. Your right it may have been a bad regulator, but the charging circuit still worked on my boat when the pump did not so I believe the regulator was working ok.. Tracing the wiring on the schematic showed it's power from the alternator while running, whether the diode is in the alternator or in line somewhere I don't know but for abt $65 it was a simple fix. Will be interesting to see the outcome either way.

 

[bruceb58]

Re: 4.3 GL Fuel Pump Issue

The regulator can appear to be good and the alternator be charging and the L2 terminal could be bad. If someone took your diode out for some reason it could be the reason your regulator failed.

In this case, I think its going to end up being his alternator as well.