Fuel Pump Relay Keeps Burning Up

[gigbuilder]

I have a Cruiser's 320 with dual Merc 6.2 engines and an interesting problem.

Two weeks ago my port engine wouldn't start. My mechanic told me to reset the 50 amp breaker on the engine. I did so and the boat started -- only to blow the main breaker a day later.

He then told me to bypass the 50 amp breaker because it seemed to "feel wrong" as if it were not fully resetting.

The engine didn't start and we located the lower fuel pump relay. One of the terminals was black.

I replaced the relay and everything ran fine for about two days.

Then the new relay blew. Since I bought several relays I had a spare. This time the boat ran until I docked it.

A few hours later I tried to start the engine and the third relay was blown.

In between the first and second relay I had the engine tuned up and fuel filters replaced, thinking a dirty filter might cause the pump to work harder. It didn't solve the problem either.

The boat is one year old, but the engines have some time on it (we use the boat a lot).

Before proceeding to replace the fuel pump (which does work when a functioning relay is in place) is there anything else I could check that would cause the relay to fry so quickly?

 

[Don S]

Re: Fuel Pump Relay Keeps Burning Up

What's the Mercruiser SN of your engine?

 

[hard-3]

Re: Fuel Pump Relay Keeps Burning Up

check the amp draw of the fuel pumps and see if they are drawing more than the relay is rated for also replace the terminals if they are loose

 

[gigbuilder]

Re: Fuel Pump Relay Keeps Burning Up

The engine serial number is 0W395974 and still has two years on Merc's warranty, so the repair should be covered, but it won't help me with this weekend as our shop only has one mechanic and he's busy through the end of next week.

I'll check the amperage, and it looks like the relay is rated for 30 amps.

 

[strngcru99]

Re: Fuel Pump Relay Keeps Burning Up

if there is(was) a 50amp breaker on the circuit and only a 30amp relay that would explain why the relay is burning up... i would replace the breaker and find a 50 amp relay to go along with it. if you can't find a 50 amp relay i would pick up a ford starter relay from napa or other car parts store... just don"t do that with out a circuit breaker because those relays are rated at 150 amps plus and you can wind up burning your pump up...

what terminal was burned up? that will help guide you in the direction of the fault also....

 

[gigbuilder]

Re: Fuel Pump Relay Keeps Burning Up

I don't have the relay in front of me, but from what I remember there are 6 pins -- 4 on one side and two on the other.

The pin that burns is always the lower left pin.. I'll find the relay and provide the actual pin number.

 

[hard-3]

Re: Fuel Pump Relay Keeps Burning Up

don't use the ford starter relay for continous use . they are for momentary service. get a continous duty relay for this application.most are rated for at least 150 amps . 30 amps draw sounds like a lot for an electric fuel pump. Check out the circuit for amp draw , if its more than designed for I would replace the pump.