Accessing the fuel pump on a 4.3 EFI

[AlboranC]

The pump is on the motor so it can be dropped in, hook up and go

Another pump can be mounted about anywhere, but should be mounted low. Others have replaced cool fuel with Aeromotive, Weldon and others. If the return is routed back to the tank then no VP. Can also use another pump and not route back to the tank and just keep current setup. The regulator is what controls ther pressure.

Note: If a high output pump like Weldon or Aeromotive is used the return needs to go back to the tank. The high output pumps will push way more fuel then the motor will use so it can build more heat

It's obviously a lot easier for the boatbuilder to prepare the engine bay, complete with the transom assembly, battery and trim pump, then just drop the crate engine in and connect it up. Not so good for the poor fool who has to fix it 18 years later.

 

[AlboranC]

After removing the Cool fuel system to check the screen filter and replacing it on my 18’ Donzi my old arms looked like they are covered with tattoos from the blood just below the surface.
Pulling the manifold will make it a lot easier if their is room to get it off.
Since GM engines do not have provisions for a mechanical pump, Mercruiser had to make an adapter for the mechanical pump to be belt driven on the raw water pump. This was used on the carbureted and early fuel injected models.

I pulled the riser off and loosened the bolts on the manifold - if I have time this weekend I'll take that off next. It's time for new ones anyway.

​​​​​​In the photo you can see there is plenty of room to the port side of the engine. The floor of the engine bay is level with the engine mount, it then drops down to the bilge, leaving very little space to get under the engine from the side.

I'm hoping I will at least be able to see the fuel pump with the manifold off.

 

[maddog2112]

I recently had a similar situation on my boat. 5.0 merc carbureted. I`m not sure if the efi is the same but very well may be. The oil pressure switch needs to see 4psi before it will allow the electric fuel pump to run. Does yours have the electric fuel pump? If so, you can jumper the oil pressure switch which will allow the electric fuel pump to run with just the ignition turned to on.

 

[AlboranC]

I recently had a similar situation on my boat. 5.0 merc carbureted. I`m not sure if the efi is the same but very well may be. The oil pressure switch needs to see 4psi before it will allow the electric fuel pump to run. Does yours have the electric fuel pump? If so, you can jumper the oil pressure switch which will allow the electric fuel pump to run with just the ignition turned to on.

Thanks for the suggestion. What I have actually been trying to do is reach the harness connector for the fuel pump so that I can verify it has power at the pump - I think I might just be able to do that now.

I have verified there is power at the relay going to the pump and that the relay is operating as expected (relay comes on for a second or so at ignition switch on, then again when turning the engine over). There is also resistance across the wires that go to the pump, so at least its not open circuit.

Even with the manifold off, there is very little access to the cool fuel unit because the engine mount is in the way, making even the basic check that power is reaching the pump, very difficult.

 

[alldodge]

The fuel injected motor controls the fuel pump by the ECM, it doesn't go thru the oil pressure switch like on a carb motor.

 

[achris]

... There is also resistance across the wires that go to the pump, so at least its not open circuit.....

What resistance are you reading?

 

[AlboranC]

What resistance are you reading?

It was showing about 10 ohms which would equal 1.2 amps - I've no idea what the correct value should be but it seemed in the right ballpark.

 

[achris]

It was showing about 10 ohms which would equal 1.2 amps - I've no idea what the correct value should be but it seemed in the right ballpark.

That value is about right... So, if you're seeing a circuit, you know you have power on that circuit, but the pump still isn't spinning, then it sounds like the pump is seized....

The next thing I'd do is put an ammeter in circuit. If it's pulling current and not spinning...

Chris.....

 

[AlboranC]

That value is about right... So, if you're seeing a circuit, you know you have power on that circuit, but the pump still isn't spinning, then it sounds like the pump is seized....

The next thing I'd do is put an ammeter in circuit. If it's pulling current and not spinning...

Chris.....

Well I had time to get back to the boat and I put my ammeter in place of the fuse in the circuit. With the key turned to the on position I got a reading of 12 amps (for the correct length of time) which has to be too high as the fuse is only 15 amps.

Do you know how the cool fuel unit is mounted? Does it bolt to the engine mount?

 

[achris]

Well I had time to get back to the boat and I put my ammeter in place of the fuse in the circuit. With the key turned to the on position I got a reading of 12 amps (for the correct length of time) which has to be too high as the fuse is only 15 amps.

Do you know how the cool fuel unit is mounted? Does it bolt to the engine mount?

Yes I do, and yes it does...

Chris....

 

[AlboranC]

Yes I do, and yes it does...

Chris....

Thanks Chris. It looks like it is held on by two nuts (#28 in the drawing) I can get to. I'll take them off and see where that gets me.

 

[achris]

The nuts aren't the problem, it's the fuel lines...

Chris...

 

[scoflaw]

The hoses aren't that bad either. Undo hose 31 and 32 at the filter housing. take the 2 mounting nuts off , drop the unit down and slide it back a bit. Take the step pin #9 out and pull the fuel hose #26 out. the whole unie can now be pulled forward and out without removing the plenum which the manual suggests.

 

[AlboranC]

An update for everyone on the saga of accessing the fuel pump on my 4.3EFI. In the end it was pretty straightforward, so I thought I would document it here for anyone else in the future.

I ended up pulling the whoIe cool fuel unit out from the front of the engine. I didn't need to pull the engine as there was just enough clearance in the boat, but I did unbolt the front engine mounts from the floor and removed the rear engine mount bolts which allowed me to move the engine around in the engine bay. This is what I did:-

I undid the two nuts (5/8") holding the cool fuel unit to the port forward engine mount, undid the fuel line from the throttle body, undid the fuel line that goes from the fuel tank to the fuel filter, unbolted the fuel filter mount from the engine, disconnected the tube that goes from the cool fuel unit to the spigot on the flame arrester on top of the throttle body and cut the hoses from the power steering cooler and the water pump (these could have just been undone, but I am going to change them anyway while I have the chance).

By pulling on the now free hose from the water pump. I managed to pull the whole unit out. Its fiddly and I had to feed the rear hose and fuel line through the maze of hoses and cables at the back of the engine and disconnect the fuel pump power connector by feel, but it wasn't hard.

Thanks everyone who contributed to this thread and I hope you never have to use this information.

 

[Scott Danforth]

remember to re-align the motor after you replace the fuel pump assembly since you loosened the engine mounts.

 

[Bt Doctur]

Scott the actual motor mount bolts are not touched, the mount itself is mounted with a stud type bolt and the CF bracket is mounted on the stud with the 2 nuts

 

[Scott Danforth]

Scott the actual motor mount bolts are not touched, the mount itself is mounted with a stud type bolt and the CF bracket is mounted on the stud with the 2 nuts

OP stated he loosened the motor

I ended up pulling the whoIe cool fuel unit out from the front of the engine. I didn't need to pull the engine as there was just enough clearance in the boat, but I did unbolt the front engine mounts from the floor and removed the rear engine mount bolts which allowed me to move the engine around in the engine bay. This is what I did:-

 

[AlboranC]

remember to re-align the motor after you replace the fuel pump assembly since you loosened the engine mounts.

Thanks - its on the list.