Fuel pump fault

M

muc

"Retired" Association of Marine Technicians...
Joined
Jul 7, 2004
Messages
2,144
There is no "fuel pump" fault.
There is a ------

FUEL PUMP RLY CKT/ #151
Fuel Pump Relay Circuit
♠ ‑ Bell
♥ ‑ Warning
♦ ‑ 90%
Open circuit in fuel pump relay
circuit. This fault cannot detect any
problems in fuel pump circuit.
Wiring problem.
Connector problem.
Relay problem.

The ECM doesn't know if there is a fuel pump. It can only monitor the relay and the 2 wires that control the relay. So a bad fuel pump or clogged filter will not show up on a scan tool. A fuel pressure tester would be used to diagnose those 2 problems.

Whoever scanned this engine should have looked to see when the code #151 was set, it's possible this code was set when the relay was replaced under warranty. When this code comes up, most good techs will preform a wiggle test while the scan tool is still connected and if it passes the wiggle test. Sell the customer a new fuel pump relay and tell them to call if there are still problems. At that point it would be a good idea to disassemble the harness and take a closer look.

MerCruiser is recommending can bus based scanning on the newer engines.

I think you have found a couple of shops to avoid. Maybe find someone else. Or start the engine and wiggle the wires identified in the service manual and listen for the engine to miss, if it doesn't ---- buy a new fuel pump relay and swap it out. While you are there, replace the fuel pump fuse, it's cheap and could cause this problem.
 
E

Eme2685

Cadet
Joined
Apr 16, 2021
Messages
21
muc said:
There is no "fuel pump" fault.
There is a ------

FUEL PUMP RLY CKT/ #151
Fuel Pump Relay Circuit
♠ ‑ Bell
♥ ‑ Warning
♦ ‑ 90%
Open circuit in fuel pump relay
circuit. This fault cannot detect any
problems in fuel pump circuit.
Wiring problem.
Connector problem.
Relay problem.

The ECM doesn't know if there is a fuel pump. It can only monitor the relay and the 2 wires that control the relay. So a bad fuel pump or clogged filter will not show up on a scan tool. A fuel pressure tester would be used to diagnose those 2 problems.

Whoever scanned this engine should have looked to see when the code #151 was set, it's possible this code was set when the relay was replaced under warranty. When this code comes up, most good techs will preform a wiggle test while the scan tool is still connected and if it passes the wiggle test. Sell the customer a new fuel pump relay and tell them to call if there are still problems. At that point it would be a good idea to disassemble the harness and take a closer look.

MerCruiser is recommending can bus based scanning on the newer engines.

I think you have found a couple of shops to avoid. Maybe find someone else. Or start the engine and wiggle the wires identified in the service manual and listen for the engine to miss, if it doesn't ---- buy a new fuel pump relay and swap it out. While you are there, replace the fuel pump fuse, it's cheap and could cause this problem.
Click to expand...
Thanks! Is the wiggle test explained in the service manual?
 
E

Eme2685

Cadet
Joined
Apr 16, 2021
Messages
21
nola mike said:
Doubt it 🤣
Just like it says--wiggle wires and connectors and see if anything changes, indicating a poor connection somewhere
Click to expand...
I guess I was just confused to why if it passes the wiggle test and doesn't misfire, how that confirms the relay is indeed bad. I would have thought that opposite honestly.
 
E

Eme2685

Cadet
Joined
Apr 16, 2021
Messages
21
Eme2685 said:
I guess I was just confused to why if it passes the wiggle test and doesn't misfire, how that confirms the relay is indeed bad. I would have thought that opposite honestly.
Click to expand...
As he said if the mechanic did the wiggle test and it "passed" they would replace the relay. I guess I would have assumed the opposite
 
achris

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Eme2685 said:
As he said if the mechanic did the wiggle test and it "passed" they would replace the relay. I guess I would have assumed the opposite
Click to expand...
Wiggle test tests the wiring, not the relay. If the wiring is good (passes the wiggle test), then the relay must be the fault, hence replacing the relay.
 
E

Eme2685

Cadet
Joined
Apr 16, 2021
Messages
21
muc said:
There is no "fuel pump" fault.
There is a ------

FUEL PUMP RLY CKT/ #151
Fuel Pump Relay Circuit
♠ ‑ Bell
♥ ‑ Warning
♦ ‑ 90%
Open circuit in fuel pump relay
circuit. This fault cannot detect any
problems in fuel pump circuit.
Wiring problem.
Connector problem.
Relay problem.

The ECM doesn't know if there is a fuel pump. It can only monitor the relay and the 2 wires that control the relay. So a bad fuel pump or clogged filter will not show up on a scan tool. A fuel pressure tester would be used to diagnose those 2 problems.

Whoever scanned this engine should have looked to see when the code #151 was set, it's possible this code was set when the relay was replaced under warranty. When this code comes up, most good techs will preform a wiggle test while the scan tool is still connected and if it passes the wiggle test. Sell the customer a new fuel pump relay and tell them to call if there are still problems. At that point it would be a good idea to disassemble the harness and take a closer look.

MerCruiser is recommending can bus based scanning on the newer engines.

I think you have found a couple of shops to avoid. Maybe find someone else. Or start the engine and wiggle the wires identified in the service manual and listen for the engine to miss, if it doesn't ---- buy a new fuel pump relay and swap it out. While you are there, replace the fuel pump fuse, it's cheap and could cause this problem.
Click to expand...
there any way you could explain the location of the can bus on a 2003 4.3 mpi? I have read other old old forums which say they had similar problems like I'm having and have replaced the fuel pump relay, with no fix, but they disconnected the can busses and reseated then which fixed their issue.
 
E

Eme2685

Cadet
Joined
Apr 16, 2021
Messages
21
muc said:
There is no "fuel pump" fault.
There is a ------

FUEL PUMP RLY CKT/ #151
Fuel Pump Relay Circuit
♠ ‑ Bell
♥ ‑ Warning
♦ ‑ 90%
Open circuit in fuel pump relay
circuit. This fault cannot detect any
problems in fuel pump circuit.
Wiring problem.
Connector problem.
Relay problem.

The ECM doesn't know if there is a fuel pump. It can only monitor the relay and the 2 wires that control the relay. So a bad fuel pump or clogged filter will not show up on a scan tool. A fuel pressure tester would be used to diagnose those 2 problems.

Whoever scanned this engine should have looked to see when the code #151 was set, it's possible this code was set when the relay was replaced under warranty. When this code comes up, most good techs will preform a wiggle test while the scan tool is still connected and if it passes the wiggle test. Sell the customer a new fuel pump relay and tell them to call if there are still problems. At that point it would be a good idea to disassemble the harness and take a closer look.

MerCruiser is recommending can bus based scanning on the newer engines.

I think you have found a couple of shops to avoid. Maybe find someone else. Or start the engine and wiggle the wires identified in the service manual and listen for the engine to miss, if it doesn't ---- buy a new fuel pump relay and swap it out. While you are there, replace the fuel pump fuse, it's cheap and could cause this problem.
Click to expand...
Would the fuel pump relay part number be 807057T and the fuse part number be 83296920? Just want to make sure.

Thanks!
 
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