8.1L 2004 Fuel Pump Intermittent

Boat is 2004 Gibson 5000 with twin 8.1Ls. Stbd engine has two problems:
1- Fuel Pump is intermittent.
I have a remote start device and when powering the ignition (no start), the fuel pump will sometimes run for two seconds but most times remains silent. If I leave the ignition on for say 10 minutes, the fuel pump will run intermittently/spontaneously . After observing this intermittency many times,

I have done the following:

Checked three fuses in fuse block - all good and measured 13v

Checked system relay which clicked each and every time the ignition was powered (no start)

Replaced fuel pump relay - no change in intermittency

Wiggled the relays, relay cables, ECU connectors and cables - no change
Measured constant 13v at fuel pump relay pin 30 (no ignition) and at pin 86 with ignition (no start).

Activated the fuel pump by jumping contacts 30 and 87 at the pump relay
Confirmed continuity between ECU J1-6 and pin 85 at the pump relay
Measured voltage at relay pin 85 when powering ignition (no start). Before and after powering ignition, the voltage measured 13v except for intermittency times when voltage measured about 0. This indicates ECU was not consistently grounding pin j1-6 upon powering ignition (no start).



It seems the j1-6 signal is intermittent even though the ECU is constantly powered.


2- the buzzer ECU pin j1-8 does not go to ground after two seconds with ignition on, no start (buzzer constantly buzzes). However, this problem occurred about a year before the fuel pump problem began.

Insights, troubleshooting, solutions would be appreciated.

Thank you.

I have never worked on an 8.1 but....
From the manual:

Fuel Pump Electrical CircuitWhen the ignition switch is turned “ON,” the ECM turns the fuel pump relay “ON” for two seconds causing the fuel pump(s) to pressurize the MEFI fuel system.
When the ignition switch is turned to the crank position, the ECM turns the fuel pump relay “ON” causing the fuel pump to run.
If the ECM does not receive ignition reference pulses (engine cranking or running), it shuts “OFF” the fuel pump relay, causing the fuel pump to stop.
An inoperative fuel pump relay will result in an “Engine Cranks But Will Not Run” condition.

I am not sure if you have a problem or just a misunderstanding of how the system is supposed to work. So the pump running for 2 seconds to pressurize the system part seems to be working. If you are saying that the pump starts running again briefly after ten minutes of ignition on but no attempt to start then perhaps the ECM gets confused if no ignition pulses are seen and it just tries again. I would not leave the ignition on. Now if you are saying that you get a start but the fuel pump(s) are not running and the engine dies then that sounds like the ECM is not getting the reference pulses input referred to above or that it has somehow failed to turn on the pumps when it should. But the fact that the ECM gave you the correct 2 sec burst when turning on the ignition would argue that the circuits are intact and the pump is good.

I'd be inclined to change the system relay and go from there.

Agree with John that the logical conclusion is the fuel pump circuit is ok due to the 2 second prime activity.

The "leave the ignition on for ten minutes and fuel pump runs intermittently" suggests the ECU is 'resetting' - I'd suspect due to the system relay's contacts being marginal...

Also, relay's 'clicking' does nothing to verify they will pass the designed currents with no voltage drops. When verifying continuity, don't rely on an ohmmeter as they don't flow any significant current thru the circuit in question....finally, when things don't make sense, go back and find the assumptions that have been made and validate them....almost always, you can find one that doesn't reflect reality...

Thank you for your response. I am familiar with diagnostic manual and the sequence. As noted, however, the two second activation is intermittent...sometimes the fuel pump runs, sometimes not. The fuel pump relay is new and tested for operation. I am looking for sources of intermittency. Any ideas?

Thank you for your response. The problem is an illusive one because the basic operation is okay, ie, the fuel pump operates sometimes when the ecu is powered. I have reviewed the sequence of operation and stepped through each while checking signal levels and continuity. So far there is not a consistent pattern. I am looking for sources of intermittency. By chance do you own a vessel with one or more Crusader 8.1L's from the 2001-2004 time frame? Are you or do you have access to a marine mechanic with Crusader experience? That would be fantastic.

Well, I don't have an 8.1 but I think I (and likely Mark) are confused as to just what is the problem. When you turn on the ignition the pump should run for 2 seconds. If you leave the ignition on but do not start the engine the pump should not run again. But you are not supposed to do that, but even if you do, then having the pump start intermittently is a mystery but not a problem. No harm, no foul. Now if you do start the motor the ECU should get the ignition reference signal and start the pump and it should run continuously (I think...I don't have an 8.1). So if at that point the pump is only running intermittently then the engine will lose fuel pressure and misfire and then die. Is that what is happening? That gets you back to considering how the ECU could lose that ignition pulse signal, or whether it might have an internal failure. You can swap ECUs with the twin engine if you suspect the latter.

I'd be incline to think the 'remote start device' <see post #1> or its installation are the root cause....

Assuming the ECU and the wiring are functional, when the ECU gets powered up (started), it invokes the prime the fuel rail routine. the only way to get back to that point is to have a power interruption such that the ECU is restarted...which suggests a bad ignition switch or a bad interconnect on the B+ side...ground is also possible...

Mark...interestingly, using the helm ignition switch produces the same condition...intermittent function of fuel pump. In fact, using the remote start, the engine has started and run and this may happen more than once. The next time there is no fuel pump activation. Que pasa?

BTW...the remote start device is for only ignition and engine functions...powering the mefi and starter relays.

There are three or four ground points and so I will try to find them and check for corrosion.

Thank you for your help. If you think of other stuff, please pass it on.

sounds like the common point where the 'remote start stuff' and the ignition switch power up the ecu is suspect...not having a clue to what you are using for a remote start, I'd be inclined to disconnect it and see if the 'original' control circuitry behaves as designed.

Mark...I use this same remote start device on the other 8.1L and it sequences the fuel pump for two seconds, then I can start and run the engine. I will try and recreate the intermittency by wiggling the ground connections. I will also probe the fuel pump relay control and check the ground connections. The mystery is it is intermittent...like something almost works but not always. Of course, it would be beneficial to get this right before I cruise. Thanks, again

I'd serious re-think the use of a remote start device on your boat, especially a twin engine installation...if you want more details, I'd encourage you to discuss the use of the device with your insurance agent...I'm pretty sure their list of the 'cons' will dwarf any 'pros' you may have...