Fuel pump, ECM or something else?

[Shaw]

On a year 2000 4.3l EFI TBI that is over 800 hours...

Day 1 - Starts perfect all the time and have just ran very well for 2 hours. Shut down for 8 hours and then restart for the run back. 1 hour in (half way), whilst both engines are at 3800rpm, the Port engine just quit. Nothing unusual on the gauges or otherwise was noticed prior to this. We limped back on a single engine.

Day 2 - I tried the starting the engine and noticed that there was no fuel pump noise on turning the ignition. Called up the boat mechanic and explained thses to him. He says 99.9% it is the fuel pump and won't be fuses or anything else.

Day 3 - Mechanic had a look at the boat without me being present. He found a fuse blown (the stern most one, next to the 2 relays on top - sorry, I can't find reference to them in the manual) . He says it had a 10A fuse in it when it should have had a 15A. Bear in mind that these fuses hasn't been touched for a while.

Day 4 - Started fine. Went for a slow cruise (speed limit) at 1500rpm. After just 30 minutes, the engine shut off again. Ignition on does not cause the fuel pump to go. Checked the 3 fuses, all were OK. Limped back...

Day 5 - Mechanic replaces fuel pump based on original diagnosis.

Day 6 - Started fine. After 20minutes of slow cruise, during which the engine's revs jumped around twice. That is, I had the throttle on about 2000rpm, when the engine would go down as low as 1000rpm, and then gets up to 2500rpm. I suspected this was due to air in the fuel line caused by changing of pump, and so ignored it. It did go away after happening twice.

After 30 minutes, we stopped for a quick lunch. Restarts fine and I was heading to open water to test at higher speeds. Just as I was accelerating away, the port engine bogged down again - to idle. For the time, whenever I try to accelerate, it would bog down to idle. Switched off and restarted OK with fuel pump noise heard. I tried revving it right up out of gear and the engine died right down. Thereafter, fuel pump no longer kicks in and won't restart. Limped back again to the pen. When I reached the pen, I tried it again - and again, no fuel pump noise.

Day 7 - Nothing had been touched. I tried starting the engine, fuel pump was heard straight away and started straight away. I warmed it up for 20 minutes and revved it up (out of gear) without any issue. Talked to the mechanic and now he says it is likely to be the ECM. I am very worried about the costs of all this and would love some help.

At all times, oil levels, fuel level and freshness, engine temp, oil pressure was all good.

 

[Don S]

Re: Fuel pump, ECM or something else?

Volvo or Mercruiser?????

Got a SN or full model number, years don't mean much in either.

I usually don't even read the details if I don't know what it goes to. They both have different fuel and electrical systems.

 

[Shaw]

Re: Fuel pump, ECM or something else?

Mercruiser. I don't know the full model or serial number. But it is one with Throttle Body Injection with EFI. Not sure what more info I can provide.

 

[Shaw]

Re: Fuel pump, ECM or something else?

Am I doomed? Can no one shed some light on this? Please?

 

[Dunaruna]

Re: Fuel pump, ECM or something else?

You need to do an on water fuel pressure test under normal cruising conditions. And check for corroded electrical connections in and around the relays etc.

 

[Shaw]

Re: Fuel pump, ECM or something else?

Add more diagnostics... day numbers are arbitary

Day 8 - Started in the pen again. Left it idling up to operating temp, and then left it running. Occasionally revving up to 3500rpm in neutral as well as putting it into and out of gear. Noticed that the voltage according to the gauge was showing low (11-12v) unless revved up over 2500rpm. It ran for over an hour with no cut out.

Checked batteries - hydrometer indicates OK, resting voltage at the battery was 12.6v. I forgot to check it whilst running.


Day 9 - Mechanic swapped port and starboard engine's ECM over to each other. Also put in 2 new relays on the port (problematic) engine.

Day 10 - I ran it out on the water. Once again, exact same symptom - ran fine for about an hour, and then stalls. Thereafter, fuel pump does not come on with ignition. Again, I noticed the gauge's voltage is showing around 11v when running at 1500rpm.

Limped back to the pen. Carried out spark test as requested by the mechanic - there was spark when cranking over. Tested resting voltage on batteries - OK at 12.5v - cranking voltage 12.1v.

Mechanic is now suspecting loose connection to the computer - he says that if the ECM sees less than 11.5v - it shuts itself down. Sounds plausible. But which connections can I have a look at? Any other ideas??

I must apologise that on-water testing for me is a difficult task - as the only person that can come with me is my 8 YO daughter. In and out of our pen is also a challenge as the tide and wind is atricious.

 

[Don S]

Re: Fuel pump, ECM or something else?

Mercruiser. I don't know the full model or serial number. But it is one with Throttle Body Injection with EFI. Not sure what more info I can provide.

One reason you aren't getting many replies, is that no one knows what you have. You may not know the SN off the top of your head, but could you possibly go read it off the engine? Mercruser lists nothing by year, only by SN and SN ranges. You could have either a MEFI 1,2, or 3 ECM. The SN would ID which one.
Is it an Alpha, Bravo, drive, or straight inboard? Different wiring setups.
Has anyone actually got on that engine with a DVM and done any testing when the problem occurs? Or has it all been parts swapping after it starts working again?

 

[Shaw]

Re: Fuel pump, ECM or something else?

Bravo 2 drives. As for serial number, my predicament is that the paperwork shows them as om19894 and om19889 - which sounds like 1 digit missing?? I have tried to look at the stamping (near the starter) on the engine without seeing it.

 

[Don S]

Re: Fuel pump, ECM or something else?

Put a 0 between the 0M and the number and you have a winner with a Bravo drive and MEFI 3 ECM.
NOW, we are getting somewhere.
Be back with more info later.

 

[Don S]

Re: Fuel pump, ECM or something else?

For starters, go up to the Adults only sticky, find the Service manual links and download manual 25, you are going to need it. Then I can give you directions to specific information without having to post a bunch of pictures and explantations.

 

[Shaw]

Re: Fuel pump, ECM or something else?

Ah! and I had been so confused about my serial number. May I ask what resource is used to identify exact model from the serial number.

Alright - got that manual.

 

[Don S]

Re: Fuel pump, ECM or something else?

Looks lik you are going to have to go for another ride so it will die again so you can do these tests. I would suggest you try the tests before going out so you are sure of how to do them properly.
You will need a DVM to check voltages at the relay socket.
Look at the wiring diagram of the fuel pump relay on page 5I-18.
Remove the fuel pump relay (NOT the ignition relay)
Identify the numbers for the terminals from the drawing below.
When you turn the key to the run position (NOT starting the engine) you should see approximatly battery voltage at terminal #30. You should also see voltage at terminal 86 for 2 seconds. Since you have spark, if the ignition switch is turned to the start postion and the engine cranks over, you should see power at terminal 86 also.
Put the relay back in and the engine should start and run.
Now, the fun part, go for a ride till it stops running.
Now pull the relay and repeat the tests. One of those terminals #30 or 86 will probably not have power.
If they both DO show good voltage, then your problem is in the Dark Green/white wire that goes from terminal 85 of the relay socket to terminal J1-23 of the ECM.
The fact that you have spark when the pump doesn't run indicates to me that you have power at some points along the #439 pink wire that goes to terminal 86, which eliminates a lot of possibilities.

 

[Shaw]

Re: Fuel pump, ECM or something else?

Ooooh - So tempted to get out of work now and try this. At least now I feel there may be a light at the end of this tunnel.

 

[Shaw]

Re: Fuel pump, ECM or something else?

I had some time to look this morning.

1. In case I'm totally off the track, the relays on my boat is not as per picture - it is more like below

2. There appears to always have 12.6v from earth (manifold) to pin 30? Ignition on or off doesn't matter. Before and after "fault" (engine won't run, fuel pump does not turn on for that 2 second)

3. There is 12.6v from earth to pin 86 whenever the key in in Run position (engine not cranking or running)

So am I doing something wrong?

Another thing... My gut feeling (not very good when it comes to boat engines) is it could be the grounding point. That when the engine is hot enough, it would lose contact. This is described as CKT150 in Mercruiser manual #25. My question is, exactly where is this ground / earth point? I can't quite find it!

 

[Don S]

Re: Fuel pump, ECM or something else?

Numbers are the same, layout of the pins may be different.

 

[mauer03]

Re: Fuel pump, ECM or something else?

Don,
I have a similar problem. First, I have a Volvo Penta 4.3 GS serial #4110121763...43GS PHUB. I'll try to keep this short.

I was out on the lake last summer...the water pump impeller took a dump and the engine started to overheat so i cruised back to the dock and shut her down within 5 min of realizing the overheat situation. The boat has been sitting in my garage ever since. I replaced the impeller last week. I had to take all the water hoses off as well as the thermostat and remove the pieces of impeller. In the process I pulled the main engine harness cable from it's plug to get it out of the way. Other than that, I didn't screw with any wiring. Once I put all the hoses back I plugged the engine harness back in.

I then tried to crank it up to test the water pump out (I had my water hose hooked up to the outdrive while sitting in the driveway). It wouldn't start. It has started for the last four summers even after sitting all winter with no winterization. In any case, I sprayed a bunch of ether in it and it never got going on its own.

I pulled a spark plug and tested it. It has spark. All the other electrical stuff works (stereo, blower, horn, etc.).

The full pump doesn't run when you turn the key part of the way (I stopped before it cranks) like you described. I do have 12 volts on Pin 30. I don't get any voltage on Pin 86 when turning the key part way or when cranking.

Can you help?

 

[Don S]

Re: Fuel pump, ECM or something else?

I can help, but please start a new thread of your own. It gets way to confusing to remember to look at the end of someone elses post to find an new one about something else.