Starts, then dies

[kahunadon72]

"Springizing" has taken a slight turn.  Everything was good when I tucked her away last fall...

'97 Volante; Marine Power 5.7 multi-port EFI.   

When I turn the key I can hear both fuel pumps run.  I usually cycle the key twice to get good fuel pressure in the rail before a cold start.  She fires right off, gets to ~1500 rpm, but dies almost immediately.

Didn't have much time before dark last night, but here is my plan for things to look at tonight.  Input is more than welcome!
-Check the fuel tank vent / open filler cap and make sure we're breathing on the supply side.
-Check contents of water separator/change if water present
-Check fuse block
-ID where the fuel pump sensor/oil pressure switch is and make sure the wires are connected and not corroded or broken (any idea on wire colors for this switch?).

I don't believe these symptoms to be the kill switch - when the switch has no lanyard attached it will not run the fuel pumps when the key is toggled. Switch is 2 seasons old.

What else am I missing or should look for?

[buckbambino]

Sounds like all good things to look into.  Sounds like a fuel issue or a firing issue.  Is there a fuel filter to check as well?  Checking/replacing fuel hoses and checking/tightening connections. 

[backfoot100]

Get a fuel pressure gauge and monitor the fuel pressure in the fuel rail. You can get test fuel pressure gauges on the cheap at any parts store. There should be a schroeder valve on the rail someplace that you can hook up to. Pressure needs to be someplace in the 35-45PSI range (before starting and after running) but I'm purely guessing and don't know for sure. EFI fuel pressure is pretty standard in the automotive world. Hearing the pumps run doesn't mean a thing. There is a low pressure and high pressure pump and a relay for each. Any one of them or a combination of them could be a problem. I have no ideas about Marine Power engines but PCM GT40's of that age are getting to be notoriously problematic with any one of those four issues. Easy enough to replace them (if you know where they are) but troubleshooting can be a pain and the pumps aren't exactly cheap. Thus the reason I'm an old school carb guy and always will be. I want nothing to do with EFI. Sorry.

I would also doubt it's the kill switch. Especially if you replaced it already. A kill switch would normally not allow it to start in the first place and you're getting initial firing. The reason that I'm thinking fuel pressure is it's getting enough FP to initially start but not maintain it. Ron would definitely be more knowledgeable than me on this one but at least it's a start to look at something.

Keep us updated on what you find. I'm always interested to know what you find. I have a feeling that these type problems will be more frequent in the near future.

[kahunadon72]

Well I got extremely lucky on this one.  One thing I took for granted/overlooked when attempting this particular spring start-up was paying close attention to battery voltage. 

I keep a battery tender on through the winter and the boat is equipped with a Perko battery cut-off switch set to 'off' for winter layup.  For the past 5 seasons this has been a non-issue; unplug the tender, flip the switch to 'on' and fire it up.  Well my tender seems to have quit over the winter and I did not notice the battery voltage at the gauge reported ~11v.  Evidently this is enough to power the 'start' circuit but not enough to power the 'run' circuit.

Topped off the battery overnight with my big charger and she starts and runs like a champ.

[lcgordon]

Good to hear. Its always something dumb well I guess not always.

[kahunadon72]

Still scratching my head as to why the alternator wouldn't put out enough juice to power the run circuit if I've got enough initial juice to start the engine.  And now of course my mind veers off to contemplating a dual batt. setup...

[kahunadon72]

Well I got lucky last season, but not so much this season... same symptoms.  Next item to check is fuel pressure as mentioned in last year's portion of the thread.

'97 Marine Power 5.7L MPFI - pre-Vortec
Turn on key and can hear both fuel pumps run to pressure & auto shut-off
Turn key to start, engine immediately starts then dies
After it dies I can hear both pumps run to pressure and auto shut-off as if the key had just been cycled again.
Seems like some sensor is getting a fault and shutting everything down.

Troubleshooting thus far:
-Brand new battery & fully charged
-Remove fuel fill cap to bypass vent = no change
-Use multi-meter & get 11.5v at alternator purple wire before it starts, meter climbs to 12.8 after start just before it dies = alternator working.
-Kill switch disables fuel pump circuit completely when lanyard is removed so I don't suspect that.

Additional troubleshooting to be done:
-Check rail fuel pressure - not seeing a schrader valve for an easy plug-in .
-Check on/for faulty IAC (idle air control) sensor
-tbd....

[RichV]

Does this engine have a 3 prong oil pressre sensor?  If so it may shut the fuel pump off without oil pressure.  It may be a sensor fault or just a lack of oil pressure prior to the engine building oil pressure.

[kahunadon72]

Thanks Rich,
I have not found said oil pressure switch based on descriptions I have found online.  Definitely seems like the prime suspect for the symptoms I'm experiencing.

The symptoms are definitely sporadic - Friday evening with a friend (he also has an MPFI ski boat) it started on the first turn of the key and ran up to temp without issue - my friend's a good luck charm.

Sunday I fire it up to warm things so I can change the oil - she runs to temp just fine, probably ran her for 20 min or so.  Change the oil and filter (I always pre-fill my filters) but didn't try and fire her up until later.  When I attempt to fire her up she's back to her start/die routine.

Removed and cleaned the IAC, it's fully functional and wasn't that dirty.  Tried using some starting fluid and she will run on that, but once the ether fumes are gone she quits.

Called one mechanic today, explain the symptoms and he says, "doesn't sound like something I want to get involved with" - Says he's a merc outboard / sterndrive guy, not a Marine Power guy, whatever.

More to come...

[backfoot100]

As I stated last year, PCM GT40 EFI engines of the same era have been getting increasingly more problematic with the same symptoms you're having.  Most common fixes have been the low or high pressure fuel pump or the relay associated with each one. Combinations of all four are not uncommon either. Relays are cheap and easy to replace. Fuel pumps are not cheap but easy to replace.
If the starting fluid is keeping the engine running that's a pretty good indicator it's something fuel related.
I'd be checking those four things first.

[RichV]

You could electrically disconnect the injectors and turn it over with the starter until you build oil pressure.  Then you can reconnect the injectors and try to start it.  I think the is a sbc Chevy based Marine Power engine not a PCM or Indmar Ford.  If so the sensor sticks out of the china wall of the block back by the distributer.

[kahunadon72]

Thanks Backfoot & Rich,
Rich, yes she's a Marine Power engine using a GM 5.7L block.
The sporadic issues are becoming more consistent so hopefully that'll help with troubleshooting.  She fired up yesterday, ran her for 2-3 minutes, shut her down, and immediately she would not restart.
Reading up on this now: http://marinepowerusa.com/2014/wp-content/themes/mpusa/library/pdfs/MEFI-1-2-ServiceManual.pdf

[RichV]

Per the manual low oil pressure should just be a reduced rpm mode not fuel pump off.

[RichV]

You may want to look at the diagnostic flow chart A3 on MFI diagnostics page 17.  It looks like if the battery voltage after crank if it is less than 12 volts the fuel pump is not turned on.  The fuel pump does turn on for 2 second prior to crank, that would account for the start then dies scenario.

[kahunadon72]

Thanks Rich  - sounds completely plausible and I'm glad the manual was available.
I've been running short on spare time to troubleshoot so I found another local marine mechanic who was willing to dive in and to read any codes (there were none, unfortunately), but he did find that the J1 connector to the ECM had a loose pin contributing to the intermittent issue.  Now that part is sorted out, I'll test it some more on land and hopefully be in the water soon.

He did point me in the right direction to the oil pressure switch - on this motor it is a single-wire unit down by the oil filter and it only activates the low pressure alarm - it doesn't shut down the fuel pump.  It had been disconnected for the past 4 seasons as it malfunctioned and was sending a constant alarm even though we had oil pressure at the gauge.  Had him replace the switch just to get things back to a normal configuration.

I know there aren't too many of these boats up here, but if anyone is in western WA, I recommend Mick at Lynnwood Marine - he was super helpful.

More to come - hopefully we're 100% for this season.