Mercruiser 5.0 MPI engine issues

bert_florida

Hello all,

Just purchased a 2004 Rinker 290 for a really good deal, survey and sea trial showed issues, but they were all minor, I took care of all of them in the last few weeks, dumb stuff like shower sump, AC raw water pump, trim/tilt rams, water heater, etc., so all good there. Aside from these minor issues, engines checked out just fine, drives are ok, etc., no issues there, boat ran good for a couple of outings (over 15 hours so far). However, I started to experience issues with starboard engine as of last weekend:

Issue #1: Engine out of the blue started to feel "sluggish" at higher RPMs, so if feels as if it doesn't want to go past somewhere around 3200-3500 RPM, in fact if I go to full throttle to try to get on plane, the starboard engine will just not deliver enough power, so the port engine just can't get the boat on plane on its own. However, if I throttle up smoothly on both engines, the startboard engine will develop enough power to get me on plane at about 3200-3500 RPM and both engines will run in sync at cruise speed (24-27 mph).  However, if while at that speed on plane I try to throttle up starboard engine, it will become sluggish as if it just can't deliver the power and it will drop down even further in RPM down to 3000 or below. Very strange! I have done full service on this engine, oil change, plugs, fuel filters, etc., I am leaning towards fuel pump? It idles just fine, it revs up good at lower RPMs and even revs up well in neutral. Any thoughts? Could it be fuel pump or perhaps cables or something electrical? I am no expert, just dangerous enough to try to do the work myself lol

Issue #2: Same engine as above (starboard), refuses to start on occasion, not that it cranks and won't start, it won't even crank at all, no clicks no sounds, just nothing when you turn the key. Interestingly enough, I have checked the switch as well as the neutral sensing switch (by-passed that one as a test too) and still won't crank, but if I want about an hour or two, it will start just fine! It has done that on several occasions off and on in the last 2-3 weeks. I am at a loss, if the starter was bad, it would NEVER start, if the selenoid was bad, it would never start unless you jumped it, am I right with my assumption? I hate intermittent issues, I rather it just never start so I can figure out the issue. Any thoughts?

I appreciate the help in advance, hate to ask for help on two issues like this, but I am going nuts trying to get this thing running well before I run out of summer.

Thank you!

Bert

davidbrooks

Sounds like the starboard Engine is in Guardian Mode.  Some codes will throw it into Guardian mode as a protection and wont always sound an alarm.  I would buy a Rinda Scan Tool or get a mechanic to read the codes for you.  That should tell you what the culprit is.  As for not starting look at the neutral safety or starter solenoid.  Both are notorious for this.

bert_florida

Thanks for the reply, I already asked the mechanic to read codes, but interestingly enough, starboard engine starts up fine, idles fine and even revs up just fine in neutral, accelerates fine also as long as throttle is applied gently. I'll see if there are any codes.

As for not starting, I already replaced switch and by-passed neutral safety switch as well, that didn't fix it. I guess the starter solenoid is next. If I jump the solenoid next time it does it and it starts that means the solenoid is going bad, correct? But if it doesn't crank, could it then be the starter?

Thanks again!

Bert

YYZRC

I had a Volvo that seemingly ran fine but wouldn’t plane. Turned out to be a loose spark plug wire. 

Ian

Issue 1 - fuel pump(s)? Normally a code may show this. When we were buying ours (also twin 5.0 MPI) the PO said there was a miss in the port engine and the mechanic couldn't get it to happen until at higher RPM's for a while and it was a pump that I think came up on a code as well as a sensor.

Issue 2 - potential loose wire at or bad ignition switch. Now and then my starboard does nothing until I twist key a couple of times.

PickleRick

A starter solenoid can act spastic at times.   Some times they will just click and sometimes starter right away.  Check wiring connections first before replacement.   

You should have a solenoid like on the trim pump sitting starboard side front of engine then another solenoid on the engine starter.  

Fuel pressure gauges can be a very valuable diagnostic tool.

As you've just done the service work yourself id double check that.  Make sure you didnt mix up 2 plug wires on firing order. Also pull each plug to check the gap.  

If still no go, take the plug wires from one engine and swap to the other if you dont have an inline spark tester.  I've seen a bad plug wire out of the box.  You have two motors so you can do lots of parts swapping to do your own diagnostics.  

At least elimiante install error if you don't have a scan tool to quickly eliminate issues that are hard to eliminate otherwise.

If that doesn't work have a beer then order your scan tool. You seem savy on this stuff and im sure you'll use it well in the future.  

davidbrooks

I purchased the Rinda Scan tool $500 with my first boat 4 yrs ago and it paid for itself in the first year.  I was getting codes and having the boat go into Guardian mode and i was freaking out.  At first i was swapping common sense parts that were the most likely to contribute to the issue at the tune of a few hundred each time.  For the scan tool to tell me it was just a bad $50 sensor.  No real issue just an annoyance.  So now i always start with the scan tool to see if there are any codes and if not i come here to ask the experts. 

PickleRick

The o.b.d. works and it always pays to start there when you can.

bert_florida

icoultha said:

Issue 1 - fuel pump(s)? Normally a code may show this. When we were buying ours (also twin 5.0 MPI) the PO said there was a miss in the port engine and the mechanic couldn't get it to happen until at higher RPM's for a while and it was a pump that I think came up on a code as well as a sensor.

Issue 2 - potential loose wire at or bad ignition switch. Now and then my starboard does nothing until I twist key a couple of times.

Issue 1 - Thanks! I'll look into the fuel pump.
Issue 2 - Can't be the switch or the neutral sensing switch either as I replaced both and still does it, but does it intermittently. 

Thanks for the tips PickleRick as well, when the starboard engine doesn't start, it doesn't crank and doesn't even click! I would have thought that if the solenoid or starter was the issue that it would at least click or make some type of noise, but does nothing! Interestingly enough if I wait a while it will start. I have replaced ignition switch and neutral sensing switch, so next is to try the actual solenoid and then if not the starter. Hate intermittent issues because I have to wait until it does it next time to test something else.

As for other issue, I'll try a fuel pressure gauge. I asked a mechanic that works on sterndrives in the marina and he swears it could be injectors and he said to remove them and send them in for cleaning, but that will put me down for weeks, I rather try something else first, not sure how injectors on the starboard engine could be clogged to the point of doing this and port engine runs like a champ?

Thanks for the tip on the tool David, is there a place you recommend to buy it from?

PickleRick

I think each side has its own starting relay. In my passat i had one that would go dead when she got heat soaked.  No click.  No nothing. Maybe swap them? 

212rowboat

you can 'rent' an analog fuel pressure gauge from a parts store... your fuel rail should be provisioned with a schaeder valve to affix it... your problem, it sounds, is fuel delivery higher into the range... it will be impossible to detect until you 'run out of fuel'- meaning the engine can't get enough when it's demanding it.  

off the top of my head i can't recall the pressure required- but it will be manifest as a massive drop in pressure when a certain volume is achieved.  let's say the pressure should be 39psi such as many FMS applications (which this is not)- the 39psi is consistent across ALL rpm ranges whether it's delivering 10cc's per minute or 250cc's per minute.... 

you need a long hose... attach it to the rail and then run it out the engine cover where you can see it (and hit the little reset button on it)... get that engine to the RPM range and under load where it struggles, and mash the little button and see the psi... it should be the same as it was at idle- and it should match the other engine.  

as far as the start issue- typical slave solenoid... works fine- doesn't work-works fine- works fine-works fine- doesn't work- works fine- doesn't work- doesn't work- works fine- doesn't work and never works again... that's how they pass this world and into the next... 

davidbrooks

i purchased mine directly from Rinda.com.  https://www.rinda.com/rindashop/shop/techmate-pro/techmate-pro-94706 you just need to verify the tool against your engine and year.  Different engines will require a different adapter.

bert_florida

PickeRick, you mean each engine has its own relay/solenoid? That is interesting to know, maybe is is not working when hot, I'll try to jump it next time or even replace it, they're inexpensive.

212rowboat, thank you so much for the tips, I will do that, I'll check the pressure, good way to start before dumping money into random things.

davidbrooks, thank you! I'll look into it.

Bert

PickleRick

I think its a 30 amp relay, not the solenoid.  

cabo

Have  2003 290 " it won't even crank at all, no clicks no sounds, just nothing when you turn the key" had same issue. It was the engine plug.Twisted pushed got power.Removed cleaned pins pushed back on nice and tightProblem solved.If no beeps or power Im betting its that connection.
Good luck

bert_florida

Update regarding "no crank" issue. Replaced starter solenoid, started just fine Thursday, Friday and Saturday. This morning it would not start at all, dead, no click, no nothing! Waited 15-20 min and started right up. So.... Replaced ignition switch, replaced neutral sensing switch, replaced solenoid, what else to replace? Can't be starter if it cranks and cranks fine when it wants to lol Any thoughts? Where is this starting relay PickleRick? 

Thanks again!

PickleRick

If I'm not mistaken it down beside the red breaker at the front left of the motor.  

Im working on a diesel now so its not fresh in my mind.

Do you have a test light or ohm meter?

YYZRC

Ignition module (part of the distributor)?

davidbrooks

Follow your engine and starter ground wires and check the connections. Sounding an aweful lot like a loose ground.

bert_florida

PickleRick said:

If I'm not mistaken it down beside the red breaker at the front left of the motor.  

Im working on a diesel now so its not fresh in my mind.

Do you have a test light or ohm meter?

Yup, have both, light and ohm meter. Only thing I can find next to the red breaker is this part:
https://www.go2marine.com/Relay-Fuel-Pump-Ignition-System-86-865202T

But that is an ignition relay, should have nothing to do with cranking? I am assuming if that had issues the engine would quit while running or am I wrong?

YYZRC said:

Ignition module (part of the distributor)?

Why would the distributor have to do with the engine not cranking? Or are you referring to the other issue relating to top end power / sluggish performance?

bert_florida

PickleRick said:

If I'm not mistaken it down beside the red breaker at the front left of the motor.  

Im working on a diesel now so its not fresh in my mind.

Do you have a test light or ohm meter?

Yup, have both, light and ohm meter. Only thing I can find next to the red breaker is this part:
https://www.go2marine.com/Relay-Fuel-Pump-Ignition-System-86-865202T

But that is an ignition relay, should have nothing to do with cranking? I am assuming if that had issues the engine would quit while running or am I wrong?

YYZRC said:

Ignition module (part of the distributor)?

Why would the distributor have to do with the engine not cranking? Or are you referring to the other issue relating to top end power / sluggish performance?

Ian

I suggested the main and fuel pump relays earlier or ignition switch. When you turn on does it tone? And then nothing when turned to start?

PickleRick

A relay is just a solenoid. It could just not be closing the switch internally.

You can verify by seeing if it has power to starter solenoid 12v switch post when it's doing its not start symptom.  You can then go to the relays and see if you as are getting power from the switch as well ad to ignition components.

bert_florida

PickleRick said:

A relay is just a solenoid. It could just not be closing the switch internally.

You can verify by seeing if it has power to starter solenoid 12v switch post when it's doing its not start symptom.  You can then go to the relays and see if you as are getting power from the switch as well ad to ignition components.

 I will check power to the starter solenoid when it does it to see, it is a new solenoid, but the solenoid itself might not be getting power, I'll check the relays as well.

icoultha said:

I suggested the main and fuel pump relays earlier or ignition switch. When you turn on does it tone? And then nothing when turned to start?

When it doesn't start, it tones and all just fine and you can hear the fuel pump kick in for a few seconds as usual, just no crank.

reneechris14

There is a slave solenoid on the intake manifold right behind the throttle body same yellow wire with red tracer like the starter. 

bert_florida

reneechris14 said:

There is a slave solenoid on the intake manifold right behind the throttle body same yellow wire with red tracer like the starter. 

That's the one I changed.