Volvo 5.7 MPI starting issue - long story

BH523

Cadet
Joined
Sep 8, 2017
Messages
8
Hi Everyone,

I'll start with a little history - Engine is a 2005 Volvo 5.7 MPI Gi-E. The boat has always started right up with a turn of the key. This season I started experiencing intermittent hard starts. Sometimes it would fire up with a turn of the key, other times I had to put the shifter in neutral and give it a little throttle to start.

I replaced the plugs, wires, fuel filter, rotor, and distributor cap. Seemed to fix my problem - started getting easy starts back at the marina. However, I would get the same issue after being at anchor or stopping at the fuel dock. I would have to pop the shifter in neutral and give it a little throttle to start. Also started to notice some popping at around 3,000 rpms while on plane.

Next time out the engine started with a turn of the key at the dock. Went directly to fuel dock, had to give it throttle to get it to start after fueling up. Ran fine (maybe a miss here or there) for the 20 minute ride to where we anchored (a mix of no wake zones and regular zones). Anchored out for about 2-3 hours and when we were ready to go I had to give it throttle to get it started. Tried to get up on plane but it was running very rough and sputtered. Turned it off and tried to re-start the engine. This time could not get engine to turn over even by giving it throttle. Had to get a tow back to the marina.

Following day did some additional digging. Upon further inspection my flame arrestor was very, very dirty. I could hardly blow air through it. I cleaned it with brake cleaner and a strong hose and got it back to brand new. Also checked my plugs (recently replaced) they were dirty and wet, so I decided to replace them again and use the ones I replaced as a back up for next tune up since I know they are still good. Lastly I replaced the IAC valve.

Tried to start it and just wouldn't turn over. Kept trying. After about 10-15 tries it started to try to turn over. It would dieseling slightly when I stopped cranking so I popped it in neutral and gave a little throttle and finally got it started. This is on the work rack on a water hose. Once i got it started I put it in neutral and gave it some throttle. Initially was a little rough but it ran smooth after a minute or so. It was noticeably smoother than before. Had to wait until next day to put it in the water and test drive.

The next day got it in the water, again took a few tries to turn over. Once started it ran smooth, real smooth. No popping or hesitation, got to WOT of about 4800 rpms and about 53 mph. Never ran better.

The next day I get to marina and it took about 15 tries to get it started. would crank and crank and when I turned key off it would sputter a little. Got it started by shifting to neutral during that stutter and giving it a little throttle. Once warmed up I shut it off and am able to start "right" back up rather easily. However, went to the gas dock, put some fuel in and took a couple of tries again to start it after fueling up. Once started ran perfect again. WOT and top speed reached easily. No hesitation.

Next time at the marina I put it on a work rack and checked the fuel pressure (thank God for youtube and auto zone tool lending program). The fuel pressure checked out fine. Low Pressure was 12 psi and the high pressure pump was at 50psi, both within spec. Removed the fuel pressure regulator , inspected it - a very little amount of debris/dust on the screen. I cleaned it up with carb cleaner and reinstalled. No issues with the oil either.

Boat will not start at all now. Checked with marina mechanic to see if they could take a look. They told me it would take three weeks to check it out. Did some searches on the forums. Saw that someone had a similar issue and it was the coil. So I decided to change the coil. The boat fires right up. I turn it off an on multiple times...fires up each time with a turn of the key. I'm on the rack so can't test on the water for a few days.

Yesterday I get the boat in the water - fires right up. Head to the gas dock, get some fuel, fires right up again. Runs perfectly on plane - I anchor out. Turn the boat off. I turn it back on and it fires up but I sense not as quickly as before. After a couple more tries I have to give it some throttle to start up. It starts right up with throttle. Go back to the marina. Put it back on a work rack and it turns over with key.

What am I missing?

1. Anti-siphon valve? I tried to replace the anti-siphon valve but its in a difficult place to get any leverage on the nut and it seems to have some type of sealant or cement on the threads. Any tips on removing the sealant? Maybe the valve is not functioning properly after the fuel tank gets stirred up?

2. Fuel injectors? Would the boat run great once started if the fuel injectors were the issue?

3. Any other ideas? Other things I should check? I think I maxed out my mechanical ability.

The two things that I know were wrong and resolved were the coil and the dirty flame arrestor.

Thanks in advance for any help.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Hi
Have a read in Merc section about my problems with MPI...in particular one of my last responses.
I had the same issue a year ago and just recently.
After winter storage the boat would not fire up. It would crank over just fine but not fire...but...when I released the key, it would take a pop and a bang and misfire and almost start.
I did this lots of times and each time the same. Release the key and it would take a half *** attempt at firing.
I replaced the problematic diz cap and rotor and while waiting in this to arrive, charged the battery.
All was well for a year and a bit (apart from other stupid mpi problems...long story)
Anyway
Recently, after being in holiday for a week away from boat and frequent use...I went down to fire the boat up after having the stereo on for 5 mins and bilge pump running...same symptoms. She would turn over just fine but not start, until I released the key...then she would shudder and pop and misfire !
I did this about 8-10 times then thought...what if I do this again, but when I release the key and during the misfire and pop...I turn the key back in quickly ?
I did this and she fired straight up...
Turns out after a bit of reading and Merc dealer advice, this is fairly common, but Miss diagnosed. It was down to a less than perfect battery state. Battery was totally enough to crank her over quick enough to make the average thought think that it ain't the battery...but it turns out that the coil in the MPI and VP GI engines demands that much power that the cranking of the engine robs it of enough power to fire. Hence he splutter when the key is released and further more the start when you turn the key back on quickly (when there is no major draw of power away from the coil)
Have a go at this. I'd be pretty certain that's your problem. New battery solves this and rings true with my problem the other year...when I coincidently charged battery at the same time as thinking it was the diz cap....
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
11,798
That does really make sense and I believe that Volvo Penta has said in their manuals to not use a deep cycle type battery for starting for that reason; they supply less cranking amps.
So using a battery with greater capacity with respect to cca might prevent this issue. Maybe replace a group 24 with a gp 27. I have 2 GP 27s in my F/W H-200.
 

tpenfield

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Jul 18, 2011
Messages
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:welcome:

You can spend a lot of time swapping out parts and sensors with an MPI engine. In order to 'see' what is going on you really need to connect the ECM to the diagnostic computer and see how it operates, and in particular when it is having a problem.

As such, many folks are dependent on marine mechanics to run the diagnostics, but even then, some mechanics have a tough time finding the real problem.

The throttle position change for starting that you mention is interesting, because all that does is change the reading of the TPS as well as opens the throttle plate a bit. It would be interesting to see via the computer, what the engine is doing in response to that.

In absence of a computer diagnostics, I would check all of the connections to the sensors and to the ECM (MEFI). See if you find anything loose/corroded and if it makes a difference.

Since MPI/EFI engines are such a 'black box' I bought the computer program to do the diagnostics, since I do all of my own work on my boat/engines. So far so good, but I have not run into any major issues in terms of starting or running.

anyway, check the connections . . . maybe check the throttle plate and intake plenum since the spark arrestor was so dirty. See where that brings you. If you have got the $$$, maybe get the computer diagnostics. A Windows laptop is all you need to run it.
 

alldodge

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I think the lack of maintenance is the issue, and the battery is a great place to start, then move to cleaning connections.
 

BH523

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Sep 8, 2017
Messages
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Thanks I will check the battery...I have two and I did have the battery switch on the older battery.

Ted - I looked at the diacom software but the price scared me off!
 

BH523

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Sep 8, 2017
Messages
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I plan on checking battery next time at the marina. However I have a question. If it is the battery, would it start by giving it throttle? When I give it throttle it starts right up....doesn't feel like that is a battery issue.
 

tpenfield

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It probably is not, but worth checking out. I think the sensors use a 5 volt source, so the voltage regulation within the ECM should be fine with a battery that is slightly below voltage. Might as well check regardless.
 

alldodge

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I plan on checking battery next time at the marina. However I have a question. If it is the battery, would it start by giving it throttle? When I give it throttle it starts right up....doesn't feel like that is a battery issue.

Your flame arrestor was very dirty, and the IAC passages may also be a bit clogged up. Providing a bit more throttle gives the motor more air. So either the IAC might be getting stuck, air channel a bit clogged, or its not working correctly from corroded contacts or something else.

Might also be an issue with the MAP sensor, don't know but need to start with the basics and then move on to testing
 

Dave-R

Chief Petty Officer
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Mar 18, 2008
Messages
441
I thought the Diacom system was expensive until the Volvo Penta dealer wanted 250.00 just to connect their system to reset alarms. As Ted said, the new ECMs are a black box and without a diagnostic tool you are in a expensive guessing game. Too bad the new boat electronics are so unreliable. I've heard it said that everything electronic will fail. It's to bad the genius who designed this electronic stuff for boats could not be out 20 miles out when it fails. The boat engines 20 years ago are much easier to work on and keep running. People will say how the new cars are so much more reliable than the old ones. And that may be true. But if your car stalls, you can pull over to the side of the road. On a boat in a storm or at night you loose an engine and you are in real danger. And here is the stickler. Volvo penta could easily display what is wrong with the engine instead of having you go to the dealer and spend 500$. Sorry for the rant. Dave-R
 

tpenfield

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Yes, it does not take long at the repair shop to cover the cost of the Diacom software . . .
 
Joined
Aug 7, 2017
Messages
9
I had a similar issue where the engine would crank and sputter and try to start but not fire up. It ended up being my crank position sensor.
You mentioned you were at your limits of mechanical ability, can you take the old plug and pull a wire and test for spark? At least then you know you have fuel pressure and spark.
 

BH523

Cadet
Joined
Sep 8, 2017
Messages
8
Update - Friday went to marina. Engine fired right up with a turn of the key. After boating for about an hour stopped for gas, and wouldn't start with a turn of the key, but fired up as soon as I gave it some throttle.

So I think I can rule out the battery issue. Seems like it starts right up when engine is cold, but needs some throttle to start a warm engine. Engine seems to run well but I do gets some intermittent popping. Maybe not getting enough air or fuel? Any thoughts on the warm starting issue?

I was thinking of swapping out the Throttle Position Sensor. Thoughts? Is there a lower cost option than the Volvo part (Part # 3857487 $136) ?
 

alldodge

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Seems like it starts right up when engine is cold, but needs some throttle to start a warm engine. Engine seems to run well but I do gets some intermittent popping. Maybe not getting enough air or fuel?

Don't see the TPS as the issue right now.
If the popping is at higher rpm's then your running out of fuel, and the more throttle would have me remove and clean the IAC
 

BH523

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Sep 8, 2017
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Thanks All Dodge I replaced the IAC valve a few weeks ago...think it could be dirty again?

When I put the shifter in neutral and give it some throttle to start - isn't that introducing more air in the equation?

On other thing - I would like to change the anti-siphon valve but it seems to be cemented or sealed in the fitting. Any thoughts on how to loosen up the sealer so I can change it out?
 

alldodge

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Thanks All Dodge I replaced the IAC valve a few weeks ago...think it could be dirty again?

When I put the shifter in neutral and give it some throttle to start - isn't that introducing more air in the equation?

Don't think it would be dirty again, but giving more throttle gives more air

On other thing - I would like to change the anti-siphon valve but it seems to be cemented or sealed in the fitting. Any thoughts on how to loosen up the sealer so I can change it out?

Without seeing (not that seeing would help us decide) I am unable to say
 

BH523

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BarryTurano

Petty Officer 2nd Class
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Oct 26, 2014
Messages
145
The fuel line is connected to the anti siphon valve which is connected to the pick up tube. Use an open end wrench to unscrew the anti siphon valve from the pick up tube. Make sure to keep a wrench on the pick up tube fitting so you do not torque it when you unscrew the anti siphon valve
 

Chigwalla

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Jul 11, 2017
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IAC valve...

anti-siphon valve but it seems to be cemented

I'm inclined to agree that the IAC is the place to look. How does the engine behave on deceleration ? (that's the other use for the IAC)
You may have to bite the bullet and take it to a shop to see whether or not the ECM is calling for an IAC % or not. Conversely, you could probably cobble up a PWM test rig.
It's a stepper motor so it's tough to bench test it. Putting 12V directly to it will burn out the winding.


As to the antisiphon....OEMs generally do cement them in and if you try to unscrew it dry, the valve will snap off at the threads.
It's just aluminum and can't take much torque. Heat it up with a heatgun or IR lamp to soften the goo and it'll spin out.
Or use an open flame and solve all the problems in one go :)
 
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