Significant but strange engine problems. 5.7L Mercruiser MPI Horizon.

[davus]

hi all,

Some time ago (actually at the end of the previous aussie summer), i posted a thread about issues i was having with poor holeshot.

I parked the boat for winter, and now that summer is back, have been running it around over the last week, and not only am i still having problems, things seem to be getting worse. Im hoping someone can help.

Boat is a 7M australian whittley cruisemaster. around the 2 ton mark - maybe a little more.

Engine is a 5.7 Mercruiser Horizon. I think around 2002 vintage. Fuel is cool fuel I, i believe. Compression test showed up no serious issues. One cylinder is slightly down, but nothing serious.

1) When cold (ie within about the first twenty minutes of starting) then engine seems to be slightly more responsive on holeshot. After that it seems to be quite sluggish on takeoff.

2) Any time i holeshot (regardless of hot or cold), i get terrible pinging from the engine. I have emptied all fuel and have refilled it with premium unleaded (98 octane). It still pings.

3) At full throttle on holeshot, I'm barely able to achieve about 2900 RPM. To me this seems very very low. Seems to lack a lot of horsepower. When up on the plane, if i push it hard, i will get about 4100rpm on a really flat water.

4) Just today, it has started "surging" quite badly. we were cruisng along about 28 knots, and it just lost a whole lot of power. I backed right off, and it seemed to idle along fine, so i powered back up again and it seemed to be lacking even more power. Once i finally got out of the hole, and cruising at about 28-30 knots, it now has a notable surge.

5) As i was loading it on the trailer, i powered up slightly to help get up to the bow stop, and it seems that even ar around 1200 rpm it has a notavle surge now as well.

So, im trying to think of what it could be. Im happy to spend money to fix it, but if possible would rather not throw good money after bad.

Fuel Pump?, Distributor? Something else?

Would really appreciate any ideas anyone can throw my way. Thanks so much guys. Much appreciated.

Dave

 

[tpenfield]

Since it is an MPI engine, you will probably want/need to connect an engine analyzer to see if you are getting any 'codes' from the ECM.

do you know if this boat ever ran well and what the WOT numbers were for RPM and speed? It may have too much propeller, but it is best to get the engine sorted out first.

 

[davus]

Hi Ted,

Not sure on performance before I had it. I know that when I sea tested it before buying it, it seemed to perform fine.

For some time ive been thinking about wanting my own software to read codes from the engine. I have the same for my cars, but cant seem to find anything for the mercruiser for any reasonable price at all.

Dont suppose you ( or anyone else) know of any?

Dave

 

[tpenfield]

The lowest cost that I have seen with any decent display is the MEFIScan software that you can hook up to your laptop,

https://www.obd2allinone.com/mefiscan.asp

It is about $200 US

They also have a link to http://www.tunerpro.net/ on their web page for the scanning tool. It probably takes a bit of ingenuity to figure it all out. I may try myself next year.

They have the more pricier version that allow tuning of the ECM.

There is also Rinda Technologies, but their tools are in the $500 range for scanning capabilities.

 

[alldodge]

i get terrible pinging from the engine

The ping your hearing is your engine destroying in self. Need to fix this before you blow a hole thru a piston.

Can you supply your engine serial number?

If the engine is pinging your knock sensor should be retarding your timing trying to save the engine. I would suggest checking your fuel pressure should be 30 psi (207 kPa) at 1800 rpm. If your motor is MPI then there is a Shrader valve test port on the fuel rail, if its TBI then you will need an adapter to put inline to check pressure.

 

[Bt Doctur]

get a fuel pressure gauge for fuel injection and verify the rail pressure, if within range, then send the injectors out for cleaning.most shops charge $17 USD for the service per injector

 

[davus]

Hi Guys,

I have a fuel pressure tester and will test fuel pressure tonight based on the above suggestion. I know it is shrader so that's good.

In my automotive experience (which I think should stretch to marine on this issue), I have never known poor fuel pressure to cause pinging?. Is poor fuel pressure really something that will cause pre-detonation (pinging) ?

Surging yes, but pinging?. Happy to stand corrected (in fact I hope I am proven wrong! )

Thanks all. Really appreciate the help.

Dave

 

[alldodge]

If you run lean you had detonation. If pressure is not sufficient the pulse width of the injector is the same but less fuel comes out each time.

That said I'm just going by what your telling us, were unable to hear the actual sound

 

[tpenfield]

I agree with the lean running diagnosis, based on what we have so far. One key thing is that the OP indicated that the engine runs better when cold (first 20 minutes) as the ECM will make the injector pulse longer during the warmup cycle. . . . although it should be shorter than 20 minutes . . . .

 

[davus]

Thanks guys. I will do a fuel pressure test tonight when I get home from work and report back.

Another thought, the flame arrestor.....if this is restricting airflow, this could be causing the low power?.

Or, perhaps heatsoak inside the engine compartment?

 

[alldodge]

Thanks guys. I will do a fuel pressure test tonight when I get home from work and report back.

Another thought, the flame arrestor.....if this is restricting airflow, this could be causing the low power?.

Or, perhaps heatsoak inside the engine compartment?

A restricted arrestor would cause a loss in power, and the engine would be running rich. If an engine was running rich there would be some black smoke maybe but no ping.

Heat soak is only a factor if the engine would not restart after running for a while, then we would be thinking maybe vapor lock

 

[davus]

thanks AllDodge,

Good point. A blocked arrestor is going to cause loss of power (which I have), but obviously it would cause richness, and not pinging. Thanks for pointing that out.

Engine seems to start fine after sitting for a while, so heatsoak may not be an issue.

 

[davus]

hi guys,

I did a fuel pressure test when I got home from work tonight.

Results are a consistent 20 PSI. I get 20 PSI at idle, and a solid 20 PSI at 1800 RPM.

Having said this, I know its low, but it seems this is the pressure it has always been since ive had it. I had a look back through some of my notes and photos from when I got the boat (about a year ago). When I bought the boat I did a bunch of tests on it to document. Compression test, fuel pressure, leak down etc. The results for the fuel pressure test were exactly the same as when I did it today.

So, im not sure that the fuel pump is the problem??.

 

[tpenfield]

20 PSI sounds a bit low . . . shouldn't it be in the 35-45 psi range? (43 psi?) It may have been borderline previously, but maybe now the injectors have gotten blocked up a bit.

Do you have access to the Mercruiser manual for this engine?

 

[alldodge]

If your gauge is accurate your pressure is to low, according to the manual it should be 30 spi at 1800 rpm. Things that can cause low pressure besides the pump, is the regulator, leaking injectors or a restriction in the fuel system feeding the pump. Don't see leaking injectors being the issue because again you would be running rich. With engine running pull the vacuum line off the regulator, the pressure should increase.

Timing 8 BTDC
Plugs MR43T or BPR6EFS

 

[davus]

thanks guys.

I will test the guage tonight. Im thinking I could hook it inline in my air compressor and dial the air compressor to say 40PSI. This should reflect 40PSI on the fuel pressure gauge as well.

I do have a few mercruiser service manuals, but im not sure that they specifically cover my engine.

I have Manual number 31, which says it covers 0M300000 and 0M310000

I also have Manual number 24 which unfortunately does not state what engines it covers.

Would you guys happen to know what Manual I should be looking for with engine serial 0M093415?

My only hesitation about changing the pump is that this is the pressure it has always run at. Although yes I guess it could be deteriorating as runs longer, or at higher revs (which I obviously don't see when testing it out of the water).

I have a cool fuel one, and it appears mercruiser don't sell just the pump alone anymore for this system (861156A1). Looks like I have to buy a whole new assembly. 861156A2.

I will also check the timing. I am assuming a standard automotive test light, using the same approach as a car will do the trick?.

BPR6EFS are the plugs im running. They are only about 8 hours old. I replaced ignition leads with brand new ones at the same time I did the plugs.

 

[alldodge]

thanks guys.

I will test the guage tonight. Im thinking I could hook it inline in my air compressor and dial the air compressor to say 40PSI. This should reflect 40PSI on the fuel pressure gauge as well.

I do have a few mercruiser service manuals, but im not sure that they specifically cover my engine.

I have Manual number 31, which says it covers 0M300000 and 0M310000

I also have Manual number 24 which unfortunately does not state what engines it covers.

Mannual 24 is for CSB 1998 to 2000

{quote=]Would you guys happen to know what Manual I should be looking for with engine serial 0M093415?[/Quote]
That serial number is for a 1998 350 mag mpi horizon

My only hesitation about changing the pump is that this is the pressure it has always run at. Although yes I guess it could be deteriorating as runs longer, or at higher revs (which I obviously don't see when testing it out of the water).

I have a cool fuel one, and it appears mercruiser don't sell just the pump alone anymore for this system (861156A1). Looks like I have to buy a whole new assembly. 861156A2.

The older model pump can still be found just search "mercruiser 861156A1".
Also Airtex makes the mechanical and electric fuel pumps for Merc. The model you would want is E11004 (high pressure). That said, I don't suggest buying the pump until you can find out if that is the issue. The pump should be able to put out 60psi, so it needs to be tested. You block off the pump output and makes sure it does not go above 60psi or the regulator can be damaged.

I will also check the timing. I am assuming a standard automotive test light, using the same approach as a car will do the trick?.

BPR6EFS are the plugs im running. They are only about 8 hours old. I replaced ignition leads with brand new ones at the same time I did the plugs.

The engine needs to be put in base timing mode in order to set the timing. Need to connect the Pur/Wht wire (13) to set timing.

 

[davus]

thanks very much AllDodge. What a fantastic post.

Tonight when i get home from work i will test eh fuel pressure tester to make sure it is accurate.

I will then put a close off valve into the return line of the fuel system, and slowly close it off untill i (hopefully) reach 60 PSI.

I will also check the timing. However im a little uncertain as to where i actually connect the pur/whit wire to?

There are two other things i have my eye on as well, and would love to get your thoughts.

1) Thought about cleaning injectors. Im a fan of trying things myself, so keen to know if you know a DIY way to clean injectors.
2) Could the sensor inside the distributor be faulty. Im about to buy a new cap and button from the USA, wondering if its worth getting a sensor as well.

Thanks so much

Dave

 

[alldodge]

I will also check the timing. However im a little uncertain as to where i actually connect the pur/whit wire to?

The Pur/Wht wire is grounded to any good ground, battery engine block, etc. just insert a wire in the female connector and put it to ground.

There are two other things i have my eye on as well, and would love to get your thoughts.

1) Thought about cleaning injectors. Im a fan of trying things myself, so keen to know if you know a DIY way to clean injectors.

You need some special equipment to clean and test the injectors. Outside of buying the expensive equipment, I would just send them out if injectors are left as a possible problem. There are several places that will do it, but before I would send them out I would try to verify this is the issue. I'm leaning against it right now because the symptoms don't lead me in that direction yet.

2) Could the sensor inside the distributor be faulty. Im about to buy a new cap and button from the USA, wondering if its worth getting a sensor as well.

The sensor is not a hit miss item, I see not responses that would tell me this is the issue. Electronic items don't start and stop and start again, and all symptoms are telling me lean condition, and if you had a miss then this would not be a ping, it would be a dead spot

 

[Irishbrannan]

I would also check for vac leaks and like others put a code reader on it. Could also be a bad cam or crank positioning sensor