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62 MPI Misfire at 2000 revs

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Member
"Hi

I have a sea ray 240 su

"Hi

I have a sea ray 240 sundeck in Cape Town South African and suddenly I picked up a terrible misfire which sounds and feels like a fuel starvation splutter that kicks in at around 2000 revs.

Only when the boat is moving, not when revving on idle.

The mechanic has just serviced the boat and he removed the cap and cleaned it today.

The scan tool does not pick up the problem.

When he bled the petrol out of the system the pump did not pump enough petrol back to start it and he had to pour petrol down into the motor to get it started.

Once he did that boat started but the exact same splutter came into effect.

My mechanic seems to think that it is the lift pump.


Does this make sense?

Any other suggestions?"
 
Alon:

It sounds like it is

Alon:

It sounds like it is a fuel problem. What year is the engine? Fuel filter(s) changed? Fuel tank vent working? Spiders build nests in vent inlet or the vent hose could be hanging low and get some fuel in it that prevents siphon from the tank by the pump. Change the fuel pump relay when installing a new pump.
 
"You should have him do a Comp

"You should have him do a Compression test & A Cylinder leak down test. http://www.dietersmotorsports.com/Compression-leakdowntest.htm

Also you should install new OEM spark plugs and try it, Then try installing new spark plug wires and try it out.

This style engine has been known to run like this in the past do to bad spark plugs, And a few other things like valves, ect.

Also check your fuel Pressure."
 
I'd be inclined to start w

I'd be inclined to start with the fuel pressure test and don't forget the "under load" portion.
 
"[b]"My mechanic seems to

""My mechanic seems to think that it is the lift pump."

Ayuh,... Do a Pressure Test...

Guessing is going to get Extremely Expensive..."
 
Thanks for the help to date.

Thanks for the help to date.

We are a little backward here in africa and everything takes a little longer.

I am desperate to get the boat tip top for the weekend!

So the mechanic spent the morning at the boat. Replaced the fuel filter and found a half a cup of water in it.

He also tested whether it was the lift pump by using an external tank?

(Pls excuse me I am not mechanically minded.)

He is now convinced that it is not the fuel line and not the spark plugs as they are about 4 weeks and 20 hours old and for the misfire that we are getting it would mean 4 of them are shot!.

He is also going to put some solution in the petrol to separate the water out of the tank.

They are now talking that even if the computer does not show a fault there might be an intermitted fault that is not begin read but slipping the boat in and out of limp mode which is causing this misfire.

Can anybody shed any light on this or tell us where else we should be looking???
 
"Water in the fuel can cause p

"Water in the fuel can cause problems as you have described. Do a test run afterwards?

If the mechanic has added something to separate the water, how does he plan to remove it?"
 
Tx for this.

He did the tes

Tx for this.

He did the test run and the problem persists.

I am not sure.

The tank is full at moment. 260 liters.

He said that he can put a solution on the " clean the petrol"

Does this sound correct?

I am not sure if it stays in or gets removed thereafter.

Does anything else come to mind?
 
when did the problem start? gr

when did the problem start? gradually getting worse? or suddenly?
After plugs were changed?
After a fuel fillup?
 
I consistently keep the petrol

I consistently keep the petrol topped up.

So being a new run the petrol was full but only about 25 liters was put in.

The problem occurred very suddenly. about 15 mins after start up and during my journey.

There was no prior warning that it was going to happen.

The plugs are about 30 hours old.

Now for the next thing that may shed light onto this.

I had the paddle wheel fitted that determines water temperature and speed on the smart craft.

The part was faulty and resulted in an electronic shut down of sorts.

the part ended up being defective and has been disconnected.

Could this maybe shed any light on the problem.

Bare in mind the scan tool is not picking up a problem.
 
After another 3 hours on the b

After another 3 hours on the boat today the mechanic is now convinced that it is the main fuel pump and is making a device to test the pressure!

Any pointers anyone?

Looks as if I am without a boat this weekend and the weather is great!!!!
 
I do not think he does! And to

I do not think he does! And to get one to South Africa might be a mission to do the test.

He seems to have a device that he is converting to test it either today of Sat and if it is then we replace the biger fuel pump.

NExt issue is that I am not certain that the local dealer will have stock of the part in South Africa.

They charge aprox $2000 for it.

Does anybody know the part number and where I can buy it online and have it DHL'd here?
 
I now have the part number!

I now have the part number!

Does it sound right that the high pressure fuel pump would pack up if there was water in the gasoline?
 
""pack up"?????

Las

""pack up"?????

Last few fuel pumps (petrol) I dealt with did not discriminate against the liquids presented to them.

Over time, I could see where water may impede proper operation of any check valves, etc, in the loop but not the pump's primary function."
 
thnaks fot that Mark.

So in

thnaks fot that Mark.

So in a nutshell when my guy checks the pressure tomorrow and he confirms that the high pressure pump is the problem what are you saying?

That it can be repaired?

That if it is broken that water was not the cause of it?

And why would it give up the ghost at 130 hours?

You seem to know what goes on with these things.

Is there anything you think he might be missing?
 
"still don't get "pack

"still don't get "pack up" - you mean "not work"?

On the fuel pumps - they will pump water just like it was gasoline - they don't taste it or measure it and can't tell the difference.

Water can corrode metals; corroded metal parts have a habit of not working as designed.

Can the pump be repaired? yes but not without significant effort. Given your description of the local environment, I would NOT try it due to lack of parts.

Why would it die at 130 hours? Hard to say as I can't inspect the pump or the installation. Failures are usually characterized by probability distributions; I'd say you drew a "bad hand" on this round, if it turns out to be the case.

What else - most fuel pumps have their supply voltage run thru an oil pressure switch. Oil pressure switches are known to be high failure items. If pressure tests show a drop in pressure when the engine acts up, have him place a volt meter or test light on the pump's electric supply wire. If the voltage fluctuates when the pressure drops, put a jumper across the oil pressure switch. If the engine runs normally, replace the oil pressure switch and order a spare."
 
I will know this morning SA ti

I will know this morning SA time after the mechanic has done his test.

Tx for the concern.

I will revert.
 
"If this was my boat i would p

"If this was my boat i would pump the water and junk off the bottom of my onboard fuel tank.

But first before replacing any fuel pumps or any other part i would run the boat on a external tank of clean fuel.

Any 5-6 gallon fuel tank will.

Then if i found the problem fixed i would follow the fuel line to the online tank and unscrew the fitting that enters the tank, that is a anti-syphin vlave, " one way valve " when you unscrew it the fuel pickup tube will come up with it.

Look at the bottom of the tube it should have a screen on it. Is the screen clean? Does the one way valve operate correctly? Blow thru it is it clean inside?

Ok now to suck the water off the bottom of your onboard tank.

You will need any auto 12v fuel pump and about 10 feet of hose that will fit the pump in and out sides.

Cut the hose so you have about 3 feet on the out side. and 7 feet on the in side look for the arrows on the pump will tell you which side is which or hook the pump to the battery dry and you will feel the suction.

You want to stck the in side all the way in to the back of the tank on the bottom and into a clear bottle say a soda pop bottle pump all the water off the bottom of the tank and then when you see fresh clean fuel coming out shut off the pump.

See water is heavier then fuel. You will be surprised how much gunk and dirt will be on the bottom of your tank.

Close back up the tank and your done.

Me if i were you i would pump about a litre or half a gallon of us measure fuel out, into a clean container that is clear let it sit for say a hour or 2 and see how much water is realy in there.

Please post back the result."
 
"Ok

Firstly thanks for all

"Ok

Firstly thanks for all the responses and interest.

I sincerely appreciate it!

Here is where we are.

WE used an external tank and the problem persisted.

Then you can't get a pressure tester here but me mechanic got the components and made one up!

Then he tested it this am and came back to say the pressure looks fine.

Then we continued to trouble shoot including all of the sensors
being removed and reiftted etc et and then took the bot for a run and the problem remains.

Bear in mind the scan tool finds no faults.

Then he checked the injectors by removing them one by one and said there was no issue.

THEN AS WE WERE DRIVING AT 1500 REVS AND SHORTLY AFTER CHECKING THE INJECTORS THE MOTOR CUT OUT DIE THE NO PETROL!!!! AND WOULD NOT START AGAIN EVEN THOUGH THE TANK IS 96% FULL!!!!!

Then the mechanic unscrewed the pipes and connected his jerry can of petrol, hand primed and the boat started and we continued back to the mooring with the misfiring persisting.

At 7pm today the mechanic was still removing the fuel pump and we have one we can get hold of to test on Wednesday.

What I suspect now is that the mechanic tested the pressure at idle, not at 2000 revs under load where the problem comes in!!! And hence did not find pressure issues as this problem does not occur when you rev in neutral.

Failing it being the fuel pump someone suggested it could be the ECM? Or PCM?

Any further comments would be appreciated!!!"
 
"Does your guy have mercruiser

"Does your guy have mercruiser service manual part number 90-864260T00 - SERVICE MANUAL #31 V8 ENGINES 5.0, 5.7, 6.2. ???

Here are a few good threads to help give you some other ideas that have happened in the past to the 6.2 engines.

http://forums.iboats.com/showthread.php?t=313284

http://forums.iboats.com/showthread.php?t=314304

http://www.offshoreonly.com/forums/general-q/213313-6-2-trouble-shooting-help.ht ml

http://www.offshoreonly.com/forums/general-q/213193-6-2-low-rpm.html

http://www.offshoreonly.com/forums/general-q/214484-merc-383-mpi-wont-spin-past- 4100rpm-gear.html. The shift cable adjustment could be set up wrong."
 
"Do you have a fuel cooler?

"Do you have a fuel cooler?

I think after you hook up the spare fuel pump you may finally find air somehow being sucked into the line somewhere like a clamp or hose being loose.

So my opinion i would follow the hose from the tank fitting all the way, and inspect every connection and every fitting. Somewhere is a cracked fitting or hose.

It may not be water but air causing the misfire."
 
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