2007 260SD with 350MPI Will not stay running

M

Mace_46

New Member
Aug 18, 2017
11
Boat Info
2007 Sea Ray Sundancer 260SD
Engines
Merc350MPI/Bravo III
I have looked thru lots of posts and I am probably missing the answer but I am hoping someone can help me here. I have a 2007 Sea Ray 260SD with a single 350MPI / Bravo III. Computer is a Mercruiser ECM 0501 The problem is that it will start but it will not stay running. I have Diacom computer software and do not have fault codes, no horn alarm sounding.
I have spark.
New wire harness on motor
I have fuel and fuel pressure at the rail 43PSI. Fuel is new, filter is new, injectors are flow matched Bosch and new.
Will run on starter fluid and can get to idle speed with the starter fluid(will die once the starter fluid is gone)
I have checked the injectors for signal with a noid light, all get signal

When I turn the key, I hear the fuel pump, turn key more the starter engages and spins motor, after a few rotations the motor will fire off, then die. Evertime same exact response. If I pump the throttle I can get it to spit sputter and stay running (if you want to call it that while I pump the throttle) Occasionaly I can get it to rev past the 1500 mark and it will rev up and down sounding normal while I move the throttle up and down.

My question here.. could this be a computer problem or is there a sensor that could be causing this? Any help is appreciated
 
Several things can cause this, a service manual will give the values you should be seeing in your sensors.
Did this all begin with the new wire harness ? Maybe you missed a connection or bent a pin.
ECT,TP,IAC, MAP all need to be checked. I assume your fuel pressure holds steady while cranking and briefly running ?
 
scoflaw said:
Several things can cause this, a service manual will give the values you should be seeing in your sensors.
Did this all begin with the new wire harness ? Maybe you missed a connection or bent a pin.
ECT,TP,IAC, MAP all need to be checked. I assume your fuel pressure holds steady while cranking and briefly running ?
Click to expand...
Problem was before new harness. Dealer suggested new harness. Checked and rechecked all weather packs and connections.
Fuel pressure holds steady no drop.
ECT - 84.2
TP - 0% (this does change as I change throttle poistion)
IAC duty cycle - 0%
Manifold Air temp - 91.4
 
This was at idle ? MAP volts ? IAC should be higher than 0. Mine idles at a 68 count. Also you have the problematic CF3. It's possible you have a breach between the water and fuel internally. Have you looked at the 2 fuel regulators ? The upstream 1 also has a screen that can get plugged with paint chips.
 
Last edited:
scoflaw said:
This was at idle ? MAP volts ? IAC should be higher than 0. Mine idles at a 68 count. Also you have the problematic CF3. It's possible you have a breach between the water and fuel internally. Have you looked at the 2 fuel regulators ? The upstream 1 also has a screen that can get plugged with paint chips.
Click to expand...
Not at Idle. Will not idle on its own. Will only start then die, never idle.
No debri in fuel regulator, checked and rechecked fuel pressure at rail 43psi(so not a regulator). I have removed the fuel line from the pump and bypassed using another pump and fuel source to rule out bad fuel (even though its new, thinking possible contaminate in tank), same result.

The only thing I can come up with is that it is not applying fuel at the correct time. Having checked the injectors with a noid light it tells me it is getting a signal, I have spark (double checked timing, new plugs, new wires, new cap and rotor, will run on starter fluid)
Would a computer (ecm) failure cause this? Everything I find on sensor failures gives an alarm.
 
Even with key on not running IAC should be doing something. Of course ECM could cause this, but without a spare, could be an expensive guess.

Tell some back story about how this all began.
 
Bought the boat with the problem. Doing the exact thing it is still doing. Prior owner said it was running fine, they stopped using it, decided to sell it and the problem came up. Prior owner still onboard with me and answers questions. Dealer shows all maintenance was performed regularly at the dealer. No prior codes in ECM (I have a Diacom scan tool and software)
IAC will fluctuate values when trying to start. With a IAC failure in my past exp it will at least start and idle (high idle) with the IAC unplugged and throttle opened partially. When I unplug the IAC it will give alarm, but still no idle.
On the fence here with a new ECM or sending off to SIA electronics for repair... $86 to check and send back if no problem, $169 to check and fix if it has a problem. $550+ for a new ECM... Is anyone familiar with SIA electronics ECM repair?
 
With an idle air control motor, I assume that you do not have DTS?
Correct?
 
The fact that it runs on starter fluid sticks out to me.

You said you Can get it to run and idle With starter fluid. Can you do this for and extended period of time? Like 30 seconds, a minute or longer?
 
Espos4 said:
The fact that it runs on starter fluid sticks out to me.

You said you Can get it to run and idle With starter fluid. Can you do this for and extended period of time? Like 30 seconds, a minute or longer?
Click to expand...
No 30 seconds is a long time.. I can get 10-15sec..
 
What if you physically remove the IAC valve from the engine? See if it starts and runs. If it does, it will be at a much higher rpm.
 
OK, So went back to the noid lights. Very weak lighting up. Checked voltage 12.6v constant at every injector. I am thinking it is bad injector drivers in the ecm. Taking the ECM on Monday to have it checked...
Tried Removing IAT, just to see, makes no difference.
 
I'm not sure of your mechanical knowledge, so I apologize if this is too simple (or too complex) for you, but here goes....

The injectors will have 12v power on one wire with the ignition on.

The ecm controls injector pulse width by grounding the other wire for a specified time period, measures in milliseconds.
On an automotive application, a camshaft position sensor signal ensures that the injector sprays as the cylinder is on the intake stroke. The injectors don't all fire at the same time.

I assume the marine applications are similar.

Clogged injectors will have the same pulse width ( it's all premapped according to coolant temp and engine load) but flow less fuel. Automotive engines with oxygen sensors or air/fuel sensors can adjust injector pulse width to accommodate lower flow rates from clogged injector(s)

A 2007 350 MAG doesn't have oxygen sensors to give this feedback.

You said earlier that the injectors have been replaced. By you? Or the previous owner?

You could remove them and conduct a flow test to see if they are clogged.

You checked fuel pressure, but that won't diagnose clogged injectors. In fact, clogged injectors will show great fuel pressure because there is a restriction not allowing fuel to leave the rail as quickly as it should.

You said you bought the boat with these issues, I hope that was reflected in the price.
 
Last edited:
Espos4 said:
I'm not sure of your mechanical knowledge, so I apologize if this is too simple (or too complex) for you, but here goes....

The injectors will have 12v power on one wire with the ignition on.

The ecm controls injector pulse width by grounding the other wire for a specified time period, measures in milliseconds.
On an automotive application, a camshaft position sensor signal ensures that the injector sprays as the cylinder is on the intake stroke. The injectors don't all fire at the same time.

I assume the marine applications are similar.

Clogged injectors will have the same pulse width ( it's all premapped according to coolant temp and engine load) but flow less fuel. Automotive engines with oxygen sensors or air/fuel sensors can adjust injector pulse width to accommodate lower flow rates from clogged injector(s)

A 2007 350 MAG doesn't have oxygen sensors to give this feedback.

You said earlier that the injectors have been replaced. By you? Or the previous owner?

You could remove them and conduct a flow test to see if they are clogged.

You checked fuel pressure, but that won't diagnose clogged injectors. In fact, clogged injectors will show great fuel pressure because there is a restriction not allowing fuel to leave the rail as quickly as it should.

You said you bought the boat with these issues, I hope that was reflected in the price.
Click to expand...
Yes, I understand and voltage at the injector is 12.6V, but getting a weak light from Noid (this is leading me to believe the injector control is not working correctly in the ECM)
Yes I replaced injectors with flow matched new Bosch injectors, drained and replaced fuel with new, replaced fuel filter with new, checked and cleaned fuel rail for paint and other debris
No O2 sensors
No this model Merc motor does not fire individual injectors (sequential) as you are stating it is a batch fire system with two injector control modules within the ECM. Firing 4 injectors at a time.


I appreciate your input
 
Espos4 said:
How many hours on the motor?

Was a compression test done?
Click to expand...
527 hours on motor
Yes compression test was performed, I do not remember all of the exact results
Again, motor will run on carb cleaner so I do not suspect compression or spark to be an issue
Thank you for asking..

This one has me banging my head on the wall, should be easy... Compression, fuel, spark.. Vroom Vroom. I just seem to be missing fuel and have ruled out everything except the ECM..

I have found several posts of the exact same thing on the internet but they never post the fix... I will be sure to post the fix when it gets resolved
 
Your welcome.

I've got 25 years automotive experience, but I'm new to marine engines. They have similarities but can be very different.

Another simple thing to check is the ground connections.

A wiring diagram of the ecm will show several grounds. Make sure that are all good. Check the resistance between the ecm grounds and the negative battery post.
 
You must log in or register to reply here.

Forum statistics

Threads
113,095
Messages
1,425,825
Members
61,017
Latest member
IslandGirls1020
Back
Top