350 mag mpi running rich and starting issue

[silver_power]

Hello. My engine is a 2009 350 mag mpi (s/N 1A348183) with about 400 operation hours..Last year I had the known problem of corroded risers and water entered to the starboard side of the engine. I pull off the engine and it did not crank. Finally the 2 cylinders had rust and the engine did not crank. The other side was OK. So I fixed the engine,. Did a compression test with very good results and before put the engine to the boat, we did a scanning check and everything was good ( cylinder test, no fault codes, no missfires, no knocks etc). So i put the engine to the boat but i have two issues.
1.the engine starts but it does not crank as it used to crank. During cranking, it spins nice for a little, after slows down, after spins good again and it starts nice with no throtle. The batteries and wires are new. I tried new starter, but same results.
2. The other issue concerns the consuption
I have smartcraft gauges and I see that the mpg reading has changed. For example at 2800rpm the boat normally runs 3.4-3.7 mpg but this year runs about 2.8-3.0mpg. It consumes about 15% more gas with the same conditions and load. During docking I can smell some gas as well. The idle is smooth and the rpm at wot is normal about 4900-4950rpm just like always. I had no plan to check it at wot but i suspected that maybe there is no fire to a cylinder and that is why it runs rich and have the smell of gd.So i check it and the results at top end were the same as always.I Must tell that i have no beeps at smartcraft. The temp reading is perfect about 158-162oF. Is there a possibility that it runs rich because of the repair of the block and it must operate for some hours?
Do you have any ideas about these 2 issues I have.
Thank you very much.

 

[alldodge]

During cranking, how long does it crank before it starts?
Does it take the same amount of cranking once its warmed up as it does when its cold?

As for the running rich, have you looked for codes?
The think that can cause the motor to run rich are dirty flame arrestor, faulty MAP sensor, leaking fuel injectors, defective fuel pressure regulator or fuel pump. Connect a gauge on the fuel rail to see what the pressure is

 

[silver_power]

Yes it makes the same time to crank. Cold or hot.
The smartcraft reads 2.96bar fuel pressure and the flame arrestor is clean as I just cleaned it. I have no beeps so I suppose that I have no codes. I made a scan just before I put the engine in the boat and it did not have any.....i Must check the map sensor to see if it good and then the injectors. But I think that if the injector were the problem I would of have and other problems during operation......

 

[alldodge]

If the fuel pressure sensor is accurate then you pressure is good.
Your smelling gas during idle operations, so it is running rich. If you have some injectors leaking this will show it self more during idle then hard running. That said if the MAP is providing incorrect info, it to can cause this. A slight vacuum leak can also cause fuel enrichment

 

[silver_power]

I must add that the engine has great response and this is something that confuses me....one that I just notice is that if I turn off the engine while it idle and start it again in about 5 sec, it will not start easily....it will start with low rpm and after about 1-2 sec it will idle good. Is this a fuel injector issue?

 

[alldodge]

Don't know right now, we have not done much testing yet, but does lean me toward to much full and maybe a weak battery or bad connection. Could be other things, just don't know right now

 

[silver_power]

Does anybody know what is the consumption (gal/hr) of 350 mag mpi at idle and normal temperature ? Mine at smartcraft reads 0.79-0.82 gal/hr. When the fuel injectors have problem and needed to be cleaned, the consuption is bigger even at idle?

 

[silver_power]

Well I just hooked a wire to terminal 4 of the map sensor of the engine. With key to on position but engine not running, the VOM read -0,16v!?!. (I expected around 5V as the regerence voltage which was meteted at 5,01v)I then start the engine and wait until the temperature come to normal . The engine idled at 540-570rpm and the VOM at map sensor read 1,87V which I think it is very high. I pushed the throttle from idle to 2500 rpm and the voltage made a peak of 2,3v then 0,9v and finally again 1,87v@idle.
Do you think that these numbers are normal and the map sensor is good or not?
Thank you very much

 

[alldodge]

From what I can find, the MAP voltage is from 1 to 3V when motor is running. What voltage reading are you getting on the Gray wire?

 

[silver_power]

The grey wire is the pressure signal? If yes then the voltage at idle is 1,87v. I had reference voltage 5v. I think that at idle the signal voltage should be around 1-1,2v from these I read at the net...

 

[alldodge]

The Gray wire is the 5V reference voltage, and at idle it should read between 1 and 2V on the Lt Green wire

 

[silver_power]

I am on my way to the boat to check if there is any vacuum leak at intake using a car cleaner (that is what I have). I also have a new tmap sensor with me .I hope to have good news after that and to solve mu problem.......

 

[alldodge]

I should have thought of this before, but did you install the distributor according to the manual, and NOT adjust it with a timing light?

 

[silver_power]

Finally it was the map sensor. The voltage reading at idle with the new sensor is 1,68v instead of 1,87v the idle is very steady with no smell of gas. The most important is that the boat runs again with 3,4-3,5 mpg according smartcraft. So back to normal! Many thanks. Just for history...I put a bosch tmap sensor at 1/5 of the price!

 

[alldodge]

Cool, great to hear