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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a 1996 Volvo 5.8 FSI (275hp) The engine is in safe

Customer Question

I have a 1996 Volvo 5.8 FSI (275hp)
The engine is in safe mode, and limits the rpm to 2700.
It did need an impeller which has been replaced.
The temperature shows 160, and the oil pressure appears to be normal.
The battery is a new 675 cranking amp which admittedly seems marginal turning it over.
The boat has been put in the lake to ensure that a full water supply was available which did not help.
I have disconnected the battery now to see if over the next few hours it will reset.
The shop manual indicates that if the low grade problem is repaired by starting with a cold engine it will reset. So far no go.
Any suggestions?
Thanks Steve Hayward
Simcoe Marine Surveys
Over 20 years experience.
Submitted: 7 years ago.
Category: Boat
Expert:  Jeremy R. replied 7 years ago.

are you getting any codes from the motor?
Customer: replied 7 years ago.
No one has the connector for this engine series. The most experienced Volvo people I know don't have it. This is the same engine and EFI used in the Ford trucks a few years back, but again the connector is different.
As previously mentioned the battery is disconnected now, and I will try a larger CCA (1000) battery in the morning. I will also check the terminal connections & grounds on the engine. A well qualified Volvo mechanic I know has said this is my best shot, and to cross my fingers.
Here is the sister ship which runs perfectly.
Customer: replied 7 years ago.
We have a solution I believe.

I see that this thread is a couple of months old but, were you able to solve the problem? I had the same problem with my Volvo Penta 5.8fi. If the engine cuts out at 2800 rpm, it is the Slow Circuit being activated. The ECM will stop firing injectors until the rpm drops below. The ECM does not remember this mode. Once the sensors return to normal, it switches this mode off. It only works for a low oil pressure or over heated water temp. and they are controlled by seperate sensors. The engine actually has two oil pressure sensors and two temperature sensors. The sensors for the SLOW circuit connect to ground if their threshold is met. All SLOW circuit sensors are connected to the same wire that goes to the ECM. If any sensor is grounded (or if the wire has a break and is grounded) will cause the ECM to enter the SLOW mode. The ways to diagnose it are to use a code scanner and plug it into the diag port for the ECM. It will give a code indicating that the computer is in SLOW mode. (I can't remember which code it was, it was in the Volvo Penta service manual). You can also test the wire that goes to the computer to see if it is grounded. (At the back of the engine where the wires come out of the harness for for trim/tilt sensor, there are two loose wires. One is ground and the other (I believe it is brown) connects to the SLOW circuit. If you jumper these two wires, you'll put the computer in SLOW mode. You can test the brown one by itself to see if it is grounded.) The next step would be to disconnect the oil and temp sensors seperately to see which one is not functioning and then replace it. For me, it was the oil sensor. Even though the oil guage was showing proper pressure through its sensor, the oil sensor for the SLOW circuit was faulty.

Something most don't know or think about is that the ECM will go into "slow mode" if the trim indicator is not working as it should. (They didn't want high RPMs if the drive was up.)

Is your trim guage working properly?

The ECM is powered up via a separate lead with fuse that is attached to a battery and it’s always on. To power cycle it remove the fuse or disconnect it from the battery post.

Expert:  Jeremy R. replied 7 years ago.
Did it work for you?
Customer: replied 7 years ago.
I'm sure it will. It's a major rainstorm, and th eboat is going inside.
Have you seen one run?
Here is my other one.
Expert:  Jeremy R. replied 7 years ago.
It doesn't get much better than that!
Customer: replied 7 years ago.
Here are my two boys having too much fun as well.
Expert:  Jeremy R. replied 7 years ago.
That's a sweet boat.. I believe I would trade my nautique on one of those.
Customer: replied 7 years ago.
I have a 17 with a 350 in it for sale as well. MINT!graphic
Come and get it!
Expert:  Jeremy R. replied 7 years ago.
That's getting a little small for my taste.
Let me know if that works out for you.
Expert:  Jeremy R. replied 7 years ago.
so did that work?