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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3431
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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98 135 Optimax shut down while running. Compression ok. Fuel

Customer Question

98 135 Optimax shut down while running. Compression ok. Fuel pressure in both rails. No fuel passing thru exhaust while cranking. Starts and runs on starting fluid. Im guessing an electrical malfunction preventing injectors from operating. Any suggestions?
Submitted: 3 months ago.
Category: Boat
Expert:  Charles replied 3 months ago.

Hello, my name is***** will assist you.

Expert:  Charles replied 3 months ago.

Do you have the serial number on the engine?

Customer: replied 3 months ago.
There is one on there but it is several hours away. Were they each built differently?
Expert:  Charles replied 3 months ago.

There was a big change on the 2000 model. But on your 135, there is a row of fuses on the ECU, part 219 in this diagram. Make sure that all fuses are still good. The most likely cause of this is that one if then is blown. If once you replace the bad one it pops as soon as you turn the key, one of the injectors is shorted.

Customer: replied 3 months ago.
I wrote that up in the first attempt. It didn't get to your version though.
I checked the fuses. There were 4 20a fuses mounted on the side. I gave them a good visual check at least twice. I did not test with a meter however. I also looked for inline fuses and didn't find any.
Expert:  Charles replied 3 months ago.

There are just those 4 fuses. With the key on, each should show 12V of both of the small posts at the top of them.

How did you check for fuel pressure to the rail? It should be running at 90 PSI, air pressure should be at 80 PSI.

Customer: replied 3 months ago.
I will ck fuses and power to them asap and let you know if that solves it. Someone (self proclaimed mechanic) at the marina checked fuel pressure at the Schrader valves on top of fuel rails. I don't know about air pressure. How would I check that?
Expert:  Charles replied 3 months ago.

On the opti, there will only be fuel on 1 of the schrader valves. The other is for the air, which can be checked by cranking the engine over and watching the gauge go up.

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