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Low pressure fuel pump went out... replaced pump rebuilt…

Low pressure fuel pump...

Low pressure fuel pump went out... replaced pump rebuilt fuel water separator. Now have fuel getting to the fuel rail but on the #3 cylinder all I’m getting is air from the test port..... why?

Mechanic's Assistant: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.

The motor won’t start after replacing the low pressure fuel pump and rebuilding the fuel water seperator with new o-rings. I verified there is fuel going to the fuel rail but all I get is air from the #3 test port

Mechanic's Assistant: Is there anything else important you think the Marine Mechanic should know?

The entire system only had 20 hours it’s a 2010-90 Optimax

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Customer reply replied 1 month ago
The motor is 90 DFI 3 cylinder
Answered in 3 hours by:
3/11/2018
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 16,746
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
Verified

Good morning, my name is ***** ***** m I speaking with? I read what you wrote. Can I start by getting the serial number on the outboard so I can pull the correct manual.

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Customer reply replied 1 month ago
Randy and the serial number is *****
It’s a 90 HP DFI (3 CYL) 1.5L
Customer reply replied 1 month ago
Just some basic info this boat set up for too long.... I replaced the fuel supply before I ran it with a clean tank and good fuel. I was running it on a garden hose until the fuel/water seperator went empty. It was about 10 min. I guess then trying to figure out why it quit. I discovered it wasn’t getting fuel. So as I said earlier I started at the fuel pumps. I verified once fixed the fuel shot out the high pressure valve to the fuel rail. But it still doesn’t start. I checked to be sure all cylinders were getting spark. Then figured out the #2 cyl. test port on the fuel rail would spit out fuel but the #3 cyl. Test port Will only spit out air. ( the test ports look like a valve stem for a tire. ) I wondered if I needed to bleed the air out or if something else went bad....
Customer reply replied 1 month ago
E was spiting fuel
C was only air
D I didn’t try

Y​ou would have either E or D, not both. E is the fuel test port, C is the air test port. Do you have gauges to actually check the pressures coming out of these ports?

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Customer reply replied 1 month ago
No but I see why now it was only air and that’s why I didn’t try D it’s not there.. I just assumed fuel would come out of all of them....
Customer reply replied 1 month ago
Since the fuel rail is there my guess is there isn’t any carburetors. It’s a direct injection into the cylinders

They redesigned the fuel rails. So you would have either E or D, but not both. The fuel rail has 2 chambers inside of it. 1 chamber is for fuel, the other chamber is for air. The pressures will need to be checked for both. Fuel pressure needs to be 110 PSI. Air pressure needs to be 95. If you want to test these pressures yourself you need a gauge kit, mercury part number 91‑881834A 1.

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Customer reply replied 1 month ago
I will have to find my old one to see or get another one..... but am I correct in assuming there is no carbs on these motors?

That is correct, this is a DFI engine, Direct fuel injection. The engine has fuel injectors and air injectors.

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Customer reply replied 1 month ago
Ok I’ll test the pressure first then look at the injectors my guess is they are dirty and clogged....

T​hese are pretty complicated engines. Are the fuel injectors clicking when the engine is cranking over? Do you have a stethoscope to listen to those injectors to see if they are clicking?

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Customer reply replied 1 month ago
I do have one I will try that as well

Okay let me know what you find.

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Hello, just checking in. How did you make out?

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Customer reply replied 1 month ago
Call brother I got called back out on the road it’s a truck drivers world but I’m hoping to make it back within a day or 2

O​kay just post back when you are ready, and we will take it from there.

Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 16,746
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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