2000 Pro Air Nautique - fails to start, already replaced a lot of parts

[comanche344]

Hello All,

So I've posted a couple times about my Pro Air Nautique. Its a 2000 with the PCM 5.0 HO engine (275HP , Chevy 305, TBI). When I purchased it a month ago (not running), there were several major systems that needed overhall (mainly the fuel & cooling). Here is what we have replaced so far.

Fuel System
- Low Pressure Pump (Replaced) - https://www.nautiqueparts.com/produc...-pcm-ra080018/
- FCC (Fuel Control Cell) (Replaced) - https://www.nautiqueparts.com/produc...part-ra080031/
- Fuel line between Low Pressure Pump & FCC (Replaced) - https://www.nautiqueparts.com/produc...-pcm-ra085062/
- Both send & return fuel lines from the gas tank (Replaced)
- Injectors (Replaced) I also removed and cleaned the housing for the injectors
- Fuel Sending Unit from tank (Replaced) - https://www.nautiqueparts.com/produc...6-inches-long/
- Cleaned all connectors between the lines (Tank, TBI feed/return)
- Drained about 25 gallons of bad gas out of the tank, still had about 1-2 gallons of bad fuel that the pump I was using could not drain out. I then filled it up to the brim with 93 Octane fuel (30 Gallon Tank). This might be the issue still, so that's why it is in bold

Cooling System
- Thermostat Housing, Alarm (Replaced) - https://www.westmarine.com/buy/sierr...8?recordNum=18
- Water Circulating Pump, temp sensor (Replaced) - https://www.nautiqueparts.com/produc...ing-pump-5-7l/
- Raw Water Pump, Impeller (Replaced) - https://www.nautiqueparts.com/produc...-crank-driven/
- Cleaned water strainer

Cooling system seems to be flowing correctly after part swaps, don't believe this is the current issue)

Power
- Spark Plugs (Gapped & Replaced)
- Verified spark on all cables and checked distributor for wiring placement to the cylinders

Dash
- Temperature Sensor, Oil Pressure, Fuel Gauge, Battery (All working)

Oil & Filter Replaced

What I still need to replace (broken)

- RPM Gauge
- Speedometer

Current Issue:

So last weekend my friends and I finally took it out on the water after working on replacing the above parts. We still had issues with idling, so we routed the full send/return lines to a 5 gallon gas tank, and the motor had zero issue (drove up and down the creek at up to 40MPH (GPS phone). As soon as we attached the lines back to the tank, we ran into more idle and revving issues.

Yesterday, I replaced the raw water pump (old one was leaking), connected a hose up to it, and fired it up and ran perfectly idle for about 10 minutes (See Video Below). I noticed that the raw water pump was wobbling slightly, so I stopped the motor to tighten the bolts. When I went to fire it up again, the engine would not fire up properly (tried about a dozen times with various positions of the throttle)

Sorry for the long post, but I wanted to give as much detail as possible. What do you guys think is the issue here?

https://youtu.be/y8xgo6rs6rk

[functionoverfashion]

The fact that it ran fine on an independent 5 gallon tank tells me the problem is in the fuel system "upstream" of wherever you interrupted it for the connection to the external 5 gallon tank. You said you replaced the fuel lines and sending unit, but that, as you put in BOLD, there might have been a couple gallons of bad fuel in there?

So what do you mean by bad fuel exactly, that was in the tank? If it could have been a bunch of water, then yeah you could still be having issues from that, and will need to more completely empty the tank to proceed.

When you ran it after messing with the raw water pump and you said it ran fine at idle but then wouldn't run later, was that on the internal tank?

Also, the fuel pickup in the tank could be getting clogged with debris, if there is any in the tank; then when it's clear, of course it would run fine. At higher speeds (with more fuel flow) it would tend to get clogged up more easily.

Long story short: Running the boat on the water on a separate tank is a great diagnostic method to separate fuel issues from potential spark issues. If your boat runs great on an external tank, you've got a problem in your internal tank or otherwise "upstream" of the external tank.

[Blamey]

Did you replace the anti syphon valve at the tank?

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[comanche344]

Q: So what do you mean by bad fuel exactly, that was in the tank?

A: So the owner that we bought from said it hadn't run in at least a year (I suspect maybe 2). There was originally about 25 gallons in the tank so I have no idea how old that gas is but I suspected it had been there a while.

Q: When you ran it after messing with the raw water pump and you said it ran fine at idle but then wouldn't run later, was that on the internal tank?

A: From the video, that was running off the tank directly. We used the gas can last week when we took it out on the water.

Q: Also, the fuel pickup in the tank could be getting clogged with debris, if there is any in the tank; then when it's clear, of course it would run fine. At higher speeds (with more fuel flow) it would tend to get clogged up more easily.

A: When I replaced the fuel lines running to the tank, i pulled the fuel pickup and visually inspected it. No debris in the tube or in the mesh filter at the bottom. I still proceeding to flush it with water and some carb cleaner, then let dry and reinserted into the tank.

Q: Did you replace the anti syphon valve at the tank?

A: Can you clarify what this is? I cleaned the connectors that attach the hoses to the tank, did not clean any valves.

Thank guys for the fast responses!



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[Blamey]

For the anti shiphon. It's a value on the feedline from the tank to the lpp. It's know to cause issues. Much like what you are seeing.

I am not familiar with your specific engine but if I were you I would get a fuel pressure gauge and check that if possible.

It's the easiest way to eliminate a fuel delivery issue. If pressure is good then it's probably bad gas.

Because you didn't have an issue on the 5 gal tank, I assume that it's either the bad gas or some type of blockage at the tank.

https://www.nautiqueparts.com/produc...-siphon-valve/

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[swatguy]

Far from a super tech , but it sounds like bad gas .


Sitting for long periods of time , especially depending on where it sat and what kimd
of temps changes it was susceptible too can really wreak havoc on fuel. My best guess is there is water in the file from condensation. I would empty the entire tank. Don’t even mess around with additives ,and fill it with fresh gas.

[Evening Shade]

Like Swat said far from high tech, but it sounds like it is picking up some water from the bottom of the tank. I would I would try to drain the tank completely.

[functionoverfashion]

Like Swat said far from high tech, but it sounds like it is picking up some water from the bottom of the tank. I would I would try to drain the tank completely.

Especially with the answers you gave, and the fact that it ran great on an independent 5 gallon tank, I would do that next. You may still need to drain some water from the fuel filter, if you've been running it on the internal tank and there's some water in there.

Grab one of these:
https://www.amazon.com/Hopkins-10801.../dp/B000EH0ORI