Mercruiser 3.0L Fuel Pump Diagnosis?

[SnappaHead]

2008 Mercruiser 3.0L GM 181 / I/L4 (Mechanical Fuel Pump)

Hey guys, first time posting, but have spent the last two weeks on the forum, thanks for everyone's time spent helping others with their boat issues!

My issue:
My boat would start and idle fine and run well up to 7 mph. After that if would bog down when throttle was applied (no where near plane). The boat ran fine under 7mph though. (Keep in mind everything ran fine 2 weeks prior)

I brought it home and changed the fuel filter in the fuel pump

Next time out - no change, but now it was a little harder to start after the engine was warm.

Next I changed:
Fuel pick-up (no debris in old screen)
replaced anti-siphon valve (old seemed fine, but replaced it anyway)
Cleaned out inline fuel screen at carb (slightly dirty, but nothing major)
Checked vent lines (no issues)
Replaced plugs (very dirty)
Replaced cap and rotor
Replaced water separator
Cleaned flame arrestor

Today I started it in the driveway on the muffs
It ran well for a about a minute - then died and wouldn't restart (even after opening the fuel cap)
I pulled the fuel line to the carb and no fuel would pump into the bucket when cranked.

My question:
Is this a fuel pump issue? Do I need to bleed the fuel line somehow after all the fuel line work above (If so, how)?

I don't have a fuel pressure gauge, but would be willing to buy one if necessary to diagnose (of course $20 gauge vs $95 fuel pump maybe just put the money in the pump). But would the fuel pressure gauge work anyway if no fuel is getting to carb?

Any help would be great, trying to avoid the mechanic and learn a few thing along the way.

Thanks,

 

[ThomW]

This might be a silly question, and I am not trying to insult, but are you sure you installed the anti-siphon valve the right way? Is it stuck? Seems like it started and ran for a minute on the gas in the carbs and then died.

 

[Rick Stephens]

Might try priming the fuel water separator.

 

[SnappaHead]

Yes, it can only be installed one way. 1/4" NPT on one end that threads into the fuel line pick-up and a barbed fitting on the other end for the fuel line.

 

[SnappaHead]

Good idea on priming the separator. I assume you just prefill the separator prior to screwing it on?

 

[Bondo]

Good idea on priming the separator. I assume you just prefill the separator prior to screwing it on?

Ayuh,..... Welcome Aboard,...... I usually fill 'em nearly, but not full, to cut down on the spillage,......

 

[SnappaHead]

Thanks guys, after priming the engine is now running. whew! Now to put it in the water and see if it still bogs down, not something i can recreate in the driveway. Fingers crossed...

 

[Scott Danforth]

Now spend $35 on a carb kit and clean the carb

 

[Scott06]

Now spend $35 on a carb kit and clean the carb

In addition to the carb rebuild have checked the timing and confirmed the ignition is advancing

 

[SnappaHead]

OK, after getting the fuel flowing- everything ran great on the water. I believe the original problem was ignition related. One plug looked horrible and the points were super dirty in the cap. I would have bet money it was fuel related prior to reading through this forum. Thanks for the tips. It does seem strange to me though that it seemed to idle fine, but at increasing throttle it would have ignition issues? I guess I just assumed you had good spark or you didn't - regardless of throttle position.

Anyway, things are running well now, thought I would post the follow-up. Seems like some threads have lots of back and forth but the original poster never posts the final follow-up so we don't know if things got worked out. Anyway, tight lines!

Rene