SJ120 fuel pump question - light pulse of fuel

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Daley

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Jun 30, 2009
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After letting the boat sit for a couple years and then not able to get it started, I began my troubleshooting. Here are the steps taken so far:

1. checked fuel lines for cracks and dryrot
2. tightened all hose clamps to make sure no air is leaking in
3. replaced fuel pump diaphragm per service manual (putty-knife method, etc)

With still not much more than a light "pulse" of fuel at this point, I suspected a clogged screen in the tank, so I pulled the hose from the tank and stuck it in a gas can. Same results - barely a pulse of fuel at the fuel pump outlet hose.

What am I missing?
 
aksor

aksor

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Re: SJ120 fuel pump question - light pulse of fuel

Did you replace the gaskets and the gasket behind the pump and engine did you check the check valves and the filter on the fuel pump? How about your pulse line hose.
 
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Daley

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Re: SJ120 fuel pump question - light pulse of fuel

Aksor, your advice seems spot on based on the performance on the water yesterday. It starts right up and momentarily goes to full RPM at WOT, but immediately falls on its face under load. To me, your advice makes perfect sense - while I did check the filter and replaced the INTERNAL gasket, I did not replace the gasket between the pump and engine. I also did not check the check valves.

I don't have that gasket right now, but I'll be ordering one today. Meanwhile, I'm off to the garage to check those check valves and pulse line hole.

Thanks so much for the advice - I'll post my results after taking it out today.
 
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Daley

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Re: SJ120 fuel pump question - light pulse of fuel

I'd like to thank Aksor once again for his spot-on advice. After replacing the gasket between the block and fuel pump, I noticed a world of difference!
 
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Anders67

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Re: SJ120 fuel pump question - light pulse of fuel

Hi.

3 valves in the pump. Look so they work and are closed in their seats.


Pressure shall be 3,5 on idle 6 Psi on WOT.


Look so you put the lid on intake to the fuelpump, with inlet for hose/gas in 4 o klock position.



Arrivid. !!! Anders
 
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Daley

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Re: SJ120 fuel pump question - light pulse of fuel

Thanks Anders!

I did check those valves, and they LOOK LIKE they seat, but as you suggest - there is no good way to know for sure without a pressure test. I can say that the inlet hose was originally in the 3 o'clock position, but the service manual clearly says it should be (as you said) in 4 o'clock - which is how I reassembled it.

The performance is MUCH better now, thanks to all the helpful advice in this thread.

I appreciate it, and my family appreciates it!
 
aksor

aksor

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Re: SJ120 fuel pump question - light pulse of fuel

A good test is to take her out for a nice wot run and see if it hesitates, if not your good to go:)
 
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Anders67

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May 23, 2012
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Re: SJ120 fuel pump question - light pulse of fuel

Check the fuelflow so it?s correct. Becaurse you can melt the pistons if you run the engine a little lean.

This #&%!!" poltergeist engine , run so ruff, even when it runs as it shall ( not spinning like a cat). So it hard to hear if its just leaning a little.



I know the hard way . On 120 engine mine nr 4 cyl (lower) was cutting of one time, took out the sparkplug and it had started to be overheated, ok that time. But now it happend again, and now i need a new piston :facepalm: .

On mine it was probably a little flake of debris in fuel hose from tank, clogging before fuelfilter on full throttle. Hard to hear .
 
aksor

aksor

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Apr 21, 2009
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Re: SJ120 fuel pump question - light pulse of fuel

what kind of sparkplugs do you guys use? zero gap surface plugs or champion gapped plugs?

Sorry to hear about your engine woes Anders67
 
D

Daley

Petty Officer 3rd Class
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Re: SJ120 fuel pump question - light pulse of fuel

I've read a number of posts here on iboats where people haven't had great luck with anything BUT the Champion plugs. While Champions haven't always been my first choice for anything else (motorcycles, cars, etc.), they seem to be the best in our engines - so that's what I'm running.
 
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Anders67

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May 23, 2012
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Re: SJ120 fuel pump question - light pulse of fuel

Here they recommended NGK BZ7-HS10. To this engine.


Nippondenso,Bosch,NGK is probably the first choise around here.

Autocraft and Champion i haven?t used so mutch.


Then all fabrics have special plugs, for special engines.


Halo and Brisk is something they testing around here to. Point to use them are that you don?t have the side electrode.


Have that in one of mine motorcycles.


And sometimes when thinking it around, is it better with one electrode ? , i wonder, is it not better if sparks come in same place every time? ( for burning chamber,ingnition, injection, valves et.c).


Regards Anders
 
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