1991 Force 90 HP: need to pump bulb to keep it running

[BarryK3]

Hi all,

The motor developed a new problem today. The engine quit while going slowly in the harbor. I pumped bulb about 5 or 6 times until hard, then it restarted fine. It quit again after about 2 minutes. I had to do this repeatedly to limp back to the boat ramp. Earlier in the day it ran fine at WOT, 35 mph as usual. The rpm increases prior to quitting, like it is lean just before running out of fuel. It takes quite a few pumps until the bulb gets hard which implies to me that the carb bowls are empty.

The bulb does not go flat, so I assume it is not a restriction at the fuel tank inlet. No fuel leaks, bulb gets hard.

I checked the screen in the fuel pump and there was only minimal debri. I don't have a fuel filter or water separator. I recently replaced the pump bulb and fuel lines.

I assume it is a fuel pump problem? Is any other troubleshooting needed before replacing the diaphragm and gaskets?

Thanks,
Barry

 

[jerryjerry05]

More than likely it's the fuel pump.
It can also be that the inline connectors can be bad.
And the squeezie can be bad too.
There are seals in there that can go bad from age and Ethanol.
The squeezie has a 1 way valve that can go bad.
Even NEW squeezie's can be bad.

Get a remote tank with no connectors.
Hook it up and go for a ride.
If it does it again?? rebuild the pump.

The 91 usually had the 8 shaped diaphragm.
I think they sell them here.

 

[BarryK3]

Thanks Jerry!

There are also "check valves" in the fuel pump. They are not included in the rebuild kits which have the diaphragm and gaskets. Do these also need to be replaced?

 

[BarryK3]

Check valve part number 21-8M0082362: 3 per assembly?

 

[jerryjerry05]

Not usually.
If they are still complete, they can be reused.

Since 1986 I've only seen 1 valve that needed replacing.
It fell apart and yet was still working when I changed the diaphragm.

 

[BarryK3]

OK Jerry, you are right again "Even NEW squeezie's can be bad".

I rigged up a fuel pressure gauge, got a 0-15 psi gas pressure gauge for Home Depot for $10. I pumped it until the bulb was hard, read about 7 psi. Then I started the motor. It worked its way down to 0 psi, with a lot of fluctuation due to the engine pulses.

Then I connected an old fuel line and bulb that I recently took off (since the rubber was old and got my hand black). I put the end in a 5 gal. jug of gas mix. The engine settled at 3 psi (with fluctuations due to engine pulses) and ran just fine! I think I read somewhere that 3 psi is the correct spec. for fuel pressure.

Then I examined the "new" bulb and gas line. It was very hard to blow through it from the tank end. The "old" fuel line and bulb required almost no effort to blow through. I think the old was is OEM and the new one is a cheapo from Amazon.

I blew through the hose barb fitting on the engine well back to the main gas tank and this line was wide open, no restriction.

I hooked up the old bulb and fuel hose to the motor and main tank and I will run the motor on the muffs tomorrow and see what happens.

I should probably change all of the fuel and vent hoses too but I think the cheap bulb is the culprit!

The attached video is the "bad" bulb connected to the main tank.

 

[BarryK3]

This video is of the old OEM bulb drawing fuel from a gas jug.

 

[BarryK3]

A couple of tank questions: How would you open up the fuel tank to clean it and clean the pickup tube? Would you open the round metal plate or the larger black plate which includes the gas line connections? How do I seal it afterwards?

Thanks!
Barry

 

[jerryjerry05]

The square plate might be real hard to reseal??

Me, I'd pull the sending unit and see how bad the tank is from that hole.
Most times the pickup tube is just a hollow tube,some are plastic and some are stainless.
Some tanks have a filter/ screen on the bottom of the pickup tube.

I hook up a longer hose and siphon off the fuel first.
Have a fire extinguisher close.
Use NO electrical equipment, battery drills included.

Away from the tank I have a high output fan that I use to blow the fumes away.(my lungs ain't the best)


Bad squeezies, went through 4 in one day.
Seems Tempo had a bunch of bad ones.

 

[BarryK3]

I connected a new Moeller primer bulb to the gas line to the main tank and I saw only about 1 psi on the gauge with a lot of fluctuation of the needle. I had already ordered a fuel pump rebuild kit , so I took the pump apart. I found that there was a fairly large hole in the diaphragm and the gasket between the pump and the transfer port cover plate was missing entirely!! The engine was rebuilt a few years ago for a previous owner...

With the new diaphragm and the proper gaskets I saw a steady 3.5 psi on the gauge! I also cleaned out the tank and replaced the 1990 vintage fuel line from the tank to the hull fitting. The tank did not have any water or debri in it and the old fuel line was intact. I took the boat out yesterday and it ran great. The fuel leak that I wrote about a while back finally seems almost cured. A lot of it was coming from the pump.

So. if your fuel pressure needle bounces, you need a new diaphragm. The needle should be steady at over 3 psi.

 

[BarryK3]

Here is a video of the fuel pressure with the rebuilt pump and Moeller primer bulb:

 

[jerryjerry05]

Thanks for the update.