I Need opinions AQ120B

[oldrenken79]

Hey all, just signed up here. And I'm stumped.

1979 Volvo-Penta AQ120B. New timing belt, head redone, carb (Solex) rebuilt. Timing fine at 10, entire ignition system replaced OEM.

Here's the problem. Doesn't want to idle until it's been run awhile. Coming off idle position, runs okay up to about 4200 rpms.

As it's running along if I throttle up beyond 4200 up to WOT she screams along fine, then suddenly dies as if the fuel has been shut off. Throttle back quick enough and it catches and keeps running. If it stalls it always starts right back up and runs okay.

Tank vent has been cleaned and vent line replaced. The tank is a 26 gallon aluminum and it had about six gallons of the bad stuff in it, but I topped of the tank at the local Exxon and added HEAT to clean it up. I replaced all the fuel lines tank to water seperator and seperator to fuel pump with the same size that was on it, which is 5/8" marine fuel hose. Also replaced seperator filter.

Two questions.

Is it possible the fuel line is too great a diameter and the fuel pump simply can't keep up?

Is it possible I have some kind of blockage in the fuel pick up?

I appreciate anything you guys can come up with!

 

[Don S]

Re: I Need opinions AQ120B

The 5/8" hose is for the vent line for the tank. The fuel pickup hose should be 3/8"
You may very well have fuel problems. But there are also tests for that.
Have a read at this.

http://forums.iboats.com/showthread.php?t=283269

 

[oldrenken79]

Re: I Need opinions AQ120B

Outstanding, thank you!

It's always the simple stuff that causes the biggest headaches.

I'll get back after I do this and let you know. Spent six years restoring the old boat and this is the only thing holding me up.

 

[Gary H NC]

Re: I Need opinions AQ120B

If you had 6 gallons of fuel you know was bad and was maybe water contaminated then topping it off and adding snake oil is not going to solve the problem.
Now you have 26 gallons of crappy fuel.

I would install a water seperator filter if it does not have one.

And read the stuff in the link Don gave you..

 

[Paul Ryan]

Re: I Need opinions AQ120B

Here's the problem. Doesn't want to idle until it's been run awhile.

Just got through rebuilding my AQ125A and really really don't like the Solex. I'm assuming you know that the Solex does not have a choke assy. Mine WILL NOT idle until after the thermostat opens (hot engine). I have to pump the throttle 2 or 3 times start and run at 1200/1400 until 180 degrees. Then it will idle just fine. If the engine sits for a few minutes not running, I have to pump the throttle to get it started again. What I have heard from others here, this is normal.

Guys have got you covered with the other issue's.

 

[oldrenken79]

Re: I Need opinions AQ120B

Thanks guys, it is appreciated.

Today I pumped out the tank (only had a half tank) and replaced all the fuel lines, clamps and fittings. Mounted a new water separator and installed a clear glass inline filter.

Trip to the gas station (geeze, $2.80 a gallon) and pumped in 15 gallons and took her to the lake.

Here's what I've got now. No air bubbles in the line while she's running, but it looks like I might have a weak fuel pump. The inline filter filled up at first, and was okay running slow, but as soon as I throttled up I could actually see the flow slow down and the next thing you know I was looking at an empty filter.

I don't know, what do you think? Should I go with an electric unit or try to find a brand new 30 year old fuel pump? According to the shop manual I only need 2-4 psi to the carb.

 

[captmello]

Re: I Need opinions AQ120B

http://www.volvopentastore.com/Fuel_System_Aq120b/dm/*******.313965825--**********.091433877--store_id.366--view_id.325818


OEM part right here from Iboat. Darn right affordable I'd say.

http://www.iboats.com/Volvo_Penta_Fuel_Pumps/dm/*******.313965825--**********.091433877--view_id.269370

Aftermarkets also available on Iboats.

Sounds like your close to solving your problem.

 

[Don S]

Re: I Need opinions AQ120B

and installed a clear glass inline filter.

Not a good thing to do. Those aren't supposed to be on IO boats.

What are your test results from the tests in the link I gave you in my original reply? That will tell the story.
I seriously doubt you have a weak fuel pump. But you could check the pressure ............ IF you can get the fuel out of the tank.

 

[captmello]

Re: I Need opinions AQ120B

Could be the pickup tube or anti siphon clogged up.