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briggs archer
briggs archer, Marine Mechanic
Category: Boat
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Experience:  30 years professional marine mechanic=skilled in all phases of the marine service industry.
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I have a volvo penta 5.0 Gi throttle body injection. It sat

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I have a volvo penta 5.0 Gi throttle body injection. It sat for 5 or so years. I got it to run bad on bad gas, I added a full tank of good gas to a very empty tank of bad gas and added an injector cleaner as well. At this point is gets so much fuel into the intake the engine hydrolocks on the raw fuel. (not water, fuel). Fuel rail pressue is 27 psi. Pressure loads up when the key is turned on than dropes rapidly to zero 10 seceonds or so.
I see a fuel pump above the seperator (new seperator just changed) then the lines go to something on the back of the engine before it goes into the throttle body. I have removed the wires to the injectors to stop fuel flow from there but also notice a flex line from the unit on the back of the engine to the base of the throttle body. What are the recomendations to get the boat running.
JJ [email protected]
The fuel is being forced through the open injectors causing excessive fuel in intake and loss of fuel pressure. It will be necessary to clean the fuel system. Purchase a product called power tune or engine tune.This chemical will break down old fuel residue called "varnished". The fuel lines go back to the VST(vapor separator tank). It will be necessary to remove it from the engine to service properly.This tank has a float,needle and seat and the high pressure fuel pump inside. Remove the top and fill it with engine tune,let sit for 24hrs . Empty,reassemble with new gasket and 'o'Rings.Install back on the engine. Also fill the water separator with engine tune ,Run low pressure fuel pump to fill lines to VST. Remove the two injectors and soak them in engine tune as well. The low pressure pump above the separator should hold 4-5 psi. The high pressure pump inside the VST should hold 30-35 psi. The injectors can be activated with 12v.... good luck.
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Customer: replied 6 years ago.

Finished the work and it runs, still rough may need to do more work on the injectors. Root cause was a stuck float in the fuel reservoir.



That's real good news! Did you try to activate the injectors while soaking? that helps. If they continue to inject poorly just replace them...Too cool.
Customer: replied 6 years ago.

Activate while soaking? 12V and engine tune sounds like a recipe for disaster. I all ready had a bilge fire cleaning out the hydro locked fuel, scared the crap out of me. I had an extinguisher close so little damage, I feel like a fool. Lake tomorrow afternoon to run a ton of treated gas thought it. We will see how clean they come.


Well, good thought. But what I meant was ,soak then lift out of solution and test then soak again. Just make sure the test leads are connected to the injector and touch the other ends of leads to 12v battery away from engine tune . Flash point is much higher than gasoline. At any rate, after running engine for a while they may clear out fine .

Customer: replied 6 years ago.

Had the injectors flowed last week "cleaned and checked in spec" Could not get an answer from the guy on the as recieved condition. Took the boat to the lake this afternoon runs better, but still has an issue. I run wake less for about half mile, then when I get after it, the boat stumbles, likes to run at 3/4 or 7/8 not full throttle. After a lap or two around the lake it is better but not 100%. I think it is loading up on fuel in the wakeless, then takes a bit to blow it out. I checked for leaks around the throttle body, looked fine. After the wakeless gas is blown out i get about 4600 RPM.

What are your ideas?



HERETake a look at this picture.(#20) is the Idle air controller. Remove it and make sure the pintle and seat is clean. It can get rusty. Most likely the pressure regulator(#1) is allowing too much pressure and pushing fuel past the injector at low rpm.The whole top assembly (#2) must be purchased.
Customer: replied 6 years ago.

I had 27 psi in the rail at the beginning of this mess. The regulator spring and diaphram looked good, no leaks spring was not rusty in good shape. I will take a look at the pintle tonight.



Ok. Caution! do not try to run the iac after it is removed. It will come apart.
Customer: replied 6 years ago.

Remove clean and reinstall pintle. Then run. Come apart? as in overspeed? Cool :-) been a while since I gernaded an engine. Or are you saying do not put 12v to the IAC because it will come apart?

Yes. do not apply 12v to iac after it is removed.
Customer: replied 6 years ago.

Pulled and cleaned the IAC, little soot, but looked fine and dandy. I also rechecked the fuel pressure, jumps straight to 30ish and still falls off in 3 to 5 seconds. I did it a couple of times and the injectors stayed dry. I have pulled apart the throttle body and the pressure regulator and spring looked good. I would assume that when I started and ran the pressure would hold steady as long as the HP fuel pump would run. Did the same to my Truck it holds ROCK steady at 40ish.


I was thinking about looking for codes but did not see the Data Link Connector. do I need to pull one of the connectors on the ECU?


What about the TPI I noticed that it does have a throttle cable but it is not HARD linked to the butterflies could that system need cleaning or lubrication.


I am open for suggestions.


Thanks for your time and patients


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