98 Volvo Penta 5.7 GLI throttle body injection fuel pump issues, help please!!

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stang32

Chief Petty Officer
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Jul 16, 2004
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a little background:
the boat was bought this year with 850 hrs on it, the PO told my friend no issues about the boat however it has an overheat problem, which I have a seperate thread regarding, now I find that it has a stalling /no start problem,
the boat has a constant stalling problem, which was there prior but not as constant as it is now, now it is not running more than is is running. i have checked the fuel pumps & i am not sure i am getting enough fuel pressure. the shreadder valve on the fuel line is reading 14psi, the schreader on the rear fuel pump assy is ony 10 psi, i have read that i should have 29psi . the boat has throttle body injection. i have read about the black paint chips in the screens but i believe that is on the newer EFI models, can anyone confirm?
also which pump is which, high presusre & low?
one pump is in front above the water separator & 1 is in the back of the motor on top of some sort of box, also were the shredder valve is.
does this engine have a pressure regulator?
where are the screens located that get clogged?
the rear pump got brutally hot at 1 point but cooled down shortly after. the IR gun read over 150 degrees.
 
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evantful

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May 11, 2014
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The high-pressure fuel rail should be getting 29psi +/- at idling or momentarily switching the ignition on. The low side seems somewhat high with a 10psi reading, but not terribly out of spec.

The TBI do have a pressure regulator built into the injector pods bracket.

What is the exact model number of your engine, it should be listed on on the engine somewhere. Make sure to include the letter string (letters vary), i.e. "Volvo Penta 5.7GSI PWTR"
 
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mklearl

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Apr 21, 2013
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I would also test the low pressure side. Just because the pressure is low on the high side doesn't mean it is faulty... it may not be getting enough fuel from the low side, which is probably the case since your high pressure pump was too hot to touch (running fine but no fuel going through it). Unfortunately, you may have fried the high pressure pump now.
The low pressure pump brings fuel to that tank thingy... the vapor separator tank. This tank is a means of delivering undisturbed fuel to the injectors. It works a lot like a carb, has a float in it, and can clog where the high pressure pump attaches and draws from. The float may not be set right. There is also a water inlet and outlet on that tank which cools the fuel so it doesn't turn into vapor, hence vapor separator tank. That has a tendency to clog with corrosion and could cause a stalling issue if you are getting vapor rather than fuel. I don't think so in your case, but if you are checking it it would be a good idea to clean it out.
You do have a pressure regulator as stated above which can also be cleaned. Again, I think your problem is before that. Your high pressure pump is not getting enough fuel. Change the fuel filter and recheck the pressure. If the low pressure pump is functioning properly and filling up the vst then check the vst for cleanliness. Look in the stickies as to how to test BOTH pumps. Good luck!
Model number will help also... think it is just 5.7 Gi (injectedl) with some other letters after it?
 
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ericga

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Mar 4, 2012
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Check your fuel pressure regulator. You may have a broken spring or someone installed a 15psi spring (common in automotive GM TBI). Also inspect the diaphragm. You can get a rebuild kit that include the gaskets, diaphragm and screws to compress the spring.

Check your IAC and clean it if necessary while you're at it.
 
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mklearl

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Apr 21, 2013
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ericga said:
Check your fuel pressure regulator. You may have a broken spring or someone installed a 15psi spring (common in automotive GM TBI). Also inspect the diaphragm. You can get a rebuild kit that include the gaskets, diaphragm and screws to compress the spring.

Check your IAC and clean it if necessary while you're at it.
Click to expand...

Would the pump get hot to the touch if it were the regulator?
 
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ericga

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Mar 4, 2012
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I missed that part. The regulator shouldn't impact the pump temperature.
 
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stang32

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mklearl said:
Did you change the filter and test both pumps?
Click to expand...
yes the filter is new, the pumps were tested in line, not disconnected from the fuel system.,
the lp reads 10psi from the Vapor tank, the high side reads 14psi from the rail,
this boat already has a replacement LP pump. I would hate to condemn another pump without absolute confirmation.
 
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mklearl

Petty Officer 1st Class
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Apr 21, 2013
Messages
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High pressure should read 29 psi on the valve on the fuel line. If you only have 13psi you need to figure out why before you fry that pump if you haven't already. Test the low pressure pump following the link above and possibly from an external portable tank. In short, you will grab some clear plastic hose and hook it up to an external fuel tank. Run that hose to your fuel filter. Look for bubbles in the fuel. T a pressure gauge into that clear hose to check the pressure on the low pressure pump. Again, the link above gives a detailed instruction on how to test both pumps.
I'm not sure what the valve on top of the vst is for but it won't test the pumps.
 
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