high output pressure on low pressure fuel pump

duane.mosley

 i have a volvo penta 2006 5.7 osi-ef with MPI injection with a carter 21545138 pump. i am having issues with the low pressure pump not filling the reservoir.

i have bi-passed the anit-siphon ball by using a small gas can so i know i have good fuel flow to the pump.
i put a small electric pump directly to the fuel line from the tank and it is providing fuel through the test pump.
i have checked both plugs feeding the fuel pump and they both have 13.5 volts when key on and both back down after a few seconds. connections are clean between connectors and pumps.
i am getting 17psi on my low pressure pump when it's only supposed to be 8psi.
the fuel separator is only filling half way not providing enough fuel in the reservoir for the high pressure pump.

i found a thread on here where man cave mechanic shows you how to pull apart and clean the fuel pump and the reservoir, as well as the screens on my pumps. the inside housing does not have paint flaking so i am thinking this pump might have been replaced or did not have the peeling paint problem. the float is very clean and the fuel compartment of the reservoir was clean. the screens on the input side of both pumps only had a few particles of dirt in the screens, definitely not clogged causing issue. the chamber where the water flows around the fuel was a different story. it was not completely clogged but it needed a good cleaning.(possibly not cooling the fuel properly causing a hard start when motor is hot?).


i had an operator error issue after changing the fuel separator one time on this fuel pump and knocked the plug loose for the low pressure pump. after removing the fuel pump thinking i needed to replace it, i noticed the plug for the low pressure pump not connected. reinstalled the pump and made all connections and the pump worked great!. had to rebuild the engine this winter due to spinning a rod bearing and this pump has not worked since. the issue is presenting as if the low pressure pump is bad. switched plugs from the wiring harness supplying the fuel pumps to double check a wiring issue and it doesn't change anything. the boat will start and idle smoothly but will not allow acceleration passed 1800 rpms due to lack of volume of fuel in the fuel reservoir. is there a chance the ecm is in safety mode not allowing proper voltage to the fuel pump? i know that in a car the oil pressure switch could interfere with the fuel pump operation but wasn't sure about in a boat. oil pressure is 40lbs so i know that is not the problem.

is there a possible ecm issue or is this simply a bad fuel pump? should i rebuild myself or just by a new one? it was rather easy to disassemble so reassembly shouldn't be hard and the price comparison is considerable.



any and all assistance will be appreciated.

BellevilleMXZ

Sounds more like a Hp pump issue......if u have lots of LP pump pressure that pump can't be bad?

duane.mosley

although the pump is putting out higher pressure, it is not providing enough volume to fill the reservoir. i bypassed the fuel line and anti-siphon by pulling straight from a gas can and results were the same.  the fuel separator is only filling half way as well. either way, i ordered the rebuild kit. i am replacing both pumps, as well as the fuel line and anti-siphon just to eliminate any future problems. there where no paint chips present in the fuel cell or the screens of the filters. no evidence of any clogs. i put an electric pump  onto the fuel line from the tank and it was drawing fuel just fine. rebuild kit is supposed to be here tomorrow so i will keep you posted

BellevilleMXZ

Cool......bunch of Merc lovers on here no other replys....lol

rmfriday

I have chased the VP fuel pumps issues around a good bit, I would start with replacing the low pressure pump. If you have high pressure on the output but low fuel draw I would think you have a restricted input within the pump.
For the $100it cost I would start at the low pressure pump

duane.mosley

rmfriday said:

I have chased the VP fuel pumps issues around a good bit, I would start with replacing the low pressure pump. If you have high pressure on the output but low fuel draw I would think you have a restricted input within the pump.
For the $100it cost I would start at the low pressure pump

206 for both high and low pressure pumps, with o-rings for the fuel cell, shipped priority mail. supposed to be here tomorrow. will post updates. supposed to try for a lake trip this weekend. hope it works out.

 

tniggel

Did you check this thread
https://rinkerboats.vanillaforums.com/discussion/3652/bad-fuel-ecomomy-fuel-pressure-is-the-key-volvo-penta-bulletin-p-23-7

duane.mosley

well, 200 bucks later and the problem was still there. just when i thought i had it diagnosed. went back and forth, back and forth about what it could be before i bought the pumps. with the high pressure, the half full fuel filter, i thought for sure it was a fuel pump issue. NOPE, not it! i couldn't for the life of me think of what in the world could be causing a perfect idle, but would not go over 2000rpm. well, after all the connectors i checked, ecm connections i checked, fuel pressure this, fuel pressure that,  for some crazy reason, i decided to move the distributor cap(while not running of course). turns out that my timing was off! it was close enough to fire right up with the bump of the key but wouldn't allow it to advance enough to fire at higher RPM. time to buy a scan tool so that i can get it just right.