Re: volvo penta 5.0 GXi-E fuel pump question.
i dont feel comfortable running it without the low side pump so just ordered the whole assembly, damn...?700 later. ordered new seals for the fuel pipes as well, hope the fitting is easy cant afford to have it fitted now im skint
If you run without the low pressure pump then you are asking a bit much of the hp pump although I suppose that once the fuel is on the move, and on condition that the tank/delivery layout together with the filter offer very low resistance, then it should work tolerably at low speeds. Most of the time, the hp pump is simply circulating fuel back into the reservoir; the lp pump only has to provide enough fuel to replace what's expended via the injectors. The top of the reservoir is connected to the manifold, so if the lp pump isn't working then as fuel drops, I think the vapour valve will drop open and manifold vacuum will help to suck fuel through. I doubt the engine would run under load at much more than a crawl, though; did you try it?
I have just solved a fuel-cell issue ona VolvoPenta 4.3GXi-J. I was approached by a mate who bought an old (1983) Sunseeker 23 with a brand new engine/sterndrive unit - just 8 hours on the clock. The first time he opened it up above 3000rpm the engine faffed about and died.
I read up the issues on this brilliant forum and decided we had nothing to lose by stripping the fuel cell. I checked low pressure and this was fine at around 6-8psi. Nothing at all on the high side (the testpoint is on the common rail next to the pressure regulator on the port side). As regards stripping down the pump, the only difficult bit was pulling out the inner sleeve. I used some jubilee clips, levers and patience. Sure enough, the top casting on the reservoir side was full of bubbled paint which fell off with a fingernail. Completely stripped and cleaned everything. The high pressure pump has a screen at the bottom and I gently blew it clear backwards using a cheapo electric car tyre pump.
After re-assembling and refitting I re-tested pressures and the lp was fine but the hp was now too high! The engine started absolutely first spin and ran tolerably but I thought it a bit lumpy. The pump was a little noisy. We told the marina we might be stranded and stand by to pull us in - and went for a test run (in the northern end of Milford Haven). The noise was indiscernible at most speeds and the hp pump was running cool. This was fine all through the tests 1200rpm, 1500, 2000, 2500, and 3000. Fast enough for me on water, thank you very much, but the skipper is my motor racing driver from the old days! So he tested it at 3,500rpm whilst I cowered down below!
Anyway, the problem occurred when we were running at LOW revs. At <1200 rpm and pulling, the HP pump was getting hot and then eventually whining. Managed to re-berth ok and I then sat back and thought. The pressure regulator , if blocked, would surely prevent the injectors from delivering properly and the engine would either not run or else run badly?? Well I pulled it off, being a simple enough job and lo and behold there is a very fine screen which was clogged with - I guess - paint as a slurry. Anyway, I cleaned this up and re-fitted it and the engine now runs perfectly. Cool pumps and the whine is gone - engine silky smooth.
So, the restricted flow led to the high pressure, cavitation (the whine), heat and fuel evaporation in a horrible cycle which would have ended in engine stall and possibly pump burnout.
I am now an expert on the worst design and build I've come across.
What a rubbish design to put on such a nice engine. Has anyone converted to an in-tank pump with return line? You might not be allowed to that in the States.
Finally, I am now ready to tackle the ECU. I'm a bit of a programmer but desperately need info for pinouts of the ECU and particularly the test plug, and also some guidance on interfacing to the laptop. I can write the software once I've got a serial connection going. Anyone got any ideas? Someone achieved this with cars? Perhaps this needs a new thread so feel free to start one.
