ATTN: EFI gurus! Walbro external cavitation problems...

[stealth]

Hey guys I've got a very annoying cavitation issue with my Celica.

1jz converted, standard motor with stock boost, FMIC and 3" exhaust. Completely new fuel system from tank to engine and back (5/16 hard lines).

I have a GSL392 255 lph pump mounted just behind the diff with a 3/8 suction side and new pick up into the deepest part of the tank. IMPORTANT NOTE: The pump is mounted above the tank slightly. The pump ran fine for about 3 days originally, then I noticed after a bit of a boost, the pump was making a horrid screeching noise. Cavitation due to inlet restriction? At first I thought the hose on the suction side was sucking shut, but I replaced that with reinforced hose and steel hardline. Same issue. The car will run fine until boost, then will die of fuel starvation. Voltage is stable and pump has its own 40A relay and 20amp fuse.

Every time I take the suction side apart, it seems to be in vacuum, air seeps in when i loosen the fittings. First time the pump is run after then it sounds fine, the car drives perfectly until a hard boost (lots of fuel demand) then the noise starts again, and starvation is back.
The only way I can stop the noise is to loosen a fitting on the suction side and let the pressure equalize again.

So. I need a lift pump right? Because the walbro doesn't have enough suction without some help? My research tells me that EFI pumps are terrible at suction, hence why most of them are mounted in the tank with the inlet dipped in the fuel. I'm guessing my mounting of the pump is the problem...

Does it sound like I'm on the right track?

p.s. Im well aware the pump is probably screwed by now but here's hoping its okay. Ive only driven it a few times...

Cam

[lexsmaz]

As you said most external pumps require a lift pump too, but check on your specific pump, but i would say you also have a problem with something collapsing inside the hose to the pump as you first mentioned, have you taken the pick up out of the tank & had a look at that too & are you running a filter screen etc on the bottom of the pick up, maybe that could be sucking in too ?? & check on the rubber fuel hose in the tank that it is the proper ( intank fuel line ) as normal EFI hose goes to jelly after some time when submersed in a fuel tank..

Because as i see it if its lacking fuel delivery as soon as the usage decreases i cant see why it would just normally then come good but you say you have to crack the inlet line to make it come good ..

[stealth]

The pick up is all steel line, no screen just yet, i will have one at one stage. The new hose is definitely not sucking shut. There is no rubber in the tank at all. I have no filter for the moment on the suction side, a 40micron efi filter inline after the pump.

I've since read that walbro 255s need a 1/2" suction line?? But the pump only comes with 3/8 fittings and the internal thread of the input is 10mm, so I wouldn't think anything bigger than that would do anything in terms of flow... Ive read guys on vette forums commenting on how small a 3/8 suction line was. The factory suction line for their external pumps is 15/32"!!

Yeah I cant figure out why when i turn it off it doesnt just return to normal. Can i plumb in a low pressure electric carby FP with 3/8 lines? Really don't wanna drop the tank for a 5th time and install 1/2" pick up...

[thechuckster]

Do you have the vent line from tank to charcoal cannister in place and that system working (so the tank can equalize to atmo pressure, perhaps pump is pulling against a tank that's increasing in vacuum as you use fuel)?

out of interest, why not go in-tank pump with an EFI tank? My RA65 has the factory tank with a walbro out of my old car in place of the factory pump. RA65 or MA61 tank will fit your SA63 and both are EFI.

[oldcorollas]

either you have crap floating around tank and blocking the steel line pickup

or (more likely)..

Do you have the vent line from tank to charcoal cannister in place and that system working (so the tank can equalize to atmo pressure, perhaps pump is pulling against a tank that's increasing in vacuum as you use fuel)?

rather than undo the fittings, take off fuel cap and see if air gets sucked in.
if so, you could leave the cap off, and see if you get cavitation issues (just don't go corneing hard so that fuel sloshes out )

[mx32vvti]

hi there im just chasing some one out there with the know how on wiring up a 1jz gte vvti into a mx32 cressida

[George]

+1 to thechuckster for checking in-tank pressure
I've had the same issue some day even with the pump mounted well below the tank. I had to loosen inlet valve in tank lid (I didn't install vapour adsorber system) so the pressure could not fall too much below 1bar

[oldcorollas]

or you could get a different petrol cap.
old ones are sealed.. some newer ones allow air to be sucked into tank (but not go out) to prevent tank vacuum

[stealth]

All very good ideas thanks lads...

Re: tank venting, the line is just left loose, no carbon canister yet. In fact i plugged up the vent hose and that was the first time i noticed it cavitating. I bought a lift pump from work today and ordered a surge tank, but I will try leaving the cap off and seeing what it does.

Everything I read about external pump say they have terrible suction so gravity feed or lift pumps are needed... So I still think that's my problem. I just hope my 3/8 suction pipe in the tank is big enough.

RA65 EFI tank is still a better option if I can find one...

[TERRA Operative]

In fact i plugged up the vent hose and that was the first time i noticed it cavitating.

Pow. I would try unplugging that hose and see how it goes.

[lexsmaz]

All very good ideas thanks lads...

Re: tank venting, the line is just left loose, no carbon canister yet. In fact i plugged up the vent hose and that was the first time i noticed it cavitating.

..

As has been said & due to chucksters input it looks like you have the answer to your original question & so it sounds like there is probably no real need for a lift pump & it wont fix the problem either, unless you unblock the line at the same time ..

[stealth]

That vent hose has been unplugged for a few days now, same issues. Tried driving last night with the tank cap off, had the same issues.

I'll see how this lift pump goes, I havn't ruled out a damaged pump, cos its been driven 3-4 times with the cavitation (just limping home)...

Thanks for all the help guys.

[thechuckster]

pump should be able to run dry for 10 minutes tho I suspect an ugly noise says something has been borked.

Other things that come to mind are:
- mounting of pump - is it horizontal or vertical (if the latter, is the inlet on the bottom)?
- polarity of power supply - got them right? (beginner's mistake, but we all make them)
- does it have a mesh filter inside the inlet port (my in-tank unit has one as well as the external mesh sock filter)? and if so, has it been drawn into the pump?
- has the suction pipe got a kink in it somewhere (I did that to the tank in my RA40)
- are you getting a clean 12V for the pump? (I vaguely recall some early megasquirt discussions about people using one power source for the whole EFI setup and at epic boost levels the current draw for injectors, igniter, ECU etc would result in a voltage drop).
- return line from fuel rail & FPR - is it going to the return line at the tank (not the smaller vent line)?
- fuel filter not clogged?
- fuel lines in engine bay OK (no kinks or squashed stuff or feeding the wrong end of the rail or the pulsation dampener borked)?
- hard lines at tank not being squashed?

fwiw, I would hunt around for EFI-suitable tank if possible anyway - otherwise at below 1/4 tank you will get surging - RA65 or MA61 will fit your car as is - you just have to swap over the fuel level sensor from your current car. RT142 (EFI) looks like it will fit but is infact too tall (and lines will crush if you try to fit it into place). Am not sure about MZ1x tank tho I suspect they will fit - some of them are EFI suitable and have external EFI pump (that comes with a handy pump mounting & isolation bracket).

[stealth]

-Pump is mounted level with the top of the tank, 15* to the horizontal, inlet side facing downwards to the tank. I guess this isn't helping either.
-Polarity and voltage are good.
-All the lines are fine, no restriction or kinks, this was the first thing I thought was the problem. I've got reinforced fuel hose (that I have to use two hands to kink, and the suction hose it pretty much straight.)
-return line is a 5/16 hard line and hose back into the tank, new hole drilled in the plate with its own grommet.

The strange thing is that it will run perfectly quiet and drive fine, until I use more than about half throttle, or 5mins of driving. The first few days it was fine for about half an hour before the noise started, if at all. Last night I took the pre filter off the suction side (thought it was a restriction problem) and it make the problem much worse. Its almost as if the pre-filter (holds about 20-30mL) is acting as a little surge tank, holding enough supply to cruise around. Now since I've replaced the suction side with just hose and a good pick up, I cant even drive 1km without it actually stalling on me. I can turn the engine off for a a few minutes, then the pump is fine again for another km or so...

One thing I thought of the other day was the first time I tried to start the engine in the halfcut, I connected the fuel pump into the wrong lines, so I had high pressure fuel going the wrong way through the FPR, only for a few seconds though.

Would that be enough to damage the FPR, maybe the diaphragm is split?


I've decided to go down the surge tank/lift pump road, the surge tank is something I wanted anyway. Lift pump goes in tomorrow.

[oldcorollas]

cant mount pump lower, closer to the bottom level of the tank?

what FPR is it? probably should be ok if a stock one