My turn: LTFTs +31% (1MZ)

[Jason.MZW20]

Well, it seems the bug has bitten me. I haven't pressure tested the system yet, but I already have a feeling on what it is: fuel pump.

I replaced the stock pump with a Walbro 255LPH/HP unit. Two problems are likely occuring: 1) the FPR in the tank popped off leaving an open fuel bleed line (the MR2 wasn't made for a returnless system); or 2) the pump is failing (meaning it was a cheap Chinese imitation as it was brand new).

I've noticed my Walbro is whining a LOT less of late, which has pointed me in those directions, as well as the large increase in LTFTs.

Fuel trims:

STFTs are 0 at this time.

Bank 1 - 31.25% (from +2-8%) - P0171
Bank 2 - 25.78% (from +2-8%) - almost P0174

Happened a few days ago.

While the tank is out, I'm moving back to an OEM Denso unit, likely from a Supra N/A (turbo flows too much; hell my Walbro was overkill too). I'm also moving my system to an external adjustable FPR (hidden from CA smog Nazis, of course).

[RU2CHKN]

is your car boosted?

[Jason.MZW20]

Originally Posted by RU2CHKN

is your car boosted?

Nope. I put in the Walbro in case I decided to use the TRD S/C on my 1MZ sometime down the line (or do something else). I could've been fine with a Walbro 190LPH, but I wanted an extra safety margin, since the TRD S/C is known to make the 1MZ run lean.

It didn't run rich. I used the in-tank FPR from the Camry, which is set at 50 psi. I had to tee it into the fuel pump supply line because our pump housing doesn't have the in-tank FPR provision.

[RU2CHKN]

ok gotcha hey do you know a place to get a fuel sending unit for cheap other than the dealer?

[73sport]

Bummer - it do anything to the temp running that way? Dumb but where is the tank on that? Is it behind the front tires or sandwitched between the cab and rear tires?

I know you were talking about modding the fuel rail, is it worth it to mod the whole system and make it a return type? Any chnace yoda was kind enough to make the pump/sender unit mount interchangable to 95 camry return type?

On the bright side your not in flames or anything like that!

[Nervous]

Originally Posted by RU2CHKN

ok gotcha hey do you know a place to get a fuel sending unit for cheap other than the dealer?

Did you try "online dealers", such as www.partznet.com?
What's about Rockauto.com?

[Jason.MZW20]

Originally Posted by 73sport

Bummer - it do anything to the temp running that way? Dumb but where is the tank on that? Is it behind the front tires or sandwitched between the cab and rear tires?

I know you were talking about modding the fuel rail, is it worth it to mod the whole system and make it a return type? Any chnace yoda was kind enough to make the pump/sender unit mount interchangable to 95 camry return type?

On the bright side your not in flames or anything like that!

Not really. The AFR sensors don't let the engine run lean for long. It's an instantaneous adjustment, which is why I usually see my STFTs at 0. The fuel tank is in the middle of the chassis. It runs from below the dash up front to the rear firewall.

Unfortunately, due to CA smog, I can't run an FPR on the rails, so I have to use a remote mount adjustable FPR and hide it. I had to convert my MR2 to returnless since its fuel pump setup is made for a return system.

I can also use the 94-96 1MZ return style rails since it looks OEM; the problem is aftermarket FPRs usually stand out. The return pipe on my fuel pump housing is currently capped, but going back to a return system isn't difficult.

Oh and the MR2's fuel pump housing is unique. The fuel sender is separate as well, but that's a good thing as I've never had to mess with it. Still works great at 200k miles.

[73sport]

^^
What fixed your trims back then? Was it the FPR issue in the tank?

[fenixus]

Jason, have you tested the fuel pressure at filter yet ? i mean you have dropped the tank already, correct ? ... so probably a lil too late for that now... so you putting OEM fuel pump back in ?

[Jason.MZW20]

Originally Posted by fenixus

Jason, have you tested the fuel pressure at filter yet ? i mean you have dropped the tank already, correct ? ... so probably a lil too late for that now... so you putting OEM fuel pump back in ?

Ah, I suppose I should've followed up. Fuel pressure was a stout 53psi, which is a slight overrun of the 50psi FPR with a high flow Walbro pump. But that's okay because I'm running two fuel filters connected inline with each other, so fuel pressure should be about 50-51psi at the rails.

The fuel trims were high because of an exhaust leak right at the rear bank manifold's y-pipe mounting.

The EGR pipe gasket on the manifold was also leaking a bit because it was the wrong one. The right one is a 3-layer MLS gasket much like the exhaust manifold gasket. I had a single layer EGR gasket on there and the gasket severely overheated.

I also had to remove the ECU ground from the COR because Walbro pumps like a constant 12V feed. The 1MZ ECU varies the COR voltage at idle.