O ring is perfect. I may still do the mod, but many are telling me that the O ring is sealed much better than a fuel hose with clamps could ever be .

Gauge in a few days, but I still think this gauge is pointless as I know I am getting a pressure drop..., but why?

Only things that makes sense... remember this is 1/4 tank or less.....

1. Fuel is heating up too much. Maybe from the aluminum fuel rail and not enough fuel to cool the fuel.. I do not believe it is due to any restrictions.

2. Pump isn't covered all the way and heating up which in turn brings us also to #1

3. Vacuum? Vacuum or pressure . No one ever mentioned that before until today. I was speaking to an old school master and he said run it with the cap loose..... seems like a cheap test to do..... good possibility as the less fuel the harder the pump has to work and with a vacuum it is even worse.

4. Pump starving itself under the MASSIVE G FORCE from acceleration!!!? LOL....

There is another guy on here having the same issue with a stealth pump and single setup with high quality fuel system.

The tune is perfect. So how to fix it?

1. Don't run much less than 1/2 in boost.
2. Insulate the rail and get a vented hood.
3..... so the pfc fuel temp correction was mentioned and I was told it was mainly for starting.
20°c - 68°f correction of 1.000
40°c - 104°f correction of 1.020
60°c - 140°f correction of 1.039

So why can't these figures be modded even more to like
40, 60, 80 and bring the 80 to like 10% or so. Or even leave the same, but instead of 60 move it to 70 and up the correction? 25, 45, 65... whatever.

Would this be better for the tunning group maybe?

Again this is not isolated to me and I bet there are people out there who don't even know this is occurring.. If a "tuner" got in my car and drove around he/she would say this is flawless and would never take the time to run through a whole tank of gas. If this was on a dyno with a 1/2 tank or more it would be off in no time thinking the job is done.
I am not trying to reinvent the wheel here, but it is possible that this could actually be something many experienced guys have never thought about.... I know, I know.... practically impossible!!!!!!, but there could be a small chance...

I'll say it again, I'm still not a fan of the Supra pump. My gut feel is a Walbro 255 will solve this.

If you have stock fuel rails with the fuel temp sensor you can view that on the Commander. I don't know if you can see it as a gauge but it does show in the Sensor Check screen as a voltage. It's a similar output range to the coolant sensor so you can correlate the voltage to an approximate temp. See if the temps are getting too hot. But I don't think it's going to be fuel temp related, that just seems like a long shot.

Again, THE PROBLEM IS IN THE GAS TANK. If you only see this at 1/4 tank, that's the kicker. On the vent for the tank, have you ever gassed up and had a very substantial in or outrush of air from removing the gas cap? It would have to be substantial to cause a fuel delivery problem.

Dale

Having a gauge is far from pointless, being able to pinpoint exactly when you're having an issue with datalogs is vital and the reason why I hate dealing with/going through all the hoops of a PowerFC in the first place.

I would say a decent pssshh or hiss, but not like it is trying to blow the cap off or keep me from removing it.

I have the RP rail with sensor so I should be able to see it.... temp or voltage on sensor that is.

i could change to the Walbro... not that much $.

I would have retune everything.

The gauge will go in, but again.... it's at 1/4 tank and pressure goes down or fluctuates. Ok, now what. It is a pain in the ass because I have to hook it up and log it. I have never hooked up a fuel pressure gauge to log it. Do I use AEM or the Datalogit.... I have to do a crash course on that and yes it is a major pain.

No reason to data log - again, we know the problem is in your tank, fix that and move forward.

You shouldn't have to do much if any of a re-tune swapping out the pump. Hopefully it will just have good fuel pressure all across the board and the car will run like it's supposed to without the mysterious leaning out.

Dale

I will order from Banzai

Logging and having timestamped data on mission critical systems (fuel pressure and delivery) to corroborate findings even to tertiary systems without sensors (tank itself in this case) is never a bad thing, to suggest that it is when the equipment is readily available, is making an effort in living in the past.

Anyway, hope you figure it out.

Dguy I know whatcha mean. I will Try a few things and start logging regardless as I am paranoid, but hopefully the pump will fix it.

i have the same problem, mine runs a whole AFR point richer when cold. I thought my pressure was dropping 5psi after it warmed up, but recently discovered my chinesium sensor reads 5psi too low when hot. In the process of thinking it was pressure problem, I tried rewiring the pump, now it gets solid 13.5V. I tried two different pumps, and two different regulators. I even added a fuel cooler, but it just made the problem worse, because it causes temp to fluctuate more, depending on moving or sitting still, so it is definitely heat related. So pretty sure it is not a pressure issue. I still have the resistor relay kick down circuit, and kicking the pump into high speed does not fix it. It still happens with low speed resistor kick down, so couldnt be a flow issue with the lines or my hydramat pickup. The only thing left is injectors. I am also running 2200cc id injectors, as primaries. then i found this thread, and a few other reports about these CNG injectors being affected by heat. the problem doesnt seem that common, I have not seen a lot of complaints about these injectors and most seem to be ok??

https://www.supraforums.com/threads/...id2000.636642/

Hey GXL. This is still in my mind. I was going to switch to some ID1600s as I have seen the Supra issue. I also read about a GTR issue.... I think it was a GTR. Anyway, the O ring would expand causing a leaning condition only happening well I to the dyno sessions. It was heat related and they had to swap the injectors out. There are a lot on here running these 2200s (2000s) with zero issue..... so I dunno to be honest. I really appreciate you stopping in though.

I'm not saying logging is bad, I'm saying for his particular problem there's no need to look farther than a problem in the tank. The problem has been identified and just needs fixing at this point.

Dale

Late to this party but I believe the above is referring to me. However, I'm unclear if the issue I'm facing is exactly the same. My problem is that my fuel pressure will drop seemingly with heat (ie, waiting at a very long stoplight or on the dyno with just a couple fans pointing at it), then climb back to normal when I get rolling and things cool back down. I posted some graphs showing what I mean in my build thread here:
https://www.rx7club.com/build-thread.../#post12469019
The thing is, when my pressure drops, it drops everywhere ie, you can see the AFRs get a bit leaner at idle, midrange, and in boost. From the description its sounding like Testrun's issue is only in boost? Am I picking that up properly?

If that's the case, I had that problem as well!
https://www.rx7club.com/build-thread.../#post12418376
Which the main culprit turned out to be, yep, the O-ring. I know that everyone's car is different but after that experience, I wholeheartedly recommend that anyone at all change that out even if it doesn't appear to be having issues.

Oh wow, I missed that your getting it even idling at a light for too long.. wow.
I should have read it more thoroughly.
I am only in boost... and only at higher cells.. high rpm high boost.

Roger that.

Yep, if you check out the second link, I did have that problem as well, and I know it seems perhaps unintuitive but at least in my case, the o-ring removal really did the trick. Now, my issue with the o-ring presented itself at all temps rather than just when hot, but after how dramatically the problem was fixed with it's removal, well, I'm a believer. :)​​​​​​​

.
Xander was the O ring and plastic part an exact fit on yours? I am unfamiliar with the Stealth pump. I could see having an issue if it wasn't. Like Banzai's pic of how to shave the plastic piece for a good fit on the Walbro.

That's a fair question, and my honest answer is "it seemed to fit tight" but it's been a long time and the car's PO set it up, so I'm unaware of if he made any modifications to have it fit better. Here's a picture of what it looked like before I took it off.

https://cimg8.ibsrv.net/gimg/www.rx7...31a4c9a25e.jpg

Hard to see in the pic. Who knows. I am still torn lol

For what its worth, done right (good clamps, submersible hose) it can be a dirt cheap and effective mod with no downsides that I can think of. And if it doesn't work, then you've eliminated a connection which many have had issues with, and didn't waste too much time and effort. I get that its always a bit of a tough decision to cut up a part of your car so it's your call!

You guys may just be on to something with the O ring. I pulled the pump last night and the fuel level is just under it. Given its level it was probably right there when the issue 1st started and I backed off and headed home.
I went ahead and did the hose mod as it could definitely be the problem.. Banzai said Walbro is backed up, so I am waiting on another pump anyway. I did not get to the guage installed yet as it was 2am when I finished. I will run the car today and see what happens.
https://cimg4.ibsrv.net/gimg/www.rx7...bcfa214d77.jpg

It would appear the problem is resolved. I am below 1/4 and WOT in 3rd and 4th gear are holding strong in the high10s (which is where I want it)... I never got it past 7300 rpm as my tach is now reading 2k high. This is around 13.8psi

O ring....... I will keep an eye on it of course for my next fun run, but I consider it to be an O ring problem.

Crazy how no one mentioned to do that up until now....

:icon_no2: :icon_no2: :icon_no2:

:D

I definitely appreciate your input!!!!