'95 Miata, fuel starvation on hard left hand corners, what gives?

I don't have a Spec Miata, but have the same OEM gas tank as Spec Miata.

It's a '95 1.8 and was having fuel starvation issues on hard left hand corners this weekend at Heartland Park. Had maintenance throttle, but when pressing the 'Go' button past the apex, had NO power until the car straightened out. Dangerous for people behind me expecting me to take off. So pulled off the racing line and came back to the pits.

After troubleshooting all the relays a few weeks back I did replace the fuel pump after having no starting issue. Car idles fine, and runs great in a straight line. I went to a local O'Reiley's Auto Parts on Saturday and replaced the fuel filter. No change. I added almost a half tank of gas Sunday morning and problem was better, but still existent.

Any ideas?

Ideas... Is the pickup secure and fuel pump installed properly?  OR is pump producing lower pressure to where injectors are not cracking open that is sensitive to turns?  I don't know... loose ground for pump?  

I'm having same fuel cutoff issue in a '92 Miata ITA - at recent Roebling Road race the engine would cutoff after the hard left hand turn 5 but restart before the entry to turn 6 about 150 feet later - never had the problem in right handers.  Would run ok with more than 1/2 tank of gas, but got really bad when down to 4 gallons or less.  Drained tank after returning home - pumped out all but about 1/2 gallon through the fuel test port - car had been sitting still for over a week and it 'looked' ok. Then drained that last 1/2 gallon via the tank drain plug, and it was definitely water contaminated.  Pulled the fuel pump to inspect inside of tank and found that the fuel strainer was lying loose in the bottom tray of the tank.  

Conclusion - since the fuel pump assembly is on the driver's side of the tank, and the baffle just beneath the fuel pump inlet is up against the driver's side of the tank but open on the passenger side - in a hard left hand turn the water settled in the bottom sump could slosh to the passenger side & mix with the gas being pumped, but couldn't slosh and mix in a right hand turn.  Apparently it must only take a second or two for the 'slosh contamination' to reach the injectors and cause the engine cutoff, and a couple of seconds after the car straightens out enough 'less contaminated gas' gets pumped to restart the engine.  I don't think the detached strainer played a part in the cutoff problem.  I plan to dry out the tank completely, pickle the small areas of rust in the baffle & tank bottom with acid solution, then coat both with an epoxy tank sealer.  Just to be safe I'll also clean out the fuel rail & pressure regulator, blow clean gas through all fuel lines, replace the filter, & install a new fuel pump & set of freshly cleaned/calibrated injectors.  Looks like an annual drain/flush for the fuel tank will be added to my maintenance list too... 

I'm having this in my 95 and it is definitely not water in the gas.  The inside of the tank looks squeaky clean and I drain the gas all the time.  On one course, it will cut out with less than 3.5 gallons but only on one specific corner after a set of switchbacks.  On another it will cut out with 2.5 gallons under breaking after a couple seconds of slight left hand turn leading to the braking zone.  It happens nowhere else.

People have had loose baffles in the fuel tank cause this.  I don't see ANY baffles in my fuel tank.  I replaced the coffee filter.  Maybe it's come loose or maybe this is something else entirely.

People have had loose baffles in the fuel tank cause this.  I don't see ANY baffles in my fuel tank.  I replaced the coffee filter.  Maybe it's come loose or maybe this is something else entirely.

I just completed some search and found folks with 94 through 97 have had similar issue and they had a loose/completely free baffle.
 

I'm certain there is something else involved.  I just went back into the tank and the sock was still on the pump and I felt around carefully and nothing was loose.  I was expecting baffling like the plastic grid in my old suburban but now I see what people are talking about and mine has no issues. 

It didn't always do this.  It would get down to 1 1/2 laps left before it would cough and I had better not go for 2.  It's also at precise fuel levels on different tracks where it happens.  Hopefully my tinkering with it will have now magically made it go away...but I doubt it.

I was using a stock regulator.  I just switched to an Aeromotive adjustable.  I've only had it on the dyno but I will try it on the track where it coughs at 3 1/2 gallons tomorrow. 

There are many of us who have wrestled with this problem. I had the identical problem with my '02 in the very same left hand corner at Roebling Road mentioned above by dickcdawg. Identical symptoms. Only happened to me on left hand corners with sustained g forces.

Tried everything. Fuel tank, filters, several different fuel pumps etc.  I believe Fowler finally identified it as the fuel line return was aerating and causing the pump to cavitate - had something to do with the fuel line return related to the type of Fuel Pressure regulator we were running

Tried everything. Fuel tank, filters, several different fuel pumps etc.  I believe Fowler finally identified it as the fuel line return was aerating and causing the pump to cavitate - had something to do with the fuel line return related to the type of Fuel Pressure regulator we were running

This valuable post/message ^ from THE ambassador of Spec Miata racing is fantastic. 

I was using a stock regulator. I just switched to an Aeromotive adjustable. I've only had it on the dyno but I will try it on the track where it coughs at 3 1/2 gallons tomorrow.

The reason I asked about the pump is because with the rules opened up to allow for aftermarket “OE equivalent” pumps, we now have two major types of pumps to select from, turbine/impeller and gerotor. The OE is a turbine unit. Sadly, the OE (Mitsubishi UC-T30) is expensive and having reliability problems. I have yet to find a kit for the ’99 with a turbine unit that will properly mate with either the OE bushing or the supplied bushing with the Hanger Foot. The Walbro pump is a gerotor pump. It is available with a bushing that mates the pump and hanger foot properly. The difference in these types of pumps may come into play with the cut-out some experienced with low fuel levels and hard left hand corners. Where the turbine/impeller style pump can create suction and pull fuel into the pump, the gerotor pump’s intake must be submerged in the fluid. With the very limited baffling we have in our tanks, I would not be surprised if those of use running gerotor pumps start noticing more fuel cut-out issues. If anyone knows of a quality turbine style pump that fits the ’99 hanger correctly let us know.

There are many of us who have wrestled with this problem. I had the identical problem with my '02 in the very same left hand corner at Roebling Road mentioned above by dickcdawg. Identical symptoms. Only happened to me on left hand corners with sustained g forces.

 

Tried everything. Fuel tank, filters, several different fuel pumps etc.  I believe Fowler finally identified it as the fuel line return was aerating and causing the pump to cavitate - had something to do with the fuel line return related to the type of Fuel Pressure regulator we were running

I didn't read the whole thread but Dragos system has the return coming down right on top of the pick up, to be the most efficient, IMO

J~

I question the regulator being the issue in my case.  It started last year with the stock regulator.  I just installed the Aeromotive and it did the exact same thing.  Same corner and precisely the same 3.5 gallons after much testing.  I have run this track multiple times before (The Ridge for those in the area) with no issues including a 6hr enduro. 

I did change the sock on the pump last year, but now don't remember if it was before or after the problem cropped up.  I was going to test that tomorrow until I ended my weekend one wheel short of a well handling race car but that's a subject of a different thread.

Keith, what kind of pump are you using?

???

Some times these fuel issues are intermitten and sometimes consistant. (fuel level, left, right, straight, fast, slow, G forces with lots of parts involved)

Install a fuel pressure gauge outside the windshield to the cowl where you can view the psi live during fault while driving. If you have correct pressure during fault see electrical/decision path. If you have no pressure, confirm liquid path items and do FSM checks for electric/decision path items.

Liquid path:

Fuel tank, fuel pump, fuel filter, fuel hoses/both directions, injector rail, injectors.

Electric/decision path:

CAS, throttle position sensor, water thermosensor, (< these guys feed info to the ECU for fuel timing and ammount) ECU, injector wiring harness, injector solenoid.

Danny, your input is always of value and the G force when pressure will reduce is great to know. If only I personally could generate those G forces, I'd be a happy camper.      I was attempting to re-ask the same question Chris asked. Keith, what pump are you using. Then even tho Keith is very knowledgeable, my post is a path to get to the cause. In my mind, a base line for a fuel issue would be, is the fuel pressure constant or interupted? As you well know guessing about fuel pressure isn't going to be of value.

Had a NEW OEM pump do the same in my new car at Watkins on test day.  It was one weekend old.  If the car is starving in lefts, 95% of the time it is the pump

Jim

Had a NEW OEM pump do the same in my new car at Watkins on test day.  It was one weekend old.  If the car is starving in lefts, 95% of the time it is the pump

Jim

Curious, what within the pump or pick up end is malfunctioning?

Curious, what within the pump or pick up end is malfunctioning?

I made sure both pump and tree was thrown in garbage at Watkins as I didnt want it following me around. I did not cut open or check, pump was VERY hot when we came in after the session. 01+ cars run at pretty much stock FP, so nothing to do with regulating etc IMO. We see it all the time in 99's as well

Jim