31 replies to this topic

[Keith Novak]

 I was attempting to re-ask the same question Chris asked. Keith, what pump are you using.

I'm using the pump that came with my car when I bought it as a donor.  I thought it was stock but I can't say for sure.  It appeared to me when I first opened the tank that it did not look like a 125k filter so the pump may have been replaced.  If it's not the problem, it's due anyways just for peace of mind along with any other time limited parts. It's possible something going on in my pump could explain the weird AFRs I saw on the dyno as well.

 

It's definitely fuel path related and not electrically related since it is at very precise but different fuel levels on different tracks doing different things.  What really surprises me is that it is only one corner on each course and nowhere else but very bad at those 2 spots.  The conditions are just right that it passes a big bubble through the system where it never did before.

 

What's also a bit frustrating is that it's hard to duplicate.  I can't exactly go drive it around the block taking corners at 70 mph in various ways. 

[Bench Racer]

Keith, do you have a fuel pressure gauge that you can see while driving when the engine faults????

[Keith Novak]

I don't but I can add one.  No offense but what will it tell me when it coughs other than, "ain't got no gas in it"?  I did a 20 min session just to listen to it and it sounds just like if you've drained the tank, but didn't leave the jumper in the diag. box to prime the system before trying to start.... nothing, nothing, cough, fire. 

[Bench Racer]

 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.

 

 Maybe it's come loose or maybe this is something else entirely.

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. 

 

Seems there is a message within these comments above.

Do other folks at the same track with the same year car have your same fuel issue?

Are all NA fuel tanks the same? 

No offense intended, if I knew I had zero fuel pressure under your very specific conditions I would pull the pump assembly and do pressure testing with the sock off and the inlet pluged. If no leak issue, I would install a new fuel pump.

As Dave Wheeler says, well intended. Take my comments as intended to spur thoughts to eliminate your issue.

[Jim Drago]

I don't but I can add one.  No offense but what will it tell me when it coughs other than, "ain't got no gas in it"?  I did a 20 min session just to listen to it and it sounds just like if you've drained the tank, but didn't leave the jumper in the diag. box to prime the system before trying to start.... nothing, nothing, cough, fire. 

 

Keith

I feel fairly certain the new pump you are installing should do away with this issue. That sounds like many of teh fuel pump issues we have had. I would like to know what causes it and why it always starts in those lefts.. But ultimately, I just want it fixed. Please keep us posted.

Jim

[Keith Novak]

Fuel pump it is!

I'm back at the track where it would cut out at 3.5 gallons and getting it down to just over 1 with no sign of a cutout after installing a new pump.

Thanks all!

[ChrisA]

Keith, what brand pump did you install?

[Keith Novak]

I installed a Denso 950-0118.  From Mazda now you can only buy it as the entire assembly with the steel tubing, cap, and the whole shebang.  It seemed like a decent one and it's working now.  The fuel pressure did go up one psi.  I will be very interested to put it on a dyno and see if it fixed my weird AFR rising fuel rate issue.

[Sphinx]

Ran into this problem yesterday at the turn 13-15 complex (sustained left hander) at Atlanta Motorsports Park.  Car had 4 gallons at the start of the session and then "lost power" at 5800 RPM for about a second.  And then back to normal.  Happened no where else on the track on two laps back to back.  Was told by the on-site prep shop that this is common in that turn in an SM, some cars worse than others.  Mine had about 2-2.5 gallons left when it lurched.

 

Will look at getting a new fuel pump per this thread.

[Jack Martin]

I had the same problem in my 92 NA.  New Denso pump from NAPA. Made no difference how much fule was in the tank.  Thinking it might be electrical, I ran a new ground wire and  a new hot wire from the battery through a toggle switch and direct to the pump. I went to a solo and with toggle switch off it cut out in hard lefts.. With the switch on it ran fine. Went to Hastings for a track day and it cut out with switch off and ran fine with switch on. Someone suggested the roll over safety relay but there's so much stuff under the dash I couldn't figure out what the relay was. Anyone have a picture?

[Bench Racer]

Can't look at my 1990 Spec Miata, sold it.

 

Roll Over Valve & Check Valve (Scroll to picture on right hand side which shows both valves)

 

https://www.google.c...=Qmo08ogjoiJdmM

 

 

 

Circuit Opening Relay (Picture on right hand side, relay near steering column, take steering shaft dash guard off)

 

https://www.google.c...=KcagwkXPOdD0GM

[Jack Martin]

Thanks, I'll check that