Vancouver Miatas

For the past while I have been fighting what appeared to be a fuel starvation issue on my '91 Miata.  This first manifested itself during autocross, where the car would stumble coming out of left handed sweepers but it eventually progressed to stumbling on all heavy acceleration.

 

I first changed out the fuel pump, because the symptoms could be corrected by running more than a half tank of gas, but that never cured the problem.  I then went on to changing out the fuel pressure regulator with the spare one that I had on my spare engine.  Again, this didn't cure the problem.

 

Each of these repairs helped somewhat, but the stumble was still there when accelerating hard.  I then started looking at related things, assuming that my friend Bob's suggestion of an electrical issue might be worth investigating.

 

I did the obvious and changed out the plugs and wires, given that I was running 3 year old wires, but again that didn't fix things.  I also swapped out my overclocked ECU for a stock one without getting anywhere.

 

This left me looking at the coil pack.  

 

Since I didn't want to buy a coil pack and igniter I decided I should test the coils and see how they looked.  In doing so, I found that my cheap Canadian Tire multimeter wasn't working, so I just pulled things apart and gave all the contacts a good sanding.  I figured that doing this would help make the time spent be worth something and I would get another multimeter from work to do testing later.

 

Anyway, cleaning the contacts for the wires between the igniter and the coil packs appears to have fixed things.  I can no longer get the car to stumble on hard lefts or on acceleration.  At least, my late night testing in SFU's B-Lot couldn't reproduce the problem.

 

So, the moral here is check the connection between your coil pack and igniter if your car appears to have a fuel delivery problem.  

 

Too bad I didn't guess to try this before I was at National Tour back in August... 

 

I should have written this last weekend, but I was sidetracked.  I'm now avoiding writing a paper that was due in mid-August, so I'll post this here.

 

I replaced my fuel pump last weekend with a Carter pump from Lordco.  Incidentally, that Carter pump is actually made by Walbro and is slightly larger than the stock pump.  I'm not sure what the lph on it are though...

 

Anyway, while doing the fuel pump replacement, I found out why we can usually autocross a Miata without problems with the fuel gauge reading below E.  The fuel gauge float sits out in the main chamber of the gas tank while the fuel pump sits down in a well that appears to be about as big as a 2l milk carton.  So, when the fuel gauge reads empty you will still have about half a gallon left.

 

Having done  the pump R&R, the car feels better and doesn't appear to starve anymore, so I guess I can go back to running the tank below E when racing.  Woohoo! 

 

Now I just need to check the plugs again and source out a set of 1.8l injectors...