Anyone know the thread size for those little screws that tighten the fuel pump assembly to the fuel tank? They're rusted and rounded out and I'd like to replace them with fresh new ones, but I can't figure out the thread size. Any help would be much appreciated.

 

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M4x0.7 thread, ~12mm total length. Readily available at any Lowes.

Just so you know, using phillips screws here is probably THE dumbest thing Mazda has ever done. Do yourself a favor and replace them with stainless steel bolts coated with anti-seize.

When removing the screws, soak them in PB Blaster in the morning, then re-soak them in the evening. The next day, soak them down a third time, wait a couple hours and then try removing them. the method that worked for me is using a 1/4" socket with a phillips bit slipped in it. Add on the ratchet handle and you can put a LOT of downforce directly on it while turning, and you'll need to. What I did was push down with my left palm with all my weight, slowly turning the ratchet with my right hand. A couple might strip the heads, but you'll be able to clamp a pair of Vise Grips onto it. Luckily, none of them broke off and I only had to use vise grips once on my own car.

Something you should do is run a thread tap through each hole to clean the threads. Harbor Freight has tap & die sets with the proper thread pitch for about $15. Since this is inside the tank, place a small cup under the hole when running the tap through, to catch any funk that falls through.

Another useful bit of advice is to get a couple longer bolts, maybe 30mm long. The longer bolts will help locate the cover and line up the remaining bolts. Once the remaining six bolts are in, pull the long ones out and put the proper length ones in.