Looking for a source of information to repair my 2002 Miata, on the page to tell about me the didn't even go back that far! I've got a 2002 with about 260k on it, its been a blast to drive it in the Georgia sunshine for years, but unfortunately no more until I get it repaired. I'll be looking through the forums on losing fuel pressure overnight and hopefully find something that I haven't tried yet!

 

Welcome to the forum
Are you a Ford 460 engine fan? Or does the number mean something else.

There are basically 4 things that can cause your fuel pressure to go down in the time mentioned. You have likely tried them already but missed the one that is faulty.
It does require testing equipotent that the average DIY don't have? So wondering also how to test those few parts?
Better to state what you have done and what you used to test to save all the guessing games on a forum?

 

Thank You!

 

Actually no! I use this on several groups, at the time I came up with this from my Cruisers boat and the engine size of the truck that pulled it rather inefficiently. I swapped over to a 7.3 dually and solved my boat pulling problems but kept the Cruisers460 to use.

 

At this point I've changed the fuel pump (actually had a younger more nimble guy do it) the injector O-rings fuel filter and the damper on the front of the engine. Builds pressure runs well and if you immediately crank it again it's fine. Walk off and come back and it's lost its prime. Then to crank it takes a lot of starter time to build pressure again and it might start or not. When the pressure does build it starts right up.

 

Assuming the replacement fuel pump even new was not faulty which you verify both fuel pressure regulator and fuel pump using a F/I fuel injector pressure testing gauge. Ok well that actually reads like a leaking fuel injector(s)? Do you get a strong smell of fuel when it finally re-starts or any smoke from the tail pipe? If not, then back to the fuel pressure regulator and have fun with that service if you need to change it. Easy enough to do just time consuming getting to it. Unless by your production date and VIN you were lucky to get the replacement that the regulator is in the FI rail on the engine? You can visually determine if yours is on the rial.

 

Just spoke to the guy who has it in his shop, got the engine to pressure and clamped it off, engine maintains pressure. The pressure loss is in the tank. new pump, regulator, tested the injectors. He ordered a check valve for the tank to stop it from losing pressure. Not sure if one was in there originally. Not sure where the tank would lose pressure but never a gas fume smell.

 

Interesting? what you are posting makes no sense??? maybe it how you interpreted his information.
If it is at the rail an hour or less to replace the part if it is in the tank 2+ hours and what would he be replacing, then?? LOL

 

If the engine is clamped off at pressure it loses none. The tank is leaking off pressure. He expected a check valve on the pump but it doesn't have one. His solution is to put a check valve in the fuel line in the tank, reasoning is that the engine will not lose pressure but if the pump has lost pressure the engine will still crank at full pressure, about a foot of the line may have drained back in the tank. He is a heck of a diesel mechanic expanding into gas engines. I'll admit to seeing his reasoning but also am concerned.

 

If it is dropping overnight it's no big deal. At most a little extra cranking on startup so if it were mine I wouldn't worry. If it drops within seconds yes there may be an internal leak either the pump check valve or a common problem is the hose between the pump and the outlet pipe usually after someone has replaced the pump. Is there a particular problem with the car?