seems to lose fuel pressure when warm

[weststar240]

bought a 93 mx_3 v6 all stock took it for a nice long test drive it ran fine. I literaly drove it about 15 km and it the engine started cutting in and out hard. Took it to work pulled one code 17. Narrowed it down to low fuel pressure. pulled the pump nasty rust inside the tank. Cleaned the tank as best I could with water, CLR and steel wool drain and dried it. Filled the tank and it ran great for about a quarter tank then started doing it again engine cutting in and out hard accompanied by a misfire no power and rough idle. So I swapped the tank and fuel pump and a third fuel filter. fired it up only put 10 bucks worth of gas in it, it ran fine but only up the street then started doing it again I've ruled out TPS and I think the Fuel pressure regulator but not sure about that one. I have pretty good feeling if I fill it, it will go away for a quarter tank or so then come right back. I can't hear or find any vacuum leaks.

here what it does to the best of my descriptive capabilities.

Runs smooth cold revs fine, Once it warms up or is under load (even cold) it gets a bad bogging noise like a carb with crappy floats, partial or slight throttle applications will get the engine to about 4 or 5k rpm then its like the fuel cuts out. A WOT application causes it to bog hard right down to just above idle then it starts cutting in and out if you hold WOT eventually it'll start back firing back into the intake

[weststar240]

I am at a total loss. With a full tank it runs great tons of power no misfire no cutting in and out. By three quarters it'll do it but only cornering right. By half a tank it gets worse. under Quarter tank it runs like a bag of crap as soon as its warm.

[RobMinhas]

Sounds like an issue with your fuel pump.

[crazycanadian]

Sounds like an issue with the fuel pump sealing internally in the tank... Could be the pump/lines..

Have you put a fuel pressure tester on it and watched whats going on??

[weststar240]

Fuel pressure is solid right in spec. Found a bad connection to the TPS. Just touched the plug and it started high idling disconnected it and idled even higher plugged it back in and it went to normal idle unplugged again and it stalled instantly. Also cleaned all the connections to the crank and cam position sensors. It runs better but still quits going around right hand corners and randomly while driving straight.

[weststar240]

I've also been through three fuel pumps and it does the same thing with all of them. The original one. One that came with the replacement tank and a brand new one. Pretty sure I've ruled out fuel pump as the cause.

[weststar240]

K filled it to 3/4 tank runs amazing as soon as I turn right all power is gone . Engine just cuts out go back straight and all is well. I'd say wiring but gauges, signals wipers all still work and no check lights come on.

[mitmaks]

Does it give any codes? Did you replace fuel pump strainer/filter sock?

[weststar240]

No codes and I changed the tank it came with a pump, tank was from a wrecker but spot less. It's still doing it and then changed the pump complete unit strainer sock and all. Now that it has over half a tank it does it only turning right. Not even hard right like you even look right and it starts sputtering and cutting out. Once it gets lower on fuel it will do it all the time cars barely drivable under a quarter tank.

[crazycanadian]

No codes and I changed the tank it came with a pump, tank was from a wrecker but spot less. It's still doing it and then changed the pump complete unit strainer sock and all. Now that it has over half a tank it does it only turning right. Not even hard right like you even look right and it starts sputtering and cutting out. Once it gets lower on fuel it will do it all the time cars barely drivable under a quarter tank.

Its not the pump its self.. its a connection or a line that connects to the pump that is leaking/blowing out.. possibly.. Either that your you don't have the right sending unit/gas tank set up, or its not installed right... IT really sounds like you are getting fuel starvation..

But thats assuming you fixed the connection issue with the TPS correctly.. so that its not an issue anymore..

[weststar240]

TPS is fixed and adjusted properly to warm idle between 6 and 7 hundred rpm. I've been on google looking for other people with this problem and found a protege forum lots of ppl saying baffels inside the tank are the culprit. I know the fuel filler neck is interchangeable I was working at a mazda dealership till just recently in parts and looked up a bunch of things. I just don't see mazda (or any manufacturer) not recalling such a design flaw.

[Daninski]

Now that it has over half a tank it does it only turning right. Not even hard right like you even look right and it starts sputtering and cutting out.

I say you only drive the car in NASCAR problem solved .

Funny because we had another member here with the same problem a coupe of years ago. Turned out it was a loose connection I think. A plug just barely on but I don't know which one. You could start checking your fuel rail plugs. Crazycanadian may be right, the wiring going to the pump may be the problem. Did you replace the entire pump assembly or just the pump itself? The wires from the pump through the top of the pump housing could be faulty/loose.

[weststar240]

Fixed it. took a pair of tin shears to the box the fuel pump sits inside. Cut three slits of varying depth into either side and bent the edge of the box into a louver sort of shape on each slit, took it for a burn. Runs like a watch. I ran it right down to under an 1/8th of a tank symptoms gone completely. Kind of hokie but it worked.

Thanks for the help everyone.

[[LVPA]93GsSe]

I like the your way to put, it took me a sec to get it but I like it.