New engine issues

Fuel issues

On my gen 1 speed 3 I just had to put a new engine in and I’m still working out lots of kinks. A major one of which is that with key on engine off my access port reads that the act pressure is 2280psi. From what I understand this number is supposed to be like 60psi. This engine has probably been sitting for a while so it really could be anything. It will start after a few tries but it won’t get above 20mph and pretty much dies if I give it more than like 10% throttle. I traded the fuel pressure regulator from the old engine since it wasn’t too hard and I know it works. My next inclination is that the fuel pressure relief valve is seized or something along those lines but that seems like a pain to change so I wanted to see if anyone else had any ideas before I did it just in case. Thoughts?

 

Any codes?


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“Fuel rail pressure high input”. I don’t remember the exact code though.

 

P0193? Sounds like you either have a bad ground on your main harness or your fuel pressure sensor is bad.

Edit: I should also mention that a HUGE amount of problems after engine swaps are related to improper grounding. Triple check all your grounds using the wiring diagram for your car. Then check them again. If you’re still not 100% sure, have someone who is check them again lol.


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The code was 0193. So you think an improper ground is causing the pump to run constantly?

 

Update: replaced HPFP and fuel pressure relief valve and checked all the grounds on the main harness and I’m still getting 2281psi HPFP act pressure. I’m stumped

 

Check your fuel rail pressure sensor behind the manifold passenger side, see if you have that connected if not then change the sensor,
also check the hpfp spill valve connector. and the ground by the hpfp bracket where the 2 main harness connectors are, kinda hidden there skinny singe black ground wire.

But that problem is normally is Fuel Rail Pressure sensor. if you dont dont have any spare you can buy it from here https://www.autozone.com/engine-man...njection-pressure-sensor-800-90002/295083_0_0

its the fuel rail sensor for a cobalt. which is the same as the speeds
ive been using it in my gen2 for about 2 years now

 

The HPFP is a mechanical pump. If the engine is off, it isn't pressurizing the system because there's nothing mechanical moving. That's why it should read ~60psi -- because that's all the in-tank pump (which is electrical) can supply. It's almost definitely an electrical fault in the sensor wiring somewhere or a bad/damaged sensor.

@Maisonvi had the same issue a while back and it turned out to be a broken sensor. Obviously, check wiring first and make sure it's all connected before you start throwing money at the problem.

Disclaimer:
Mazda officially states the sensor is not serviceable due to a "structural issue" and they replace the entire fuel rail, which Maisonvi did. However, I've taken the entire fuel rail apart and put it back together again many times and replaced a few sensors. It's not that big of a deal but it is always a risk. It is, however, absolutely critical that you pull your in tank fuel pump fuse and run your car completely out of gas before you start taking apart your fuel rail. That system is mega pressurized and you can do serious bodily harm if you just crack that sucker open while it's pressurized.

 

That looks like the part I changed yesterday morning to no avail. I thought it was the fuel pressure regulator though. My AP says that it’s sitting right at 2280 but moves +or- about 2 psi during start up and while the engine is running. So far I’ve swapped the HPFP, the relief valve, and the sensor. Could it be anything else?

 

Anytime a sensor reads the max PSI it is almost always a bad wire or bad sensor. Since the sensor has already been replaced, I would pull out the multi meter and check voltages at the sensor then trace wires back from the sensor connector to the end of that harness and make sure there is not a short or a break in a wire.


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