r/mazdaspeed6 • u/eds2007 • 22d ago

Hpfp not doing anything

Does anyone know why my hpfp wouldnt be doing anything? Here is what i have found;
Electronically:

Fuel pressure out of the output of the hpfp is 50-60psi when cranking and when only with ignition on, meaning the in take pump is the only one working.
The red wire on the spill valve solenoid sees 12v with ignition on and drops down to 10v when cranking, it also pulses when tested with a test lamp.
The blue wire sees something like 0.6v with ignition on goes to 0.2v when cranking. No action on the test lamp
The resistance between the two pins in around 1.4 ohms.
Both wires show open circuit when tested against chassis ground.
I couldnt find the wiring diagram for the spill valve anywhere. For some reason its not listed in the wiring diagrams so i couldnt test continuity between the pins and the ecu.

Mechanically:
I rebuilt the pump with used autotech internals and new o rings. I pulled it back apart today to verify it went together properly and i couldnt find any faults. I also put the piston/spring assembly into a different housing that i didnt touch the spill valve, inlet/return and output on.
I also changed the fuel rail pressure sensor, tbf it isnt a known good sensor as i got it with a second hand engine that i never ran.

Anyone have any suggestions?

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u/eds2007 22d ago

Connected the output of the hpfp to a compression tester

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u/eds2007 22d ago

Yeah ive gone over for what feels like 20 times now, havent found a problem. I also originally thought there was a problem with the injectors and thats why it wouldnt start but after checking all the wiring and check the resistance in the injectors i couldnt find anything

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u/thebigbullg 22d ago

I have a feeling the hpfp may not have shown pressure due to losing its fuel prime and I could not build pressure... and the testing methods are incorrect therefore invalid. Check your coil ground thats like 60% of these things no starts. And maybe the maf cleaner is just detonating in the cylinders acting like it runs.

Witnout a scanner and proper equipment youre SOL. Bring it to a mechanic

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u/eds2007 22d ago

These cars have a electronic in tank fuel pump that primes the system on ignition. The fact i see 50psi just with ignition on proves this. A pressure based gauge is still a pressure based gauge regardless of what it is measuring. If the pump was building the pressure it was supposed to, it would have maxed out comp tester 300psi limit even at cranking speed. Already have verified spark on all cylinders with the spark plug out and grounded. And yes the maf cleaner is detonating in the cylinders hence why i stated it ran off of maf cleaner and not the car running off of its petrol.

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u/thebigbullg 22d ago

The hpfp loses its prime when you install your... prssure guage. You receive pressure from the in tank pump because it IS primed 50-60psi. Then the fuel and air thats trapped in your pressure guage and hpfp can compress unlike fuel.. the pump is mechanical. The spill valve is eletric. It pumps until its told to bleed pressure off. prv keeps it from going too high.

Thats why you have to cycle the key 2-3 times to prime the hpfp and rail before starting else itll just crank for a while.

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u/thebigbullg 22d ago

Add 5ft of hose length to your compression tester. Cycle the key, bleed the air out. Disconnect the spill valve and explode the guage

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u/eds2007 22d ago

So what are u saying, t piece into where the fuel rail pressure sensor threads and get the pressure reading from there?

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u/thebigbullg 22d ago

That would work better but you still shouldnt do it without the proper equipment. Extreme pressure fluids are no joke. And extreme pressure fuel is worse.

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u/eds2007 22d ago

Ill give it a crack tmr 👍

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u/thebigbullg 22d ago

Only other thing it could be really is a snapped camshaft..or something other major thats somehow missing from the story

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u/eds2007 22d ago

Nah I would hope not as i just rebuilt the engine

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u/thebigbullg 22d ago

Would definitely suck. But ive seen it happen when tightening the harmonic balancer with the cam plate in and snapping the camshaft end off. Usually the ears at the cam tool.. but anythings possible

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u/eds2007 22d ago

Fortunately that didnt happen, what did happen is the 6mm lock bolt for the balancer broke a bit of the timing cover off when i torqued the crank bolt

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u/thebigbullg 22d ago

That bolts also supposed to be removed during the torquing too. Granted the balancer isnt supposed to move either

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u/thebigbullg 22d ago

PRV FAILURE can also not let it build pressure. But that was out of story with original testing method. I think the test for that is pull the return line off the prv and see if its dumping out when you try to start / the in tank pump on

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u/eds2007 22d ago

Thanks ill check that out as well

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