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Discussion Starter · #1 ·
I have a Mazda 6, 2004, 2.0D Turbo, 136 hp. The main issue is that it doesn't allow me to go over 1600 rpm. The check engine light is OFF, which is strange. There is a knocking sound while cranking, which I don't think that it is related to the main issue. There are the following error codes:

P0088-FF Fuel rail pressure sensor circuit high input
P0629-FF Fuel Pump A Control Circuit High

The fuel rail pressure is around 46-50 Mpa, not sure what it is supposed to be. The limit is between 0 and 200. All fuse boxes are okay and F18 (Fuel pump fuse box) was replaced as well as the fuel pump relay.


Live data during cranking and engine start up:
 

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Unfortunately, there are only a few members who have the diesel variant.

For industrial diesel engines (generator), a knocking sound is an indication that you need to adjust the tappet clearance. I don't know if this also applies to your model.
 

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Hello,

In my opinion it is either the rail pressure sensor or the SCV which is mounted on the high pressure pump (you must reset adaptation before you put knew part). I think it is SCV and the error for high pressure is because of the SCV, the SCV is responsible for fuel pressure control.
The knocking sound is heard right before engine starts ? If this is so than the knocking sound is because wrong fuel pressure is delivered at wrong time ( too advance k). Btw i think that pressure required for engine start is 600bar max and at idle 350bar.
 

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Discussion Starter · #5 · (Edited)
@jovanzac, thanks for your answer! Yes, the knocking sound is heard right after the engine has started cranking. We just found out that there was a fuel pump under the back seat, we're gonna check it tomorrow. The fuel rail pressure sensor was replaced and the problem still persists. When we disconnect the cables for the high pressure pump, the error code goes away on the diagnostics. Btw, all fuses and the fuel pump relay are okay.

This is what I could find about the problem: PartsAvatar.ca - Generic Car OBD Error Code P0629 and about the tappet clearance Mazda 6 Service Manual - Valve clearance adjustment - Valve clearance
 

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Discussion Starter · #6 ·
Looks like the fuel pump on the back seats works fine and its cables as well. I have no idea what could be wrong. I think the high pressure fuel pump is the last possibility.
 

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Looks like the fuel pump on the back seats works fine and its cables as well. I have no idea what could be wrong. I think the high pressure fuel pump is the last possibility.
Hi,

As far as i know there is no electric in fuel tank lift pump on the Mazda. Lift pump is incorporated in the high pressure pump. Try this: disconnect all injectors and crank it, you should see >1200 bar after 2 seconds of crankink. If this is so then the high pressure pump is in great shape. Look for actual and demanded fuel pressure. If they are different of more than 20-50 bar i think it is the suction control valve. It is 100% responsable for fuel pressure control.
 

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Discussion Starter · #8 · (Edited)
@jovanzac, thank you very much for the descriptive answer!

I made a GIF, which is below. @Fuel Rail Pressure A. It was 0 in the beginning and when we started cranking for 2 seconds, it went up to 146.23 Mpa which is 1462.3 bar (> 1200 bar). It means the high pressure pump works fine and the problem is caused by the injectors?

The GIF below presents the fuel rail pressure with all injectors deactivated:


EDIT: We changed all injectors with the previous ones and the fuel rail pressure increases while cranking and then once the engine turns on, it sticks to 48-49 Mpa (490 bar)

The GIF below presents the fuel rail pressure with all injectors attached



The following GIF presents the Injector Control Pressure. It's ~35 Mpa while engine is on and drops to 25 Mpa while cranking.

 

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@jovanzac, we're about to replace the SCV. What did you mean by "you must reset adaptation before you put knew part "?
I have ELM327 with hs/ms can switch. I am using forscan. In service procedures you click reset fuel pump adaptation.
More than i year i had problems like misfire, vibrations when accelerating smoothly, dpf regen every 50km etc. I changed the injectors with new ones, i cleaned egr, i removed dpf etc but no luck. When i changed SCV car goes like a dream. Smooth acceleration and an average fuel consumption of 5 l/km.
 

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@jovanzac, thank you! I ordered this one 38.5US $ 47% OFF|FORScan Pro ELM327 V1.5 USB for Ford Coding OBD2 Scanner Adapter Car Diagnostic Tool HS/ MS CAN Auto Switch F150 F250 F350 F450|Code Readers & Scan Tools| - AliExpress. Is that the only thing I need? Because it looks weird that it says ELM327 for FORScan. Isn't it the whole thing?
Hi,
That's it, than you download forscan for free. Forscan works with ford and mazda.

Btw this is mine:
242473

Btw you can use it for many tweaks with your car, you can memory more keys etc.
 

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Hey,
I do not know but i think it is newer one. But i think you should register it first. Trial registration which lasts 3 months trial. Without it you are limited to execute some service procedures. Sorry i forgot to mention this :( You must create account in forscan forum which is free. When mine limited trial period is over i create one again. Please try this and let me know what happened.
 
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