How-To Properly de-pressurize DI fuel system

[mazdaspeedjay]

First i'll start off for some new people out there to the MZR L3 Turbo motor and anyone new to direct injection fuel system. there is a right and a wrong way to depressurize the fuel system. this is to help show you how to do it the right way without chopping off any of your fingers or seriously hurting yourself. This should be used as a helper for people doing their own C.D.H.P.F.P. ( Cam Driven High Pressure Fuel Pump ) like what mr lil guy sells and if you buy one you should buy his ( there's a little plug for you lil guy LOL ). first be warned. this is not like your old honda. the DI systems use two fuel pumps. the traditonal one sits in the fuel tank operates about about or between 40-60 PSI or so and all that pump does or it's job is to bring the fuel from the tank to the high pressure fuel pump driven off the cam shaft. Now your direct injection high pressure pump uses heavy duty lines for a reason and thats because the operating range for pressure on the D.I. ( Direct Injection ) fuel system can range from 900PSI to 2000PSI I shit you not. This is why i said if your not careful you will seriously injure or hurt yourself. So Be careful.
*** Tools Required : Common sense and a pair of plyers or fuse pullers ***

Basicly this will take about 15-20 minutes tops to perform. First thing is go under your hood and locate your fuse box. find the fuse for your fuel pump and the relay for it also it should be labed under the cover. For those that don't know the high pressure pump is a mechanical pump not electrical. the fuse your pulling is to kill power to the pump in the tank so it stops sending fuel to the CDFP ( Cam Driven Fuel Pump ). Remove the fuse and relay. Removing the fuse works just fine and is good enough i remove the fuse and relay to be safe and ceertain.

Ok now that the fuse and relay is pulled you may think thats it right car shouldn't start. WRONG. The car should still start and almostt certainly will. LET IT START AND RUN. There is so much pressure in the system that the motor should run for a good 5-10 mintues tops before it will finally cut off and die. Maybe 15 minutes at the most. If it's be 30 minutes and the car still runs then you pull the wrong fuse so go back and double check everything.

Once the car finally dies or stalls out. try and re start it again. If it starts let it run till it dies aor stalls again. Repeat the process above till the car no longer starts up and runs. IT may try to kick over and start for a split second thats fine. After everything is said and done continue cranking the motor for about 20-30 seconds just to get the last little bit of gas out. After that you are now ready to work on the fuel system gas will still come out of the lines and spill alittle and thats ok and normal.

This sounds simple to some but my not for others just be safe and take your time. Your dealing with a system thats contents are under high pressure till you kill that pressure so have fun and be safe. If you still have any suggestions feel free to PM me.

[Laloosh]

i didnt pull any fuses, i simple unscrewed the pump and maybe 2 tablespoons of fuel came out....

[occschemguy]

same here but i hadnt started the car for 3 months lol, anyways thanks for the write up.

[dadasracecar]

It's not the fuel pump relay. It's the third one down. The fuel pump relay is the first relay. There is one below that - I'm not sure. The one below the second on - the third one down - says "module relay." If you look in the technical service manual that's the one to pull for doing a fuel pump swap. It'll take seconds for the car to die after pulling this relay.

[mrlilguy157]

I used to have the fuse guide listed, but I didn't know 100% certain the fuses for the ms6 or cx7.

the fuel pressure in the rail with the car off is about 40-60psi according to the dashhawk.

regardless, thanks mazdaspeedjay! I like to live life on the edge.

[Haltech]

You're lucky you didnt shoot your eye out!

[Laloosh]

like i said, when i pulled my pump without pulling any fuses i stook back and was kinda scared as to whats going to happen being that my pump came with no directions as i was one of the first to have it. But nothign happened, like 2 teasppons of fuel came out and that was about it.

[NYpest]

I have done the pump swap a few times already never once pulled the fuses or relays ....OOps

[mazdaspeedjay]

Well it's not really a must. Just more or less a precausion. This is just what they told me when i went to mazda school when the MZR engine first came out. It's not needed if the car has sat for awhile. I was just amazed at how much pressure are fuel system uses.

On top of that. I was also amazed at how long the car will run when the fuel pump in the tank is dis abled. First time i had to do one the car ran for like literally ten-fifteen minutes on just what was left in the lines. I had to double check to make sure i pulled the right stuff and then the car died LOL. This is really for the less experience people out there i just didn't want to see someone hurting themselves.

[Haltech]

Do you realize how much smoke would be pouring from my tailpipe after 15 mins of idle? lol

[winniep]

Originally Posted by Haltech Do you realize how much smoke would be pouring from my tailpipe after 15 mins of idle? lol

LMAO! I would run myself out of the garage with just under 3 min of idle