M35 Aftermarket Fuel Pump

[Dose Pipe Sutututu]

Should be more than fine, especially the overall fuel pressure would never exceed 3.5bar (assuming that thing never gets more than 0.5bar of boost in stock form).

According to the chart, it's 11amps.

[GTSBoy]

2 hours ago, iain_ST44GA said:

I definitely know the first rule here, look first, ask second. I've seen many people get roasted 😂

I found a few diagrams for the RB, but I'm yet to come across one for the VQ. From what I have read, the pump gets the +12v along with the FPCM, and it's the negative wire that gets passed through the resistor to regulate the voltage. So I assume I can just ground the negative wire at the pump to eliminate the FPCM control. But I really wanted to see the VQ circuit diagram first to make sure I understood it correctly. Once the new pump is in I'll do some testing to see how it behaves, and in the meantime, I'll keep looking for a wiring diagram.

Thanks for your help mate, your time is greatly appreciated.

My apologies. I forgot we were talking about weird beard M series stuff. Had been talking elsewhere with someone about an R33 with similar subject and got confused.

[iain_ST44GA]

17 hours ago, GTSBoy said:

My apologies. I forgot we were talking about weird beard M series stuff. Had been talking elsewhere with someone about an R33 with similar subject and got confused.

All good mate, the info helped me a lot 

Once I got the pump out of the tank, it was clear why it shit itself. The pump assembly and tank were full of mud and rust. Yukk! 🤮

It took f&%king hours to clean everything up properly!

[iain_ST44GA]

For those who might be interested, the below is the wiring to the pump hat on the M35.

[GTSBoy]

Yeah - that's pretty gross.

[Dose Pipe Sutututu]

did someone fill up the tank with rain water? lol

[iain_ST44GA]

1 hour ago, Dose Pipe Sutututu said:

did someone fill up the tank with rain water? lol

also possibly backed up to my filler and shat down it! 🤣

[Dose Pipe Sutututu]

Here's the chart for fuel pressure vs. current draw, assuming your base fuel pressure is 3 bar and you run like 0.5bar boost on WOT, you should only momentarily hit 9amps here and there.

(Ignore my prev post, I cannot read a chart these days it seems)

[MBS206]

3 hours ago, Dose Pipe Sutututu said:

Here's the chart for fuel pressure vs. current draw, assuming your base fuel pressure is 3 bar and you run like 0.5bar boost on WOT, you should only momentarily hit 9amps here and there.

(Ignore my prev post, I cannot read a chart these days it seems)

Pressure when IDLING, is meant to be 51PSi... So that amperage value needs to go up a fair chunk... I'd personally be factoring for more like 12amp at least on those runs, and at that point you need to hope the already there wiring doesn't drop you a volt or two, as that's a lot of fuel pressure flow drop off from 13.5 to 12V!

Taking idle pressure of 51psi, means the pump will be drawing a MINIMUM of 9amps all the time based on your reading of the graph (3bar base, then allowing an extra 0.5bar for boost = roughly 51psi)

Edited yesterday at 09:08 AM by MBS206

[GTSBoy]

15 hours ago, MBS206 said:

Pressure when IDLING, is meant to be 51PSi... So that amperage value needs to go up a fair chunk... I'd personally be factoring for more like 12amp at least on those runs, and at that point you need to hope the already there wiring doesn't drop you a volt or two, as that's a lot of fuel pressure flow drop off from 13.5 to 12V!

Taking idle pressure of 51psi, means the pump will be drawing a MINIMUM of 9amps all the time based on your reading of the graph (3bar base, then allowing an extra 0.5bar for boost = roughly 51psi)

Have you done your thinking backwards?

3 bar, 43.5 psi pressure drop being the presumed specification for an injector, means you need 3 bar upstream when they are firing into atmospheric pressure, and more upstream pressure than that when on boost (you add your boost to your rail pressure to maintain 3 bar across the injector) and you need..... less pressure upstream when you have vacuum in the manifold. So, presuming that you're idling at -10 psi, then you only need ~23 psi in the rail.

I realise that I did not need to say all of that to you specifically Matt, once you'd realised your mistake. It's mostly there for complete clarity for others.

[Dose Pipe Sutututu]

Yeah, I don't believe the M35 uses a deadhead system.

[MBS206]

6 hours ago, GTSBoy said:

Have you done your thinking backwards?

3 bar, 43.5 psi pressure drop being the presumed specification for an injector, means you need 3 bar upstream when they are firing into atmospheric pressure, and more upstream pressure than that when on boost (you add your boost to your rail pressure to maintain 3 bar across the injector) and you need..... less pressure upstream when you have vacuum in the manifold. So, presuming that you're idling at -10 psi, then you only need ~23 psi in the rail.

I realise that I did not need to say all of that to you specifically Matt, once you'd realised your mistake. It's mostly there for complete clarity for others.

I may have my math slightly wrong, I'm not double checking that again, but the factory spec for fuel pressure is to set it with the engine IDLING (in vacuum). That spec is 51PSi while idling.

So now add +10psi for atmospheric, and +7 for 7psi of boost, and we need 68psi of fuel pressure at full noise, and 51psi idling.

That's according to the FSM I found last night for M35. So MINIMUM fuel pressure should be 51psi and it climbs from there.

[GTSBoy]

20 minutes ago, MBS206 said:

That spec is 51PSi while idling

If true then....wierd. That's a very high base fuel pressure for a shitty old early 2000s Nissan.

[MBS206]

57 minutes ago, GTSBoy said:

If true then....wierd. That's a very high base fuel pressure for a shitty old early 2000s Nissan.

I thought the same too, and more than happy for others to bring another source for what it is. Just throwing so me caution out there, as potentially an extra 30% current needed than expected.

 

Well worth more investigation, but right now, I'm going over my Cypher knowledge while Expendables 4 provides mundane noise in the background, ha ha!

[MBS206]

1 hour ago, GTSBoy said:

If true then....wierd. That's a very high base fuel pressure for a shitty old early 2000s Nissan.

I went and found the actual FSM again (Yeah, I squirreled...) Screen grab of the FSM for M35.

51PSi with engine idling.

 

[Dose Pipe Sutututu]

Wow... What in the fk, it's a dead head system...