billyjo

The last couple of weeks I noticed that my K/5 was going lean in the upper RPM ranges. I noticed from my logs that my fuel pressure is falling off above 3000 rpms and was a little higher than normal @ idle. I started playing with my fp regulator and it had no affect so I thought I must have a bad regulator so I bought another one (I'm using a aeromotive return bypass on mine) with the same results. If I open it up fully my pressure still drops.

From all of this I'm guessing that my fuel pump is going out since it's the only other thing in the system that can fail. I've only got about 10,000 miles on it but I did run it out of gas once in the garage so maybe that's why.

I know that the magna charger kits come with a walbro 255 but it seems there is also a 255hp. I was thinking that instead of going with larger injectors (my IDC is @ 101%) that if I got a pump that had more pressure I could up the pressure, adjust my injector flow rate and have more fuel up top, is the plausable?

Does anyone know what the replacement pump part# is, mine is the one that came with my radix kit for a 2005 hummer.

Any input or other options that I haven't thought of would be great input.

BlownChevy

iTrader: (20)

31-12-00-026 Is the Magna Charger part number for the in-tank fuel pump. Give me a shout if you need one....I think I owe you a favor anyhow

BigTex

iTrader: (16)

I'd like some info on your fuel system. What tank are you running? Any pics? Does this have a newer fuel pump bucket installed? Which aeromotive regulator do you have? I'm trying to figure out what tank and pump setup I'm going to run on my C10.

OK, on to your problem.....
Most aeromotive regulators have a vacuum/boost hose connection. It sounds like yours isn't working or isn't hooked up. That would cause higher fuel pressure at idle and lower pressure under boost. And yes, you can raise fuel pressure to increase the amount of fuel the injectors can deliver, but it reduces the total volume the pump can output. If you have plenty of pump, you'll get more fuel to the motor. If not, its not going to make a difference.

By the way - I love the Blazer. I watched a couple of your snow videos last year. On one of them I didn't think you were ever going to get off the throttle. I was thinking 'man I hope he has a good cooling system, somethings going to blow'.

Good luck.

billyjo

I do need one, is that part# for the HP? I think I want to try and pump up the volume.

My tank came from Rock Valley it's all SS and the fit was excellent. It does have the newer style bucket in it I'll take some pics of it when I switch the pump out. I'm running the Aeromotive A1000 injected bypass regulator I have it plumbed in between the fuel rail on the front of the motor, easy access for adjustments.

I've never had the vacuum reference hooked up, until now I was able to maintain a constant 58 psi through the whole range. I did try messing with it now but I'm convinced it's the pump.

Thanks, I'm running a griffin radiator with a built in oil cooler so I can utilize the oil cooling from my block.

DrX

iTrader: (7)

Hooking up the vac ref will get your InjDCs down somewhat(once you replace the pump or find the in-tank leak). Just have to rescale your IFR table.

The pumps in the Magna Charger kits would be the high pressure versions(its just a different relief valve setting). e.g. GSS340, GSS341

BigTex

iTrader: (16)

Do a little research on the vacuum reference under boosted applications. Without the vac reference, you are going to have to have one heck of a fuel pump to keep pressures at 58psi during a hard run.

You know the funny thing about the vac regulator - without it, you "think" your fuel injectors are flowing the same amount of fuel through out the whole rpm band - constant 58psi. The reality is opposite. At idle, the 58psi fuel pressure gets pulled into the cylinder by vacuum pressure, effectively increasing fuel delivery. Under boost, the opposite is true and fuel pressure if fighting against the boost to deliver fuel, decreasing the fuel delivered. Thats where the vacuum regulator comes in. It effectively keeps a constant fuel delivery rate from idle through boost.

billyjo

Thanks for the replies, I'm going to install a new pump and hope that fixes the problem.

Here is a screen shot of a log of my fuel pressure, seems pretty constant to me but maybe my idea of constant isn't steady enough. Let me know what you think.