Fuel pressure for 36lb injectors

[GMCBurb99]

I know this subject has come up before, but I'm pretty much new here and needing some help with my situation.


99 Suburban with mild build on the vortec 350.
Bottom end freshened up;
Mild Lunati cam 211/219 508/515 112
LSA
AFR Enforcer heads with full roller comp
1.6 rockers.
Hooker headers
MSD Ignition
AUS Injection 36lb MPFI spider.

Now here's my problem, when I mash it to the floor, whether from a dead stop or at 60mph and once I get around 4000pm or higher, she starts stumbling and acts like it's not getting fuel. I've checked the fuel pressure and it's right around 52psi at idle and when I throttle up it gets to 60psi. So I'm assuming I'm not getting adequate fuel pressure, right? I have not changed the fuel pump
around 52psi at idle and when I throttle up it gets to 60psi. So I'm assuming I'm not getting adequate fuel pressure, right? I have not changed the fuel pump and I have no idea if it's ever been changed or if it could possibly be the original, because I've only owned it for a little over a year. Now I realize that for this AUS Injection unit it does call for 62psi. Just wondering your thoughts on this. Thanks

 

[EJ_74]

What kind of pressure regulator are you using?

 

[Supercharged111]

I don't see a tuned mentioned.

 

[GMCBurb99]

I don't see a tuned mentioned.

It’s been tuned

 

[GMCBurb99]

What kind of pressure regulator are you using?

The fuel pressure regulator on the spider unit has been set by AUS Injection for the correct pressure for the 36lb injectors

 

[Supercharged111]

Did it at one point run correctly with the tune and now it doesn't?

 

[GMCBurb99]

Did it at one point run correctly with the tune and now it doesn't?

It’s been doing it since the tune and it’s been tuned twice by a well known respected tuner. I’m thinking the fuel pump just isn’t keeping up with my build and injectors, but I could be wrong. The injector unit calls for at least 62psi, but I haven’t checked the pressure at wot under load. As of now I’m looking into a Quantum 340LPH pump which is a high volume pump that’s a direct drop in replacement that supports up to 600hp and is ethanol safe which I’m planning to run in the future. Going to take a chance and hopefully that solves the issue.

 

[Supercharged111]

It’s been doing it since the tune and it’s been tuned twice by a well known respected tuner. I’m thinking the fuel pump just isn’t keeping up with my build and injectors, but I could be wrong. The injector unit calls for at least 62psi, but I haven’t checked the pressure at wot under load. As of now I’m looking into a Quantum 340LPH pump which is a high volume pump that’s a direct drop in replacement that supports up to 600hp and is ethanol safe which I’m planning to run in the future. Going to take a chance and hopefully that solves the issue.

If he's so respected, why did he give it back to you running like crap? If he felt you were running out of fuel, he should have stopped the tune and said so.

 

[GMCBurb99]

If he's so respected, why did he give it back to you running like crap? If he felt you were running out of fuel, he should have stopped the tune and said so.

Because he didn’t have the truck and just had the ECM and fixed everything from the jackass that tuned it the first time that actually had the truck and for almost two weeks. The guy that tuned it the second time had my ECM in 2 days. I failed to mention that it was tuned twice by two different tuners

 

[Supercharged111]

Because he didn’t have the truck and just had the ECM and fixed everything from the jackass that tuned it the first time that actually had the truck and for almost two weeks. The guy that tuned it the second time had my ECM in 2 days. I failed to mention that it was tuned twice by two different tuners

Well then there's your problem. Maybe the fuel pressure is falling off (we can't know without you actually checking), but not having the truck to tune and tuning without any data logging isn't going to get you squared away by any means.