fueling issues

[SquadXX]

So....my 2000 has built motor with RSI triple pump system and Paxton and aem. Made 830 then crank about broke blah blah. So engine rebuilt and my tuner is running into the issue of running out of fuel at about 4500 rpm (and 6lbs boost), running lean (12.2 to 12.4). Had injectors cleaned and new fuel filter and checked fuel pump relays (all pumps work). Lost in what to try next. Could it be the AEM unit? We are planning to replace the socks on the fuel pumps to see if that helps. Any suggestions?

 

[TalonTSi90]

You consider 12.2 to be lean, what afr are you shooting for??

 

[SquadXX]

Tuner wants to keep it at 11.5. Also it goes from 11.5 to 12.4 as the rpms hit 4500 and it would likely continue to lean out if the rpms continue to climb. I think the issue is that why would it start running lean at 4500. Its enough pumps to support over 1k up and at 4500 (6lbs) it's only at 557hp, so nowhere near the pumps limits.

 

[TalonTSi90]

Sounds like a restriction somewhere that's getting "blown" open. What stuff is on the exhaust side?

 

[speedracervr4]

logged your fuel presure?

 

[TalonTSi90]

logged your fuel presure?

Or this...

 

[SquadXX]

logged your fuel presure?

If I recall correctly, fp is 14. I'll confirm. Tuner even added more fuel but same condition up top. Next step is to change out the socks on each fuel pump but I doubt that will yield anything positive.

 

[SquadXX]

Sounds like a restriction somewhere that's getting "blown" open. What stuff is on the exhaust side?

What do you mean by stuff on the exhaust side?

 

[TalonTSi90]

What do you mean by stuff on the exhaust side?

Porting, headers, cats, pipes ect.

 

[SquadXX]

Sorry. Ported heads (gg), full exhaust, no cats.

So you think there's a restriction with the heads or exhaust causing it to run lean?

 

[TalonTSi90]

Sorry. Ported heads (gg), full exhaust, no cats.

So you think there's a restriction with the heads or exhaust causing it to run lean?

What size piping?

 

[SquadXX]

I believe 3inch

 

[SquadXX]

Just confirmed fuel pressure is NOT being logged. I only have an air/fuel gauge on car. Also tuner said he is adding fuel but still running lean.

 

[TalonTSi90]

Then you don't have a blockage, so I would look at the intake side. Is it at ALL possible that the Paxton is slipping before then and all of a sudden coming alive/getting traction?

 

[EllowViper]

So....my 2000 has built motor with RSI triple pump system and Paxton and aem. Made 830 then crank about broke blah blah. So engine rebuilt and my tuner is running into the issue of running out of fuel at about 4500 rpm (and 6lbs boost), running lean (12.2 to 12.4). Had injectors cleaned and new fuel filter and checked fuel pump relays (all pumps work). Lost in what to try next. Could it be the AEM unit? We are planning to replace the socks on the fuel pumps to see if that helps. Any suggestions?

So it worked fine before the rebuild....not running out of fuel. What did you change and start there. At 6 PSI you are not going to get 830. Something's fishy here..unless you are saying you are also losing 6 PSI of boost..? What's the TOTAL PSI you are (or were) running? Oh...I assume a boost-referenced FPR set for nominally 55 PSI of fuel pressure.

 

[speedracervr4]

Just confirmed fuel pressure is NOT being logged. I only have an air/fuel gauge on car. Also tuner said he is adding fuel but still running lean.

I would be looking at hooking a fuel pressure gauge to see what the actual pressure is while boosting. Even if you temp install it just for the tuning. Just because he is adding fuel electronically doesn't mean it's actually getting to the cylinders. Are you sure you trust the tuner...

 

[TalonTSi90]

Yea, and not knowing much about the fuel system, are you using the right fpr?

 

[SquadXX]

Then you don't have a blockage, so I would look at the intake side. Is it at ALL possible that the Paxton is slipping before then and all of a sudden coming alive/getting traction?

The dyno is not showing any belt slippage.

 

[SquadXX]

So it worked fine before the rebuild....not running out of fuel. What did you change and start there. At 6 PSI you are not going to get 830. Something's fishy here..unless you are saying you are also losing 6 PSI of boost..? What's the TOTAL PSI you are (or were) running? Oh...I assume a boost-referenced FPR set for nominally 55 PSI of fuel pressure.

Yep was fine before rebuild. Only thing changed was the Paxton pulley to one making less boost because the original one was making 16lbs after the rebuild at 838rwhp and prior it was 10lbs at 830rwhp. Tuner didn't want to run that much boost, neither do I however I don't understand why it would need more boost to make same power. The tuner is saying its at 6lbs at 4500 and that's where it starts to run lean. So the boost will likely cont. to increase but we don't know because it's leaning out. I was running 55 or 60 believe prior and the injectors were at 85 percent duty cycle, I think I'm saying that right.

 

[SquadXX]

I would be looking at hooking a fuel pressure gauge to see what the actual pressure is while boosting. Even if you temp install it just for the tuning. Just because he is adding fuel electronically doesn't mean it's actually getting to the cylinders. Are you sure you trust the tuner...

I'm thinking about picking it up and towing it to a dealer I've used in the past and trust and is viper friendly (Jeff at Sanford dodge in Virginia).

 

[SquadXX]

Yea, and not knowing much about the fuel system, are you using the right fpr?

I know the fuel system was done right, so I'm not to concerned about that and everything I'm told is that all components of the fuel system are working properly and only thing left to try is replacing the fuel pump socks.

This car has been down for a long time and I just want to get it on the street again.

Could the aem unit be faulty, I'm assuming no because everything see,pls to be fine up until 4500 but not 100 percent sure.

 

[TalonTSi90]

Well, since we got the basics out of the way, there's really no way to tell without being with the car.

 

[EllowViper]

Very strange. So the injectors were "cleaned"...Hummm. I wonder if something went askew internal to the injectors? Pintle or some other internal issue. Don't know. Injectors are one of the things I've never actually taken apart. I know when Tony Armor did mine and I let them sit for a few months unused, all 10 of them were stuck shut and wouldn't work until I bench cycled them a few times with some penetrating oil. Very weird that your set-up works to a point then falls off. Duty cycle seems about right. Head scratcher for me....

 

[speedracervr4]

I'm thinking about picking it up and towing it to a dealer I've used in the past and trust and is viper friendly (Jeff at Sanford dodge in Virginia).

Not sure I would take a highly modified Viper to a dealer unless they have done Paxton installs and such before. It's easier to hook up a fuel pressure gauge (temporarily) than remove the pump assembly to change out the socks. I have not used an AEM ECU on a Viper, but I have on other platforms (3000GT VR4s) and have had two go bad. Those were earlier version ECUs and not the newer Infinity models.

Are the two additional fuel pumps turned on via a boost reference? Are you sure the other pumps are actually coming on?

 

[TalonTSi90]

Are the two additional fuel pumps turned on via a boost reference? Are you sure the other pumps are actually coming on?

Head/nail maybe?

 

[SquadXX]

Not sure I would take a highly modified Viper to a dealer unless they have done Paxton installs and such before. It's easier to hook up a fuel pressure gauge (temporarily) than remove the pump assembly to change out the socks. I have not used an AEM ECU on a Viper, but I have on other platforms (3000GT VR4s) and have had two go bad. Those were earlier version ECUs and not the newer Infinity models.

Are the two additional fuel pumps turned on via a boost reference? Are you sure the other pumps are actually coming on?

The dealer is really good and has worked on plenty of modified vipers in the past, including a previous one I had, so I'm pretty comfortable with him doing some checking around.

All 3 pumps come in at the same time. When I had the fuel system done, I didn't think to have 1 or 2 come on at a boost reference.
The tuner says they are but I'll confirm because that would make the most sense to me, only 1 tuning on.

The car has been sitting for some time so thsts why we changed the fuel filter and had the injectors cleaned and will replace the socks next.

 

[SquadXX]

Thanks for the help so far everyone, definitely appreciated and as I come a ride anything else I can share or what the problem was once it's fixed, I'll post.