Just got back from getting tuned, dissapearing fuel pressure at 4500 rpms

[MakeItHappen]

So i just went to get my GTS tuned for the first time, has a Roe w/8lb, all the bolts ons, W/M (not used for this tune) and the MSD voltage up box hooked to the stock fuel pump.
At 4000 rpm or so, its putting down 535rwhp and 600rwtq and the charts inc A/F look good i believe they were mid 11's.
Checking voltage on the MSD box, i believe it was 16v at 11" of vacuum, 18v at 0 psi boost, and 20v @ 9 psi.
I have about 50 psi of fuel at the rail up to 4400rpm or so, and then it drops off drastically to about 25psi after that.

Question is, has anyone dealt with a fuel pressure drop off like this ? Likely culprit ? Stock fuel pump can handle 650rwhp or so ?

Was planning on starting with fuel filter, as idk how old it is, but apparently its on national back order for at least a month from the dealer, so i will likely try and find online unless someone has one ?
If the fuel filter is clean, would it likely be the pump ? Is that voltage too high on the MSD box and burnt out the pump ?
I mean it works fine until about 4400rpm under all apparent conditions, and im running out of fuel ?!

Thanks

 

[BlackSnake99]

Dump the BAP. Get one of the new Walbro 400lph pumps from Will at RSI. Fits in with a little modification to the stock basket and uses stock wiring. Supports my 8lb Roe to the tune of 680whp with plenty of fuel.


The BAP is a band-aid.

 

[BlackSnake99]

Stock fuel pressure is 55psi, btw.

 

[99 R/T 10]

AS long as the Boost-a-pump is hooked up properly and truned up for max voltage at 3PSI or more, I say it is your fuel pump. RSI might have the new Walbro 400 available and would be a great replacement for a weak or failing stock pump. The 400 should support 800+ HP. Call Will at RSI.

 

[MakeItHappen]

Dump the BAP. Get one of the new Walbro 400lph pumps from Will at RSI. Fits in with a little modification to the stock basket and uses stock wiring. Supports my 8lb Roe to the tune of 680whp with plenty of fuel.


The BAP is a band-aid.

Sure seems that way, the car came to me like that and i didn't think twice until now. I guess i will order the new pump then.
If im getting good pressure through 4k rpms, should i even wait on the back ordered fuel filter to install the pump ?
Do i need to order a fuel pressure regulator for the new pump, or can i just use the BAP somehow as a regulator for the new pump ?

 

[BlackSnake99]

Sure seems that way, the car came to me like that and i didn't think twice until now. I guess i will order the new pump then.
If im getting good pressure through 4k rpms, should i even wait on the back ordered fuel filter to install the pump ?
Do i need to order a fuel pressure regulator for the new pump, or can i just use the BAP somehow as a regulator for the new pump ?

No separate FPR needed. I reused the stock one that is in the basket. Get rid of the BAP (IMHO). A new filter can't hurt but I'm not sure I would wait too long on it.

 

[Dan Cragin]

Be sure that a replacement intank module pump is the "siphon jet type" that fills up the bucket in the module. If not then you could run the bucket dry in a open road top speed test.

 

[Jack B]

Be sure that a replacement intank module pump is the "siphon jet type" that fills up the bucket in the module. If not then you could run the bucket dry in a open road top speed test.

Is there a higher volume pump available that also fills the bucket?

 

[MakeItHappen]

http://www.xenocron.com/walbro-400lph-intank-pump-p-684.html

That's the link the the 400lph some specs on it. It's $25 cheaper on amazon, but they don't have as many specs listed on there.
I'm going to change the filter regardless, as i don't know when it was done.
If i can have the pump working in a week, versus waiting 3 weeks for the filter to put the pump in, i'd like to get back on the road sooner then later.
Being that my pressure is good through 4k rpm, im going to assume after the responses that my filter is likely ok, and my pump is likely too small...and i should be ordering the 400lph at the link above...

 

[BlackSnake99]

http://www.xenocron.com/walbro-400lph-intank-pump-p-684.html

That's the link the the 400lph some specs on it. It's $25 cheaper on amazon, but they don't have as many specs listed on there.
I'm going to change the filter regardless, as i don't know when it was done.
If i can have the pump working in a week, versus waiting 3 weeks for the filter to put the pump in, i'd like to get back on the road sooner then later.
Being that my pressure is good through 4k rpm, im going to assume after the responses that my filter is likely ok, and my pump is likely too small...and i should be ordering the 400lph at the link above...

Not to sound like a nutswinger, but RSI beat any price I found by $30. Make sure you include the install kit. I would call them before ordering.

 

[MakeItHappen]

Not to sound like a nutswinger, but RSI beat any price I found by $30. Make sure you include the install kit. I would call them before ordering.

Edit - Just ordered from them for $170 shipped, a couple dollars higher but worth it for a specialty shop, ordered an inline filter oem replacement from partsgeek for $27 shipped as RSI didn't have any on hand, and dealer is backordered 3 weeks. Got your pm as well, now we will see if i end up having issues with a fuel shortage due to injectors. I apparently have the 2nd Roe Kit ever made, Has green top injectors (42lb ?) which i guess was all existed for the kit 10 years ago, and now they offer 56lb ? What color or size injectors are you running on your car ?

 

[BlackSnake99]

What color or size injectors are you running on your car ?

I have the black top injectors which I believe are rated at 69lbs at 57psi.

 

[MakeItHappen]

So in your opinion do you think i'm going to run into more fuel issues running the green top injectors trying to get to the mid 600's ? I'm not sure what fuel pressure i would need to support 9.5 pounds of boost at 5600rpm. I know with the new pump i will be able to keep up with injector demand, but i guess im hoping that the injectors don't demand more fuel then they can deliver.

Anyone else running green top injectors on their Roe making in the 600's ?

 

[BlackSnake99]

Stock heads?


I'll tell you that I made 680whp/656wtq with 8lbs and no w/m, but I have ported heads and the bigger injectors.... and plenty of fuel. With stock heads and smaller injectors I would think that mid-600whp MIGHT be optimistic. That said, I am no engine builder so my estimates may be inaccurate.

 

[MakeItHappen]

As far as i know so far, this thing has an Arrow Racing Built motor, diamond forged pistons, gen 1 cam, port and polished heads etc...i verified it was built with arrow and installed in 2011, but i have not yet gotten the build sheet from Arrow so i do not know the specs for sure. I'll sling the bigger pump in and go back and finish the tune and report back in next couple weeks. Thanks.

 

[speedracervr4]

I believe my injectors (not able to confirm right now) are green tops...630rwhp/670tq @ 10lbs boost.

 

[MakeItHappen]

Ok so i'll break this into a couple posts so you can share in my suspense..

Alright so i received the 400lph walbro from RSi and install kit a few weeks ago. Tator's was backlogged with work and being my impatient self, i had someone else put it in. This car had the original fuel pump, BAP setup and original fuel filter installed. They had to go. The install kit for the pump is needed for the electrical connecter, but DO NOT cut your stock fuel line hose connecting the pump to the sender. This guy didn't realize the install kit hose was 5/16" rubber fuel line. After a little rigging (didnt watch him do this) of a brass elbow to make the bend to connect the two, the pump was placed back in the tank. The pump fit ok into the bucket, i didnt need to modify that at all, as compared to what i had heard. He said the connection was good, and put it up on the lift to change out the filter. Pics attached of the non flex fuel line in the install kit, and the rusty old fuel filter that i thought may be the problem.

New pump and filter installed, BAP still connected (to be removed in a couple days), and a few hours later, away i go !

 

[MakeItHappen]

Tow truck time

Great....100 miles later this is the view i get.

You must be registered for see images attach

Driving around enjoying the car, waiting on my appt a few days later to get tuned again, bob and weave doing 50-70mph and i roll up to a light and start loosing power. Yup..out of fuel. Roll to the corner just in time for the black Gallardo to come laughing by me on the side of the road of a 6 lane by 6 lane intersection. I click the key and get a little whir from the back, like the pump is kicking on, but not all the way. Very odd. Call useless Geico who will only tow me to dealer. hang up and call a local guy who sends an Air ride freightliner flat bed so he can scoop me up problem free. $300 tow to the Mechanic/Tuner. I told him i dont want it back until im 625+rwhp, whatever it takes. Errrr.

 

[MakeItHappen]

So this guy goes through the car, and turns out the rubber fuel line had blown itself off the pump. Either a loose hose clamp, too much restriction with the elbow, or voltage increase from the BAP. Either way i blew the line off the pump. So he gets the proper line installed, and removes the BAP. Says im back to 55-58 PSI of fuel at the rail. I make an appointment and go up a few days later to get it on the Dyno. We see the timing is off on the car as well, was still set to factory timing ar 25-29 degress, worked it down to 16-19 degrees to account for modifications, and now runs MUCH smoother. Everything is going good......all the way up to 5k RPM and then we get drastic fuel drop off. *** ?!

So process of elimination says voltage or regulator could be the only other culprits. Check the voltage at idle and all appears well. Now on to the regulator. Call up RSI and apparently it is common for the Fuel Pressure Regulators to stick on these cars ? They say that is the likely culprit and offer to send a good used one at no cost straight to the shop, good business ! So now the FPR is my likely culprit and i have an appt this thursday to go back, put that in, and get back on the Dyno for hopefully the last time this year.

Anyone ever had an issue with their FPR sticking in higher RPM that they know of ? Leans the car right out..

 

[EllowViper]

While they are back in your fuel basket, make sure that fuel line they are using is the type that can be submersed in fuel...not just standard 3/8 fuel line. It will decompose in short order. I can't tell in the picture, but it looks suspect to me. The fuel line spec is SAE 30R10. I believe NAPA carries it. And I haven't had any issue with my FPR sticking.

 

[BlackSnake99]

And I haven't had any issue with my FPR sticking.

Me either.

 

[Red Snake]

And I haven't had any issue with my FPR sticking.

Me either.

Me N3ither.

 

[Roysviper]

Me N3ither.

Me either....ha....

 

[MakeItHappen]

Me N3ither.

Hmm I guess i'm just that "lucky"....May not help that my car has 50k on it, who the hell knows
Just seems like such an odd issue to be dealing with, i'll get the answer to the most recent problem on thursday when we change that FPR out and go back on the dyno, and see if the guage stays strong past 5k rpm.

Ellowviper - yea we should have the proper line on there now, the one in the kit is no good, but was replaced at the 2nd mechanic after it blew off for some reason. I'll dbl check him when we pull it out anyway.