383 stroker with 190ccAFRheads, Miniram intake, 58mm T.B., Isky roller cam 225/234 505/530 112LSa at .050 Hooker 2210 Long Tubes with 30lb SVO injectors. All normally aspirated. This is what I have changed so far

1) Brand New GM fuel tank
2) Brand New Walbro 255ltr/hr high pressure fuel pump
3) Brand New Aeromotive fuel pressure regulator
4) Brand New AC delco fuel filter

I would also like to add that the car has a Holley Commander fuel management system that is completely tunable with a laptop during the dyno session. The car is leaning out thats why the pressure is turned all the way. The car just needs more fuel because the pressure drops.
Pressure is turned to 70psi and stops dropping at WOT on the dyno. The pull has to be stop at 5500rpm. Injector pulse has to be increased before it leans out because the fuel pressure doesn't hold. I thought I had a defective fuel pump and order a new one. I replaced it but this did not solve my problem. It help the problem a little but it still remains. Recently the regulator had to be change because as soon as TPIS regulator was changed in favor of the Aeromotive the pressure was able to hold. However the car ran out of gas during the dyno session. Further dyno pulls afterwards still show the car unable to reach peak power because the pressure begins to drop so more and more gas has to be added before the pull has to be cancelled. What could be the problem?

Car is making 303RWHP and 357RWTQ before it starts falling in its face.

 

Check out your FPR and see if there's anything wrong, I had a brand new diaphram go bad on me once and it caused the same problems.

 

30 lb injectors will support upto 600hp at 40lbs of pressure. Why do you have your fuel pressure at 70 psi? Your injectors cant handle that much pressure! What all have you changed in your PROM? I would lower fuel pressure to 40 lbs. and start adding/subtracting fuel and timing in the PROM according to your results from having the car on a scanner.

I'm making more power than that with 24 lb injectors at 39.5 PSI.

I would say that something is wrong in your PROM. But thats just a guess.

 

Agreed- why 70 PSI? 40 PSI should be plenty to get the job done with proper chip tuning.

Putting that aside:

1. restriction in the fuel line up to the engine somewhere (kinked line, obstructed line)

2. not getting full voltage to the electric pump. Could be a million reasons why but without full voltage even the best pump won't get the job done.

 

Check your fuel line from the pump to the front of the car.

I have a high flow fuel filter, you may want to get one, I think the stock fuel filter maybe a restriction. I have the filter that unscrews so you can pull out the element and clean it.

Like everyone else said, turn down that fuel pressure to like 45 psi.

I was running 74% duty cycle on the 30 lb injectors, so I got some 36's now and the duty cycle is around 63-64 %. Try some larger injectors.

 

flow and pressure have an inverse relationship.

 

Allright, I have decided to do a fuel volume test but I need the specifications to check against. I have the walbro 255ltr/hr hi pressure fuel pump. How do I get hold of this information to check if the pump is pumping the right amount of gas? At this point I don't know what else to check for. This is the second Walbro 255ltr/hr hi-pressure pump I have ordered from Autoperformanceengineering.com and everyone seems to swear by it. I hope this last new one I installed about a week ago didn't take a dump on me. So I want to make sure I have volume.

 

Try www.racetronix.com

 

Well, here's the update. Sunday my mechanic and I did the fuel volume test on the fuel pump and it pass with flying colors. The pump was able to fill over a gallon a minute which is well its supposed to me for a walbro 255ltr/hr at over 70psi pressure. The funny thing is that the brand new Aeromotive Fuel pressure regulator WOULD NOT lower the pressure from 70psi no matter how far we adjusted the screw on the regulator. Knowing the fuel pump is producing enough volume, the mechanic has decided to order yet another new fuel pressure regulator and try that. He is perplexed and does not imagine what else could cause such a drop in pressure at high rpm's. I mean from 70 psi down to 35 psi is a huge drop. What else can anyone out there recommend to look for?

 

Free flow volume has practically nothing to do with it's ability to supply fuel under load.

Just noticed another tid bit from an earlier post. Apparently you swapped regulators at one point with the new fuel pump and it worked fine. Then you ran it out of gas. And it hasn't worked right again since?

Congratulations, you just demonstrated how bad running an in-tank pump dry is. Yes you really could have killed it in such a short time with no fuel on it. And from your symptoms i'd say thats what you're looking at. A FPR is just a bypass device. It gets no feedback from the engine with regards to RPM. It simply bypasses fuel to keep the rail constant. If your pressure sudddenly drops under high RPM / load driving, you are outrunning your fuel pump, or lines / filter are restricting you. The hardest situation for an FPR to control is idle when the pump is at max vulme and the injectors are barely opening. High load / flow just makes teh FPRs job easier because it has to bypass less fuel to keep the pressure up.

 

It's possible that at 70psi your injectors are sticking open therefore causing your FP loss under load. Without the load the vacuum lowers the FP considerably (roughly 10 psi) which is still too high. Hopefully a new AFPR will fix it.

 

Well, here's another update. The technician decided to contact Aeromotive the manufacturer of the FPR. The technical advice given to us about the regulator not regulating the fuel pressure was that the return line was getting clogged up at such high PSI and I needed to install a bigger return line -6an equivalent to the feed line which is about 3/8". So rather than replace the regulator, the techinician decided to replace the return line with the recommendation of going bigger. Well guess what. IT ABSOLUTELY DID NOTHING. THE PROBLEM REMAINS. We have taken into consideration that maybe the 30lbs SVO injectors are sticking open at such high psi causing for the rapid fuel pressure drop at higher RPM's. However, if that would be the case the car would run rich on the dyno and not lean out like it is. I guess were going to try changing the regulator and then the only other thing to do is to drop the fuel tank and replace the fuel pump for the third time. What else can we check for?

 

 

I agree with Ed totally.

I made 364hp at the rear wheels with my stock 350, MiniRam, AFR heads, 230/245 cam, and 30lb SVO injectors. The injectors were only at ~80% duty cycle ... thus, I can say that yours are not going static at only ~310hp.

Tim

 

Are you sure the FPR is hooked up properly in regards to the return and supply? Which aeromotive unit is this? Does the FP drop at idle with the vacuum hooked up to it? I tihnk once you can drop the pressure this may help your problem.....as already pointed out, as FP increase fuel volume decreases, the 70 PSI is "overtaxing" the pump. IMHO

 

Yea - I didn't even notice that! 70psi is absolutely rediculous. I'm running 45psi and using stock lines. It's obvious I have plenty of room for growth. There's nothing wrong with your setup. It's either the rediculous pressure you are running or it is the fuel pump itself.

Tim

 

Could there be a short in the fuel pump wiring?? This may be a dumb hunch, (don't throw tomatoes at me guys) but I don't know what else to think if every part of the fuel system is new and working properly. ???

 

While I agree that the pump may have been hatched by running it dry, I kind of doubt it in this particular instance...

What kind of tune is in there and what are the specs on it? (ie injector constant)...... What duty cycle are the injectors at (at WOT)? What does the WBO2 say from the dyno when all heck breaks loose?

 

Another update: The car hadn't been started for over a week. The battery was a little dead so I put the battery charger for half hour. Then I notice something when the car finally started. There was a nice fuel leak that puddled right underneath the fuel tank. I turned off the car and then started it right back again. The leak stopped. It sort of fix itself. So what we decided to do is to drop the tank and check all the lines. This makes sense why the car is running lean at high load. There's air in the tank somewhere where that leak is at. First time I notice it though. This is likely the cause of my problem. I'll keep the board posted as to our findings when I drop the tank.

 

Cool, sounds like you've really got fishy problem figured out. Good luck and keep us posted on how things turn out.

 

That leak is probably the problem! However, that high of pressure has been known to kill injectors. Just a thought!

 

is your car speed density or mass air?
are you using the stock air inlet for tpi?

i had the same problem with my car under load at high rpm. i just replaced the fuel pump & fuel filter, but the car still ran the same. i have speed density so i tried running the car with out the air inlet. the car ran fine, put the air inlet back on & had the problem's. the air duct between the air filters & throttle body was collapsing under load, causing vaccum, making my fuel pressure drop, & causing other sensors to mess up.