rp0029

iTrader: (1)

So I have an lq4 with an ls3 top end and 42lb injectors. Engine makes no more then 500 crank HP. Dyno tuner told me it runs out of gas at 5400 rpm but that the injectors are nowhere near max duty cycle. He says I need to upgrade my fuel pump to a walbro 255. But previous mechanic installed a walbro 255 already just a few months ago. Tuner thinks bad gas hurt pump, as the injectors were so dirty he had to take them out and clean them. What do you guys think?

rp0029

iTrader: (1)

Could it be a problem with my fpr?

buick_lsx

if your injectors got clogged...that same crap went through your fuel pump

rp0029

iTrader: (1)

Right. But before I drop my tank and spend the money on a new pump, is there a way I can test it? I'd hate to drop $180 on a new aeromotive 340 pump and a Saturday dropping the tank only to find out my fpr got clogged.

dlandsvZ28

You can test fuel pressure by attaching a fuel pressure guage to the fuel line - drive side of manifold. It contains a shrader valve. I believe pressure should be 58 lbs. Your tuner should know where to attach it.

You will probably want to install a new fuel filter before testing fuel pressure. It's quite possible the fuel filter has never been changed.

Before you drop the tank find out from previous owner if an access hole was cut from inside the car over the gas tank. It's the easiest way to remove or install a fuel pump.

rp0029

iTrader: (1)

It's a 1968 camaro. Guess I forgot to mention that. The tank isn't that hard to drop. So will the pressure be the same under load?

dlandsvZ28

Yes it has to be - if not it can go lean.

It's why some install a digital or manual fuel pressure guage with power adders (turbos and superchargers). They don't want to go lean under boost.

With an in-cabin guage you can monitor fuel pressure. The guage readout, if you decide to install a guage, is determined by the fuel pressure specific to your application. Some applications don't require 60 lbs of pressure.

I have a digital. When I turn the key off, the guage still stays at 58 psi (bottom gauge).

http://www.flickr.com/photos/1835930...57623345499537

It's not unusual for sender to go bad or not be entirely accurate. If so, then test again with a very good manual guage.

Tip: A good pump might not operate at its full potential with some electrical systems. As a result Racetronix supplies it own wire kit and booster kit to assure that pump always get the correct amount of voltage in order to supply the maxium amount of fuel at all times. Racetronix recommends the wire kit to be wired directly to the alternator.

There are stickies in the fuel forum with lots of good information.

https://ls1tech.com/forums/fueling-i...twire-kit.html

https://ls1tech.com/forums/fueling-i...ump-chart.html

hth

ddnspider

iTrader: (26)

You're nowhere near maxing out a walbro 255 so why would you spend $180 on an aeromotive 340?

dlandsvZ28

I think Racetronix literature states about 550 -600 crank hp as does most of the advertisements from various vendors who sell this pump.

I guess we can assume this is an external pump?

IMO - you should check the wire kit to the pump even if it is producing 58-60 psi under full load. It's kind of like a brownout - not enough voltage and it will fail prematurely.

ddnspider

iTrader: (26)

A single intank walbro with a hot-wire kit will support 550-600rwhp. It's been done by many people. At that level injectors are usually more of a problem depending on what the motor has.

rp0029

iTrader: (1)

It really is a relatively mild motor. Lq4 w ls3 heads, stock ls3 manifold/injectors, can is comp xe with 222/230 /.050 .570 lift. The pump should not lean out like that. Either the pump is faulty because old gas ran through it (the same gas that trashed the injectors) or something else is preventing the fuel from hitting the injectors at a high enough psi at 5400 rpm to get the right afr.

I think that the causes could be:
Bad fuel pump.
Cavitation from a problem with poor tank venting.
Lack of enough current to drive fuel pump.
Bad fpr.

Right now I'm not running a filter - so that is ruled out.

Any thing else that could cause a lean condition despite injectors running at less than full duty cycle?

rp0029

iTrader: (1)

Also this is an internal pump with a spectra tank.

dlandsvZ28

Looks as if the Spectra tank has issues because of its design - fuel starvation.

http://www.camaros.net/forums/showthread.php?t=186401

Is this your build or someone else's?

Is your tuner a reliable tuner with a good reputation for modifying a tune specific to your engine fuel and air requirements?

I spent nearly $3000 in tunes with four different tuners before I found one who actually knew how to modify the tables in a base tune which had to modified extensively cell by cell from one rpm level to the next coordinated with timing as well. It took hours and hours on a Mustang Dyno to finally get it right.

Even then, you have to have all of the right equipment installed and all working correctly to get it right - fuel pump, alternator, injectors, O2 sensors and installed in the correct location, MAF, and the list goes on and on.

I ended up with an SD tune. When done correctly it like driving a completely different car - all because of the tune.

It hard enough with a semi stock car - 1998 - 2002. Can't imagine what its like to redo a 1968 and modify all the sytems to bring it up to date to run correctly with a PCM and electronic systems.

I did own a 1968 GTO at one time. I wouldn't know where to start to try to convert it over to what I have in my 1998 Z28 Camaro. But would be an interesting project for sure. I have been working on mine since 2002.

http://www.flickr.com/photos/1835930...57623345499537

You might want to post your questions on the first link I inserted. Good luck - I have no doubt it will be a fun car to drive when you get all of the bugs fixed.

rp0029

iTrader: (1)

I'm aware of the spectra problems. They seem to stem from fuel slosh/baffle problem, which only appear at low fuel levels. My tuner is Dan Maslic. From what I understand he is the best guy in the south east. Check out masport.com. The guy literally wrote the book on tuning.
He reports it leans out at 5400 rpm. So he put my shift point a tad lower than that. If the car leans out at 5400 rpm and the injector is spraying at 70% of what it can at max it probably isn't the tune. I'd think a guy like dan, running on a mustang dyno, would know to try to adjust the tables to compensate for the lean condition. He said no matter what he did, the car leaned out at that rpm. He said the pump couldn't keep up.
Like I said, the pump doesn't seem bad. It is a walbro 255 that was installed to replace the weak failing spectra pump a few months prior. It starts and runs fine without issue. I am just going to have to put a gauge up to it.

I suspect the problem is in the wiring as suggested above. I have a 30 amp relay and I think I may have about 8 feet of 16 awg from the fuse box to the pump, which I calculate will only support 5 or so amps. At full tilt, the walbro will require 13 amps. I think therein is the problem. If the pump was going out, I highly doubt that it would only fail at 5400 rpm. It would probably choke throughout the band intermittently, no?

rp0029

iTrader: (1)

Brother there is a forum on this site dedicated to exactly that. Check out conversions and hybrids. People put these engines in all kinds of things. Fox mustangs. Nissans. RX7s. BMWs, All gens of camaros. Jet boats. Airplanes. You really ought to check it out. I drive my 68 to work everyday with this engine. It still has bugs and has only been on the road for a month, but it is still very reliable.

dlandsvZ28

If Dan is your tuner then you have one of the best. I have one of his books and plan to order the new revised edition for EFI live.

However, I would have thought that he would have already attached a fuel pressure guage to test fuel pressure at WOT or perhaps he has, but just didn't mention it since his diagnosis is the fuel pump.

I suppose it is possible to that the wrong type of hose was used inside the tank, it is starting to deteriorate, and is what trashed the injectors. It's hard to believe that a relatively new Spectre tank could have accumlated enough trash already. But why aren't you using an inline filter?

Is there a sock in the tank? If you had trash then is the sock contaminated as well restricting draw at WOT?

Or perhaps you have been one of the unfortunate to have gotten a bad tank of gas with more than 10 percent ethanol.

As for the wiring, 16 guage is way too small. Wire it with 12 guage from the pump all the way to alternator the way the Racetronix hot wire kits are designed.

Is your alternator capacity up to the task of supporting all of the new technology you have on your car - PCM, upgraded high capacity fuel pump, high capacity fans if you have them, etc. ? It's not a 68 anymore.

rp0029

iTrader: (1)

Im not running an inline filter because the vette fpr i have is also a filter. The alternator is a cs 130. It came with the ls. I do have a mark 8 fan, but no stereo or ac or anything. Dropping the tank is kind of a pain. Id rather do that last.
I don't know whether the walbro has a sock - it was put on by someone else.
Im going to re wire the pump this weekend and perhaps put a fuel gauge on it.

01ssreda4

iTrader: (96)

In-tank fuel line will deteriorate, and cause symptoms like you are having. Further diagnoses is required at this point. The one failed "walbro" I have seen gave us fits throughout the rpm range where the fuel was being trimmed (even at idle) in excess of 20% to create suitable afr levels. The idle psi was in the mid 40s. We replaced it with a known good stock pump and everything went back to normal. And, I say "walbro" because it was supposed to be genuine but I suspect it was a Chinaman knock-off.