No, he is 100% correct. That was a very poor guess by the tuner at the customer's problem. If the tuner knew how the Lightning fuel system worked, and just had an overall knowledge of how things work, he would not have suggested that.

Base fuel pressure on the Lightning is about 40 psi, and that's with the pumps stepped down to 7 volts. In order for his fuel pressure to drop all the way down to 30 psi, from a voltage loss, battery voltage would have to be dropped well down to 5 volts (while the pumps were on the 12v side of the relay). The truck would have shut off long before it ever hit that low. There is no possible way he's seeing 30 psi from a "draw" on the battery at WOT.

The fact that he's hitting 50 psi shows the high side of the fuel system is working. Pressure dropping off after it hits 50 psi, means that volume or pressure is being lost at that point. Since we know he's got enough pump, it's gotta be a leak in the system.

 

double post

 

I agree, that's why I said , i'm not saying that this is his problem, but not all fuel systems work the same.

Maybe he does know how the lightning system works and that's why he said it but not all systems work the same so to say that he would just fire this guy imediately is kinda dumb because it's not so far fetched.

What if this guy tapped a power wire somewhere that is tied in with an engine management system, or fuel pump system.

Did he check to see what the voltage was across the battery???

I still agree with everyone that it sounds like more of a fuel line/clamp issue but you should never rule something out right away until it's checked.

 

Right, if the BATTERY was to draw that low....... Meaning when the subs kicked in with the amp, the battery would drop to say 7 volts. I don't think it's possible to draw a battery down that fast without severe damage to the battery.

BUT.....

If there was a draw or a short on the power going either to the relay or the pump itself, it is definetely possible for the pump to drop to 5 volts, or even less. Am I wrong?

It could also be a bad ground on the fuel pump relay or just a plain bad relay.

I've seen resistance internally on relays where you only get 10 volts or so across it. Usually they get all hot and gooey shortly after. Sometime..........fire!!!!!

 

ok guys didnt mean to start a war here, I just wanted to get yalls thoughts on this b/c I do actually trust yall more than this tuner...like I said I just met him but he "seems" to know what he is doing. I thought this sounded stupid too when he suggested it so he pulled up the kenne bell web page and showed me exactly why and what causes this from the tests that kenne bell performed. It is explained in great detail on their site and why this "fuel pump booster" works. I admit that I dont know anything about tuning..thats why I pay him to do it and ask yalls PROFESSIONAL opinions. I really thought Sal or Johnny could shed some light on this for me and invite your suggestions. But, me being inexperienced in tuning/mechanics I dont have any reason to doubt him....especially after he showed me the write up on kenne bell. He said this has happened on more than one mustang he has tuned and one other lightning. But regardless, we ordered this part from kenne bell, I'm putting in the walbor's tomorrow and we will see what happens when I go back to the dyno after this...I will definately let you know b/c of the questions this has brought up. PLEASE READ THIS AND SEE WHAT YOU THINK.

http://kennebell.net/techinfo/genera...heory_kens.pdf

 

battery draw and pumps runnign out of juice is a huge problem on the returnless cars. the good 03 cobra tuners found that in some cases battery voltage dropping too low caused lean conditions. id say it was a good guess and smoething that should be checked into. electric motor 101 if the circuit drops juice then the usually so does the motor.

 

Oh, let me add. I do trust this tuner or I wouldnt let him work on my truck...... I just value your opinions b/c of the things I've read on here. I know you guys better just from time spent on here. Please read the link to kenne bell's write up on this and then give me some opinions again. Thanks

 

Very true, but the Lightning is not returnless.

My point was you need to be familiar with how a specific vehicle works, before you make the customer buy a $250 part, because of a mis-diagnosis. Or at least, that's just how I feel.

If the amps were somehow tapped directly to the fuel pump power, then he'd never see the fuel pressure go to 50, it would just be always low. Amps that are just "powered up" and not feeding any music, aren't going to be drawing more power at high rpms where is fuel pressure is dropping off.

 

The obvious would be to simply pull the fuse to the amp and re-run the test.....

 

Ok,
I ruffled some feathers here and I'm sorry for stating my opinion so strongly. certainly don't mean to start a war on here. I do however stand behind my commit. I don't know what kind of credentials you would hope to see, but I'm degreed mechanical engineer from one of the best Engineering schools in the country, I have a strong background in automotive electrical systems, and now currently work for one of the largest companys in the world designing electrical power distribution equipment for big industry. Prior to graduating college I have over 10 years experience working as a professional car audio and security installer.

The reason for me stating my opinion like I did is because it is one of my pet peeves where auto techs, service writers, etc. blame the first thing they see that wasn't OEM or that they don't fully understand. Not saying this guy is a bad guy I just think it's better to admit you don't know or understand something than tell somebody who's paying you to help them wrong information.

I've seen some crazy stuff in my day, and I'll give you credit for almost anything being in the relm of possibility. I have personally never seen or heard of an amp drawing extremely large amounts of power while being idle, but I guess anything is possible. I've seen some amps shorted internally and seen shorted wires, but those will typically cause fuses to pop or wires to burn.

The fuel pressure symptom is a mechanical symptom. I would begin to look for mechanial problems first. It is possible for there to be an electrical draw on the fuel pump circuit that would not allow the pump circuit to get full voltage, however that doesn't make sense if it could reach full pressure some of the time. But power draw on another circuit of the truck, like audio amps, would have to be extremely large (>100 amps) in order to cause that kind of total system voltage drop at the fuel pumps. My point is that you would be seeing blown fuses and other very serious symptoms like fire if that were the case.

 

no ruffled feathers. Just discussing all angles.

The guy said he would fire his tuner imediately if his tuner told him that and I felt that was a very stupid statement because it is possible for that to happen. Maybe not on a Lightning as Sal described, but it's possible. Then a few other posts backed my statement up.

If the guy who said he would fire his tuner knew the lightning system well enough to know this.......Then my appology. But you can't paint every problem or issue with the same brush, which people tend to do, and people will over look a problem because someone told them there's no way......and guess what. WAY!!! We've been overlooking valve springs for years on these trucks and everyone said No, would cause it........not the problem. Look at all the info coming out of the wood work now. Valve springs nearly sufficient enough to keep the valves closed at stock set up??????

My bad again. No means to ruffle feather. Just trying to help you out. Sal says on your truck, this wouldn't be the case so............NEXT

 

OK, for everybody that has been involved in this thread I appreciate your help and suggestions and maybe I can lay some thoughts to rest here or give you guys something else to think about when tuning. So, like I said my truck couldnt maintain its fuel pressure under WOT so we started trouble shooting it. After changing the fuel filter no luck, checked all the hoses/clamps with no problems found so the tuner wanted to put the Kenne Bell boosta pump on it b/c he thought my stereo system was drawing to much voltage from my fuel pumps and they couldnt keep up with the demand under WOT. Obviously I was hesitant of this idea which is why I posted in here asking for yalls opinion. Well, yesterday was day number 2 on the dyno and I really wasnt sure about the boosta pump theory so prior to going back to the dyno I changed my fuel pumps out thinking that it was probably just a problem with them. I put in the walbro 255's and everything from the pumps to the fuel rails ckecked out fine....I also changed the plugs the day before (tr'6), no damaged/pinched lines or clamp problems along the fuel system. So last night before we installed the boosta pump we made a pull....same problem...leaned out at WOT due to dropping of fuel pressure to 30 psi. We checked the relays they were fine....even changed them out for good measure. No change! So we installed the boosta pump AND ON THE FIRST PULL fuel pressure spiked and held at 60 psi at WOT. We ended up cutting back the fuel pressure on the boosta pump (its adjustable) to 50 % and on the next pull it spiked at 60 then gradually fell to about 50 and held so we left it there and began dialing it in. Now, after 3 years of running a 6lb lower with filter /chip at a air/fuel of 14% when Wot (how the hell did this thing not bolw up on me b/c its ran hard regularly) I now have a safe tune with 16 degrees of timing/ and air/fuel of 11.6 and 400hp to the ground and its a daily driver with a nearly 200 mile round trip to work. Guys I dont know exactly how/why it works all I know is that that kenne bell boosta pump DID fix my problem on the first pull we made with it and everything else had already been changed w/o effect. I know several were skeptical of this approach but all I can say is that it worked and the dyno proved it, maybe if you ever run into a fuel pressure problem it might be something to look into. Its good insurance for the motor regardless...atleast you know you'll always have fuel even if you have stereo amps or an alternator going out. Hope this helps somebody. Thanks to Strategic Performance in Jasper, Alabama for the safe tune.

 

I'm glad to see you got your problem resolved. In my opinion, and you can take it for what it's worth, your truck has a different problem. Increasing the voltage to the pumps via the BAP is a band aid fix that's taking up the slack. In no way, shape, or form, should any stereo system cause that kind of voltage drop on your truck, especially if it's OFF.

You're truck should be ok for now, but my suggestion is that if you plan to bump the power up in the future, you'll need to address the real issue at that time.

 

Thanks Sal. I just dont know what else it could be though. Nearly every component of the fuel system has been checked, New and bigger pumps, The tank was clean when we checked no crap floating around in there or anything, all the hoses were tight and connected, no clamps were cruching or pincing hoses of, my wye still looked like new, the filter was replaced and the relays work fine on both sides. I dont know what else to check. Do you think my alternator could be slowly giving up on me and causing this? Its still stock and is running all my stereo components...possibility? Anyway, if youve got ideas I'll check it but for right now it is working. If I can figure out how to do it I'll post my dyno sheets.....so is 400hp respectable for a daily driver?

 

Since you did all the mechanical stuff already, and the BAP DID show a change, I would say that there is an issue with the wiring to or from the pumps. You have a 12 volt feed TO the pumps. Then you have a ground back from the pumps. The ground is what goes through the relay. One side (the low side) goes through the dropping resistor and the other side (the high side) goes right to direct ground. If I were working on this truck, I would start by checking the full ground side. That seems to be where your voltage loss may be coming from.

For example.. If you are getting say, 11.5 volts from the battery at WOT, you might be losing 3-4 volts through a bad ground. That's going to drop your pumps down to about 7 volts or so, which would be similar to if your high side relay didn't work, and would cause your problem. Now that you've added the BAP, it may be kicking the FEED voltage to about 15-16 volts. But you are still losing that same 3-4 volts on the ground side. But now your total voltage is over 11 volts, so it's back to battery voltage. That's how I think the BAP is acting as a band aid fix.

Make sense?