Voltage Drop and WOT Lean Condition Related?
Voltage Drop and WOT Lean Condition Related? EDIT: Problem Solved. See Post #22
I've been chasing a lean condition at WOT and have a few questions. I currently have no way of monitoring my fuel pressure, but I have noticed that both my in-dash voltmeter and autotap logged ignition voltage dive to 11.XX volts at WOT. However a digital Volt gauge plugged into the cig lighter doesn't budge from 13.XX Volts during the entire run.
I suspected belt slippage at the alt, so I installed a Katech tensioner, which didn't change the condition at all. Anyway my real question is, if the voltage at my alternator is dropping at high RPM, would that affect my fuel pressure enough to cause a WOT lean condition, or would the battery be able to supply enough voltage for that short (say 10 seconds) period of time?
The car has a stock intank pump, an inline Walbro 255, and SVO 42lb injectors. Most other mods are in my signature. Thanks guys.
I've been chasing a lean condition at WOT and have a few questions. I currently have no way of monitoring my fuel pressure, but I have noticed that both my in-dash voltmeter and autotap logged ignition voltage dive to 11.XX volts at WOT. However a digital Volt gauge plugged into the cig lighter doesn't budge from 13.XX Volts during the entire run.
I suspected belt slippage at the alt, so I installed a Katech tensioner, which didn't change the condition at all. Anyway my real question is, if the voltage at my alternator is dropping at high RPM, would that affect my fuel pressure enough to cause a WOT lean condition, or would the battery be able to supply enough voltage for that short (say 10 seconds) period of time?
The car has a stock intank pump, an inline Walbro 255, and SVO 42lb injectors. Most other mods are in my signature. Thanks guys.
Last edited by GC99TA; May 9, 2008 at 05:25 PM.
Teching In
Joined: Apr 2008
Posts: 21
Likes: 0
From: Ill
I've been chasing a lean condition at WOT and have a few questions. I currently have no way of monitoring my fuel pressure, but I have noticed that both my in-dash voltmeter and autotap logged ignition voltage dive to 11.XX volts at WOT. However a digital Volt gauge plugged into the cig lighter doesn't budge from 13.XX Volts during the entire run.
I suspected belt slippage at the alt, so I installed a Katech tensioner, which didn't change the condition at all. Anyway my real question is, if the voltage at my alternator is dropping at high RPM, would that affect my fuel pressure enough to cause a WOT lean condition, or would the battery be able to supply enough voltage for that short (say 10 seconds) period of time?
The car has a stock intank pump, an inline Walbro 255, and SVO 42lb injectors. Most other mods are in my signature. Thanks guys.
I suspected belt slippage at the alt, so I installed a Katech tensioner, which didn't change the condition at all. Anyway my real question is, if the voltage at my alternator is dropping at high RPM, would that affect my fuel pressure enough to cause a WOT lean condition, or would the battery be able to supply enough voltage for that short (say 10 seconds) period of time?
The car has a stock intank pump, an inline Walbro 255, and SVO 42lb injectors. Most other mods are in my signature. Thanks guys.
Yes, your pump isn't getting enough volts to keep up with the fuel demand.
Do you have a hot-wire kit?
How old is the alternator?
Do you think the problem is with the alternator itself, or is there just too much of a voltage demand running both pumps? I should also say that I do have underdrive pullies, but I would think that would be more of an issue at low RPM and not at high. The car charges fine at all other RPMs and conditions except heavy load and high RPM.
Now that I see two problems at once (voltage drop at WOT and lean condition at WOT), I was more likely to associate the two together. However, I still may remove the inline and try making a few passes on the stock pump alone.
Have you seen an inline pump cause a lean problem before? Thanks.
Figure out what is causing the voltage drop...that would be my primary concern. Once that comes back, your fuel pressure should too, and that'll take care of your lean condition. Voltage drop like you are having at WOT is not a good thing.
Teching In
Joined: Apr 2008
Posts: 21
Likes: 0
From: Ill
No hot-wire kit. The alternator was replaced about 6000 miles ago. Bought it from Advance.
Do you think the problem is with the alternator itself, or is there just too much of a voltage demand running both pumps? I should also say that I do have underdrive pullies, but I would think that would be more of an issue at low RPM and not at high. The car charges fine at all other RPMs and conditions except heavy load and high RPM.
Do you think the problem is with the alternator itself, or is there just too much of a voltage demand running both pumps? I should also say that I do have underdrive pullies, but I would think that would be more of an issue at low RPM and not at high. The car charges fine at all other RPMs and conditions except heavy load and high RPM.
How many things/accessories do you have on when the car is under heavy load? These all play a part in how much voltage the pump will be getting.
I've never dealt with a in-line pump, so i can't help you out there. I know the principle behind the pump. How does this wire up?
Also, I would not be spraying the car until this is figured out.....
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Yeah, I posted in the electronics forum asking specifically what could be causing the voltage drop issue. I want to get it solved whether it's causing the lean condition or not.....although I highly suspect it is after all this feedback. Since I'm not getting any feedback in there yet, any ideas in here about what could be causing this? Can a bad ground cause this? Too much load from having two pump? Bad regulator in the alt? Remember, it only does this at high RPM.
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Verdad Gallardo I think the problem is somewhere in the charging system, rather it be the alternator or battery. I don't think the underdrive pulley has anything to do with it.
How many things/accessories do you have on when the car is under heavy load? These all play a part in how much voltage the pump will be getting.
I've never dealt with a in-line pump, so i can't help you out there. I know the principle behind the pump. How does this wire up?
Also, I would not be spraying the car until this is figured out.....
How many things/accessories do you have on when the car is under heavy load? These all play a part in how much voltage the pump will be getting.
I've never dealt with a in-line pump, so i can't help you out there. I know the principle behind the pump. How does this wire up?
Also, I would not be spraying the car until this is figured out.....
There isn't much on at all.......headlights are off, stereo system and AC have been removed completely. The only things I can think of that are being powered (aside from the obvious like the PCM ect) is the additional fuel pump.
My inline pump is powered by a dedicated hot wire coming off of the battery. This dedicated hot goes through a relay, which is triggered by the stock pumps 12V source. Basically, when the stock pump gets power, the relay gets triggered and the inline gets power straight from the battery.
Oh, and yeah, there's no way in hell I'll be spraying this thing anytime soon
I hate seeing it go that lean just on the motor. Scares the **** out of me, but oddly enough, I get very little if any KR. I would think my Wideband was giving false readings if it weren't for the stock O2s showing lean too. 
Bad grounds.
Corroded bat ends.
Pump feed wiring fubar.
Pump grnd[s] bad.
Relays bad.
Batt cells going south.
1 of the two pumps took a crap?
GET a FP gauge, and see WTF the FP reads when this happens?
Corroded bat ends.
Pump feed wiring fubar.
Pump grnd[s] bad.
Relays bad.
Batt cells going south.
1 of the two pumps took a crap?
GET a FP gauge, and see WTF the FP reads when this happens?
Does anyone know where I can get a manual FP "test" gauge with a lead long enough to hook to the schrader valve and still be able to tape the gauge to my windshield? At this point I really don't want to buy a more permanent type FP gauge (although it probably wouldn't hurt).
I ordered one of these to make sure I do not have this issue.
http://www.speedinc.com/cont.cfm?cid=C0000096
I had heard of it before and liked the concept.
http://www.speedinc.com/cont.cfm?cid=C0000096
I had heard of it before and liked the concept.
I ordered one of these to make sure I do not have this issue.
http://www.speedinc.com/cont.cfm?cid=C0000096
I had heard of it before and liked the concept.
http://www.speedinc.com/cont.cfm?cid=C0000096
I had heard of it before and liked the concept.
I would look towards the alternator as a possible problem source...seems that if anyone has problems with them, they have been from the ones they got from Advance/Auto Zone with the lifetime warranties. They don't tend to be the best quality...if you are seeing the drop in voltage on your in dash volt-o-meter, I'd look no further than the alternator.
I would look towards the alternator as a possible problem source...seems that if anyone has problems with them, they have been from the ones they got from Advance/Auto Zone with the lifetime warranties. They don't tend to be the best quality...if you are seeing the drop in voltage on your in dash volt-o-meter, I'd look no further than the alternator.
I'll be sure to post up once this is all resolved. I've searched and found a few other people that have had this exact problem (at least one with a reman alternator). I PM'd two of them about the resolution; one guy hasn't had a chance to replace his alternator yet and the other guy said he thinks his was from belt slippage from not having his manual tentioner installed properly?
Well, as already suggested in this thread, you may want to try a hot-wire kit and, perhaps, the voltage booster. Both are pretty simple fixes and they may help. However, I found that the in-tank FPR can be a real liability. I'm not making anywhere near your power (<112 MPH), but I was unable to solve a similar high RPM lean-out until I had a stable, deterministic fuel pressure. I went through a Racetronix pump and hot-wire kit (after my stock pump failed) and I also use the voltage booster (you do need to make sure you're getting 13+ V at the pump at WOT). Both helped, to a degree, but didn't solve it. Cutting in the external regulator seems to have taken care of that.
Just some food for thought.
Just some food for thought.
Well, as already suggested in this thread, you may want to try a hot-wire kit and, perhaps, the voltage booster. Both are pretty simple fixes and they may help. However, I found that the in-tank FPR can be a real liability. I'm not making anywhere near your power (<112 MPH), but I was unable to solve a similar high RPM lean-out until I had a stable, deterministic fuel pressure. I went through a Racetronix pump and hot-wire kit (after my stock pump failed) and I also use the voltage booster (you do need to make sure you're getting 13+ V at the pump at WOT). Both helped, to a degree, but didn't solve it. Cutting in the external regulator seems to have taken care of that.
Just some food for thought.
Just some food for thought.
Where did you plumb your regulator? Is it physically on the rails, or just mounted on the DS inner-fender? Still stock rails I assume? Thanks.
Yep, stock rails, I don't need anything more at the moment. I used the external regulator to replace the stock fuel distribution tee in front of the left rear tire (it's where my return line goes back to the tank). Set it once to 59 psi and have now forgotten it.