Good Morning!As usual I start my day working on my car!I finally got the Code 42 problem fixed.I still have a bad loss of power at even 13-15psi of boost.In driving it with a scanner the only thing that does not seem normal is the voltage reading.When the car cuts out the reading will drop from a high of 13.0-13.2 to a low of 12.2-12.6.The hotter the car is the lower the reading and the worse the car runs!I also have had to turn the fuel pressure regulator up to even get 43psi static.The fuel pressure rise erratically under load.The more the load te lower the voltage.Only under no throttle coasting do I see 13.0-13.1 when warm.Under load I only see 12.2-12.6.Could this be the cause of my fuel issue?I replaced the battery a couple of weeks go and had to lower the fuel pressure at the regulator-it went up approx 10psi!The battery was replaced because it seemed to not hold a charge.Now that I have a scan tool it seems that the alternator is not charging enough to keep the battery up-yet alone any accessories.Am I correct?What should the low to high voltage range be?Thanks again!
Help!Alternator Voltage?Fuel Pump Relation?
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The Radius Kid
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Sounds like your alternator may be bad.I usually see around 13.8 all the time,except when the car is doing initial charging which is around 14.1-14.3.
Steve Wood
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First thing to do is to check the voltage at the back of the alternator and at the battery with a voltmeter. Reading voltage with a scantool will not show you if the system is charging correctly with any precision as the voltage loss may be between the battery and the ecm.
VOLTAGE AT INJECTORS
While checking voltage at various locations, be sure to check voltage at the injectors.
More than a few aging harnesses are out there, and there are six injector leads to go bad, so it's worth checking.
John Spina offers an upgraded injector harness.
If you want/need a new one, or are running large injectors,
you can check it out at www.casperselectronics.com
HTH
While checking voltage at various locations, be sure to check voltage at the injectors.
More than a few aging harnesses are out there, and there are six injector leads to go bad, so it's worth checking.
John Spina offers an upgraded injector harness.
If you want/need a new one, or are running large injectors,
you can check it out at www.casperselectronics.com
HTH
I just checked the voltage at the battery and at the terminal on the back of the alt.When the scanner said 13.50 the battery showed 14.18 and at the alt showed 14.28.This is at idle only.I amhaving a voltage drop as I accelerate or if I put the car under a load. At anything near wide open throttle it is like you hit a rev limiter. At that time the voltage on the scan tool reads like 12.4 - 12.5, so at the alternator it might be 13.2 or at the battery13.1; if the drop stays constant at idle. Also, I took the battery out of the car and charged it for a couple of hours and put it back in.When I took it out on the scan tool it indicate 12.6 volts, after putting it back in it indicated 13.0 volts. The car did not cut out as soon, also I now had 60psi static were as I had 43psi before charging the battery. I had to reduce the fuel pressure. Then I drive the car 10 miles and the static fuel pressure is done to 28psi! This is all so weird. The fuel pump is a Walbro and it is hotwired if that matters. I also got a code 42 again after driving the first 5 miles and restarting the car.AAAAAGGGGHHHH! This is so frustrating! After shutting the car off and restarting they light went off ad no 42. Also,when I got back I preloaded the converter to the point of wheelspin and the voltage dropped to 12.6 on the scanner from 13.2 at idle! Anybody want to buy a real nice 52,000 mile 87 GN that seems to be haunted! Please help!
GET THAT TR GROUNDED
How are your grounds?
It's always a good idea to upgrade (and add) grounds on TRs!
www.casperselectronics.com addresses the multiple electrical problems these cars are famous for...like your current poltergeist...no pun intended!
HTH
How are your grounds?
It's always a good idea to upgrade (and add) grounds on TRs!
www.casperselectronics.com addresses the multiple electrical problems these cars are famous for...like your current poltergeist...no pun intended!
HTH
I have checked,double checked, and triple checked the grounds. I replaced the negative cable because the cover was burnt and I was unsure of the integrity. I checked, cleaned and secured the 3 grounds on the firewall and the 2 grounds on the fender. The only one that I have not checked is the one on the back of the head. I will check this when I get access to a lift as I want to check all connections to the starter as well. Is a voltage drop of .7 volts from the battery to the ecu to be considered normal?This is my readings at idle after warming up in park,the readings are lower in ear with the foot brake on. It is 13.2 on the scanner-13.9 at the battery-14.0 at the alternator. If I am underload with boost would the difference stay constant,be lessr or greater. The reason that I am learning towards a voltage issue is just charging make the static fp go up like 15psi! But,after driving the car it will go back down and the battery voltage will also go back down. It seems that when I charged the battery at idle it was like 13.6 volts and the fuel pressure went from like 43.5 to 58 and befoe charging the voltage was 12.9.So .7 in volts meant a change of like 14.5lbs. After driving 10 miles the battey voltage had dropped to 12.8 and the fp dropped to 30 static after I had adjusted it to 43.5ps1. So in this case a lose of 13.5 psi of fp like a .8 drop in voltage. So real close to the same. So it would appear that .1 volt would make a big difference! So to recapp I went from KOIO on the scanner at 13.6 volts to 12.9 after driving 10 miles and restarting the car 3 or 4 times. The fuel pressure loss at this time was like 13.5 psi. Not very good huh! I can't help but think the alternator-maybe a diode-as the voltage ALWAYS drops as you give it throttle-the more throttle the larger the drop.Any ideas? Keep in mind these readings are at the scan tool.
Steve Wood
Active Member
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- Messages
- 2,338
It is a fairly common problem. The GN that I bought new does it. The T that I bought which was rode hard and put up wet, does not.
There are several splices in the power distribution circuit that could cause a drop, and, it could be in the bulkhead connector on the firewall that feeds the fuse block.
John Spina also mentioned that it was common for the fuseable link that comes off the positive post of the battery that feeds the ecm memory via the orange wire to develop resistance problems. That does not seem to be the problem on my GN.
I read similarly dropped voltages at the fuse block.
Altho the ecm tries to reference the voltage and manipulate the injectors to make up for changes, a drop in voltage supplied to the ignition will affect it. At some point, it must affect injectors.
The fuel pump hot wire should come off the alternator. If you have lower voltage at the the fuel pump, say more than a couple of tenths, then you probably need to look at the fuel pump grounding. As the car is basically grounded thru the sheet metal, Any external fuel pump ground should go to the rear sheet metal and not the frame.
You might also put your meter across the the ground from the battery to the sheet metal and see what kind of voltage drop you get at that point. It should show no more than a few microvolts.
There are several splices in the power distribution circuit that could cause a drop, and, it could be in the bulkhead connector on the firewall that feeds the fuse block.
John Spina also mentioned that it was common for the fuseable link that comes off the positive post of the battery that feeds the ecm memory via the orange wire to develop resistance problems. That does not seem to be the problem on my GN.
I read similarly dropped voltages at the fuse block.
Altho the ecm tries to reference the voltage and manipulate the injectors to make up for changes, a drop in voltage supplied to the ignition will affect it. At some point, it must affect injectors.
The fuel pump hot wire should come off the alternator. If you have lower voltage at the the fuel pump, say more than a couple of tenths, then you probably need to look at the fuel pump grounding. As the car is basically grounded thru the sheet metal, Any external fuel pump ground should go to the rear sheet metal and not the frame.
You might also put your meter across the the ground from the battery to the sheet metal and see what kind of voltage drop you get at that point. It should show no more than a few microvolts.
To let you all know what I have done at this point. I took the car to the Dealer that I work for and did a load test.At idle the alt showed 13 volts. At a 30 amp load 13 volts. At a 60 amp load 13 volts. At the point at the 60 amp load the idle noticably decreased, but the voltage never changed from 13 volts. The tech said that the alternator is doing as it should. Would this seem correct? Would the regulator not kick up the voltage at the 60 amp draw? This may seem like a weitd question, but all of this was at idle with no load on the engine (i.e. Boost).This car according to the scanner the more throttle that you use themore the voltage drops. This seems so backwards to me. I was a police officer in the late 70's through the late eighties and the 440 mopars had volt meters. The harder you pushed the car the more the alt charged-as much as 14.9 volts or so. But still the weird thing is when I left the new car store I had 40psi of fuel pressure on the gauge with th vacume line connected-after driving 5 miles I had an indicated 20psi. What in the world is going on? Also when I got back for grins I backed off the regulator and turned the screw all the way out. The gauge went to like 2psi and no change in idle at all. This also seems kind of strange. The regulator is an accufab billet regulator and it is like maybe three years old. The FP is a Walbro and is approx the same age. Should I just go ahead and change both? Any ideas? Thanks
Well, here is what I would do, or in other words my 2 cents for what ever it is worth.
I think you are loosing FP because there is an overall, sustained, drop in the system of useable voltage. If memory serves I think the way to think of it is amperage is a measure of the ability to push or supply voltage. I never can keep the AMP/Volt relationship right in my head so please, no flames, corrections welcome!!
The alternator should output more, at load, to compensate for demand. I think what I am trying to say is it should step up Amps to continue to push the 12v supply as demand rises. Voltage will possibly rise a little as well, depending on the efficiency of the regulator. Think of FP. Push more pressure through a given size fuel line to be able to supply a steady gallon per hour on the other side of the regulator as demand (use) beyond the regulator increases.
The alternator's real job is running the car's electrical system; it is not a battery charger. I am guessing the alt cannot keep up and you are running off battery. When you stomp it your are sucking its will to live as it has a finite amount of Amps it can support for a finite amount of time as part of its design. Think of the need put on the electrical system by the ignition and FP plus everything else at high RPM. Liken it to pulling the ECM power and cranking the car nonstop until the battery dies.
I would pull the alt and take it to a shop that specializes in alternators and have it tested.
Like I said, my thoughts, which are often flawed and make sense only to myself!!!
BTW, if the alt is toast swing over to gnttype.org and get the rebuilt article from the electronics section. It is very easy to do and a lot cheaper than a new 120AMP cs-144. You also get to keep the right part number on the case if that matters.
Brent
I think you are loosing FP because there is an overall, sustained, drop in the system of useable voltage. If memory serves I think the way to think of it is amperage is a measure of the ability to push or supply voltage. I never can keep the AMP/Volt relationship right in my head so please, no flames, corrections welcome!!
The alternator should output more, at load, to compensate for demand. I think what I am trying to say is it should step up Amps to continue to push the 12v supply as demand rises. Voltage will possibly rise a little as well, depending on the efficiency of the regulator. Think of FP. Push more pressure through a given size fuel line to be able to supply a steady gallon per hour on the other side of the regulator as demand (use) beyond the regulator increases.
The alternator's real job is running the car's electrical system; it is not a battery charger. I am guessing the alt cannot keep up and you are running off battery. When you stomp it your are sucking its will to live as it has a finite amount of Amps it can support for a finite amount of time as part of its design. Think of the need put on the electrical system by the ignition and FP plus everything else at high RPM. Liken it to pulling the ECM power and cranking the car nonstop until the battery dies.
I would pull the alt and take it to a shop that specializes in alternators and have it tested.
Like I said, my thoughts, which are often flawed and make sense only to myself!!!
BTW, if the alt is toast swing over to gnttype.org and get the rebuilt article from the electronics section. It is very easy to do and a lot cheaper than a new 120AMP cs-144. You also get to keep the right part number on the case if that matters.
Brent
I too have my doubts about the alternator. The techs at our new car dealer seem to think it is okay. The part that bothers me is that the voltage goes down as you turn more rpms-it seems to me that the voltage should go up-at least stay constant-not go down. However, I also suspect problems in myfuel system as when the car is turned off I loose all fuel pressure immediately. I just ordered a Walbro 340 with a 80psi rating at 255lph and a new Billet Regulator. The whole driving the car 5 miles and loosing 20 psi of fuel pressure led me to suspect the fuel system, although it could be a compound problem. The really strange thing is turning the adj screww all the way out on the fp regulator showing only 3 psi and the car still ran the same. How could that be? Surely it needs more than that to even fire the injectors. Or could fuel somehow bypass the regulator and just stay at a given pressure whether indicated on the gauge or not. This is all weird and I am still learning. I owned this car before and never had such a time, but it only had a Syclone fp and regulator, a cold air set up, and a lower temp t-stat and spring cleaning. With all the mods when it runs right all is good, when it runs like this all stinks! Thanks again for your imput and maybe someone can tell me if I am going in the right direction!
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Steve Hill
New Member
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- Jul 13, 2002
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- 114
it's not weird.
-- In a dc circuit there is a direct relationship between the fuel pump motor speed and voltage. If you lower the voltage to the pump it can't pump very well.
-- As you rev the engine you are making the ECM command higher injector duty cycle as well as making the fuel pump work harder, and a few other electrical items. So your total electrical system load is much higher at WOT than idle.
Those little injectors need specific voltage and current to work properly and will get weird if they go too low on voltage.
-- If your electrical system can't hold 13-something volts at WOT then there is a problem.
If it does hold that then you have a problem somewhere in your circuits, maybe even with the injector drivers in the ECM.
(I'm just throwing out some guesses here)
First thing you should do is verify your voltage, at WOT, to a specific point....such as your fuel pump. Nice place to start, and go from there.
But from your first comments I was thinking "voltage regulator"
-- In a dc circuit there is a direct relationship between the fuel pump motor speed and voltage. If you lower the voltage to the pump it can't pump very well.
-- As you rev the engine you are making the ECM command higher injector duty cycle as well as making the fuel pump work harder, and a few other electrical items. So your total electrical system load is much higher at WOT than idle.
Those little injectors need specific voltage and current to work properly and will get weird if they go too low on voltage.
-- If your electrical system can't hold 13-something volts at WOT then there is a problem.
If it does hold that then you have a problem somewhere in your circuits, maybe even with the injector drivers in the ECM.
(I'm just throwing out some guesses here)
First thing you should do is verify your voltage, at WOT, to a specific point....such as your fuel pump. Nice place to start, and go from there.
But from your first comments I was thinking "voltage regulator"
>But from your first comments I was thinking "voltage regulator"
Steve,
I would agree, I was thinking the same thing myself. I am still leaning toward alt shop to test the thing correctly. Its the easiest thing to do right off the bat before Mustang 1 goes chasing down every possible connection in the car.
Mustang 1, as for the FP, look back at Steve's point about FP speed and voltage. I still think you are running mainly on battery and sapping it for almost all it has at WOT. There is then little left to run the pump. Being a DC motor that pushes a liquid I can see where it would have high power demand. Think of a DC battery in a flash light. Leave the light on and the light begins to weaken. It still works, there is still some voltage, but less than 1.5 (in the case of a D cell). Due to the nature of a battery at the end of its life it has less available amperage to push what little voltage remains.
Brent
Steve,
I would agree, I was thinking the same thing myself. I am still leaning toward alt shop to test the thing correctly. Its the easiest thing to do right off the bat before Mustang 1 goes chasing down every possible connection in the car.
Mustang 1, as for the FP, look back at Steve's point about FP speed and voltage. I still think you are running mainly on battery and sapping it for almost all it has at WOT. There is then little left to run the pump. Being a DC motor that pushes a liquid I can see where it would have high power demand. Think of a DC battery in a flash light. Leave the light on and the light begins to weaken. It still works, there is still some voltage, but less than 1.5 (in the case of a D cell). Due to the nature of a battery at the end of its life it has less available amperage to push what little voltage remains.
Brent
It is the original alternator. I am going to go to an alternator shop that I know locally when I get a chance. I called him yesterday and he said that he could step it up to 145amps from the 120 rating. Also, I would still have the original alternator. I am leaning towards a pump or regulator problem so I ordered them and may even get them on before the alternator. I will fix it one way or the other! Maybe go broke trieing.....
Good morning all! As usual I will be working on my GN again! I just got the fuel pressure regulator and the Walbro 340 fuel pump from PTE. I just put the regulator on and no change! Still lost 20 psi of pressure after 5 minutes of driving. Also still looses fuel pressure as soon as you turn it off. The fuel pump will be the next thing put on today. All lines and clamps will be replaced also. Then if I still have the same problem I will check the wiring and replace the alternator, which testing good but you could not duplicate the same conditions; i-e wot and under load in gear with 15psi up to 20psi. I will keep you informed.
Mustang 1
Do you have contact info fot that alternator shop? You said they can step up your cs144 to 145 amp. I am going through a cs144 now for my TTA. I picked up a spare to clean, smooth, then powder coat. While I had it apart I was replacing all of the wearable parts plus considering an amp upgrade.
Brent
Do you have contact info fot that alternator shop? You said they can step up your cs144 to 145 amp. I am going through a cs144 now for my TTA. I picked up a spare to clean, smooth, then powder coat. While I had it apart I was replacing all of the wearable parts plus considering an amp upgrade.
Brent
Good Morning! Update! I replaced the regulator first. No change. I then replaced the fuel pump. I THOUGHT that fixed it. It did fix a problem. Before, when you shut the car off the fp would drop immediately drop to 0. Now it holds fuel pressure. So one problem. Went for a run in the car setting the staticto start out at 43, after driving the car the fuel pressure again dropped to 20 psi! What is the deal? So I adjust in more fuel pressure and the car ran terrible. I parked it for the night showing like an indicated 38 psi with the vaccume line connected. I started it the next morning and the indicated fuel pressure was 80 psi! Maybe I have a bad gauge...HMMM. So now to buy a new fp gauge. Would excessive fuel pressure cau a high end cut-out? Like hitting a rev limiter. One other thing, I have a slight header leak on the drivers side header- would that cause any issues as far as vaccume and the fp regulator. Thanks in advance!
Steve Hill
New Member
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- 114
well I'm confused as to which "regulator" we're talking. Do you mean as in 'fuel pressure regulator' or 'voltage regulator'?
Because the fuel pressure regulator can really mess you up.
Have you verified your fuel pressure vis-a'-vis boost pressure at WOT? As you are probably aware, this has to *exactly* match your boost pressure (plus base setting).
Denis K. and I have chased crazzy stuff back to faulty fp regulators. One we had was exactly TWO pounds higher than boost, which made spool-up real lazy, and then the engine came on strong, then went lean. This drove us crazy for days.
Another time I went through 3 'name brand' regulators that were all off, in one way or another.
Based upon this experience I always suspect a fuel pressure regulator and is one of the very 1st things I check out.
Good luck!
Because the fuel pressure regulator can really mess you up.
Have you verified your fuel pressure vis-a'-vis boost pressure at WOT? As you are probably aware, this has to *exactly* match your boost pressure (plus base setting).
Denis K. and I have chased crazzy stuff back to faulty fp regulators. One we had was exactly TWO pounds higher than boost, which made spool-up real lazy, and then the engine came on strong, then went lean. This drove us crazy for days.
Another time I went through 3 'name brand' regulators that were all off, in one way or another.
Based upon this experience I always suspect a fuel pressure regulator and is one of the very 1st things I check out.
Good luck!
O.K.! The good,the bad,and the ugly.As for the good.The fuel pressure gauge was the culprit.Over fueling caused the numerous driveability issues. Just before putting on the new gauge the indicated fuel fuel pressure at operating temp with the vaccume line connected was an indicated 28psi.The indicated fuel pressure making no adjustment restarting immediately was 65psi!So all this time I was adjusting up the fuel pressure and replacing parts due to a bad gauge!The bad also was that on the way to work I kept getting a code 13 after only 1 month of use on the Denso 0-2. I guess the high pressure and the 110 leaded caused its early demise-just 300 miles.Now for the ugly. I had bought a external fuel pressure gauge with the stainless hose from Caspers and I overtightened the hose stripping the fitting on the hose and ruining it. I had to remove the gauge and attach it directly to the fuel rail with no 90 degree fitting-just pointing straight out. Will this hurt anything? The gauge is glycerin filled. I think that I might have fixed this problem since after replacing basically the entire fuel system I now have and hold pressure.I replaced the 0-2 and drove the car with no codes and it seemed to run well. Now just to fix the drivers side header that is leaking....
