ASenna

OK so after sorting out my charging debacle, I found out that I still have low fuel pressure related to the fuel pump, but I've helped it somewhat. Here's some info: Walbro 255 inline pump on a circuit from a Megasquirt relay up front through about 10ft of wire. Very simple setup. Power goes to relay, opens, allows current to flow to pump. Aeromotive FPR. With 12.5V across the battery at idle, I'm getting 11V at the pump. So I wired in a hotwire from the positive battery terminal straight to the pump and got around 12.1V at idle, which is obviously better, but really weird considering I've got a direct connection from the battery to the accessory so it should be the battery potential (12.5V). So I decided to take grounding out of the equation by wiring another wire from the negative on the battery terminal to the negative side of the pump. Still got 12.1V. My fuel pressure evens out at 39psi, and then bounces around from 39 to 37 for about 2 seconds, then evens out again. It's really weird. Should be 40psi rock solid. Any ideas?

YES! So I got a new battery, free since it was less than 2 years since it was bought. I found the firewall ground, but mysteriously one wire went down to my MS relay box and the other went in an enormous cable that was cut at the end. Oh well, decided to clean it up anyway. After fixing the battery terminals and cables, cleaning the firewall ground, and chucking in a new battery, I now get about 14.1V around 2000RPM. I ran her for about 5 minutes and went and checked the battery potential again. Hadn't changed so I was thrilled. Took her down the driveway to go down the road and back and my gauge lights go out before I even hit the road! Looks like I messed with one too many grounds... Anyone have the location for the gauge lights ground?

Hm that's interesting. I am using a reman ZX alt if that makes any difference. I could probably throw on a smaller pulley and that might do the job ( assuming I can fix this issue ). The battery's drained for sure, but it wasn't always that way. This isn't my problem correct? It's just an unfortunate side effect. Any suggestions on tracing down the real culprit?

OK, so today I made sure it wasn't my battery terminals by cutting off the cables just before the terminal ( they were one piece ) and putting fresh cable into new terminals. The negative side looked a little corroded so I had big hopes. Had the battery charged up to 12.8V and chucked it into the car to try it out. Started it up. Had really good fuel pressure. Idle bobbed around from 750RPM down to 500RPM. After 10 SECONDS, the car shuts off. I turn the key to start her back up ( standard procedure with the car by now ) and *CLICK*. Nothing. Check the voltage across the battery. It's 12.25V. Pulled it out of the car and set it on the floor. Between yanking it out of the car, setting it on the floor, and grabbing my multimeter again, the potential had dropped to 12.05V, in about a 10 second span. An hour later I check it and it reads 11.6V. Time for a new battery?

UPDATE: Alright, so I got the car back from the shop. They put in a new ground from the alt to the body. It seemed to run better, so they checked the voltages. Apparently the alt is putting out 15V, but it's only getting 13V across the battery, so, due to liability reasons, they recommend ME to put in a cable that goes directly from the BAT connection on the alt to the positive side of the battery. A hotwire if you will. I get home and do it. Big 4 AWG cable from the alt to the battery. Start it up. I get 11.9V across the battery, give it a rev or two, and it settles around 12.5V at idle. I wasn't happy since I'm supposed to be seeing 14.5ish. So I think, "OK well I've driven on less voltage and the alt seems to charge a little while moving" so I take it out. Car runs fantastic. Fuel pressure's all there matching the manifold pressure increase I'm seeing. Get to the end of my road ( about a mile away ) and she dies, never to start again. Had a buddy bring me another battery and I get her home. OK so I've got a direct connection from the alt to the battery and the correct voltages in all the wires going to the alt. What am I missing here? Cleaning up the battery to body ground here in a bit.

Thanks. I wish I had the car in my possession or I'd try that myself! I'll call the shop tomorrow and see if they can just run a ground to the chassis and confirm that that's in fact what's wrong. Apparently this is a classic problem for old Zs? Where does the ground from the alternator run? All that wiring is covered in piping ( or electrical tape for an OEM harness ) just out of the alternator, so I haven't been able to really see where it runs. I've got a rear mounted battery.

I'm running megasquirt, so another ecu wouldn't help me, but it wouldn't hurt for a suggestion for a car with a stock ecu Apparently, the shop thinks the problem lies in the ground cable from the alternator. The rest of the wiring looks good, but there's a breakage somewhere in the line and they're just trying to find it.

The fusible link connections in my car are good. I'm taking the car to a mechanic on Tuesday. A few of the guys there have Z's, one's building an '83 turbo and knew what I was talking about when I said Megasquirt, so we'll see how this goes. Cross your fingers!

WHOOPS Forgot to mention that the alt was converted over to an internally regulated alt via this thread here: http://www.atlanticz.ca/zclub/techtips/alternatorswap/index.html All the wiring and connections are confirmed good ( I've redone them just to make sure ). Also, the car has been running like this for well over a year, so the connections had BETTER BE good ha. Problems resulted from the last alternator blowing out and then the fuel pump starting to make a horrendous whine. New alt. New fuel pump. No fix.

I have a thread for my car's issues, but this one is dedicated specifically to the electrical system which has new developments. Bought the car needing a fuel pump. Replaced the fuel pump. Found out the car doesn't recharge the battery. -Battery's GOOD. -Alternator's GOOD. ( on my 3rd alt now! First one tested good, then bad. 2nd was from a parts car, good then bad. 3rd is definitely GOOD ) -Wiring going to L and S connections ( exciter and sense ) for the alt input is GOOD ( checked this myself and had this checked by an alternator shop...which told me the alt I had in the car was bad and that my wiring was GOOD ). So by the guy's recommendation, In had the alt swapped for a known GOOD unit. Throw the thing in the car, and what do you know, no dice. Runs around 12.1V across the battery. Car doesn't charge sitting at idle. Will charge around 13.0V around 3000RPM, far lower than the 14.45V that the sense connection aims for out of the alternator. Fuel pressure should be 40psi at idle. I get 36psi. Upon increasing RPM, the fuel pressure increases to about 40psi ( it should increase ), and then drops down to about 33psi. I'm thinking low voltage across the pump is causing it to lose fuel pressure. I'm going to tear my hair out trying to figure out what's wrong! Any ideas??? I've been at this for a MONTH. OH YEAH. Doesn't like to start. At all. Will start and die. Takes about 5 start and dies before it will start and run, and will run very low at 500RPM.

For now, I've remedied the problem. I went back and tested the alt AGAIN and it still showed it passing. I was still skeptical because of the diode situation. At the suggestion of another boosted Z driver, I wired a small indicator lamp into the exciter circuit. He thought that with the rewired system, like on his car, that little resistance would aid in exciting the circuit and function as a charge warning lamp in the process. After charging the battery and installing the lamp, I started the car and took a multimeter around all the connections. The output of the BAT connection showed 13.6V at idle and around 14.6 at ~2000RPM. Not sure if that's a sure-fire fix, but it runs smoother and my battery doesn't die! I still have a little bit low fuel pressure due to the new pump and not messing with the regulator and the car does start and die occasionally, so I believe I might still have a vacuum leak, but it's much better. Thanks for all the help and suggestions!

they do. This one has been converted.

The alternator is internally regulated. It has undergone the swap as mentioned in this thread: http://www.atlanticz.ca/zclub/techtips/alternatorswap/index.html It has also been done correctly ( I have checked and double-checked ). I'd rather not unplug the battery while the car is running as Wizardblack suggested. I'd rather not fry things. What I believe is happening now is either the alternator is not getting enough resistance to excite it, or the diode responsible for output after being excited is malfunctioning. Either way, the data I found testing each point in the charging system does not lie and the fault should be in the alternator.

Yes... I realize this is the problem. This was from testing the voltage across the battery and the output from the alternator. I know the alternator is not charging the battery. I had the alternator tested at a different place than where it was bought. I do have a battery charger and yes it has been used. The question now is WHY does the alternator not excite when prompted to give at least 14.5V potential at the BAT connection. The results above should explain that the problem rests with the alternator receiving an excite potential without fomenting an output. The question of what is the problem has been passed. I'm trying to understand why it occurs and how to remedy it without chucking random parts at the car trying to fix it.

Voltage isn't spiking, it's staying very steady very low ha. Someone else with a boosted 260Z suggested that I need to put in a lamp in parallel with the exciter circuit in order to put enough resistance to excite the alternator. It also functions as a charge warning light. Any thoughts to the validity of this?

Well...yes...this is true and its why I suspected a voltage problem initially...but I need to know why my alternator tests well on a bench but refuses to excite in-car. The battery is fine ( albeit drains because the car's only running on the battery ), but isn't being fomented by the alt.

Update: Took a digital multimeter to all the connections of the alternator and across the battery and here's what I found: When engine's off: -12.35V across battery terminals -12.35V at the BAT connection out of the alt ( where the alt connects to the battery...this is the output connection of the alt that should be a few volts higher than the 12V supplied by the battery when running ) -12.35V at the flat part of the "T" connector ( top of the T ) -0V at the straight part of the "T" connector ( middle of the T ....this should be 0V because it is only on when the ignition is on to "excite" the alt ) When engine's on: -11.83V across battery terminals ( uh oh ) -11.83V at the BAT connection out of the alt ( uh oh...this should be around mid to high 14's ) -11.83V at the flat part of the "T" connector -11.83V at the straight part of the "T" connector ( this is good because it means the circuit used to "excite" the alt is functional ) So does this mean my alt is bad even though it tested well and functional???

The sad part is that I did not find the problem. It looked promising, but it didn't remedy my problem. I refocused my efforts toward the wires crossed for the external to internal regulator swap as mentioned here: http://www.atlanticz.ca/zclub/techtips/alternatorswap/index.html Everything looks pretty good but I may just undo the connections and redo them to make sure there's no corrosion. Also, the main wire that connects the alternator to the battery is white with red stripe. It also has a crossed connection that I may check as well. Any ideas? Recap: -Low voltage across battery, starts and dies, runs lopey, sketchy fuel pressure. -Battery's good. -Alternator's good. -Thought relay board might be shorting. It's good. Keep in mind this car has ran perfect for 2 years up until 2 months ago when the old alternator blew and the fuel pump started whining along with the fuel pump circuit blowing its 15A fuse. Does anyone want general engine bay pics that might help?

Might have found the problem. Checked the MS relay board for possible corrosion or broken solder. Tony had always suspected that it wasn't weather resistant despite MS's guarantee that it was fine to run the relay board under the hood. Here's what I found: The blue nastiness forms a perfect circle around what looks to be some white residue, which is what happens when standing water finds an electrical current. So, if the relay board is too close to the undertray, a little bit long of a solder + a little bit of water = short to ground. When looking to find under which relay this grossness belonged, it turned out to be the fuel pump relay. This might also explain why quite of bit of voltage is lost somewhere in the system. I plan on drilling a few holes in the tray underneath the relays, covering the tray in vinyl tape, and poking the holes through. This way the standing water can drain and it won't accidentally ground due to flex or anything else.

I actually don't think I have a seatbelt light anymore lol. I have 4 point harnesses and ( if I remember correctly ) the seatbelt light is in the dash around the A/C unit which I definitely do not have since I have gauges that sit there now. What's the purpose behind the seatbelt light coming on?

A/F ratios are stoichiometric. I'm not watching actual numerical values, but during idle and run up the AF gage stays put with very little variation and no creeping into the lean or rich. It's very interesting considering I've seen it spew raw gas out the tailpipe while still having a stoichiometric AF ratio. Haven't tried confirming spark yet, but she runs up excellently. After talking to another guy with a boosted Z on MS, everything I've mentioned is pointing towards a lack of voltage either caused by a faulty alternator ( which is new...still could be bad ) or a ton of resistance through the board. Apparently MS will still work on low voltage, it will just exhibit the signs I'm seeing now, which was confirmed with the battery voltage being tested while running. It wasn't even running from the alternator, just straight from the battery, so I had to get it home quick. When I was having the battery tested, after the car shut off, I opened the relay board to check the fuses and the relays were HOT. Really hot. Maybe there's a bad solder somewhere.

I took Tony's advice and made a new ground for the fuel pump to no avail, but the car loped around until it warmed up and when it did, it idled fine around 725rpm and the fuel pressure steadied out to around 39psi. Something else Tony told me was to check and make sure that I was getting the right voltage out of the alternator and across the battery. Well the multimeter I have at the house I don't trust at all, so I grabbed a few 15A fuses and went down the road toward autozone. The battery tested barely over 12V in the car while on, which apparently indicates that either my alternator isn't putting out enough voltage or my wiring is choking it somewhere. They couldn't test the alternator in car, so I'm going to tear it out and bring it to them tomorrow to test. It's a remanned alt but there's a chance it could be bad already. Someone else mentioned something about the voltage regulator. The new alt is internally regulated, so that may lead back to the alt again. Oh well. It's a journey.

The previous owner suspected that might be the case. He drained the gas tank, took all the fuel lines down, and blew them out. Nothing. It was nice and clean, although maybe there's still something that's come loose in the tank? The tank was refurbished 2 years ago and a sump was added for the fuel lines. The tank was covered in this rubberized stuff. I'd think if it were crud, it wouldn't run up as well as it does. I started her a few minutes ago. Here's my symptoms: -Started on second try. First try, start and die -While running, the fuel pressure bumped around 40-41psi and wouldn't stay put. While bumping around, the engine rhythm went with the bump. Would rev up to 750rpm or so and drop back to 600. -Did this bumping around until it finally bumped too low and decided to die. -Started again and immediately died -Started again and immediately died again -Would not start. Would turn over forever, but no fire. Does this help at all?

Voltage regulator? Tied to the alternator assembly? A newer Hitachi unit was just installed because the old alternator went bad.

First some specifics: 75 280Z with L28ET running on Megasquirt II. OK so before I bought the Z, I knew it needed a fuel pump. This was evident from about 5 weeks before I bought the car when Tony ( Tony C ) lost his alternator and the fuel pump starting making loud noises ( maybe from voltage drop ruining it...I don't know ). Another habit the car had as of recently was blowing the fuel pump fuse ( which subsequently stranded me about 25 miles from home ). So I got the new fuel pump last week, installed it, and the car ran fine. Pretty decent I might add ( not that it ran terrible before ). However, it needed a jump to start ( odd ). Took her down the road. She ran a little lean, but with definite fuel pressure ( something the other pump didn't have ). Maybe it was just the difference between the pumps and I need to mess with the regulator. Anyway, I get back in my driveway and start rolling down its 200 foot length and it dies, no fuel pressure, no chance of starting again. Open up the hood, check the fuses, sure enough, fuel pump fuse is blown. The fuel pump circuit runs on its own line for the MSII system. The only reason it would blow would be something from THAT circuit. I ran the lines back through the car and couldn't see anywhere where the hot side might be grounding. Took her out of the garage yesterday to investigate again. I think I might have a vacuum leak for one, but two, once she died ( from me investigating the vacuum leak ), she tried to turn over about 4 times and then quit. No start. Not even trying, like the battery was dead. Had the battery tested today and turned out to be good. Maybe not enough cold crank amps? Any ideas? Here's the symptoms ( cliff notes of the thread ): Takes several turnovers to start, often starts and dies, sometimes when it dies it doesn't even try to turn over, when it revs up coming back to idle almost kills her ( sometimes does ), brake pedal sinks to the floor ( brake booster leak? ), fuel pump fuse blows every now and then. Ideas? Should I set the car on fire? ( kidding...but not really )