Just thought I'd update this thread. Today I installed a brand new Remi alternator and gatorback belt. Nothing changed. The voltage still drops off immediately at high RPM.

I also unplugged my inline fuel pump so I could hear my stock intank pump cycle on with the key turned on. Both pumps seem to be working fine.

I visibly inspected all the grounds and they all "look" fine and don't appear corroded, but tomorrow I'm going to take them all apart and clean them. I just want to make sure I'm not overlooking any grounds. Here are the ones I checked:

1. Battery to inner-fender.
2. Battery to passenger-side of engine block.
3. Drivers-side inner frame rail to drivers-side of engine block. (flat braided copper strap)
4. Back of drivers-side cylinder head to ???? (single wire; I did have to repair this ground when i did my H/C swap over the winter. The wire had pulled out of the retaining ring.)
5. Back of drivers-side cylinder head to ???? (two wires to ????)

Anything I'm missing here?

 

Problem Solved!

After checking and cleaning/sanding every possible ground I could find with no change to my problem, I started to mess with the exciter wire that plugs into the top of the alternator. I tested the voltage to the wire with the key on and got about 10.5v; consistent with what I've read it should be receiving.

However, I noticed that moving this wire around while the car was running affected how well the car charged at idle. You could actually hear the engine's idle tone slightly change as I moved it around. Watching the volt gauge, it would range from charging in the high 13s, high 12s, or not at all depending on how/where I moved this wire. It was obvious there must be a bad connection in the wire or plug. The only thing I can figure is that the connection was good enough for low load charging, but couldn't supply enough to keep the alternator "excited" under higher load/demand.

Luckily, I was able to find an AC Delco dealer that carried the plug end in stock. None of the local chain auto stores (Advance, Autozone, Pepboys, Napa) listed it, although they claim to carry AC Delco parts. Anyway, it is AC Delco part number PT1136. I paid $26.00 for it. You can also get it from GM under part number 15306009; lists for about $40.00.

The new plug came with four nice long wires. I simply cut off the three I didn't need close to the plug and insulated them with silicone. I then spliced the remaining wire into the factory wire and was done. Took it out for a test drive and I couldn't get the voltage to drop off even if I wanted too. I'm very pleased. Now I can get back to my WOT tuning.

I just thought I'd post up the solution to my issue so maybe this will help someone else some day. I find a lot of threads that talk about the problem but never follow up with how it was fixed. Thanks for your help guys.

 

Well, that's great news! And not something one would normally take a look at.

 

Thanks. Yeah, it's probably not a real common problem unless someone has had their alternator in and out quite a bit, or done a lot of work in/around this wire. I had my alternator out twice recently; once for the heads and cam swap, and then again to replace the shitty Felpro head gaskets that never sealed (whole other story).

From the factory, the thin-gauge exciter wire stays pulled fairly tight when it's plugged in. It can be tough to release the retaining clip and the plug while the alternator is still bolted up, so I think it probably takes a lot of undue abuse when the alternator is lowered down to unplug it. In my opinion, this wire should have been a little longer and possibly a heavier gauge from the factory. Luckily the replacement plug has heavier gauge wire on it.

On a real bad note, I just went back out into the garage and while walking around the car I noticed one of my MT Front Runners was flat. It has a nice gash in it. I must have ran something over when I fixed the car and took it out for a quick test drive. I just can't win......

 

Sucks to hear about your tire, but good job on figuring out the other problem. That exciter wire was a shitty design...it should have been much heavier from the get-go and at least had some strain relief built in so it didn't get so much abuse during alt. swaps.

 

Thanks man. If it's not one thing it's another . I guess I'll just pick up a new tire and move on. Hopefully now that this votage issue is solved, I can get it back on the road again, finish tuning this thing, and start upgrading my fuel system so I feel safe using my dry shot.

 

AWESOME WRITE UP I have a very similar problem that I have posted https://ls1tech.com/forums/showthrea...43#post9339443 However, I have tried to watch the factory voltmeter during WOT and did not see a drop in voltage. However, with our shitty guages, who's to say that it even reads right.

I have the Racetronix hot wire kit and didn't install the ground portion of it. After having the same identical issues you are having, I installed the grounding part using my own technique. I ran a ground straight from the battery to the ground lug of the pump using #8 awg. I still have problems at WOT only.

I am going to check my alternator like you have found with yours. Hopefully, this will be the find and you have helped me. I would have never thought to look at the alternator.

Again, THANKS for the write up.

 

Thanks, and no problem.....I really hope this helps you out. Since you don't completely trust your in-dash volt gauge (I don't trust mine either), do you have any type of scan tool to log your ignition voltage during a WOT run? I verified my in-dash gauge readings with Autotap.

My voltage drop was a very obvious condition. If you watched my gauge, it look like I had a WOT switch that was turning my alternator off when the gas pedal would hit the floor. Basically, when the exciter wire was losing connection (or when the poor connection could no longer suffice) it would just quit charging all together. An inspection of the wire, to include a continuity test showed nothing obviously wrong with the wire itself, so I suspect my problem was with the connection at the plug. The new plug snapped into place much more firmly and securely than the old one. Again, good luck and let us know how things work out for you. I'll be following your thread.

 

WOW, I never thought about using my HPTuner. How stupid am I. Got a great tool and not smart enough to think about using it. Will trace both O2s, rpms, tb position, and voltage. Do you suggest anything else I should track?

 

Glad you finally got the problem figured out!! Thanks for posting on what the problem was and how you solved it!!!

 

No, I'd say that would be enough information for this issue. So, what type of fuel pressure gauge do you have? I assume it's like an electric Autometer inside the car, right? I'm sure it's pretty reliable, but you may also be curious about injector duty cycle when it goes lean (log pulse width then calulate DS). If it's a voltage issue, I'd think the injectors would be loosing a fair amount of voltage too. That MAY show up as an unexpected change in the pulse width.

 

Thanks. Trust me......no one is happier than me!

 

I appreciate the info. Great ideal on the duty cycle. The weather here has been hideous. Won't be able to try till weather lets up which will be in a few days. However, I think you have hit the nail on the head with the alternator bit. I remember in the past (a couple of years ago) prior to getting my electric gauges installed, all my lights would dim for no reason for just a moment. I could never track the problem down. Even when I had the car dyno'd, it never had this problem. Since then, I never drive the car at night. I had forgot about this previous problem. It would only happen rarely. Something that I thought would not turn into a big problem.

It being mother's day and all, I won't have a chance to check things out for now. However, after getting back from work tomorrow, I will definetly check the alternator's plug and connections.

This is the most information I have recieved about the problem I have been having with the fuel pressure. You don't know how much I appreciate your help. Thank You.

 

Just an update. I haven't had much time to look at this until today. It was a real pia to remove the alternator so I could look at the exciter wire plug. When I removed the alternator, I found 2 things. 1.) The alternator sounded like a bad squeeking hinge on a door when you turned it. It was not the pulley rubbing. It is actually inside of the alternator. 2.) The exciter wire is way too small and too short. It appears when the engine would torque up, it would pull hard on this wire. Possibly causing this wire to come disconnected.

It's too late for me to make it to a stealership to get the parts I need. I will try tomorrow and if weather permits, will give it a road test.

 

Thanks for the update. I'd say the squeaking alternator is a sure sign the front bearing is going out of it. It probably wouldn't affect the charging ability of the alternator, but I guess it's possible it could lock up when the bearing gets hot which would obviously be a big problem. It's probably best to just replace the alternator, or even have it rebuilt by a reputable shop.

I think you'll be pleased with the gauge of wire used on the replacement plug once you get it. Plus, it's plenty long, and since you're splicing it in, you can make it as long as you'd like. I definately left myself some extra slack in mine.

 

Theres Some New 200amp Alternators On Ebay W/4 G Wire

 

Good info in here.

 

UPDATE!! The weather finally let up to allow me to test out my new alternator and plug. I still have the same problem. At least I did find an alternator about to go out. The only thing it cost me extra was the plug. The factory plug was a piece of crap anyways.....too short to allow for the engine movement. Will keep searching until I find it.

 

OK, so you're saying your voltage looks fine on the in-dash gauge and scanner, but the fuel pressure is still dropping at high RPM? If so, it looks like it's time to check the voltage at the pump, and if that checks out OK, I think the stock intank regulator would be the next thing I would check. Of course, I'm simply regurgitating what others have already said in this thread because it sounded like good advice to me.

 

Just checked my fuel pressure at the fuel rails with analog gauge you screw onto the fuel rails. The pressure at idle is 65 psi and when I shut the engine off it immediately falls to 50 psi. Is this normal or should the pressure gradually bleed off? I watched it for about a minute and quit watching after that when it didn't go below 50 psi. I'm starting to think possibly I may have a stuck injector. Is this possible to have this condition? I don't run cats or muffler and I have severe black carbon on the exhaust pipe after running only about 5 miles. The carbon on the pipes, the rich smell, and the burning of the eyes tells me (maybe wrong) that I am running rich. But the A/F meter and fuel psi tells me different.

Could it be if a stuck injector tells the car to lean out to read correctly on the O2s and when at WOT, the fuel pump can't keep up due to a bad injector.

Just fuel for thought. Any input would greatly appreciated. I will begin pulling the spark plugs tomorrow to check the conditions for possible imbalance injectors.