1997 7.3 370k miles

truck has been gone through and upgraded every which way excluding engine internals. I’m talking high end electrical system, two brand new optima red top batteries, DB Electrical 200Amp alternator, upgraded grounds and terminals and everything. I cannot get the truck to stay running without being jumped from another diesel for the life of me. Truck starts great when jumped but the voltage gauge stays at the absolute bottom, 8 volts. Doesn’t matter how high the rpm’s are. Took the alternator to get tested and Oreillys passed it with flying colors. I even threw my old stock alternator in to make sure and same thing happens with it. I disconnect the jumper cables and it’ll die within 30 seconds and has zero juice left over to try to crank again. I’m pulling out my hair at this point. Considered it might be my hydra tuner making it retarded but even after disabling it, no avail. Please any advice

 

Check the batteries...yes, I have had bad 'new' stuff. Carbon pile I believe is the best testing to perform.

Also, eyeball the fusible link from alternator to solenoid. Perhaps it failed with a 200A alt over the stock 130A so no *** going to the batts.

I have had other vehicles flip out with low voltage to the on board computers. Use a DVOM in that 30 seconds it runs. This will tell you if it is charging. I would start at the +B on the alt and work your way around the rest of the charging system.

Alt does ground to its bracket, make sure no corrosion there!

 

These trucks take very little power to run, once they are started. Visibly dim headlights, after maybe 200 miles and several starts with dead alternator, no problem running.

Shutting off 30 seconds after jumper cables pulled suggests the batteries are very badly discharged. While there may be rare and funky ways for bad batteries to prevent the truck from running with a good charging system, I would expect those scenarios to also prevent running when jumped to another, running, truck.

I suspect that you have a problem in the charging system and have run the batteries way far down. Suggest charging the batteries back to full, checking battery voltage with key off, then restarting diagnostics.

Another potential failure point is the regulator connector on top of the alternator. We tend to lay heavy things across it when servicing, bending and possibly breaking the wires right at the connector.

You are checking volts with an independent multimeter, and have checked the multimeter on a working truck? The dash gage isn't reliable, and a bad multimeter would make diagnostics, um, "painful"?

 

Batteries are good and holding charge. I trickle charged them both separately while disconnected and both held a charge even two days after being filled. Only a minute drop in voltage on either one. I did however run an independent ground and positive cable to the alternator to bypass any potential bad wiring. Even while running, with an independent multimeter, the entire system was sitting at about 10.95v and after about 5 minutes of idling, dropped to 7v. Even when running higher RPMs, no change in the voltage. Batteries are not being charged enough at idle or at speed. and no large draws that I know of. However I noticed in all this that my glow plug relay was hotter than hell itself, likely a separate issue.

 

Did you load test the batts? Holding a charge can still have weak CCA. Also, what is the CCA on those?

Just unplug the GPR from GPs. Two pin connector.

 

haven’t done that but they crank well and are 1000CA (800CCA) each. However I just tested the alternator output with the positive disconnected and the alternator and my old stock one are only putting out .2 - .02V. Harness?

 

I tested the alternator positive with the batteries disconnected from it while running and both alternator separately are putting out .2 - .02v. Harness issues? The wiring is intact but wondering if there might be other issues

 

There are three wires to voltage reg. One runs to the stator, white. Jump yellow to +B. Green/black to switched 12V.

I had a batt from my Suburban down 30% on CCA. Started and drove fine, always maintained sitting voltage. Load test the batts.

 

Okay, i'm confused. You are here looking for help, but I just replied to another thread you have saying your DB Electric Junk Alt failed...what am I missing

You say high end electrical system, I'm not seeing it. Also, not to rain on your parade, but DB and Optima was a waste of money. I'm curious what you used for your upgraded battery cables. Is it possible that you miswired something

 

if GRP is getting hot after 5 minutes, i dont think it is turning off

 

Most likely bad contacts on the alternator regulator pig tails (single wire and the 3 prong one) very common for them to fail.

 

Sounds like several things going on.

GPR very hot after 5 minutes suggests GPR is stuck on. I don't recollect what glow plugs draw, but it's enough to very noticeably drop voltage prior to start and when running with good alternator. If charging system isn't working, I can see that glow plugs stuck on with non-functional charging system could quickly deplete battery, even when hooked up via jumper cables. The glow plugs aren't quite a dead short from battery to ground (think welding current), but still a very high current draw.

If this were my vehicle, I would disconnect the glow plug system. One of the heavy gage wires is +12v feed from the batteries, the other heavy gage wire is switched +12 to the glow plugs. I would disconnect the +12v feed to both disconnect the glowplugs and ensure that the relay doesn't have high current feed. Then charge up the batteries with a multi-amp charger, not just a trickle charger, to ensure they are topped up.

Now, check the battery voltage across the battery terminals. You should see about 12.6 v with engine not running. Start the vehicle. Without glowplugs and in cold weather, it might take some cranking time to fire. Extended cranking will drop the battery voltage while not running by some amount. But once it fires, you should see somewhere in the mid-to-high-13 v to 14 v range across the battery terminals IF the charging system is working. If you're only seeing 12.6 v or lower, the charging system isn't operating.

Personally, I like checking voltage across the battery terminals. It's easy to scratch the lead and get a good connection, and if the volt measurement is bouncing around, I take the highest reading I get and figure the low readings are from high resistance due to localized oxidation. I've had very bad luck getting good voltage readings between a steel positive and steel ground... ie alternator positive stud to body ground.

From what you've provided so far, I suspect you have two issues combined:
1) Glow plug system is stuck on, with resulting high current draw. If charging system isn't working, this is quickly depleting your batteries. Most likely cause is relay is failed ON, but definitive diagnosis requires checking the signal voltage after glow plugs should have shut off. That is, relay could be good but truck is signaling glow plugs to stay on.
2) Charging system isn't working. Since alternator tests out OK, suspicion falls onto wiring and connections. Is the positive terminal connection good? Scratched the stud to bare steel, ring terminal and wire at terminal intact and not corroded? Is the regulator connection intact? Wires at the connector not broken, contacts not corroded?

For connector corrosion, I found that "CopperGlo" (or "CopperGlow"?) cleaner for copper cooking pans works really well on old, gunked-up electrical connectors. There are some electrical contact cleaners available, but "CopperGlo" is nicely aggressive on things like trailer connectors. Might be an option here.