trying to get my 51 up and running. anyways i would like to be able to see the vitals on the engine. the only problem is..... 1. alternator is only showing 11v all the time. engine dies after about 5-10 seconds if i unhook the battery. maybe bad alt? 2. engine oil pressure is reading an odd75-90 psi. i have never seen oil pressure read this high in anything before. also if i rev the engine the oil pressure drops??? usually i see it raise if the rpms go up. im thinking faulty oil unit 3. everytime i start the start up the fuel gauge is reading a different level. could this be a bad ground or sending unit? 1&2 are more important. #3 can be solved with gas jug in back of pickup bed. lol
alternators should kill the motor if you disconnect the battery. Some immeiatly, some after a few seconds. Usually after the cut out kicks in.
The alternator should put out 14.5 volts. Anything lower than 13 volts wont keep the battery charged. Oil pressure? Is this a electrical gauge? If so, you may have an incorrect sending unit. 90% of all automotive electrical problems are caused by a bad ground or connection.
Please quit disconnecting batteries in alternator equipped cars. This is not a valid test for anything on the car, and can damage alternators or the rest of the electrical system. At 11v your alternator is not charging. Not a surprise, since you have disconnected the battery while running. Probably blew out a few diodes. Since a '51 did not come with an alternator, which alternator are you using? Overnight charge the battery with a charger. B.
actually, its ok to kill the engine by pulling the cable off the battery if the car is in gear and has pinned your leg to the pavement
51 what? If you are running an alternator and at 11 volts, you've converted it so what did you put in there and how did you convert everything after the charging system? Is the power reduced to 6 volts to the gauges?
51 chevy. engine is 350 with 12 volt system. never said i disconnected the ground. ive always disconnected the positive lead to the battery to check for alternator charging. all my other cars RUN if i do this. not sure why so many of you are bashing this method. yes all electric gauges. on the oil sending unit....yes 3 wire. ive found out on my earlier thread and doing research myself the tan wire is the only wire to hookup. the others were used to engage fuel pump and ecu or something along those lines. battery is a good battery. i have a smart charger that tells me if a battery us bad. its pretty neat gadget.
if it matters. the main cable from alt is hooked up to the battery + side of the battery. the only other wire coming from the alt is hooked to the this same cable. this way when the alternator starts to turn it will turn itself on. when i kill the engine and the alt stops turning it will stop charging.
Get a cheap voltmeter from Radio Shack. Measure voltage across battery with engine off (12+ volts usually) then again with engine running (should be around 14V). The voltmeter comes in handy later for figuring out what stuff doesn't work right.
I always check the voltage at the back of the alternator on the + and - terminals, with it running of course. This eliminates the battery. You can also do the + and any ground, engine, bracket, etc. Never disconnect the positive (on a negative ground system) battery terminal. If it touches anything, you will have an imediate short and a lot of sparks and possibly do more damage to your charging system. I've taken off the negative terminal to see if it was charging plenty of times, only on older cars, never anything with a computer in it. If it stalls, its not charging. I would take the car somewhere and get a charging system check done to it. Won't be that expensive and some places do it for under $10. Bob
is it showing a volt increase if you get above 1 - 1.5k rpm? my 230 only starts to show higher volt increase once its at a higher rpm get nothing during idle.
Because it is foolish, and not a valid test for anything on an alternator equipped car. You will never find this so called "test" in any manual, or recommended by any manufacturer. Disconnecting the battery i a running vehicle equipped with an alternator can cause voltage spikes above 80 volts on some alternators. Some newer alternators have avalanche diodes to clamp the voltage @ 20v to protect the electronics in newer cars. They can self-destruct to save the computer when tested like that. Some very late model alternator regulators have a fallback to almost no current if they don't detect a battery. I believe this "test" was a backyard idea from the days of generators. since a generator will not put out much & has no diodes it was probably ok. It is not ok with an alternator. Still needs to be charged if you are seeing 11v B.
Take your alt up the the parts store and have them test it, If it is bad replace. easiest thing to do is buy a one wire alt. But if yours test good at the parts store. let me know and I will draw you a diagram on how to wire it up correctly.
Just a thought. Is your battery grounded with the correct post. Most ground negative, but some older units grounded positive.
Depends on the alternator if it will run or not, An internally regulated GM alternator should keep the engine running. You donot need to disconnect the alt if you know it is only putting out 11 V, but I should say that some alternators donot put out full charge @ idle. That said your electrical problems are probably coming from bad grounds, you do have your engine grounded to the chassis correct? Those trucks normally have the battery under the floor and the ground runs to the chassis, start by making sure that you have your engine grounded. Then see if it will keep running. You smart charger is not as smart as you think it is. I just pulled a dead battery from a car that not only the smart charger but also the professional hot charher said the battery was fine and fully charged at that. I put a trhowaway battery from the shelf in the car it it fixed it. I checked the battery the back yard way with a volt meter and the tops off from cell to cell and found two dead cells. That said if your battery is starting the truck it is not a battery issue. Get a mechanical oil pressur gauge and test your oil pressure. Just for reference my hot rod small block puts out 80 psi at fast idle when it is cold, once it warms it drops to normal looking pressure. my stock 283 puts out 40 @ idle when cold, once warm drops to 15 @ idle and 40 on cruise. My stock motor has unverified mileage. Anmyway do the simple stuff first.
Really? No politics, nobody comes here to read about that crap. On the oil pressure deal, I would suspect an incorrect sending unit, or it's wired backwards.
after having alternator checked at parts store search here for thread: Chevy Alternator Wiring Diagram only thing to add to that is a section of fusible link in main wire from alt to battery hot, usually at starter where battery cable attaches.
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