Confirmation on two basic tests

Confirmation on two basic tests

JR74CJ5

Missing-Presumed Wheeling
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Plumas Lake, CA, USA
Vehicle(s)
1974 CJ5 ~ Fresh built AMC 360 - SM420 - D20 - D30F with upgraded 30 spline shafts and knuckles & D44R - 4.27 Gears - ARB Lockers F/R - All chrome molly axles - on 33's - YJ 4" Lift Spring Conversion
Would like to test my compression. Have a tester... Never done it before.

Testing altenator for output. Since installing msd streetfire box, dui dist, basic aftermarket stereo, and now winch my headlights are awful dim... How do i test draw vs output?
 
Would like to test my compression. Have a tester... Never done it before.

Testing altenator for output. Since installing msd streetfire box, dui dist, basic aftermarket stereo, and now winch my headlights are awful dim... How do i test draw vs output?

I'll try the compression test ?
Do the basic's like putting the jeep in N and putting the E-brake on.
take all the sparkplugs out and disconect the coil wire.
screw your gauge in the plug hole and turn the engine over a couple of times, see what reading you get on the qauge, go to the next one.
I like to use a handheld start button so I don't have to get someone else to help. (like the wife :eek: )

I'll leave the next ? to someone that knows what their talking about.:D
 
For your altenator question a bigger battery or batteries are need to run all of the extra eq. Heres a good site and explaination of the altenator and battery working together. Been reading the good book of JeepHammer! - JeepForum.com This explains that a high output alt. is not needed a bigger cold cranking amp battery or batteriers is better. Hope this site clears up alot of confusion on high out put alt.
 
Thanks guys!

I will read up on that link, i have always assumed your vehicle is running everything off alt output when running, and charging battery with what is left over.

Thanks for the info guys... Yeah i got one of those push button things, so that should make things easy... As for disconecting coil wire, with my DUI dist should i just remove the cap while testing?
 
Oh and the 3 issues with the electrical system is grounds,grounds,and grounds. You need to have good grounds to have the electrical system working smoothly!:):chug:
 
Thanks guys!

I will read up on that link, i have always assumed your vehicle is running everything off alt output when running, and charging battery with what is left over.

Thanks for the info guys... Yeah i got one of those push button things, so that should make things easy... As for disconecting coil wire, with my DUI dist should i just remove the cap while testing?


No you don't need to remove the cap, just unplug the Batt + wire on the side of the cap.

And to do the compression test properly, you need to have all spark plugs out, the coil unplugged, a battery charger hooked up (so the battery isn't weaker by the time you reach the last cylinder), and the the throttle held wide open(so your not trying to build vacuum as you test).
 
i have always assumed your vehicle is running everything off alt output when running, and charging battery with what is left over.
That's right. The battery is for starting and the alternator powers the electrical system when the engine is running plus recharges the battery.
One exception is the winch. A winch may use 400 amps. That's much more than any alternator puts out so the winch will draw current from the battery. It is possible for the winch to drain the battery even when the engine is running. At that point your engine may not be able to get a good strong spark and it could die. Then you wouldn't have the power in the battery to start you engine again. For that reason don't run your winch too much without stopping to let your battery charge back up. This is also important to allow the winch to cool down.

A good battery puts out 12 volts (actually 12.6 volts). The alternator puts out about 14 volts.
The amount of current an accessory draws depends on the resistance of the accessory. Bright off-road lights have much lower resistance than a backup light.
The actual current depends on ohms law. The current (measured in amps) is equal to the voltage divided by the resistance of the accessory.
If your lights are dim the problem is not that your alternator is not putting out too little current. The current depends on the voltage and the resistance of the lights. Check your voltage. I'll bet it's 14 volts as it should be. Although the resistance of the lights hasn't changed it could be the resistance of any one of the connectors or a bad ground. The lights need a complete circuit to work.
 
There is also a part 2 to the link 1986cj7 posted. Good stuff.

JR. do you have your headlights on relays?
 

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