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Hey Everybody,

I think I'm ready to hook up a battery to my new wiring harness and need a quick sanity check/review. First the facts: 1953 3100, new wiring harness, converted to 12v, using an alternator. I'm attaching 2 pics that show the coil area and starter area. I want to apply power to the harness and the dash gauges so that I can get an oil pressure reading when I prime the oil system prior to starting the engine after transplanting it into the truck. Currently, there are no fuses in the fuse block and the battery is still outside of the truck. So, I'm asking for you all to take a look at the pics and please tell me if I've done something wrong. This is the first time that I've tried doing this, so it is quite possible that I've got a mistake somewhere. I was especially confused about the ballast resistor and the starter bypass wiring. TIA!

PS, Sorry for my lack of skill adding lines and text to the pics....

Mike, it looks to me like you have the coil and resistor wired correctly. If you want to monitor oil pressure (assuming that your gauge uses an electrical sending unit and not a mechanical gauge like the original) you might need to temporarily power just the gauge circuit. I'm assuming you just want to crank the engine till oil pressure builds. If your oil pressure gauge is piped in to the oil gallery physically, as original, what you need to do is disconnect that starter switch to coil bypass wire so the plugs won't fire and then just crank the engine. If you don't disconnect it, the engine will start and run as long as you have the starter engaged, and stop as soon as you take your foot off the starter pedal.

Kevin,

Thanks for looking at my pics! My plan is to remove the distributor and chuck another distributor shaft in a drill and spin the oil pump with that. The sending unit is an electrical unit. I was thinking that powering up the gauges would also power up the sending units that are connected to the gauges. I want to use the drill method since the engine has been sitting for a very long time and don't want the engine internals to rotate without any oil. Probably over thinking it, again, but that's me....

I'd plumb a direct reading gauge to the oil pressure port and spin the oil pump with a 1/2" drill motor. No point in burning up a starter trying to get some oil pressure. The wiring looks right, BTW.
Jerry

Mike and Jerry, That's a good suggestion on just spinning the oil pump.

Powering the gauges will power the senders, but also backfeed the rest of the electrical system.

If you want *just* oil pressure and it is an electronic gauge, I would recommend unplugging it from the truck and just manually powering *that* gauge.

Jerry,

Thank you for looking at my pics! We were typing at the same time! As you suggested, I am planning to use the drill method for priming the oil system.

Fibonachu,

Will powering the gauges backfeed the system if there are no other fuses in the fuse block? If so, I'd have to get a standalone oil pressure gauge, since the current gauge is a part of a gauge cluster.

That's one of those questions that cannot be answered without eye-balling the schematic of the fuse block.

Mechanical oil pressure gauges are cheap at FLAPS.

Also, it wouldn't hurt to crank the engine over a few turns by hand while you have the oil pressure up.

What Bill said above. There are a lot of variables that we can't know at this point.

You could get a standalone mechanical gauge to hook up temporarily as has been suggested, or you could go through and finish the electrical before worrying about the engine.

If the electrical system is finished, then you have to hook up the battery and test it anyway so you could do that before trying to oil the engine.

I am following along as I will have a similar situation at some point in the future. I build my engine (383 SBC) over a year ago and plan to prime th eoil system with a drill motor before fisrt starting attempt. However, I also have a totally new wiring harness so a lot of unknowns that will need to be sorted out when the time comes.

OK, just to be clear, finishing the entire electrical system means everything from the headlights to the taillights and all the in between connections before connecting a battery.

This brings me to a potential dilemma. The wire harness that I bought has a couple of extra circuits that I may or may not use in the future. I had planned to simply bundle the unused wires under the dash and not connect fuses until I needed them. I was under the impression that without the fuse, there was no chance of that wire becoming energized. If I'm wrong, then I've got a real problem in that there is no way for me to remove the fuse block to depopulate it. It would be a literal cut it out, buy a new kit and start over moment.... Please advise.

You can bundle them and remove the fuse and those circuits will be safe. It was unclear to me intially how installed the new harness is.

Given that update, my recommendation would be to check out the harness before trying to do anything with the engine. Once the harness is checked out and you are confident it is good and safe, then you can do whatever engine tinkering you want without having ti worry/think about it.

If you want some advice/pointers on checking out the new harness, that would be a good topic for a new thread.

FYI: THIS PARTICULAR POST WAS MOVED INTO THIS THREAD, SO MIGHT APPEAR OUT OF PLACE.


Hey Everybody,

Looking for procedures, advice and tips for ensuring the integrity of my new wiring harness and its installation.

But first the facts: Chevy 3100, new wiring harness, 12V conversion with alternator. The harness is installed in the truck and the engine connections have been made, as have the dash gauges (and sending units), headlight switch and dome light. The wire runs for taillights are in place and the wires for the headlights, marker lights, horn and radiator fan are through the firewall and bundled out of the way. Wires that are not planned for immediate use (e.g., radio) are bundled under the dash. The battery cables are run from the battery box under the cab floor and the positive cable is connected to the starter battery lug, while the negative cable is connected to the bellhousing. Currently, there are no fuses in the fuse block and the battery has not been installed in the truck.

I'm looking for a procedure to follow or tests that I can perform (with my rudimentary knowledge of electricity and test equipment). Bottom line, I want to be able to connect the battery and not fry any components or burn the truck down.... Any help in this area would be greatly appreciated!

I would really recommend finishing the wiring before you start testing it. It sounds like you are close and that would make the testing easier/smoother. You would be less likely to miss something in your testing if you can do it all at once vs some now and some later.

I am making some assumptions based on my experience with universal wiring kits. I will flag the concious ones.

That said:

As a starting point, set the battery in place and connect whichever battery cable is *not* ground. In this case (and most) that will be the positive cable. Slowly connect the other cable and look/listen for a spark. If you hear/see one, immediately pull it back off because you have a short somewhere. Alternatively, if you don't see a spark you can connect an ammeter inline with the battery cable and look for a draw. A dead short will blow your multimeter fuse, so do the spark test first.

I am assuming here that you do not have any added things that *should* have a draw with the key off. I am also assuming that you do not (intentionally) have any unfused circuits.

Once you are confident that there are no initial shorts, you can start testing the individual circuits.

Identify what circuits you have connected and which ones you don't. Make a written list so you make sure that you test everything that is connected and don't put a fuse in anything that isn't. Ideally you created this list when installing the harness, but if not you should do it now.

Go through the circuits one at a time, putting the correct size fuse in and testing that it has voltage when you think it should (key switched or not). Then energize the circuit (whether that means turning the key or flipping a switch or whatever) and see if the device works. If not, check if energizing the circuit blew the fuse.

Be aware of what things are connected. As an example, your dome light, gauge illumination, and headlight switch are likely going through the same switch. If you don't have the headlights connected, make sure that circuit doesn't accidently get energized while you think you are testing the gauge illumination or something else.

Once you have fuses in all of your circuits and your electrical parts work, eat a victory taco. Then you can progress with whatever your next step is.

Again, I would recommend finishing *all* of the wiring up front.

That was my bad on the suggestion for a new thread. This one had gotten sidetracked onto the oilling topic.

I think we are finally answering the initial question.

Yes, it does matter which one. This comment is not specific to this thread ...

One should always connect the ground cable to the battery last and take it off first. If the ground cable is already connected and you touch sheet metal, frame, etc grounded metal (most of it is) with your wrench while working on the hot cable you will draw big sparks. If the the hot cable is connected first, touching grounded metal will do no harm if the ground cable has not been installed first.

All of my comments assume a minimum level of caution/care being taken. That said, this is good advice in general. I will amend that.