No power, shuddering under load

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Shoxr
Posts: 2
Joined: Mon Apr 05, 2021 10:26 pm

Re: No power, shuddering under load

Post by Shoxr »

Let me be a little bit more specific when the engine is running the alternator is charging we need a good ground from the engine to the body or else we run into problem that's why a good ground from engine to body helps to support the electronics that you're running a bigger coil Morris Park radio all of these things play into it so you have to have a good wire from the engine to body I usually run a wire from the tail of the transmission mount hoodie transmission mount on the body the stud that have the nut that's usually a good spot try it and see what happens
my8950
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Joined: Wed Jan 19, 2005 11:07 pm
Location: Detroit

Re: No power, shuddering under load

Post by my8950 »

Shoxr wrote: Tue Apr 06, 2021 7:11 pm Let me be a little bit more specific when the engine is running the alternator is charging we need a good ground from the engine to the body or else we run into problem that's why a good ground from engine to body helps to support the electronics that you're running a bigger coil Morris Park radio all of these things play into it so you have to have a good wire from the engine to body I usually run a wire from the tail of the transmission mount hoodie transmission mount on the body the stud that have the nut that's usually a good spot try it and see what happens
What does this say? Morris Park? Transmission mount hoodie?
zxr250cc
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Joined: Sat May 27, 2017 11:07 am

Re: No power, shuddering under load

Post by zxr250cc »

Hi all,

I used a Scotch Brite pad and cleaned every removable wire connection for ground or hot leads under the hood to improve overall results and had the benefit of the under hood light starting to work again after refusing to work previously. The other connections all benefited from the lower resistance clean connections as well, I am sure. The washer motor also worked better. Free time plus Scotch Brite pad = good electrical health for the stuff under the hood.

Cheers
1986 XR4Ti Mineral Blue Metallic
thesameguy
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Re: No power, shuddering under load

Post by thesameguy »

It's important to remember that electricity travels in a circle, so whatever the + is, the - has gotta match. The two biggest electrical doodads are the starter (hundreds of amps) and the alternator (tens of amps). You need a single big ground from battery to engine for the starter to work, and that connection will also provide (easily) sufficient ground for the alternator. You also need to provide electricity to chassis systems, like the lights and fans... anything not connected to the motor. Thus, you need a ground from battery to chassis that is capable of supporting the load. More grounds are not, generally speaking, better. The chassis itself is made of metal and unless you need to run something electrical that only attached by rubber, the single ground is sufficient. The exception is for sensitive electronics, where small fractions of a volt could result in different behavior. For these items, a home-run ground to the battery (or main ground point) or a local ground may be warranted. Often, cars will have a few major ground points sprinkled around to keep wiring harnesses orderly and provide these local grounds. The other "exception" is grounds that might dissipate static and control electrolysis, which you'll typically see in areas where air or coolant moves - the intake manifold is an example of this.

When I redid my battery cables, I ran 2ga from battery to starter, 2ga from battery to block, 6ga from battery to alternator, and 6ga from battery to firewall. I have within .2v of alternator voltage everywhere in the car. I left the aforementioned straps from body to intake manifold, though I'm not 100% sure that's necessary with the dry lower. IDK, so I left it.

More grounds is not better. The right number (typically two) of good grounds is the key. Cables can fail at the ends, but they can also fail in the middle. I replaced my alternator cable because corrosion from the end had traveled quite far up the cable... Probably people kept cleaning the terminal, overlooking the fact that between cleanings corrosion had crept up the cable. I kept cutting it back, the wire was still garbage. Eventually, I replaced the whole thing. My personal approach, on any car, is replace the battery cables from top to bottom every 10-20 years. :)
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