Electrical grounding - finer points...

[Gary - K7GLD]

Often, various electrical/electronic problems with our trucks eventually turn out to be the result of poor or deteriorated grounds at various points.



Often, engine bolts are used if they happen to be close to the point we need to ground some new piece of equipment, or perhaps one of the existing body grounds DC uses for existing grounding.





MANY of the bolts used on our engines are ANODIZED, or use a coating that totally PREVENTS voltage/current flow - here's a pic of one of those bolts from my '02, showing what happens if an ohmmeter is used to test for current flow thru that coating:







Note there is absolutely NO deflection of the meter pointer - NO current flow!



Here's another pic of that SAME bolt, with the probes moved to an area of the bolt where the coating has been removed with a wire brush:







NOW, there is a full-scale deflection, zero resistance - just what we want!



This particular bolt was used to secure the ground return for the grid heaters on my '02 24-valve engine:











There's a LOT of current flow at that point, and a GOOD electrical contact is needed for proper operation - after wire brushing the resistance coating from the thread area and underside the bolt head where it contacts the ground lug, prior to reinstallation, I applied a liberal coating of anti-oxidant paste at all contact points to KEEP the contact functional:







The sheetmetal grounding points deserve attention as well - I normally lift all the factory installed grounds up, take a Dremel tool to grind the paint away, exposing bare metal - then use the same paste to preserve the improved grounding point. Here is one such point, with the added large braid I've added to the existing one for better high-current flow - I did the same on BOTH batteries:



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Consider that MANY devices on our trucks include circuits that have very low resistance - in those circuits the addition of a mere FEW ohms resistance can make a SERIOUS change in overall circuit value - with potential radical or damaging results in vehicle operation - and erratic or intermittant contacts poorly done or suffering from the elements and old age can do the same...

 

[JyRO]

I thought you were outta here?

Gary K6 - I haven't read your post yet, I thought you said you weren't coming back?



You know what I think about your return (if you ever did leave)? Indifferent. Fine if you came back, fine if you didn't. Not bad huh? This is not a flame & I'm not insulting you (bad JyRO), just recognizing that you're here. I look forward to your good information.



- JyRO

 

[rbattelle]

Excellent post. Outstanding.

 

[HEMI®Dart]

Great Post Gary. Glad to see you back.

 

[rwitt]

Great post Gary! It's really an eye opener how many electrical problems are actually grounding problems. Again, glad you're back.

Rich

 

[JohnE]

After many years in the aerospace industry, I will concur bolts are a very poor ground source. Coatings on the bolts and thread locks really impede things. That's why the FAYING surface is your most important focus. Faying surface is the contact of the wire lead to the base metal as depicted in one of the photos. However, what looks to be a good ground point is insulated by a gasket.

Excellant observation.

 

[Dane]

Great post Gary.



And If I may add...



Old connections can become corroded over time, so when trouble shooting don't forget to remove grounds and clean the contact surfaces.

 

[LarryWard]

identify all ground locations for 1995 3/4 ton 4x4

 

[Rman]

Originally posted by LarryWard

identify all ground locations for 1995 3/4 ton 4x4

uhhh. . ground is ground... it has no identifiable connections. There are common ones though. But anything that is "grounded" can be used. Get an ohm meter and check.



Great post gary.

 

[John - K5AWO]

Ensuring a Good Ground Connection

Originally posted by Rman

uhhh. . ground is ground... it has no identifiable connections. There are common ones though. But anything that is "grounded" can be used. Get an ohm meter and check.



Great post gary.

[SoapBox ON]



Well, "ground" is supposed to be "ground". But in a vehicle that is rarely the case what with all of the different body parts having paint and other coatings on them before being bolted together.



When in doubt, bond it with a common copper wire ground system.



Gary's photos of the extra bonds added are a case in point. (Good job Gary)



Also, that grease in the photo is also available from good battery supply stores in a product known as "Noxid". It is a conductive grease specifically made to stop corrosion and provide a conductive interface for the joints.



I have an ohm meter that will measure values as low as 0. 001 ohm. When you use this meter and measure the other "ground points" on the chassis, body parts, under the dash, etc... . referenced back to the battery negative terminal-- you can see values ranging widely up to 1. 5 ohms. Sometimes more depending on how far away from the battery you go to. I have seen bumpers that showed no conductivity to the frame at all after a few years of salt spray.



Depending on the circuit requirements, 1. 5 ohms can really alter the operation. Especially if it is a high current draw circuit.



A case in point is the starter cable. 0. 5 ohms resistance in that cable can render it just about useless. 150 amps draw across 0. 5 ohms would equal 75 volts. Obviously we don't have 75 volts to work with in the first place.



When measuring "grounds", I often use the voltage generated "across the joint" or the complete length of the cable. This voltage drop is what you are really concerned with. Almost any voltmeter can give good values to work with. Knowing the approximate current draw will allow you to compute the ohmic value. This exercise isn't needed though because what you really want is 0. 0 volt drop across that ground point (perfect goal).



Very few people have access to high dollar ohm meters. They aren't practicable anyway because we need to know the "operating characteristics" of the circuit while it is working, negating the option of using an ohm meter anyway.



For the engine starter, it should be less than 0. 5 volts equating to a total ohmic loss of 0. 0033 ohms. (Ohms = Volts / Amps for the non electronic types)



The bottom line is to inspect everything for cleanliness. Check those star washers for corrosion. If you see any, replace it.



A good PM measure is to remove every ground connection on your truck and use Gary's suggestions to make it a good connection.



John



[SoapBox OFF]

 

[Rman]

sorry didn't mean to whiz in anyone's cheerios this morning, you bring good points to the table. Quality electronic devices are very expensive, and when dealing with such small ohm values accuracy is important, and accuracy is costly.

 

[John - K5AWO]

I eat shredded wheat for breakfast



I take no offense or is that offence??



I was just trying to help those who aren't as aware of things can get tripped up by assuming that a "ground" is a "ground".



The real world has a lot of examples where it isn't. Tower grounds around a microwave tower. I have measured typical values of 120 ohms, 600 ohms, and on Menefee Peak, Colorado, well... . that hunk of rock measured in the thousands of ohms.



We had to lay a "ground screen" all around the place. I covered the interior of the microwave hut with copper screening. Bonded all of the electrical boxes, ladder racks, individual microwave modules together with 4 inch wide brass strips.



And we still experienced lightning damage in bad storms.

 

[apkole]

Thanks for the good info, Gary.



We who deal with "Michigan cancer" (the DOT strain is particularly aggressive) know the challenge of keeping system grounds in good condition. On top of that, we who plow snow have an ongoing issue with corrosion of connections of all kinds. Of course, these connections never fail while the truck is sitting in a warm shop. As the temperature drops, snow accumulates and the need for functional equipment increases, the frequency of connection failures rises.



Or, to put it more succinctly, "He who fails to prepare, should prepare for failure. "



As an ex electronics engineering technician, I will now begin my meditation . . .



Ohm, ohm, ohm, . . .

 

[LarryWard]

My original question should have been more specific as to locations of the "grounds" on the engine. I am attempting to isolate reason "fuel shutoff" will not pull-up. Removed old boot and cleaned it up, was not that dirty. Replaced starter contacts, etc. , per Larry. Have two new batterys. New Radio Shack relay a few months ago. Its been ongoing for many months, but would work quite well and then intermittenly fail to pull up. It always starts when I manually pull it up. Presently it consistently fails. So I want to I. D. any and all ground locations, esp that may effect this solenoid. transmission shop recently said there were perhaps 3 or 4 locations . Thanks for your valuable suggestions so far. '95 2500, 4x4, auto, 200k,

 

[Gary - K7GLD]

I've noticed a bit of an upsurge in potentially electrical grounding related issues - probably more common in winter months with increased moisture and salted roads in some areas - so thought I'd bring this thread back to the top...



Hope it helps...

 

[msperos]

Nice to see you around Gary This is a great thread thanks for the bump

 

[Gary - K7GLD]

With winter weather, road salts and just plain humidity and moisture, I've been noticing an increase in reports of scattered electrical problems, so thought I bring this thread back to the top.



The many electronic devices used in our trucks often present a situation where DOZENS of random sensitive circuits and connections all rely upon a SINGLE ground return lead - and if THAT connection is bad, many ugly things can happen.



Naturally, ALL connections need to be treated with care and respect if we expect proper vehicle operation - this post just happens to focus on electrical grounding specifically...

 

[jakprince]

Larry,if you post that over in the 12 valve section you might get more help.

 

[Gary - K7GLD]

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FWIW - Winter, wet salty roads and all...

 

[JApol]

Started in 03, came back in 04, skipped 05 for a short stint in 06 and now starts 09 one month shy of its 6 year anniversary