While working through cleaning up power and ground connections, I noticed that the engine to body ground strap has two labels on it that say the strap must be replaced if removed, and is for "one time use only".

That seems odd.

A new strap is about $50 and they shouldn't really wear out. I can only imagine it is how the star teeth on the eyelets get bent flat on the initial installation?

Perhaps if the eyelets are just cleaned and the teeth bent back so they bite in?

Thoughts?

Part: LNB3740AA



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Probably the terminal ends are plated copper and the common practice is to put a wire brush on the block to terminal mating surface removing the plating material so it's not 100 % factory specification . In practice the refurbished mating surface should be fine but not as long listing as the original installation . In the airlines we would test the grounds on a certain hourly basis as they are very important . The testing devise is called a megger not commonly used outside aerospace . But if you use standard practices you should meet the testing standard .

This negates the wire mesh cable crimping surface on the terminal end as it bits the cable .

What type of tool combination did you use to remove it from the top or bottom ?

 

Good advice but I'd beg to differ on the megger, they're common as muck and used for checking motor integrity.
Maybe it's a different megger?

 

Thanks, I haven't removed the strap yet, but it is mounted with a nut on the starter end, and via a bolt on the frame through eyelet lugs. With that in mind, I guess the strap is also recommended to be replaced if the starter is?

My assumption was that the "teeth" on the end lugs may get bent flat on the original installation and not "bite" upon secondary installs. But not sure.

It seems like a pretty critical piece, so it is somewhat surprising it is the only single ground path from the engine and alternator. But then again, I guess it is pretty common on most cars to have a single ground path from the alternator/engine to the frame.


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I know from some other auto forums that bad ground straps can be a problem, even giving a poor idle. Some owners run a second or even more ground straps at different locations to take care of the problem.

I read on this forum of one member cleaning up the case on the alternator where it touches the brackets that hold it in place and supplying a ground.

I guess after 20 something years, a build up of corrosion and multiple loose or poor connections will add up to a voltage loss.

 

Indeed, I just bought an additional strap to run from the alternator bracket to the frame, so the engine will have two ground paths.

If one looks up the "big 3 alternator upgrade" you'll see where some owners are running direct grounds from the alternator to the frame and uninterrupted leads from the alternator to the battery to combat cumulative loss.

Since the battery is in the rear, I don't plan to run new uninterrupted leads from the alternator to the battery, but I am going to add that second ground strap from the alternator bracket to the frame.

For example:


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Al,

Never noticed that one before.

Maybe Jags way of extra income, HA.

I have installed many eaxtra earth straps on all my Jags over too many years.

Additional +ve cabling on the V12's to the firewall buzz bar, was standard "Grants upgrade" from day 1 of ownership.

The 2 S Types have 4 additional earth cables each, coz I could not find the factory cable (didnt look too hard however), and that has sorted some oddities on the Black car.

I use standard battery cables, eyelet to eyelet, and never use that braided stuff unless push comes to shove with supply issues.

 

For testing purposes I clamped on a battery jumper cable from the engine block to a grounding stud .

 

+1 on adding redundant grounds. Common practice for me on many older cars. It often makes 'things' work better and/or help ensure reliability down the road.

And, frankly, in the case of repairing a problem, adding a new ground is often a lot easier and faster than tracing and repairing an existing, faulty ground.

If working your way thru repairs on any older car you'll come across grounds here and there. Whenever you discover one take 10 minutes to remove/clean/tighten/repair, just on general principles. Ten minutes now might well save hours of frustration down the road.

Cheers
DD

 

Agreed on all points, a lot easier to add grounds than track them down, and also not too unreasonable that some are going to be having trouble after 20+ years.

I did go ahead and order the $45 new OEM engine ground strap figuring that's pretty cheap maintenance for a 22 year old part. I'm not going to pinch pennies there after a $200 alternator.

Like Grant, the extra "ground strap" I'm adding is actually a 4 gauge battery cable with 3/8" lugs on each end, going from the alternator main M10 bracket bolt to the M6 bolt that used to hold the airbox. I was looking for a better factory heavy duty bolt on the LH side under the car but didn't find any within about 2ft of the alternator (the battery cable is 24"). Lots of great bolts on the engine, but that of course does no good ...and lots of big bolts on the suspension, but that too is isolated by rubber dampers except for a small ground strap, so that would be sending the ground around the long way, also not ideal.

So on a related note, I'll try to find it in the service manual, but any idea what the correct torque is on the two bolts at the end of the factory ground strap? One end of the factory strap is attached to the flange of the starter which along with the strap holds half the starter to the engine, and appears to possibly be an M8. The other end is bolted to the frame and appears to possibly be an M6.

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I found the torque values for the starter mounting bolts: 43-57Nm

 

So when I pulled out the original 20+ year old grounding strap, I could see that the strap was pretty corroded all within the braid and the cable crimped bundles were too. So maybe that degrades its conductivity over time? I really didn't have any way to load test it, so I didn't bother.

I could also see how the teeth on the body end lug do deform when tightened to bite into the body. So perhaps that is why it is one use only?

Both open questions, but for $50 it was an easy decision to get the new strap so I wouldn't wonder.

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