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Engine Ground Strap Issues and Replacing
 

Pelican Technical Article:

Engine Ground Strap Issues and Replacing

Nick Czerula

Time:

1 hour1 hr

Tab:

$150

Talent:

**

Tools:

Set of sockets (10, 13mm)

Applicable Models:

BMW X3 Sport Utility (2004-10)

Parts Required:

Ground straps

Hot Tip:

Wear eye and hand protection.

Performance Gain:

Car will start well.

Complementary Modification:

Replace battery

Your BMW X3 engine is grounded via a main ground strap to the chassis. This ground completes the electrical circuit for the main battery cables as well as the DME wiring for the engine.

It is common for the engine ground strap to corrode and fail, causing high resistance in the engine electrical circuit. When this occurs you may experience a failing electrical system, stalling engine or the most common a stall and no start.

If you attempt to start your X3 and are only getting the dreaded click sound associated with a discharged (dead) battery, the cause may be this strap. First check your battery open circuit voltage. If 12 volts, the engine should start, suspect the ground strap. You will want to perform a voltage drop test (described later) on the main battery cables.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Your BMW X3 engine is grounded via a main ground strap to the chassis.
Figure 1

Your BMW X3 engine is grounded via a main ground strap to the chassis. This ground completes the electrical circuit for the main battery cables as well as the DME wiring for the engine. It is common for the engine ground strap to corrode and fail, causing high resistance in the engine electrical circuit. When this occurs you may experience a failing electrical system, stalling engine or the most common a stall and no start. The main ground strap (blue arrow) is near the exhaust front pipe, accessible once the engine splash shields are removed. If you experience a click and no start condition, the front strap may be faulty, and the engine may be grounding some components through the exhaust ground strap (red arrow). Start by removing the engine splash shields, see our tech article on engine splash shield removing.

With the splash shields removed, you now have access to the front ground strap.
Figure 2

With the splash shields removed, you now have access to the front ground strap. It connects the right front engine mount bracket (blue arrow) to the chassis (red arrow).

When servicing your X3, it is a good idea to visually inspect the ground strap, especially if you live a salt belt area.
Figure 3

When servicing your X3, it is a good idea to visually inspect the ground strap, especially if you live a salt belt area. Note the green corrosion (red arrow) on my subject vehicle. This is an indicator of a ground strap that needs to be replaced. If touched, it would have a brittle feel and sound to it. If you find your strap this way, replace it before it fails.

If replacing the front strap, it is a good idea to replace the rear strap as well (red arrow).
Figure 4

If replacing the front strap, it is a good idea to replace the rear strap as well (red arrow). Even though it rarely fails, if stressed from a faulty front grounding strap, it can overheat.

Lift carpet trim and remove from the trunk by sliding it straight out toward the left side of the vehicle.
Figure 5

Lift carpet trim and remove from the trunk by sliding it straight out toward the left side of the vehicle. Gain access to the battery. To perform a voltage drop test, set your DVOM to DC volts. Then, connect your DVOM positive lead to the negative terminal on the battery (red arrow). Then run the positive lead to the engine compartment and connect to a good grounding point. For example the engine mount bracket on crankcase or a cylinder heard or metal part of the timing cover. Your DVOM should read close to zero. A good reading should be below 0.5 DC volts. Usually you will find a reading of 0.1: 0.3 DC volts. If you find a high voltage drop, for example 1: 2 volts, you can confirm the ground strap is the problem. Use a pair of jumper cables, connect the negative lead to the engine mount bracket on the crankcase. Then connect the remaining negative lead of the jumper cables to the vehicle chassis. Your voltage drop should be remedied.

To replace, simply remove the two 13mm nuts (red arrows), then the strap.
Figure 6

To replace, simply remove the two 13mm nuts (red arrows), then the strap. Use a wire brush to clean the ground strap contact points. Install the new strap and tighten the nuts.

Comments and Suggestions:
7fortyed Comments: Negative battery cable issue. Hello, I'm confused. Your instructions say connect positive lead of dvom to neg. battery cable. Then run positive lead to engine compartment. Positive lead from what?
December 9, 2017

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Page last updated: Sun 12/10/2017 03:12:14 AM