w639 suspected faulty engine to chassis ground connection

[KOOLCAR]

I possess a 2008 W639 model. A week ago, I encountered a starting issue characterised by a clicking sound. I successfully jump-started the vehicle, suspecting a depleted or low battery. The vehicle was operational and utilised as a delivery van throughout the day. After a few hours, the cluster ceased functioning, and the battery ultimately failed. A technician arrived, inspected the battery after a jump start, and confirmed everything was satisfactory; however, he said, "The engine-to-body ground connection is inadequate." Successfully established a connection from the engine block to the earth point beneath the bonnet as a temporary solution, and all functioned properly.


Yesterday, I installed a new earth strap from the gearbox to the body, intending to remedy the issue; but, it did not work. Commenced examination for other concerns and discovered that the original earth strap from the engine to the body was in satisfactory condition. The sole method to initiate the van's engine is by utilising a jump booster cable connecting the engine's positive terminal to the body’s earth point. I have inspected the battery negative, and it is functioning properly; also, all ground connections in the fuse box appear to be in good condition.

[Black_raven]

Is it a foolish inquiry to ask if you removed the engine-body ground strap and cleaned the contact surfaces?

[KOOLCAR]

I left the original earth strap intact and installed a new earth strap from the bell housing to the body, anticipating that an increased number of connections would yield improved performance.

[rab60bit88]

I possess a 2007 W639 and have experienced an intermittent issue with starting when the engine is heated. It merely emitted a click, like to a depleted battery. However, if you kept the hood raised and attempted to start the engine every few minutes, it would gradually begin to turn over with the key, initially very slowly and for only a few revolutions, then increasingly faster and longer until it eventually began. The cold start was consistently satisfactory.

The battery passed the test, however it was aged (the original from 2007); the earth strap and connections were satisfactory. The battery is located beneath the passenger seat, hence it was not subjected to heat soak from the engine impacting its performance. The initial concern was a 'lazy starter motor,' a common issue with certain brands, particularly BMW. However, I opted to replace the battery because (a) it was aged and (b) this solution was significantly more economical than purchasing a new beginning motor, which ultimately resolved the problem.dk: It has been satisfactory ever since.

[KOOLCAR]

Initially, I suspected the battery; however, connecting the jump pack directly to the battery does not initiate the start. Conversely, attaching the jump pack to the engine bay positive terminal and the body ground facilitates ignition. I am currently reconditioning the batteries.

[rab60bit88]

Are the battery terminals and posts clean and secure, and are the wires in satisfactory condition?

[KOOLCAR]

All terminals and wires appear to be in satisfactory condition; I will utilise a voltmeter tomorrow to ensure everything is functioning optimally. The only noteworthy observation is that when I connect a wire, touching one end to the earth and the other to the engine block, a little spark occurs. This suggests that I may need to reposition the earth strap. I fitted it by connecting it to the gearbox mount on the body side and then to the actual gearbox housing.

[KOOLCAR]

resolved The problem was a faulty engine ground. I utilised some welding ground cable and established grounding at several spots, and now everything is functioning properly.