spark plug ground straps? - BMW Forum

325is94 · 02-12-2006, 10:34 PM

today while changing my plugs i noticed that my car only has one spark plug ground strap and i saw in this page that this car has 2 ground straps and here are the links:

http://www.pelicanparts.com/BMW/tech...lugs/pic16.jpg
(dont have this one)

http://www.pelicanparts.com/BMW/tech...lugs/pic21.jpg
(i only have this ground strap)

is this a problem or did all the 94 325is models come with only one? my car is stalling and i am thinking the previous owner maybe lost it or took it off. please let me know if you guys only have 1 or 2 ground straps.

thanks.

325is94 · 02-13-2006, 12:13 AM

anyone? any help is appreciated.

vwk · 02-13-2006, 06:11 AM

As seen here:

There is only one, so maybe the pic is of a 328i. I have a 328i, and have 2 ground straps. So I think it's more a general pic from pelican parts

Edit: Although I'm not sure it's the same ground strap...

bimmerboy328i · 02-13-2006, 10:36 AM

I am not 100% sure on the M50 motor, but there should be two. I know on my M52 motor it has one on cylinder 6, and one on cylinder 1.

Furious · 02-13-2006, 11:50 AM

yeah i believe you should have two, however i dont think its extremely crutial to have both, one yes, but two you can live without. however if you have the resources to get one , put it back on.

wavewuver · 02-14-2006, 12:39 PM

My car ran fine with only one for years. I noticed in some photo it was supposed to have two, so I added one. Didn't make any difference except peace of mind. If some BMW engineer thought there should be two of them, there is probably some good reason. Its so cheap to add that its a non issue. Do it when you change your plugs.

BMWJNKY · 02-14-2006, 01:09 PM

One is ok but having 2 is better. If you don't have one at all there is a very good chance that the DME will die. What happens is instead of the coils grounding through the grounding strap to head they will start to back feed and try and ground through the DME.

325is94 · 02-14-2006, 01:51 PM

thanks for all the responses i will get a ground strap even if i dont need it to make sure it grounds right.

Dudesky_E36 · 02-14-2006, 05:00 PM

Quote:

Originally Posted by AJ's320i

One is ok but having 2 is better. If you don't have one at all there is a very good chance that the DME will die. What happens is instead of the coils grounding through the grounding strap to head they will start to back feed and try and ground through the DME.

Aw man, don't freak people out like that :lol: If that were true, then there would be ground straps on every coil. The coils are already grounded to the head via their mounting studs. The straps are just for added assurance. There should be one ground strap per bank of wires, i.e., one for coils 1-3, and one for coils 4-6. And there is actually no grounding occuring there, unless the coils crack or become defective; that's why they're grounded. But normally, current doesn't flow on the outside of them. The grounding actually occurs at the spark plug seat where it contacts the head.

BMWJNKY · 02-14-2006, 05:21 PM

Quote:

Originally Posted by Dudesky_E36

Aw man, don't freak people out like that :lol: If that were true, then there would be ground straps on every coil. The coils are already grounded to the head via their mounting studs. The straps are just for added assurance. There should be one ground strap per bank of wires, i.e., one for coils 1-3, and one for coils 4-6. And there is actually no grounding occuring there, unless the coils crack or become defective; that's why they're grounded. But normally, current doesn't flow on the outside of them. The grounding actually occurs at the spark plug seat where it contacts the head.

The studs go into the valve cover which is separated from the head with a rubber gasket. How well is that going to ground to the block? The only connection between the head and the coil is through the small contact point at the top of the spark plug. The early M50's with the almn. valve covers provided some grounding but the later M52's with the plastic valve covers have zero grounding properties. I'm not just pulling stuff out of the air here, I work at a BMW shop and have seen this problem. 90% of the time when a coil starts to short out or isn't grounded properly and it isn't taken care of in a timely matter the DME will die.

Dudesky_E36 · 02-14-2006, 06:42 PM

^^^No arguing with that, time to stick my head up my ass

I thought I thought this through before answering, but you're absolutely 100% correct- the only electrical contact point between the head and valve cover is through the ground straps, via the mounting studs. Even the valve cover bolts have rubber washers

BMWJNKY · 02-14-2006, 07:19 PM

Quote:

Originally Posted by Dudesky_E36

^^^No arguing with that, time to stick my head up my ass

I thought I thought this through before answering, but you're absolutely 100% correct- the only electrical contact point between the head and valve cover is through the ground straps, via the mounting studs. Even the valve cover bolts have rubber washers

Its all good, I was a full time BMW mechanic for 2 years before I got moved up to parts manager. I have been working with BMW's for about 4 years and have working as a full time mechanic since early 2000.

325is94 · 02-14-2006, 11:58 PM

this forum is awesome because of all the help we get and we even have members that are certified bmw mechanics. thanks for all the help.