Car wonโ€™t start - battery fine.

Car wonโ€™t start - battery fine.

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ian332isport

89 posts

198 months

Thursday 17th June
quotequote all
I’m struggling to find a good RHD 318is engine bay picture online. What I have found doesn’t show the X20. I think it may be tucked up on the bulkhead behind the battery though.

MitchT

Original Poster:

13,735 posts

176 months

Thursday 17th June
quotequote all
ian332isport said:
Can you do a general picture of the engine bay?
I'll get one at lunch time.

ian332isport said:
I’m struggling to find a good RHD 318is engine bay picture online. What I have found doesn’t show the X20. I think it may be tucked up on the bulkhead behind the battery though.
I suspect it's hidden behind/underneath the battery. When I search online for "X20" pics I just get images of the diagnostic port, hence why I wrongly though that was it earlier.

shakindog said:
Always Start with the basics...
Battery - checked.
Starter - given it a wallop.
Fuses - checked.
Wiring - looks alright, though I'm no expert.
Volt drop earths - lost me with that term!

I have breakdown but not homestart. I'm pretty sure a guy at a small garage down the road will come and have a look but I don't want to bother him unless I run out of options. Want to get on top of this X20 thing first, then I'll give him a shout.

Thing is, the car was fine when I last parked it in the garage. The problem has arisen entirely on its own!

ian332isport

89 posts

198 months

Thursday 17th June
quotequote all
I found this picture of an E36 318is engine loom. Looks like the UK spec 318is has the X20 (and X69) plugs over next to the diagnostic socket.

You can see the diagnostic socket on the far right of the picture. Just to the left of that, under the green and white relays, are the X20 and X69 connectors. I'm not sure which is which in that photo, but only one will have a fat yellow/black wire on pin 18.


MitchT

Original Poster:

13,735 posts

176 months

Thursday 17th June
quotequote all
Now that's interesting - thanks!

I just took this...


MitchT

Original Poster:

13,735 posts

176 months

Thursday 17th June
quotequote all
ian332isport said:
I found this picture of an E36 318is engine loom...
Latest installment...

In the pic that you've posted there is, as you pointed out, a chunky cable which separates into three. One goes to the diagnostic port, the other two go to two separate plugs, X20 and X69.

On mine, the chunky cable "1", only separates to two smaller cables.

"2" goes to the diagnostic port and "3" goes to the oblong unit that's mounted on the strut. I believe this is the ignition coil.

The boot on the plug at the end of cable "3" does contain a yellow wire, but I can't tell if there's a thin black stripe on it. I certainly couldn't see one but I'll admit that I couldn't look all round it without pulling at things and risking breaking something.



Edited by MitchT on Thursday 17th June 21:28

MitchT

Original Poster:

13,735 posts

176 months

Sunday 20th June
quotequote all
Still scratching my head with this but did make an interesting discovery tonight...

I read that if you turn the headlights on and they dim when you try to start the engine, it's the starter motor or solenoid that's the problem. If the lights don't dim it's a bad earth somewhere. I tried and the lights didn't dim. What I did discover in the process is that the nearside sidelight isn't working. I took the bulb out to replace it but on close inspection it's clearly fine. As an experiment, I swapped it with the offside sidelight bulb. Still the nearside sidelight wasn't working, so the bulb is fine but the sidelight doesn't work. Could this be part of the same electrical issue that's stopping the starter motor from working?

Also, I noticed some corrosion on what I believe is the earth strap where it connects to the positive battery terminal - see pic below. Could this be a part of the problem? NB. Ignore the yellow crap in the pic - that's the foam from the padded battery jacket that's disintegrating.


phumy

5,117 posts

204 months

Monday 21st June
quotequote all
MitchT said:
Still scratching my head with this but did make an interesting discovery tonight...

I read that if you turn the headlights on and they dim when you try to start the engine, it's the starter motor or solenoid that's the problem. If the lights don't dim it's a bad earth somewhere. I tried and the lights didn't dim. What I did discover in the process is that the nearside sidelight isn't working. I took the bulb out to replace it but on close inspection it's clearly fine. As an experiment, I swapped it with the offside sidelight bulb. Still the nearside sidelight wasn't working, so the bulb is fine but the sidelight doesn't work. Could this be part of the same electrical issue that's stopping the starter motor from working?

Also, I noticed some corrosion on what I believe is the earth strap where it connects to the positive battery terminal - see pic below. Could this be a part of the problem? NB. Ignore the yellow crap in the pic - that's the foam from the padded battery jacket that's disintegrating.

That's not an earth strap connected to the positive post, all earth's should be black and connected back to the negative side of the battery. All reds will be positive (live), black are normally negative (earth).

E-bmw

6,204 posts

119 months

Monday 21st June
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The side light not working is likely to just either be a wiring fault or the metal spring connector at the end of the bulb has relaxed a bit.

MitchT

Original Poster:

13,735 posts

176 months

Monday 21st June
quotequote all
phumy said:
That's not an earth strap...
I was under the impression (maybe wrongly) that the battery should have an earth strap. Anyway, I'm admitting defeat now!

phumy

5,117 posts

204 months

Monday 21st June
quotequote all
MitchT said:
phumy said:
That's not an earth strap...
I was under the impression (maybe wrongly) that the battery should have an earth strap. Anyway, I'm admitting defeat now!
The earth will be black and connected to the other terminal on the battery, the negative side, it shows a - minus sign, commonly known as -ve, whereas the positive is known as +ve. On the picture you posted of the terminal with the red cables connected you will see a + stamped into the casing.

MB140

2,896 posts

70 months

Monday 21st June
quotequote all
I mentioned this diagnostic trick about a week ago. But so far,

1) Lights not dimming when you try to start.
2) 0.1volts drop when turning the key to the crank/start position.

This all smacks of it not even attempting to turn over which could be caused by a bad earth.

Have you taken a jump lead and connected it between a clean metal part of the engine and the negative on the battery and tried to start it.

If you have a bad earth somewhere this would show it up as the engine would start. Have you tried this?

steveo3002

8,482 posts

141 months

Monday 21st June
quotequote all
phumy said:
That's not an earth strap connected to the positive post, all earth's should be black and connected back to the negative side of the battery. All reds will be positive (live), black are normally negative (earth).
you'd think they would help you out by making them in bright red and marking the post +


no offence but if you don't the difference between +/- id step away before you do some damage to it

MitchT

Original Poster:

13,735 posts

176 months

Monday 21st June
quotequote all
MB140 said:
Have you taken a jump lead and connected it between a clean metal part of the engine and the negative on the battery and tried to start it.

If you have a bad earth somewhere this would show it up as the engine would start. Have you tried this?
I don't have a jump lead. Is there something else that would be suitable?

steveo3002 said:
you'd think they would help you out by making them in bright red and marking the post +


no offence but if you don't the difference between +/- id step away before you do some damage to it
I know which is the positive and negative terminal on the battery, I can see the +/- symbols, however, the negative terminal only has the one cable attached to it. The positive one has two cables going to the terminal and a third cable attached to the top of the bracket that holds the main two onto the terminal, hence why I thought that might be the earth strap.

paintman

6,544 posts

157 months

Monday 21st June
quotequote all
ASSUMING A NEGATIVE EARTH SYSTEM.

Multiple live feeds from a battery +ve aren't unusual.

Usually there will be a single wire from the -ve to an earth point, usually on the body in the vicinity of the battery.

The -ve earth connection points can rust & it's worth cleaning them.
There is usually another flexible earth lead from the engine to the body, either a flat woven strap or a round cable.
These can deteriorate & in the case of plastic covered ones the cable can corrode to nothing inside the plastic, effectively isolating the engine from earth - hence the suggestion of a jump lead directly from the block to the battery -ve terminal to rule this out.

We may have reached the point when letting an auto electrician look it over is your best idea.

MitchT

Original Poster:

13,735 posts

176 months

Monday 21st June
quotequote all
paintman said:
Usually there will be a single wire from the -ve to an earth point, usually on the body in the vicinity of the battery.
Yes, there's one wire coming from the -ve. I'm not sure where it goes - I'll have to look - but there is a cable bolted to the suspension strut "dome" in front of the battery, so that could be it.

Just a case now of establishing if I have something I can use to connect the -ve to the chassis (as I don't have any jump leads) so I can see if I can start the engine. Once I've done that at least I'll know what to tell whomever I call in to fix it.

ian332isport

89 posts

198 months

Monday 21st June
quotequote all
phumy said:
The earth will be black and connected to the other terminal on the battery, the negative side, it shows a - minus sign, commonly known as -ve, whereas the positive is known as +ve. On the picture you posted of the terminal with the red cables connected you will see a + stamped into the casing.
Although what you say is correct, the earth on a BMW is brown, not black.

NMNeil

2,143 posts

17 months

Monday 21st June
quotequote all
MitchT said:
paintman said:
I've always had nine years out of my batteries, hence my difficulty in accepting it might be this.
Bosch car batteries are rebranded Exide ones, which are made in China.
You are very lucky to get 9 years out of them.

phumy

5,117 posts

204 months

Monday 21st June
quotequote all
MitchT said:
phumy said:
That's not an earth strap...
I was under the impression (maybe wrongly) that the battery should have an earth strap. Anyway, I'm admitting defeat now!
To be honest I really think you have reached your limit of tech knowledge of auto electrics, you really should be seeking the experience of an auto electrician.

s p a c e m a n

9,815 posts

115 months

Monday 21st June
quotequote all
Jack the car up, turn the ignition on, make sure it's not in gear and join the cables on the starter motor together with a spanner or other big fat metal thing. Try not to scream like a girl or get flattened because the car was in gear.

MitchT

Original Poster:

13,735 posts

176 months

Monday 21st June
quotequote all
phumy said:
To be honest I really think you have reached your limit of tech knowledge of auto electrics, you really should be seeking the experience of an auto electrician.
I exceeded that point some way back! laugh