Car will not start after fuse issue

[dallasf]

Hi All,

Tonight I was changing over my power window switches in my 107 450slc, since the old chrome bezels had flaked and one switch was broken.

I noticed that right front and rear left were not working. I checked the fuse box and this highlighted that fuse 3 would be blown.

Therefore, I tried to remove the fuse and missed (fat fingers), I must have moved something as a few sparks appeared and then the car turned on (not the engine) just as if I had turned the ignition before starting. Note: the key was not in the ignition.

So I disconnected the battery and removed the blown fuse. Upon starting the car I get nothing, won't even crank over. When turning the key I lose power to those lights.

What have I done? I Assume its not the fuses as the diagram supplied on doesn't detail anything about starter or fuel pumps. Have i broken something.

I am only really starting out with cars. I need assistance please.

Thank you.

[dallasf]

My post is like the plague! :Doh:

What are your thoughts on a jump start? Would this cause more damage?
I really want to solve this myself and don't really want a mobile mechanic to come out. Defeats the purpose of my endeavour.

[TheMadRacoon]

The best place to start is a wiring diagram. Have you got one? Maybe even an old Haynes manual to start off with. You'd fond one on eBay I'm sure.

Focus on what's around & connected to the fuses you moved, and the ignotion switch. Have a look to see if there are any dislidged wires in the vicinity. I've never hot wired a car so I don't know if the ignition lights would come on in that case....I know you daid the starter didn't come on, but maybe the loose-wire theory is still valid?

[dallasf]

Thanks for the advice. I need to locate the wiring diagram and go from there. Just trying to find the right one!

I haven't been able to find anything online.

[Giles]

http://www.mb107sl-club.nl/techn/Elektr ... 201973.pdf

http://www.theslshop.com/mercedes-benz- ... nload.html

[Tony From West Oz]

Re-check the all the fuses in the fuse box.
Are they plastic bodied or ceramic bodied fuses? White metal fusible link of copper fusible links? If plastic and/or white metal fusible links, purchase ceramic bodied fuses with copper fusible links and replace all of the plastic bodied fuses.
This will eliminate poor fuses as a possible cause.

This is the recommendation for all cars which use the European style fuses.

Now you can go back to the circuit diagrams.

[dallasf]

Thanks Tony and Giles for the information.

I just got the ceramic fuses from autobarn. I will source the more appropriate fuses as described and replace.

[AMG]

What year is your 450?

There are massive differences in 107 wiring harnesses over the years, and 3 different injection systems.

While the basic systems are common to every car, they have their own idiosyncrasies.

The reference library section contains all the information you need to troubleshoot the injection systems on your 107.

You really DO need to read it. There is nothing worse than having a half-arsed guess when you try and troubleshoot these things, it will only lead to more trouble for you and more cost.

If you do not already have one, Do yourself a favour and buy a quality digital multimeter, which can also measure duty cycle.

A good multimeter will last a lifetime. If you are wanting a recommendation, ask Dave Jones (EEVBlog) as he's tested about every version on the planet.

For those of us who are 'in the industry' there are pretty much a few standard "must have" reliable brands... a Fluke 87 V multimeter and a Tektronix MSO oscilloscope.

I'm not saying rush out and buy one - but if you do choose to invest in high quality measurement equipment, then these will not let you down. I've had my 87V for over 15 years, it carries a lifetime warranty.

Scopes are useful for reading injection and spark signal I/O as well as frequency and logic. But that is a whole other realm of diagnostics learning, and not a topic that can be summized in a paragraph.

Firstly you need to establish a few really basic functions.

1. Does the car turn on at all with the key?

If yes, then you can start looking first at the starter circuit, and the fuel pump relay / pumps / ignition circuit.

If no, then you need to look at the battery voltage, the battery cables, fusible link, main earth, and feed to the fuse box.

In a 107, the fuses are in a horrible location, and moving the seat, having a good torch, removing the trim panel under the steering column and kickpanel are "mandatory" procedures to learn.

You may find that there is a degree of "non-standard" wiring in your vehicle, and this could be the cause of your issue. in which case, removal is often the most intelligent decision.
This may extend to items such as aftermarket radio installations.
Alarms and immobilizers (often a cause of "my car won't start") which tap into ignition feeds and fuel pumps and can dead-short, leaving you stranded.

But unfortunately, without any details of the ability to look at your vehicle, there is little one can do in terms of offering help. The Diagnostics you'll have to do yourself, inline with the factory ETM (electrical manual) and be aware that most copies that are about are for LHD vehicles. So component locations are often mirror reversed, but not always.

You'll find that your glovebox compartment may need to be removed to access modules, as some are hidden in there on later cars. The D-jetronic controller is hidden in the passenger side, below the glovebox. the trim panel will need to be removed to inspect, if you have a D-jet car.

But we're clutching at straws, as we simply have nothing to go on. You'll have to start with the basic troubleshooting, follow the wiring diagram, and test in accordance with the factory service manual's procedures.

If you have not got a 107 factory service manual contact the forum sponsor and get one on CD - it will save you an eternity of frustration and it's cheap.

Start with looking at the feed to the ignition, then look for an aftermarket alarm or immobilizer - and if you find one, REMOVE IT.

Then look deeper into the ignition switch on the back of the key - they can fail occasionally.
Look at the transmission 'lockout' switch and check that it's functioning correctly.
of course fuses etc, are important as are modules like the FPR (for KE especially) so checking the function of these things are important.


Let us know where you are at, and what you've confirmed to be functioning correctly. Maybe then some people can chime in and assist.

[CraigB]

Missed this first time. If what you are saying is that when you try to start, the ignition lights dim, check the voltage on your battery. Does it click and try to start or just dim? And you say "those lights" - which lights? Ignition lights that come on in the on position with the key? Another thing that can affect starting is the auto lockout switch. Have you tried in N and P?

This is just adding thoughts that others haven't mentioned, so it could be that a wire or ignition switch melting. I don't think there are fuses in ignition circuit though so sparks in the fusebox i wouldn't have thought would affect that - but maybe melting to a wire next to it and thats why your lights came on.

Good reminder to the rest of us though - if messing around with anything electrical, just disconnect battery first

[dallasf]

Thanks for all the information guys.

AMG - its a 1978 so I will update my profile to reflect this. Thanks also for all the details in regards to troubleshooting these issues. I will follow up on the multiple questions and information you outlined as I want to be across all of this. Thanks again.

Giles actually referred me to some debris near the fuses which I hadn't seen, I removed this. I also placed the car in neutral and drive to see if it was a shift lock issue. During this process I noticed the starter and fuel pump were both engaged. Giles advised to jump the car, I was tentative to do this originally but did it anyway and the car started! I am sourcing a battery today and will swap this over.

So all is resolved...for now.

[CraigB]

maybe get your old battery tested. I'm just thinking if something has melted and developed a slow leak, your battery might be ok. Just a thought.

And you are in Perth, so that is a great thing to put in your profile. Just means next time you have trouble we can suggest "go see Giles!"

[Giles]

I believe Dallas is a tad east of Perth.

Giles

[Tony From West Oz]

DallasF, would you please edit your profile so we can see what part of the world you are in.
I think you are in Australia, but maybe not.
If in Aus, what part of AUS?
A couple of members have suggested adding your location, but I really think that if you want advice on what to do , who to see, and recommendations on your vehicle then you SHOULD let us know roughly where you are. It can make a big difference to what we recommend.