Mercedes r107 suddenly won't start

[Simonstronach]

Hi
I have a Mercedes 350sl r107 and it has been running beautifully. I changed the bulb on the gearbox and managed to short something while cleaning the bulb holder with a small screwdriver, stupid I know
I don't know if this is coincidence but since I can't get the car to start, it turns over and sounds as if it will catch but then just keeps turning over.
I have looked at the fuses, the second one in has blown, but the diagram on the fuse lid is missing so not sure what this is for?
I really can't believe the short on a bulb has caused this but wondered if anyone has any ideas where to look, I have read about fusible leads, I have an inline fuse on the the lead coming from the battery, but this looks ok
Sorry to go but would really appreciate some pointers,
Cheers
Simon

 

[martyz]

Change the blown fuse and see what happens,worst case scenario it will blow again.

 

[dinoy]

what year is the car, is their spark from ignition leads to the engine as this is needed to start the engine

 

[gbjeppm]

Can you hear the fuel pump prime?

 

[jonnyboy]

when you say you "changed the bulb on the gearbox" do you mean the illumination on the gear selector?
As this is an older car - could this be a rudimentary protection against starting in gear?
You have double-checked it's not in gear haven't you? Been there...

 

[Simonstronach]

Hi, it's a 1973' , yes sparks from leads. Thanks for responding. Will check fuel pump, strange thing is after my fusing episode it started once then died again

 

[Simonstronach]

Hi john
Yes gearbox illumination bulb. I think it's a coincidence and probably blew something else, I have tried to find what each fuse is for to no avail , the diagram that is meant to be on lid has gone! Yep tried in parking and neutral cheers simon

 

[Druk]

Fuse diagram from a 1981 280SL. Ignore the jottings, they're for my car which has mods done.

Take this with a pinch of salt...a 73 is an early car and might be different.

 

[Simonstronach]

Cheers that great really appreciate your help re this, doesn't look as if any of these affect my ignition though as I thought. Think I have a bit more testing to do tomorrow , luckily admin day at home so I know what I'll be doing. Also noticed the indicators have stopped flashing so I think I have some electrical issues

 

[grober]

1972 350SL/450SL FUSE PANEL ELECTRICAL - Mercedes-Benz Forum
1972 350SL fuel delivery/Ignition - Mercedes-Benz Forum

 

[dinoy]

the fuse layout is different for pre 1974 and might well be different for 350 and 450 from 280 model, also left hand drive and right hand drive also

if there is spark, switch ignition on go drives side (RHD) behind back wheel is where fuel pump is located with ignition on you should he the fuel pump buzzing it is working if not then it means fuel pump problem or relay for it (unsure if there is one for early models).

the other problem is early ecu but not sure at the stage until u come back with findings on fuel pump

 

[Simonstronach]

Hi
Cheers for this, will check fuel pump tomorrow. I recently changed the ecu, it has run rough for last two years but I bought a rust bucket 350sl from the same year and swapped the ecu, and since then it has run like a dream . Having read the links above I am thinking that it may be a relay, but will check fuel pump tomorrow.
Thanks for all your assistance guys, I really do appreciate it.

 

[Simonstronach]

Thanks Graeme had a read through these really useful, thanks again

 

[martyz]

View attachment 50742

The fuse on top of this relay(OVP) might be blown
this is the over voltage protection relay,and can cause non-start problems.

 

[Simonstronach]

Just a quick update. I changed the fuse that blew that had no effect. I then stripped out the relays from my donor car, virtually stuck solid so hard to get out. Then tried to get relay out of my merc and stuck solid. I don't know why but I thought I'd try starting it and it did!! I then drove it up to my brother workshop where the donor car and hoist are and on arriving tried to start it and wouldn't again. I wobbled all the relays, doused it all in wd40 and it fired up. So one of the relays is definitely faulty or loose wire, just wondered if anyone has a picture showing which are which, my indicators still don't work and am guessing this a relay again. I have four spare from donor car, do they blow often as worried get stuck somewhere, guess comes with 49 year old car!!

Just stripping brakes now , scooper jammed, all good fun

Thanks again

 

[gbjeppm]

Glad to hear it is working, on and off.

I would though use a spray contact cleaner on the relays, not WD40.

 

[Simonstronach]

Thanks Matt, must admit wasn't sure what it would but a mate advised me, will get done contact cleaner

 

[gbjeppm]

Toolstation do one

Contact Spray 400ml - Toolstation

Seems to work fine.

 

[gbjeppm]

Also this is an excellent thread for an early 70's r107.

Hope it helps

The Comprehensive Illustrated Djet (72-75 350-450SL) Thread - Mercedes-Benz Forum

 

[grober]

74 450sl wont start - Mercedes-Benz Forum

If 1 2 and 3 are good the car should start. The solder joints on the small circuit boards inside can crack and sometimes they can be repaired by remelting the solder connections - other wise check the number on the can and replace.