W126 300SE starting issue

[C32Graham]

Morning all. Have a new toy to tinker with! I dragged a 1989 300SE out of a London garage on thursday from where it had been sat for 3 years. It Flew through its MOT with no advisories even!

When I picked up the car, the seller mentioned that if it ever failed to start then remove the fuel pump relay and refit it. It will start.

Well, it ran like a champ until I had the car washed on Saturday. It would start then almost immediately quit. Probably ran for about 3-5 seconds. Regardless of what RPM you are at.

I thought it was water ingress so left it over night and yesterday it ran great. Well... went to take it to work this morning and it started fine, then about 5 mins into the journey it kept losing all power, then back. Decided to turn back for home. Made it about 500 yards from home when it finally quit. It wouldnt start and was doing the start/quit thing. I removed the relay, refitted and it fired right up. Drove it back home and just as I was parking it quit again. By this time I was late for work and I just jumped in my trusty old E34 BMW and headed for work.

So my long winded question being, do I just need a fuel relay? I have no service history for the car so my plan is to change all the standard items anyway. Fuel filter, oil + filter, plugs, Dizzy cap and rotor.

Thanks in advance, Graham

 

[dinoy]

could solder fatique. there is a jumpoer bypass i am sure if u search for it u will find it, if not somebody else will let u know if this works, means to choices open and look for solder fatique and you can resolder or buy replacement unit.

being 6 cylinder units which are the same as that i believe in w123 and w124 280 or 300 i do stand corrected though!!.

check new prices in GSM and eurocaprts they may still stock it better option than 2nd hand one i would say.

welcome n good lucj

 

[C32Graham]

Thanks, Trip to MB to see how much they want first I think. will go from there.

 

[dinoy]

check the bypass first try it should confirm the need to replace, so u do not have waisted money. where abouts r u located btw as people cannot contact u easily i guess

https://www.google.co.uk/search?q=f...=eT9VV_arBszZgAaigJjABw#imgrc=DvQdxA7zb75zfM:

 

[dinoy]

another example of the bypass

http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/2508585-homemade-fuel-pump-relay-bypass.html

also check over voltage behind battery has on top of the circuit a red fuse sometimes replacing this solves the problem too

good luck

 

[C32Graham]

Do you know if they are the same pins on my 300? (i.e. the two middle ones)

I've done a bit of digging but cant find anything specific.

Also, reading their woes it would seem it cut out and wouldn't start at all. Mine starts and then fails after a few seconds. hmmmm

 

[dinoy]

6 cylinder circuit usually the same look at the pics and check out the nos.

if circuit not their car will not start putting bypass will make it start it is well known trick.

i would say yes but do not blame me if it goes wrong only trying to help

if is starts n no problem it is the circuit in the old days £50 from euro and probably £100 from main dealer, there is also pics to show the solder problems and how to repair it could be DIY

 

[syncropaddy]

As the car has been sitting for a while, I would look at the fuel filter and pump as well as the relay. Older MB relays etc, do suffer from dry solder joints as has been mentioned before so if you are any good at soldering you could have a look! Go to your MB dealer for your plugs, cap and rotor arm as the after market spurious parts are not the same. Plug leads are copper and should be ok but the connections at either end might be giving up the ghost at this stage - again MB dealer for these parts. Relays aren't cheap by the way either but ask for a discount and of all the parts mentioned, only the fuel filter could be comfortably be purchased outside the MB network - in my opinion, I have been down this road with my 300SE!!

 

[dinoy]

As the car has been sitting for a while, I would look at the fuel filter and pump as well as the relay. Older MB relays etc, do suffer from dry solder joints as has been mentioned before so if you are any good at soldering you could have a look! Go to your MB dealer for your plugs, cap and rotor arm as the after market spurious parts are not the same. Plug leads are copper and should be ok but the connections at either end might be giving up the ghost at this stage - again MB dealer for these parts. Relays aren't cheap by the way either but ask for a discount and of all the parts mentioned, only the fuel filter could be comfortably be purchased outside the MB network - in my opinion, I have been down this road with my 300SE!!

bypassing gives an idea to the problem if not yes need to move elsewhere, in saying trying to avoid unnecessary expense, but as u say could with fresh petrol injector cleaner, then moving to areas u mentioned hopefully dry solder or the over voltage fuse.

if u guys are close u might try out things

 

[dinoy]

somebody breaking one on here

http://www.mbclub.co.uk/forums/classifieds-mercedes-parts/210363-breaking-merc-300se.html