Help - W123 dies, then starts and dies

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Lance
Adenauer
Posts: 370
Joined: Thu 06 Mar, 2014 9:33 pm
Model you own: w114
Location: Altona Meadows, Melbourne

Help - W123 dies, then starts and dies

Post by Lance » Sat 13 Jan, 2018 5:19 pm

Hello all, I have a problem and am looking for assistance in diagnosis.
My W123 280E runs fine but at slow speed it dies sometime. It will then re-start but immediately die. Eventually it will re-start or last time I revved it hard and it kept going but as the revs dropped I could hear the fuel pump relay clicking.
I have a few ideas:
Relay is getting signal but problems in the relay cause it to drop out and it stops (only happens at slow speed)
Signal from ignition unit weakens and is then not strong enough to keep the relay on.
Any suggestions?
Regards,
Lance Smart

W114 280E 5 speed manual
W123 280E

mathuisella
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Posts: 408
Joined: Sun 08 Jun, 2014 7:03 am
Model you own: w123
Location: Brisbane, North side.

Re: Help - W123 dies, then starts and dies

Post by mathuisella » Sun 14 Jan, 2018 1:48 am

low voltage to relay perhaps?

alternator not charging system ?

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Lance
Adenauer
Posts: 370
Joined: Thu 06 Mar, 2014 9:33 pm
Model you own: w114
Location: Altona Meadows, Melbourne

Re: Help - W123 dies, then starts and dies

Post by Lance » Sun 14 Jan, 2018 1:12 pm

Getting 12.5 volts at the relay
Regards,
Lance Smart

W114 280E 5 speed manual
W123 280E

mathuisella
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Posts: 408
Joined: Sun 08 Jun, 2014 7:03 am
Model you own: w123
Location: Brisbane, North side.

Re: Help - W123 dies, then starts and dies

Post by mathuisella » Sun 14 Jan, 2018 4:40 pm

This may seem silly, but have you checked spark plugs ?

they may struggling to fire under compression at low rpm ?

Also, another silly suggestion.

How, about the neutral safety switch ?

is it acting up and cutting the engine thinking it's low rpm and not in neutral/park and cutting the engine ?

under the car, on the side of the gearbox there will be a plug, 4 wires. 2 are the kickdown, 2 are the neutral safety switch.

the neutral safety switch as both purple, slightly different shades, but purple none the less. Bridge those two together in a semi permanent fashion and go for a drive, starting and stopping hoping to replicate the troubles you've been having. If the troubles are gone then you know what it is and i'll let you decide where to go from there. for me, I use the neutral safety switch as a kill switch in my car as i converted it to manual transmission.

mathuisella
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Posts: 408
Joined: Sun 08 Jun, 2014 7:03 am
Model you own: w123
Location: Brisbane, North side.

Re: Help - W123 dies, then starts and dies

Post by mathuisella » Sat 27 Jan, 2018 5:43 pm

How did you go with this ?

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Lance
Adenauer
Posts: 370
Joined: Thu 06 Mar, 2014 9:33 pm
Model you own: w114
Location: Altona Meadows, Melbourne

Re: Help - W123 dies, then starts and dies

Post by Lance » Sat 27 Jan, 2018 11:18 pm

Still working on it. The fuel pump relay was suspect as it appeared to have cracked solder on the circuit board when viewed with a magnifying glass. Re-melted the solder then tried it again, it was running well for a few days but then cut out. Have now removed it and am running with a switch instead to turn the fuel pump on and off. I am also monitoring the voltage output coming from the ignition trigger unit to the fuel pump relay. This appears to be strong and consistent so I am hoping that it is OK. Have run the car like this all week without problems. A new genuine FPR arrives Monday from MBUSA (less than half local cost). I will put that in and see how it goes. I bought a new KAE relay but that just gives problems. Keep away from them. Update once I have tried the new FPR.
Regards,
Lance Smart

W114 280E 5 speed manual
W123 280E

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