1979 Mercedes 450SLC stood in a garage for many years and refusing to run and accelerate!

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Steve50

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Location
Wakefield
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Mercedes 450SLC 1979
1979 Mercedes 450SLC stood in a garage for many years and refusing to run and accelerate!

When it originally broke down a mechanic came and drained the fuel, cleaned out and replaced the fuel pump and filter and got the car running for a short time, but very roughly. It then stopped working again and was left in the garage for a further 10 years.

Another mechanic has visited recently, cleaned the system out, burnt the fuel pump out trying to rev the car and replaced it with a Mercedes pump. The car will start and ticks over, but very roughly and the fuel pump is noisy all the time. Any attempt to accelerate causes it to conk out immediately.

The following helpful suggestion from another forum has been tried but, disappointingly, was not successful

This may just be a stuck air flow plate/ fuel distributor plunger, common fault- the round silver plate in the induction plenum chamber moves up and down under varying loads and pushes a plunger up inside the fuel distributor, remove the dist block from its baseplate- do not dismantle this, just remove the 3 holding screws and turn this over in your hand. You will now see a shiny ball ended plunger that may well have stuck in place, remove gently without burring, clean in solvent and make sure it moves freely in and out. This was the most common cause of idle but no rpm and they would stick after a short time if they had been stood and plunger moved to a new position.

In my opinion (as a humble builder and not a car mechanic) the fuel pump is either struggling to pull fuel from the tank or failing to push it through to the engine. Has anyone please got any ideas on what might or might not be going on or going wrong?
 
Many things, stale dirty fuel for a start, blocked filters, collapsed/corroded pipes.
 
Could you get it trailered to the SL Shop just south of Birmingham? They will be able to help for sure:

home
 
If the new pump is noisy its likely it is struggling to draw fuel from the tank. Have you checked the fuel tank strainer?
 
TRY CAREFULLY ! [ KEEP AWAY FROM EXHAUST] RIGGING UP A TEMPORARY SMALL FUEL TANK THAT THE FUEL PUMP CAN DRAW FRESH FUEL FROM TO ELIMINATE FUEL TANK STRAINER BLOCKAGE
 
Would this engine have the old type machanical points in the dustributor ? First place i would look with rough running engine of this type.This is from a distributor off a 1975




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Points, plugs, timing were the things to do back in the day. If its got a carb, check the needles are not blocked. Fuel in carbs goes like varnish after a few years.
 
SOME GOOD PICTURES OF THE ENGINE COMPARTMENT MIGHT HELP? BOTH SIDES WITH AIR CLEANER/FILTER HOUSING OFF.
This might help?
I,m going to be a bit cheeky here - are you sure you have the distributor ht leads in the correct firing order? with CIS there's enough residual fuel in the inlet manifold for the engine to run at idle even if the firing order is wrong-- but no power obviously and a danger of flooding
 
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You really need to get hold of a fuel pressure tester that connects to the fuel distributer and warm up regulator to ensure they are working properly. If your not comfortable with that then find someone that is experienced with the bosch k-jet system, don't trust any old back street garage with this, find an expert. SL shop are good but expensive, others are still out there but getting thin on the ground. The workshop manual describes how to do the checks.
 
Thanks again for all your responses. Awaiting a fuel filter to be fitted and possibly needing a new (old) fuel tank. Does anyone have any ideas for where a fuel tank for a 79 450 SLC might be sourced please?
 
FUEL TANK WITH ATTACHMENT PARTS MERCEDES 450 SLC USA (107024)
A1074703201 PART NO
E.G.
 

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