SL500 resurrection

sahtas1

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Here is my first post, so please be gentle if the answer to my problem already lies elsewhere in the forum! :shock:
I have recently taken on an R129 SL500 that has been off the road for at least 18 months. It is in generally good condition apart from the obvious signs of not having been run for a while. Having done a basic service on it and fitted a new battery of the correct type, it turned over but would not fire. It had an immobiliser fitted for which the old owner had lost the 'plip'. I have had this removed and a new one fitted as this would have seemed to be the problem. While checking the car over, the distributor caps looked distinctly passed their best, so these and the rotor arms have been changed as well. However, it still turns over but does not fire. The fuel pump is working as the plugs are clearly wet and you can hear the pump prime. Before I go down the route of coils, crankshaft sensor, etc and start to run up further unnecessary expense, does anyone have experience of what the fault is most likely to be?
The Mercedes immobiliser seems to switch off happily when the car is opened and the key is in the ignition, so do not believe this to be the problem either.
All help welcomed as I really want to get the old girl running before my wife starts to complain I have bought another 'non runner' project! ;)
Thanks in advance.
Ashley
 

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Hello and welcome,, you do need to check that you have 12 volts on the coils,,also that the minus terminal on the coils goes to ground as the engine is turned over
 
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sahtas1

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Thanks Malcolm,
Will check voltage on coils and freshen up ground contacts as well as my next move and will let you know.
 

matthewm1965

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Have you put fresh petrol in?
If the fuel is 18 months old then you will be lucky to start it even if everything else is ok.
Matt
 
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sahtas1

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Hi Matt,
4 gallons of fresh super unleaded in the tank. It is definitely an electrical issue, not fuel. Got no spark at plugs.
Thanks,
Ashley
 

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The ignition amplifiers can fail and not too expensive
 

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It could be the EZL, and they cost a fair bit :shock:

Too true Richard,, by shorting the neg terminal down to ground on the coil,,as the short is removed, it there is a spark on the coil that would tell us alot.

Bosch paid £4 each for one of the last batches,and they retail at some £1300
 

Alex Crow

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i would suspect the old immobiliser has not been removed correctly, ie the connections in the loom have not all been remade - check at the ovp (silver realy under plastic panel at rear passenger side under the bonnet) for signs of interference with the original wiring.

please tell us the age of your car for more specific advice.
 

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i would suspect the old immobiliser has not been removed correctly, ie the connections in the loom have not all been remade - check at the ovp (silver realy under plastic panel at rear passenger side under the bonnet) for signs of interference with the original wiring.

please tell us the age of your car for more specific advice.

This will be the 129066 from 1990 to mid 1995 before they changed to the electronic ignition
 

Alex Crow

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cheers malc. suspect that old immobiliser wiring then. when removing an immobiliser i meticulously trace all the wiring and determine its function - this avoids the possibility of such problems.

obviously it is equally possible that the guy did a perfect job, and it has nothing to do with him at all - so bear this in mind please, we can only guess.....
 
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sahtas1

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Thanks for the advice so far. The car is a UK car, delivered in September 1989, chassis 129066, engine 119960 for information. Will go through suggestions today and post outcomes!
 

Richard Moakes

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Being optimistic, I would look at the crank sensor, if that fails, then the EZL won't drive the coils, so no spark.
 

Richard Moakes

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Thanks for the advice so far. The car is a UK car, delivered in September 1989, chassis 129066, engine 119960 for information. Will go through suggestions today and post outcomes!


That's a very early car, I would love to compare it to my 1991 500SL :)
 
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sahtas1

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Richard,
I will email you some pics across of the car for you to compare to yours.

An update - the coils appear to have power but I still suspect the crank sensor and it isn't looking in very good condition so have ordered a new one (Bosch part 0261210055) at a very pricey £109 plus vat. I will fit it tomorrow when it arrives and update again. This is my first venture into Mercedes ownership and while the people (on this forum) are very nice and extremely helpful, the costs of parts seem very high compared to some of the other makes I have had (Jaguar, Renault Alpine, even Maserati!). Just glad I'm not sticking it into a dealer to do this! :rolleyes:
 

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The part would have been cheaper from Bosch service center,,you might be shocked to see how much prices have increased on other car parts
 

Alex Crow

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that £109 is a pricey gamble my friend. crank sensors are not usual suspects on this car.

did you check the wiring?
 

Richard Moakes

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This is my first venture into Mercedes ownership and while the people (on this forum) are very nice and extremely helpful, the costs of parts seem very high compared to some of the other makes I have had (Jaguar, Renault Alpine, even Maserati!). Just glad I'm not sticking it into a dealer to do this! :rolleyes:

Electrical parts seem to be very expensive, however mechanical parts always seem reasonably priced to me.

Ebay, Starpartz, Euromerc, GSF, Eurocarparts enable me to run my car for approx. half the price I would pay if everything came from the dealers.

Inchcape's online service is very good for parts as well, Domenico who processes the orders is very efficient and friendly.
 


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