E12 518i hard starting problem!?

[Eben Bosman]

Help!
My 1982 518i has this puzzling problem! Car starts easy enough when cold in the mornings. When good and hot, stopping at the shop and running in and out, not more than 10-12 minutes away from car, she starts immediately. Problem is when returning to the car after say 20 minutes or more. Motor spins over but nothing! After about 2-4 minutes of turning the starter motor on and off, she eventually starts, but very rough, sometimes on 3 cylinders, before eventually settling on 4 cylinders again and smooth. I changed the ancient Bosch spark plugs for new NGK's, but still the same. Tried fuel injection cleaner and valve ease, still the same. Motor has 233k km on it, but really still very good, no smoke, very little oil usage. Motor quite, no loose tappets either. I'm using the Shell lrp replacement additive and Caltex petrol. Any ideas!?

 

[Blue Shirt]

Check if any of the injectors is leaking.

If the engine is cold or has been standing for a short while, it will not drip enough fuel into the cylinder to cause a problem, but when standing for a longer period will eventually flood the cylinder.

 

[Sankekur]

As above, get the injectors checked out, this sounds very much like a leaking injector(s) problem.

I have had a very similar issue and it was injector leaking related.

 

[Eben Bosman]

Thanks guys.
Can I do the check myself, or must the car go to a qualified mechanic?

 

[Blue Shirt]

Just run the engine for a few minutes, switch off and pull the injectors one by one. Check the tip carefully, you should easily see if one or more is wet around the tip.

The alternative is to remove the injectors completely and have them tested at a Bosch agent.

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Also check the cold start valve if your car has one, the early Bosch K-jetronic systems had this. It is essentially an extra injector in the intake that assists with enrichment of the mixture for cold starts. This can also leak fuel into the intake and cause hard hot starting.