I have had a leaking Fuel Injector for over 100,000 miles! It filled the top of the tappit cover with boiled fuel and it turned into Tar.You will notice a black oil drip on the front left side of the head/tappit cover. REMOVE your plastic cover on top of the engine and inspect the injector valley. It will be obvious if your injector/s are leaking.
Now if the injector valley is filled with the tar you will need to replace an injector seal/s.There are two way this will go, and the $ differance is big.
The tar is going to get into the injector fork bolt threads, and when you remove the bolt on the fork to remove the injector it will SNAP! now you need to 1. pull the head, have it cleaned and remove the snaped bolt. 2. buy a new head at $2,700.
So it is best to clean all the tar out of the valley, Buy chipping and using solvents then heat the injector bolts so the tar will thin from the heat and release the bolt to be pulled. 7 out of 10 sprinters I have looked at with 100,00 miles had signs of leaking injectors!!!!!!!! So let my painfull story be the lesson of the day. you can E-mail me at jfrogers01@yahoo.com if you need more info. Thanks J F Rogers (Express-1 3 1/2yrs)