Weird connected faults
 

Hi
I've got a 300 24 sl. 1992. Every so often all the following faults start happening at once. The ABS warning light comes on. The MPG dial reads incorrectly. The car is very difficult to start. Wont't catch for a while then takes some time when it does start to build up revs. I am sure these faults are all connected. Any Ideas? It is now becoming a more permanent problem.