Glow plug light flashing
2000 Ford Focus 1.8 turbodiesel 160,000 Km. For five years it has stopped every 3 months or so and gone to tickover. No response on accelerator. Turn off and restart engine and it's ok for another 3 months. Except 9 months ago and 2 days ago it did the same thing every minute on the same 30 Km journey and with same wet weather. Next day it started and did it once or twice and then no more problems for months. The car is nearly 14 years old and has been a workhorse carrying building materials. It's not worth spending much money on it. Any ideas?