1993 Jetta Mark III won't start sometimes

Hi,

I have a 1993 Jetta Mark III. About a half of a dozen times it has failed to start. We replaced the battery after diagnostic tests didn't turn up with anything. It tries to turn over but it won't, it seems that if you let it sit for a little while it will start however once that didn't work and we had to have it towed. That is when we had the battery replaced and diagnostic tests done. We garage we don't have any other problems and we had a tune up last month. There is about 118,000 miles on her and we have had a lot of work done, let me know if you want details of the work done.

We were wondering if it could be a fuel issue; pumps, injectors etc. Does anyone have any ideas? Thanks in advance