I have an 88 W150 with a 318 tbi. It is stock with 134k miles. I am having a bad time restarting it after it runs for a while (20 minutes or so). Sometimes I can bump the key and it will start, but if it sits more than 5 minutes it cranks and cranks but will finally catch. I replaced the distributor because it was corroded and the Hall Effect sensor was as well. (I did clean it up and had same problem but replaced it and installed a rain deflector over the distributor.) I removed temp sensor wires and set timing to 10 btc according to the sticker on the hood. I have replaced the fuel pump and lines, rebuilt the tbi and a set of plugs and wires. I think the timing may need advanced, but I haven't had to think about any of this in 25 years. Once it starts, it runs fine, never a stutter or stammer. the IC motor was replaced when i rebuilt the tbi. I did not replace the cap, rotor, plugs or plug wires when I replaced the distributor.
Any suggestions on this problem will be much appreciated, and I will do any testing suggested.
Thanks for your help.