We have been working on a customer's TJ in the shop recently that was having some hard start issues when hot. We did all the typical recommended mods for dealing with under hood heat like the DEI heatshield and fuel rail wrap kit. We also wrapped the header and Y pipe with heat wrap as well as a hood louver kit. It was still having some chugging and sluggishness after a hot restart. I put some thermocouples under the hood near and on the fuel rail and the results were shocking. After a 30 minute drive and left to sit for another 30 minutes the fuel rail was approaching almost 300 degrees. When we restarted the engine it would slowly drop back to 175 or so. As a test we brazed some fittings on the stock fuel rail and rigged up a return line going from the rail back to the tank. The fuel temperature dropped almost instantly to ambient temperature. Driving the Jeep again for 30 minutes and hot soaking for another 30 minutes the rail was again almost 300 degrees, but the moment the key was cycled the temperature dropped almost 100 degrees. The hot restart issue was gone and the engine ran smoothly. Moving forward with this solution we designed a regulator assembly and fuel rail to be a return style system without brazed and modified parts. The regulator block is a direct replacement for the OEM unit and uses a Bosch 3 BAR regulator unit inside it. The fuel rail is bolt on as well. We did have to run a new fuel line from the back of the rail to the tank as a return. That was really the only custom work that had to be done. Everything else is bolt on. I did make a few extras and they are on our new website dedicated solely to Jeep parts.
https://texasjeepproducts.com/products/jeep-wrangler-fuel-pump-replacement-regulator-with-return
https://texasjeepproducts.com/products/jeep-wrangler-fuel-pump-replacement-regulator-with-return