A year or so ago, I purchased a 1990 F150 Custom with the 4.9 Inline Six. Mileage was about 115K. It ran great but was hard to start, especially in cold weather. I've wrestled with it for about a year and recently, decided to to change the fuel injectors with a rebuilt set. After reading this forum and others, I tackled that job last weekend. I opted to remove the upper intake to do the job. For me, the hardest part was getting the new injectors back in the fuel rail and then back into the fuel ports. I put a little motor oil on the o-rings and worked them back in until I thought they were seated properly. After putting everything back together, the truck fires right up and runs better than ever, even in the blizzard this past week in SC. However, I am now getting a heavy fuel smell when the truck runs. I have not been able to find any of the injectors leaking. I have read that the Computer needs to re-learn something and may be causing the truck to run rich. Any truth to that or other suggestions? Because of the bad weather, I have driven it very little since the swap.

 

The EEC will constantly adjust the fuel trims based on what it sees from the O2 sensor. Still, the odor of running rich and that of raw fuel are noticeably discernible. I'd make absolutely certain you don't have a fuel leak.

 

Did you mistakenly put 19lb(yellow top) injectors in instead of the stock 14lb(grey tops)?

 

No, I used the grey 14lb injectors. After looking at it again, I think the number 5 and or 6 injector may not be seated properly. I'm vertically challenged and had a hard time getting to those, especially with my left hand. It may be time to seek professional help and take it to my mechanic.