When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
my friend just bought this truck and the fuel pump went out. so we changed it and the filter. we left the fuel line to the filter from the pump off and ran the pump for a second to flush the lines and a bunch of black stuff came out. so we changed the filter again and added more gasoline truck started right up after backfiring in the air inlet a few times then it ran smoothly for a few minutes then died again. it had sat in the guy's yard for five years before my friend bought it. but when he bought it we put a fresh battery in and tapped the starter and it fired right up and we drove it home then the fuel pump died and we replaced it. what would cause it to backfire into the air breather?
If it backfired into the intake, there is a good chance that it blew off a vacuum line or plug. After that, the engine will run poorly, or not start, and may throw a check engine light. Check the vacuum tree near the back of the manifold by the driver's side for loose hoses or missing plugs.
As to why it backfires, it seems to happen more with the EDIS engines, when the "waste spark" fires a plug at the wrong time, combined with a bank-fired injection system that's constantly spraying fuel into the intake port whenever the engine turns. It happens on my 4.0L if I don't hold the starter long enough for the engine to fully catch. The backfire almost always blows off a vacuum line or plug.