I have a 1990 F150 XLT Lariat with the 300 CI inline 6 cylinder EFI. I have owned the truck for almost 17 years with virtually no problems. The truck has 143,000 miles on it. Recently as I pulled up to a stop sign the truck started skipping. When I got back home and started pulling plug wires the number 1 cylinder wasn't firing. So far I have replaced all the plug wires, all the plugs and the fuel injector for that cylinder with no success. Any help will be greatly appreciated.

 

How does the rotor and the inside contacts of the distributor cap look?

 

Check out this thread. Your experience may differ.

https://www.ford-trucks.com/forums/1...-no-spark.html

 

Need to see if spark is getting to the plug, that thread that sheep man cited is a good one to start on.

 

Thanks for the comments everyone, sorry it has taken me so long to get back on here. I am getting fire thru both the plug wire and the plug, both of which are new. Since I was getting fire into the cylinder I figured the injector was bad so I replaced it. The cylinder is still dead. I haven't had a chance to do a compression check or to check voltage on the wires going to the injector. One thing I have noticed while test driving the truck is that the engine seems to smooth out about 35 mph. When running about 50 mph I floored the accelerator pedal and the truck down shifted and accelerated quickly, the engine sounded smooth and the power output from the engine felt normal. To say the least I'm at a loss.

 

Time to do a compression check to see if that cylinder is good enough to make power.

 

Ok, did compression check on dead cylinder ( #1). With compression gauge installed, started the engine gauge went to 120PSI. When I mashed the release button the compression fluctuated from 65 to 70 PSI with the engine idling. To verify that this was correct readings I installed compression gauge in #4 cylinder, which is operating correctly, and got the exact same readings. I was going to do a voltage check on the wires going to the injector but my volt meter died, so hopefully I can pick one up tomorrow and check it. I did disconnect the wires from the injector on the #2 cylinder and it started missing on that cylinder. When I replugged the wires that cylinder went back to normal. Hopefully I'll know more when I get another volt meter tomorrow.

 

You started the engine when doing the compression test?

 

Yes. Should I have pulled the coil wire and just spin the engine over?

 

Yes. Should I have pulled the coil wire and just spin the engine over?

 

Not exactly. Remove all the spark plugs, disconnect the coil connector and remove the fuel pump relay. When cranking the engine depress the throttle- you want it fully open to allow as much air as possible to fill the cylinder.

 

Thanks. Will give it a try. Now we know why I'm on a forum

 

I’ve leaned things here as well but you could have Googled (or your favorite search engine) “How to do a compression test”

 

I went to youtube after I got your reply and one video said do it like you said, another said do it one plug at a time, both said to pull coil wire and disable fuel pump. I agree with you that pulling all the plugs is best. Thanks again.

 

I want to extend a big thank you to all who commented and made suggestions on my post! The problem is resolved. The problem turned out to be a blown intake manifold gasket. Merry Christmas and Happy New Year to everyone and Thanks again for the help!