Truck won't start

[PnwWoodsman]

After changing the fuel filter on my 89 Comanche, truck can't seem to run for more then a couple seconds, if at all. Engine turns over, and cranks, it just doesn't always combust. I'm no master mechanic, so I could use all the help I can get.

[Pete M]

any chance the filter is on backwards?

[PnwWoodsman]

Unfortunately the filter didn't have a arrow on it, but it said in and out. I put the in coming out from the gas tank, and out towards the engine

 

[Pete M]

If that's the only thing that has changed, maybe something is wrong with inside the filter?  maybe?    I mean, I've heard of plenty of other parts being bad out of the box, but not a fuel filter.   

[gogmorgo]

If it ran fine before you changed the filter, and now doesn't run at all, and the only thing that changed was the filter... Yeah I'm with Pete on this one. There's a slim chance pulling on fuel lines down there disturbed something, so it might be good to check the fuel pump's plugged in and there isn't a leak somewhere.

You should be able to confirm fuel flow at the rail either with a pressure gauge or even by just disconnecting a line and turning the key, just protect your eyes while disconnecting in case there's pressure. If you can hear the pump running but you've got no flow at the rail, then I'd go pop the line off the filter and confirm flow there before changing the filter again. 

Forgive the dumb question, but I've encountered filters with caps over the lines to prevent contaminant ingress... no chance at all they'd still be there?

[Fryedaddy]

I had a similar problem, kind of strange, I have an 88 with 4.0.

 

Mine wouldn't crank (turn over but not fire) so I replaced the CPS, it cranked then but wouldn't run for more than 5 seconds.

The CPS was a portion of the issue but the Fuel Pump Ballast was the issue once that was replaced.

 

I'm not sure if an 89 has it but on the drives side fender look for a rectangle shaped white piece (in front of the airbox) with two connectors.

pull the connectors and use a 15amp bus fuse to jump them.  After the fuse was installed mine ran perfectly.

I'm getting ready to delete the Ballast when I have a chance.

[Pete M]

cranking = turning over = engine is rotating after proper starter engagement

 

 

ballast resistor:

 

 

[gogmorgo]

Ballast resistor is likely if it will fire and run for a second or two then quit, as it is bypassed during cranking. 

Easy enough to test, just unplug and jump the two wires together to bypass it. If it fixes the problem then either leave it bypassed or find another one if you really care about quiet fuel pumps.