Sporadic starting issue

[RichLo]

This problem has been slowly getting worse and it started a month or so ago.

The truck is a 1993 k1500 5-speed and has a new fuel pump and fuel filter 2 years ago along with a TBI rebuild with new fuel pressure regulator components. Only thing that isnt new is the fuel injectors.

So, most of the time it will start up and run just fine with no problems at all. Once in a while it will crank for a while then I have to hold the gas pedal open for a second or two and it'll fire up. Now, I just tried flipping the air cleaner lid because I didn't think I needed that pre-heater in the summer and it fired up just fine immediately after doing that but the next day nothing. Girlfriend needed it and she said it cranked and cranked but no fire with pumping the gas pedal like a carburetor so she gave up. Then I got home from work and the same think crank, crank, crank and no fire with all different throttle positions. I didn't think it was fuel related because of all the new parts but to eliminate fuel I dumped some gas down the throat and it fired up and ran just fine, revved and no stumbling at all once it was running.

Now, what would cause this? I un-flipped the air cleaner lid that night just in case that was the issue and it fired up no problem the next few days and it ran fine driving down the road. Before I flipped the air cleaner lid it was just a random annoyance but now I really want to figure out the problem so I can have her rely on in again without any worries. I'll check fuel pressure this weekend when I get time but I dont think that'll be an issue with the new parts

 

[sntrym]

Try testing the Throttle Position Sensor. If it's giving inaccurate readings, you will experience what you are describing.

 

[Mountianjustice]

I'm betting on cap,rotor,ignition control module related and when you were in there working on the air cleaner you bumped it. I would start with checking all the plug in connectors on the cap and the coil especially the two connectors on the bottom of the distributor just under the cap at the back. Good luck this can be a nightmare I know I started at the rotor button and worked my way out. Naturally it was the ECU behind the glove box. The absolute last thing in the chain. Even did new injectors and still wouldn't start I was devastated for weeks and at wit's end. Try getting a loaner ECU if you can they are super easy to change and are $11 at my local upullit