4.9 straight 6 It has 55lbs of fuel pressure at the rail & spark, starts when you turn the key but as soon as you let the key go it shuts off. key switch is moving the rod. so I was thinking the key electronics box, we have had an issue with the brake idiot light being on for the last month & I noticed a sensor on the pedal not sure if that could be involved with the running issue. heres the run down my wife was working yesterday half way thru the day the van wouldnt start she tried for an hour a friend came over lifted the hood & it started right up. she went to 2 more homes where she turned it off & it started right up stoped for gas & it started right up. arrived at the last home got finished up there & it wouldnt start. I arrived lifted the hood changed out a fuel pump relay it still wouldnt start had AAA tow it home. Got up this morning & it started right up. started all day & I couldnt get it to repeat the start issue. was on the phone with a friend & he had me put the shiffter to reverse & try to start it to see if the neutral safty switch was working, it wouldnt even turn over I then moved the shifter back to park & low & behold the problem returned. So now the problems back im hoping to figure out what to check. Who's got an idea of where to start?

 

sensor on brake pedal is for tail light rules that out. Im back to the key switch or ignition box.

 

There are a couple of causes for the brake red light being on. One of them could be the brake fluid level sensor located under the brake master cylinder. These were quite troublesome as I recall. Another could be a brake fluid loss somewhere and the proportioning valve has shifted. Best to check the truck over carefully for any brake fluid leaks. The level in the master cyl will go down for two reasons. One is a leak in the system and the other is normal front disc pad wear.
As for the intermittent no-start, check the inertia switch located on the passenger side kick panel in the truck . What you can do is give the area a strong rap and you will hear the steel ball roll and shut of the fuel. Then all you have to do is feel the depression on the top and push the plunger in to reset it. Does it have fuel and spark at the time it won't start?

 

thanks hanky

the solution ended up being
1: replaced computer 1 pin was bad & there was a burnt section on the board.

2: replaced the distributor control module failed for spark timer.