no cel ever, weak spark
 

have a 89 bronco 4.9 5 speed 4x4..
cranks, some times farts, weak spark. no CEL ever. not koeo not ever. is good.
checked alot of stuff. check out my post at http://www.fullsizebronco.com/forum/...-question.html
over fueling has nothing to do with it by the way

wondering if anyone has seen this situation before, thanks

The lack of a CEL when cycling the key from Off to Run and the inability to pull codes are good indicators you have a bad computer.

Since the truck tried to run that indicates the EEC relay is pulling in to supply power to the computer. Given the symptoms above still points to a bad computer.

Pull it out, open it up then inspect for signs of a leaking capacitor and/or burned components.

Al, Scott and the others are leading you in the right direction on the other forum.

thank you very much rla2005, you're suggestion led me to some new information.

the owner i got the bronco from had originally had trouble getting it to run. they had purchased a new computer and done A BUNCH of other things to try to get it running. i thought it was a bad diagnosis so i put the old computer back in. so it turns out the CEL was burnt out but i still wasnt getting a CEL after changing the bulb. so i went back to the "new" computer and i now get a CEL!

obviously the first thing i did was try to crank it. still no start. so i am getting the codes 63, 31, and 84. i looked up what they are and they are basically low voltage to 2 sensors ( TPS and PFE ) and a failure on one sensor ( EVR ). I havent yet verified that the "new" computer actually matches for the engine/trans/year but i hope it does.

you guys have any ideas what might be causing these codes? other than the obvious EVR sensor failure, which i havent looked into yet. going to this weekend. thanks very much

rla2005 knows more than me. And he knows allot more about codes. But I personally have successfully used this crank no start trouble shoot decision tree:

Part 1 -How to Troubleshoot a No Start (Ford 4.9L, 5.0L, 5.8L).

that is a really good link, although it glosses over what i think is causing my no start ( the weak spark ) the spark is there on time on all cylinders and there is plenty of fuel. did all the tests like compression, fuel pressure, checking timing

the more i think about it these codes would not stop it from starting. i've read many posts where they had gobs more codes and the damn thing ran so i just dont understand

new coil and ignition module, took out the jumper on hanging off the distributor and put the time close, ran for 10 seconds then died

every time i try to start it pops and possibly back fires? i did a compression test all cylinders came up great wouldnt they not come up good if the valve timing was off? i had the timing cover off the gears looked fine and stuff. i dont know.. any help would be appreciated i'd love to drive this

-- redacted double post --

yea computer was replaced with a good one, you were correct about that. checked codes and got bad tps. found out that tps was not installed correctly and was also broken. replaced TPS

finally got it running, it runs pretty good! the new TPS is i think what did it. I siphoned all the gas out, put 10 gallons of fresh gas, and bought new sparkplugs (rather than just cleaning the old ones, i bet this made no difference). So yea it runs pretty good still gotta time it and all that but thank you guys very much.

edit : just wanted to follow up on this for anyone that has the same symptoms. no start or barely starting. the 3 main problems were BAD gas, improperly installed/broken TPS, and non-functioning computer(as well as a burnt out CEL bulb).

I know my posts are terrible and hard to follow. so thank you all for helping me out.