hey guys, this is my first post here but I've used this site many times for help before.

anyway, I have a 99 bravada and for some reason it wont start. I drove it sunday and monday just fine, I didn't use that car tuesday, and I went to start it this morning and all it will do is crank. I pulled the codes and it's only got 1, for p0122 tps low input. I checked the fuel pressure purge valve and the pump was priming. We replaced the pcm a few years ago. What are the odds it went again?

what do you guys think the problem could be? it ran fine since I put it back on the road a few weeks ago (I use it as a winter car) and now it wont even start. I noticed the tach would bounce back and forth when I would crank it I don't know if that's normal but thought I would throw that in as well. I'm going to try and change out the distributor cap and rotor as well as the tps tomorrow but right now I'm stumped.

any and all help would be great
thanks
Bob

 

What brand did you replace the pump with? If it was an airtex, chances are good that it is bad. But still, I would start with a fuel pressure and leakdown test.

 

^^^X2^^^ Just because its priming doesn't mean its got enough pressure to start the truck or keep it running. Like 50 said do the pressure and leakdown tests and I bet you will have the answer to your problem. If you aren't sure how to do it just do a search and you will find all the info and specs you need!

 

ok guys, weird but good news my bravada started, I got a pressure tester yesterday but it was down pouring so I didn't feel like doing it, but I hooked it up, turned the key on and went to check the pressure and it was at like ~47psi so I tried starting it and it started! I have no idea if it was maybe bad gas still in there or what but it started, smoked like a pig for about 5 minutes and then calmed down. but hey it started. thanks for all the help!!

 

There's the problem..... low fuel pressure. Key ON, engine OFF, fuel pump running, pressure must be 60psi to 66psi and must remain above 55psi for at least 10 minutes after the pump shuts off. Check pressure and leakdown and post your results.

 

but I was reading in the repair manual that it should only be 41-47 key on not running and 3-10 less running, but it doesn't bother me right now because it's running like a champ but we will see come morning time I guess.

 

Must have been a Haynes or Chilton manual. They're both good for learning how to change oil. Beyond that, put it back on the shelf and use a GM factory shop manual.

On your 1999 Bravada, the poppet valves require a minimum of ~43psi of fuel pressure before they will open and allow fuel into the combustion chambers. Next step is check maximum fuel pump output pressure at the fuel filter. Fuel flow and pressure must end at the pressure tester. While the pump is running, pressure must be 73psi to 108psi and must remain above 55psi for at least 10 minutes. If it fails either part of the test, check for battery voltage at the fuel pump module connector, (grey wire) and less than 5 ohms resistance from chassis ground to the fuel pump module connector, (black wire). If voltage & ground are good, the pump has failed and needs replacement.

 

ok well I went to go start it this morning and no go, so I hooked the tester back up and it was at about ~60 with the key on so I'm guessing new fuel pump for me oh joy

 

Erratic pump operation could also be a poor or loose connection for the pump somewhere. If it ends up needing a pump, use AC Delco or Delphi only. Keep us posted.

 

60 at the test port could be Ok, if you look at Hook's post those high # 73-108 are at the filter. By hitting it at the port you are not ruling out a bad regulator or confirming a bad pump. It needs to do two things 1) Hold the high pressure at the filter (pump is good) 2) hold 60-55 for ten at the test port. With small effort you can pop the plenum and look for fuel wash down. These are areas of, let's call it "cleaner then the rest" most often golden in apperance as opposed to all gunky as the whole thing should be. It indicates you got gas leaking in there. The reason I bring this up is you said when you did get it started you had alot of smoke.