RedKnight79

I've been reading through all these posts today got alot of info. I figured since this on my car, I'll start my own thread.
I have a 91 formula with a 350 tpi. When this little nightmare of mine started, I could start my car when it was cold with no problem. It ran like a champ until it would reach operating temp and would act like it ran out of gas and die and it would crank and no start after that. If i let cool down for awhile, it starts up only to have the same thing happen again. I figured it was a fuel issue. I posted a thread about this and somebody mentioned the ignition module. I has the module tested it failed so i replaced it. After that the car started and ran alot longer than previously. So i went on a test drive and drove around and when i heading back to home and was on the home stretch I put the gas pedal down to engage the detent and all of a sudden the car spuddered, was running rough, had no throttle reponse but didn't stall out and I limped home driving under 5mph. It felt like I was running on 4 cylinders. So next day I picked up fuel pressure gauge and duplicate that moment again and monitor the fuel press. Installed gauge, started it up drove it around and when i step on the pedal, it would sputter but didn't do the samething it did the night before. It would come out of it when i let off the gas. Doing this a few times I was able to monitior the gauge and it was jumping. Came to the conclusion it was a bad pump. I replaced the pump with a walbro 255 pump and since my gas gauge was off and my poteniometer on the sending unit was worn out, I replaced the sending unit also since I was there. So at this point I replaced the ign module, fuel pump and replaced sending unit to fix the gauge. After installing the new pump in the tank and got everything back together enough to for a test drive. I had 50 psi when the pump came on and around 48psi when it turned off key on. Had some troubles starting at first due to air in the lines but eventually started and got easier each time i started it. When it was running pressure was at 45-48 psi, which is good. When on a test drive, the car ran like a champ Got back home cleaned up my area and when I went to go to the store, cranks no start.
So I started from square one checked for spark at the coil and wires, good spark. Checked fuel pressure, got good pressure. I checked for codes and got the code 12 with no codes following, that gave me the assumption that the ecm is working. So I tested the tps sensor before I proceeded down the diagnoisis tree for fuel diagnosis it was .6v closed and was 4.8v WOT. Done tests where I had to pinch fuel pressure lines and led me to the fuel pressure reg. This caught me wrong cause in the beginning of all this fun when I first did fp tests before I found the bad pump, I would pull the vacuum line off the regulator and pressure would go to 50 psi on the gauge indicating a good regulator plus wouldn't the regulator leak if u pulled the vacuum line off? With that in mind I kept going and tested the fuel injector wires with a test light and had a flashing light on all injector wires while cranking. Checked and tested wiring to the fuel relay all ok. After those tests I cranked over the engine just to see what would happen and the sucker now had a hard start condition so i was happy that I was making progress but not finding a solution. It would crank over and eventually start but it would idle rough and then stall out. A few times when I did this the engine seemed to be compensating on the stitation and when it seemed to get itself out of it, it would sputter and stall out (like it ran out of gas). I watched the fp gauge and it maintained good pressure til the eng died and i checked for amperage at the fp test wire and had a little over 8amps so again I believed that the fuel pump and the ECM was working and I had good spark. So with that in mind the only thing I got left is the injectors. Possibly clogged? So tomorrow I'm going to do a pressure test to verify that. I also want to check resistance on them too. What is the resistance value on a good injector? I don't have that magic number in any of my books to compare to mine. If there is any more things to check, please let me know. This is one drivability problem that i don't wish on anybody. lol I'm already going bald, i don't need to pull the rest of my hair out A huge thanks for all those who will reply, I really appreicate it. Us Fbody guys got to stick together, part of a dying breed now. Good wrenching

RedKnight79

well today I prefomed a pressure test on all of the injectors and found the #3 inj was bad. I left it unplugged and it started up and ran So I learned today that a bad injector will prevent pwr going to all injectors. Which makes sense since they are in series and a break will kill the circuit. I hope my situation will help and give light to others having similar problems. Well time to order some injectors

flexj

I am having some of the same issues...how did you pressure test your injectors?

southbay08

get yourself a set of bosch lll's

www.southbayfuelinjectors.com

RedKnight79

To flexJ
What I did was an on-car procedure. The easiest way to explain is to prime the fuel system and when it kicks off u pinch the return line at the flex hose by the intake (u do this each time u test each injector). Then u have this box that is powered by ur battery and u hook up the other end to the inj, hit the button and it will pulse the injector to see if it working. Also on the injector pulsating tool there is 2 holes where u can stick in ur voltmeter leads to monitor voltage too. What I had was actually a Kent Moore J tool which is used at GM shops, a friend of mine actually had one. There is aftermarket verision of that same tool but I'm sure it is not cheap. That's how u would test an inj or u can do it unplug each injector one at a time and crank over til u find the bad one when it starts. Also u can take ur injectors to a local parts store and have them tested but I would only do that if I was for sure that i had a bad injector to prevent any uneccessay work.