SloFormula

First off hello to everybody. This is my first post in this excellent forum. My vehicle of choice is a White 1991 350 Formula Firebird. Now on to the issues. This car was stored for 3 years and rarely driven by me in that time. My father needed a vehicle to drive so I gave him the bird to use until we found him a new car. The bird slowly started to give him trouble (never mentioned to me). He states that the car would die at stoplights and take a few cranks to re-start. Finally one day it just wouldnt start anymore. Well after sitting for 3 months I finally found time to go look at my poor car again. Upon initial inspection she would fire up for a few seconds than die. I tested for spark and fuel pressure and both turned up ok. I ohmed the injectors and found one bad one. sooo I dug through my pile of parts and found a used injector from a rail off an old Z28 of mine. I swapped the bad injector for the good one and the car ran and idled great for 10 minutes. I turned the car off to inspect everything before I drove it. Well after that the car would not run again. It would only fire up when I pressed he pedal to the floor while cranking it (essentially a limp mode that shuts off the injectors) While performing this step the car fired up and revved fairly easily. The second i would remove my foot from full throttle the car would die. SOo I assumed I needed all new injectors. Sounded like a perfect time to upgrade to some Ford 24lbers. Ordered some flow matched injectors swapped them in and the car will still only run if the gas pedal is to the floor. I am essentially looking for any advice into figuring this issue out as I would like to drive the car to storage before it snows. I will be giving the car a full tune up this weekend to eliminate any issue with a possible week spark from old plugs. My other question is, is there any sensor that controls when the injectors fire other than the ecu? I am not very familiar with the TPI engine. Hell I wouldn't care if the car bairly ran just so I could drive it the 35 minutes to my house so I can work on it in my garage instead of outside. Sorry for the long read, any and all help is greatly appreciated and yes I have tried the search function which is what lead me to purchase the ford injectors. I need to get this car running right so the modifications can begin. It is sad when the V8 performance car is slower than my 4 door family car by a few seconds.

MP81

A friend of mine had the same issue with his '92 Crown Vic. Wouldn't start unless you floored it and kept it floored.

What they found to be the problem was moisture on the spark plugs - not sure what it had to do with a fuel issue, but after they changed them, it ran fine.

Check those.

SloFormula

See thats my next theory that the plugs are soo old that they aren't igniting with the fuel being sprayed into the combustion chamber. This saturday is the fun of changing the plugs and wires.

CreepingDeath94

iTrader: (4)

Do you have any codes? Check engine light on? I had a similar problem with my '87 T/A years back and it was the MAF (Mass Air Flow) sensor. Though you probably have a Speed Density set-up on that '91...but just thought I would throw it out there in case maybe you have a MAF motor in it. Not sure if the Speed Density set-up could potentially have the same issue if the sensor takes a dump...but may want to check. Sounds like the ECU is having trouble telling the injectors how much fuel to deliver based on incoming air. Mixture issue. May want to see if there are any sensors that dictate what fuel mixture/regulate fuel delivery needing replacement.

TexasSilhouette

iTrader: (4)

One injector won't cause a no-start, a misfire maybe but not a no-start.

TPI 91 SD l98s already run a little fat so your bigger injectors without updating the code just made that worse. It is conceivable that you will carbon foul your plugs in time.

I seriously doubt the spark plugs and wires are conspiring to quit simultaneously and kill your motor, I'm sure your barking up the wrong tree there too. The wires? Have your tested them or do you just want to change them for the fork of it? If you have the extra $$ go for it, the parts houses won't mind. Again, I can't imagine all eight wires deciding to quit together.

I suspect that when you changed the injectors you may have caused another problem.
Are you sure your MAP sensor is connected?
Fuel Pressure Regulator Connected (Vacuum)?

When you floor it, it goes into clear flood mode (little fuel like you said). If it fires off then, it may be an indication you are getting too much fuel. Both the MAP and FP regulator can cause that. The oversize injectors will exacerbate the problem.

Things that can cause a no start
No Spark – Module, coil, pickup and every now and then a rotor.
No (or too little) Fuel pressure – pump and/or associated wiring.
No fuel injected – No signal from the ECM, no signal to ECM (Module)
Too Much fuel – leaking FPR, MAP, freaked out electronics.

SloFormula

All of your comments are appreciated. I have tested fuel pressure and it is rock steady, I have spark so that is not the issue. I just know that the spark plugs are very old in the car and since I have new wires already I figure I might as well change them while I am swapping plugs. In my younger haste I had installed bosch platinum plugs(yeah I know they suck...of course this was literally 5-6 years ago. Rememer the car was in storage for a few years. soo I will update this weekend after I work on it on saturday.

Slow89Iroc-Z

TPS bad? MAP sensor bad?

SloFormula

Could be MAP. The TPS tested within Spec. At this point it could be a bad ground somewhere.