92RS4US

working on a '97 Firebird LT1 just got done rebuilding the engine, the damn thing will not start! if you hold the pedal to the floor it attempts to start but nothing. Security light goes out, no codes, new plugs, new injectors, new fuel pump and filter. At this stage I pulled the opti-spark off and found oil/dirt inside it. Ordered a new one I'm hoping this cures it. If not I'm gonna just drop and cry like a little girl!!!!! I just don't know what else it could be. I did get it to run on seafoam with the fuel system disabled and used one of those fuel injection flush canisters. Ran like **** but ran nonetheless. Hooked the stock fuel system back and nothing. Oh and yes it has gas in the tank... any ideas would greatly be appreciated.

red rock

iTrader: (2)

Plugged fuel filter, pinched fuel line, faulty fuel pump, Have you disconnected a fuel line and seen if you had fuel pumping out? Fuel lines on backwards?

Mayt13

Try connecting a fuel pressure gauge to the fuel rail before/during cranking. Also check your fuses (fuel pump, ecm etc.)

Also did you double check your timing chain gears position? Even one tooth off can wreak havoc and make it easy to end up with wet cylinders during cranking.

Gumby

starting fluid is the best test ever for no start.

It it does try and run, you know its a fuel problem,

If it won't even pop, you got bad spark.

Only time it can confuse you if it does start with it, and then the car runs n starts fine then on. Then ya just knock on wood.

92RS4US

As stated, new fuel pump and filter. Timing chain lined up correctly. Optispark was installed correctly. I replaced the Optispark and my new one is messed up it set a P1371 key on eng off. I have a new one I need to change it then try again. Right now when I crank it I have to hold the pedal to the floor and it trys to start but dies. Acts like its flooded. I checked the injectors, none were stuck, all hold pressure with no leaks. I will keep you posted.

92RS4US

So new optispark again, no more codes. Go to crank with fuel pump relay disconnected, it starts, idles then dies, naturally no fuel. Restarts a couple of times to get fuel out and dry up. Code P0336 CKP sensor ckt performance pops up. Crank hasn't been learned obviously, cleared code has not come back. Several restarts and dies. Plug fuel pump relay back in, cranks over, have to hold throttle down 100% and will start then die. Check grounds, ok. Unplugged MAF sensor, no change. TPS reading 0% to 100%. MAP sensor, KOEO 4.92v. BARO 97Kpa, MAF will read when cranking. Have cranking RPM. Have low and high resolution signal. Have sufficient spark. Have fuel pressue and volume. As stated new engine, cranks evenly good compression 195psi. I'm lost.

Gumby

check ign switch n the lot, maybe only good spark/fuel when in the start position, not run.

Mayt13

Hey, I have something to think about, maybe you miss wired an injector! None of us third generation guys would know to mention it because we have non-sequential 'batch fire' injection. But I think the LT1 went to sequential fuel injection in '96. Double check your routing. Since its apparently a fuel issue, this could be your gremlin.

92RS4US

sorry guys I know it's not a 3rd gen car but I thought since some of you guys run LT1's I'd give it a shot. On the '97 the injectors have the cylinder#'s on them and they are connected correctly. The spark plug wires are connected correctly. UPDATE: just put a new ecm in it and same thing. Thinking it could be a VATS issue. Going to check the resistance at the connector under the dash. Is there a way to totally bypass the system? as in bypassing the module completely aside from the resistor trick? and not wanting to buy a bypass module?

Gumby

should be the first thing anyone does when they buy a vats car is disable it, causes more trouble then its worth. Thieves learned long ago which cars are easily stolen or not. At the time it came out, vats was great but its done it jobs, and is just a PITA for the most part.

92RS4US

ck key resistance at connector under dash, has 1640ohms, ck hz at pin 25 on ecm from bcm, 46hz. just cranks like its flooded, hold pedal to floor it starts and then dies. Unplug fuel pump relay starts idles for a couple seconds then dies.

OrangeBird

iTrader: (1)

This sentence is all but screaming "one or more injectors are stuck wide open , or your regulator is leaking !" Yes , you may have pressure at the rail , but have you done a leakdown test ? One or the other is flooding your engine with the pump properly running , and with the pump relay pulled you are able to run out the flooded condition by repeated starting attempts .

92RS4US

you would think so, but the injectors were sent out and flowed and tested all work good. Pulled them out and double checked to see if they hold pressure and didn't leak after being pressurized.

92RS4US

UPDATE: PROBLEM FOUND!!!!

So I threw in the towel and paid to have a professional diagnostic service to come out and check this thing. I'm embarrassed to say this....the problem turned out to be plugged exhaust! We disconnected the AIR tubes at the headers to let the exhaust escape and low and behold...she started and runs!

Sadly this car is a career ender for me. After 29 years of being a professional mechanic/technician I had met my match. Never thought the cats would be THAT bad that it wouldn't allow the car to start. Good it runs, bad I'm now unemployed.

Gumby

nearly common as people think they last forever or are to cheap to replace them. [ they can last forever as in gas flows through just fine, but they don't clean forever ] an O2 should last forever but they get contaminate just the same.

If the engine needed rebuilt, how did it go? could of dumped stuff in there, those tiny path ways are easily clogged if there isn't enough running time to burn off what goes in. Also why oil has been losing zinc, it causes cat problems.

red rock

iTrader: (2)

Don't beat yourself up too bad, we all have had issues kick our butt if some would admit it. I had a 86 monte do the same thing, it took a mechanic 2 hours to figure it out 25 years ago. Just be glad it's fixed.

92RS4US

I never really got the full story on this car, it came from Michigan and had the heads replaced. It came in running on 5 cylinders. Found 3 injectors not firing but getting a pulse. The coolant was nothing but oil/water goopy mess. I was able to get it running despite fouled plugs and bad injectors. Never could find the root cause of the oil/water mix. Engine was completely rebuilt, block magged and heads pressure tested and checked for cracks. Oh well its over now. They can throw new cats in it and call it a day.