I replaced my opti spark in April of 2010. I've since only put on 13k miles on it. So why when I crank it, does it not catch and fire up until always the 3rd attempt? The first two times it will always just crank. The third time it actually fires over. I've heard if this before, but can't remember what it was. If I remember correctly, its the opti going bad?

 

Doesn't sound like the opty, most likely the fuel pressure is not holding when engine is off. Try priming the system by turning the key ON & OFF several times before attempting to start. If engine starts right up after priming, there is a fuel problem. Bad check valve in fuel pump, bad fuel pressure regulator, leaky injector.

 

^^^what pete said. sounds like lack of fuel.

 

Or just turn the key on and listen for the sound of the pump. Once it primes (builds pressure) it will stop humming. Then try to start it.

 

unless you start the engine the fuel pump stops in a few seconds no matter what.

 

Ty guys for all ur input. I already replaced the fuel pump and sending unit w original Gm fuel pump and sending unit $950 and yes, I always prime before starting, sometimes it will catch after preloading once,but I usually need to prime the fuel system 2- 3 times. I never smell fuel the from outside the car, could the injectors be leaking internally? The fuel rail is always dry. Hmmm....

 

could also be the fuel pressure regulator. test fuel pressure and fpr
4th Gen LT1 F-body Tech Articles

 

What type of pressure is desirable?

 

if you click the link you would see this


Checking Pressure Loss in the Fuel System



A fuel pressure test gauge can be bought at your local auto supply for ~$35. Attach it to the schrader valve that is on the fuel rail. Schrader valve location on 1994-1997
Normal pressure when the engine is not running and lines have been pressurized is 41-47 psi. This same pressure should be observed at wide open throttle (WOT). Removing the vacuum hose to the regulator at idle "simulates" the same vacuum condition as during WOT (but is not a substitute for WOT testing as noted in the next paragraph). At idle (because of the effect of the vacuum to the regulator) pressure will be less than what you observe with the vacuum line off (less pressure is needed at idle because of the lesser demand). There may be anything from a 3 to 10 psi difference. Note: any indication of fuel in the vacuum line to the regulator, means the regulator is leaking and should be replaced. Check the line for fuel or the smell of fuel.

To fully determine that you don't have a pressure drop off during actual WOT situations, you should tape the gauge to your windshield and take it for a test run. This will tell you if the pump can meet actual fuel flow demands at pressure and not just at a "simulated" WOT condition (as when removing the vacuum to the regulator).

When you have a gauge connected and the pressure looks initially good and then bleeds off quickly when you shut the engine off, you can do a couple of tests to help you figure out where the pressure loss is.

What the factory manual says to temporarily install, is a set of "fuel line shut off adapters" (probably something the normal guy is not going to have available). You remove the fuel lines from the rail and connect these valves in between. This lets you shut off either side of the lines for testing.

You can do the same thing by pinching the flexible lines to shut them off, but risk breaking them. You might be able to do it (your risk) by using a needle nose vise grips and putting some scrap hose as cushions on the jaws. Then use that to clamp off the line just enough to seal it. Obviously, this is not the best way to shut off the lines and could result in breakage. Heat and age can make the hoses brittle. If you don't want to risk it, don't. It's just a suggestion.

You can use the fuel pump prime connector for pressurizing the system (jumper 12v to it to run the pump).

Watch your gauge as you jumper the prime connector. When you have good pressure remove the jumper and clamp off (or use shut off valve) the fuel supply line (3/8 pipe). If pressure holds, you have a leak on the feed line somewhere before it gets to the clamp (or shut off valve) or at the check ball in the pump. If it still goes down, release your clamp (or open shut off valve). Pressurize the system again, then remove the jumper and this time clamp (or shut off) the return line (5/16 line). If pressure holds, then the regulator is faulty. If pressure does not hold, you need to locate leaky injector(s).

If you can't tell a leaky injector from reading the plugs, you can look and see if injectors are leaking by removing the fuel rail screws and pull the rail and all the injectors up, so you can see under them. Leave them over the injector ports. Pressurized the system and look under the injectors to see if any are dripping.