Guys,

After dealing with a hard start issue (Would take between 3 -4 cranks to get the car going). I finally replaced the fuel pump and the problem was solved.

However, it now takes about 5 seconds on the first crank to get the car started. I would like to know if its normal or if it should start right away when the key is turned?

I think I might be having an optispark poblem, I just need help diagnosing this problem.

Note - I've rechecked fuel pressure as a precaution and the fuel pressure is normal before ignition. The pump primes up to 40 PSI.

 

mine starts in less then a second... literally crank, crank, vroom!

Is your starter lugging at all or does it spin the engine well? Check your battery voltage also while cranking... the PCM needs enough juice to work right. Low voltage will cause a lot of injector offset which could be your issue.

 

Started is good. Checked out voltage today and its good as well. I am replacing the fuel pressure regulator as a hunch.

 

throwing parts at these cars is not a good idea, as they can be complicated, and expensive. Do a little investigating first, such as pulling the vacuum line off the regulator and look for gas or the smell of gas from the regulator. If not, its probably good, and I would take the 4 bolts holding the fuel injector rails down, pull the injectors and fuel rail off the manifold carefully, then turn the key on without starting the car. This will tell you if you have a leaky injector. That is what I would be more suspect of. So do those two things first, as they are FREE. Your new fuel pump could also have a defective check valve, so a fuel pressure tester could be a good tool to have anyway.


hth

andy schuck

 

The injectors are only sealed on the fuel rail. If you take the fuel rail off and pressurize the system you risk blowing out an injector soaking your entire engine bay and garage with gasoline.


You need to check your battery voltage while activating the starter. You will need a friend to start the vehicle if you don't have remote start equipped on the vehicle. It will be less than 12V, could be as low as 9V.

Check the fuel pressure key off then key on, then engine running, then with the vacuum hose off of the regulator. Replacing a regulator may not solve your problem if those pressures are okay.

 

There is very little risk in blowing an injector when doing the testing as descibed in post 4...in fact it's a pretty good diagnostic tool. If you pressurize the system but don't crank the engine you can readily see if you have a leaky injector.

That said, I wouldn't start there. I would try to start the engine in 'flood clearing' mode. Put the accelerator to the floor and crank the engine over. If it starts faster that way, start looking for fuel system issues like leaky injectors, etc.

 

I wanted to replace the fpr with an adjustable one anyways. It seems that after about a week of driving around on start the car isnt priming to 40 PSI anymore; I have to prime the car before starting it to get it going.

 

Adjustable fuel pressure regulators are one of the most overestimated and unnecessary modifications for these cars. Rarely is one needed, and the questionable safety issues (both in mechanical reliability and injector pulsewidth modulation) are often overlooked.

For the record, my 455whp 383 uses a stock regulator, Walbro 255, stock lines and rails with 42# injectors and maintains right around 80% DC. The only time I plan on upgrading to an aftermarket regulator is if I were to change to aftemarket fuel rails. And even then, fuel pressure would remain stock.

Out of curiosity, why do you feel you need an AFPR?

I always turn the key to ON and wait until the pump is finished priming before I turn the key to START. Have you done a fuel pressure "leak down" test to verify you don't have a leak (be it in the fuel tank via the feed line, check valve, injectors, or regulator)?

 

When I do that on my 1996 Z28 it will not start at all? I have same issue my car will not sart up right away. I have to prime it (igniton on and off) 2-3 times then it fires right up. I have not checked it with a fuel pressure gauge yet? But why does mine NOT start at all when I try to start it floored?

 

Maybe it's not flooded. Maybe it's not getting fuel at all. If you're losing fuel pressure at prime because of a faulty check valve in the fuel pump or fuel line leak internal to the tank, there is no need to put it in "clear flood" mode, and it's not going to start on the resulting reduced fuel. Clear flood is going to help if the injectors are leaking. Not for other problems that reduce the fuel pressure after prime.