Stephen G

Hi, I have a 1993 Z28. The problem I'm having is the car is extremely hard to start after setting all night. It turns and turns to the point that It will kill the battery. It keeps firing out of the intake. You have to get the car seemly flooded before it starts. After you get it started the car runs excellent, and will start well the rest of the day. The car has as much power as ever.
The car has a new fuel pump, and new spark plugs.
Any help would be very much appreciated.

Injuneer

Did the problem occur before or after you changed the fuel pump? Check the fuel pressure, to see if the pressure drops suddenly after the pump primes.

Check the coolant temp sensor in the water pump housing for accuracy.

GRIDERMAN87

try priming the pump turn the key on and off a couple times

Stephen G

I'm not sure when it started its kind of a long story. The car had been running poorly, and then finally would not start.
I brought it to a mechanic and told him i thought the optispark was failing. He checked the car out and said my ignition switch had a faulty wire. He said this was my no start problem, so he put a new ignition in it. After it still would not run right, he checked the fuel pressure and found it to be very low he installed a new fuel pump. The car still would not run right. He had the car for over 8 months and was to busy work on it any further. I decided it was time to try and fix it myself.
I brought the car home, got it started it was very doggy and was not running up to par. I looked it over and found a broken vacuum hose. I fixed the hose and the car immediately ran as good as it ever has. It actually burned rubber when it shifted gears at 40mph.

It seems to be getting gas as it blows all kinds of black smoke when you get it to fire up. I have been using the car now for about a week and it runs perfect besides the starting issue. I know im going to burn my starter out before to long.

Injuneer

OK... if its flooding, put the accel pedal on the floor BEFORE you turn the key to "start", and hold it there until the engine starts. Do not "pump" it - that accomplishes nothing. If it starts easier with the pedal on the floor (aka "clear flood mode"), it may be a different problem.

Stephen G

ok I'll give that a try in the morning when it gives me a issue. I was putting the peddle to the floor to clear it out, but did not put it to the floor before i turned the key on. I have found i have to put the peddle down to just under a 1/4 and then it will stumble and eventually start.

Stephen G

I gave the pedal to the floor a try this am, and no go. It will only fire seemingly when I put the pedal a little less then a 1/4. It then will start popping out of the intake and what not and eventually start.

Stephen G

Does anyone have any ideas on my problem? Any help would be greatly appreciated.

Paxky99

Did you ever figure this problem out? My 93 lt1 just starter this. Same thing press throttle petal down a little and excessive cranking it will finally start. Putting the throttle to the floor nothing.

Injuneer

“Stephen G” hasn’t signed in to this site since 2012.

Is your problem EXACTLY the same? Engine takes excessive cranking before it starts, with backfiring through the intake, then runs fine once started?

Paxky99

Yes exactly the same.

GaryDoug

Sounds like it is not flooding. I would check the TPS since it starts eventually with slight throttle. If the pcm sees it as wide open with no pedal pressure it won't deliver any fuel. Just a wild guess by a car computer geek ;-)

Chimera96

Paxky...

in addition to advice offered, You need to confirm what your fuel pressure is when you turn key on and what it is after engine starts. Should be 42-47 KOEO and drop about 5 psi once running. You will need a FP gauge with a Schrader valve attachment

If "fuel pressure" is good, then pull vacuum nipple off FPR with engine off, ideally once you shut engine off after running. If there is any sign of fuel in that nipple the FPR (fuel pressure regulator) is bad This is a long crank before start issue of the FPR going bad.

The backfire through intake, assuming that is also a symptom, is often opti spark or ICM...but rule in/out fuel delivery before going to ignition diagnostic.

GaryDoug knows his way around data...sensors like the one on the front of WP reading wrong temp will f with the PCM.

Aside from the 2 very qualified response you got, this site is very helpful

4th Gen LT1 F-Body Tech Aids (shbox.com)

Paxky99

Thanks for the reply. I've checked the fuel pressure and it's pretty much perfect. I'm starting to think it is the opti, with the weather change I try to start it in the AM and it won't even try to kick over but as it warms up in the afternoon it will kick over after a long crank and with a little throttle. The opti is fairly new but I bought it at Napa as a remanufactured. Does anyone know a reputable place to buy a good remanufactured ac Delco or delfi or know of another brand that will be good? Thanks again
Oh and by the way it's a 1993 LT1.

Injuneer

On a cold day, when the starter is cranking the engine, but "it won't even try to kick over", 1) check for spark at the plugs. Also, 2) look at the tach while its cranking to see if the tach needle moves up a couple hundred RPM. That would indicate the Opti is working.

Do not assume its the Opti without doing some real diagnostics.

If it ends up being the Opti, go here:

https://petrisenterprises.com/collections/frontpage