Why don't they start right up?

[Schrade]

Does any one know with certainty why LT5 doesn't start right up immediately?

Was it the same way on the showroom floor?

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This is the first electronically FI car I've owned that didn't do so instantly. Even the first one I owned, an L-98 that was in a poor state of tune when I got it, would start immediately. Foreign, domestic, 4's, 6's, etc.

On RARE occasions, it WILL fire almost instantly. But most of the time, it's 2 - 3 seconds. And I'll let off the starter then, and re-try.

I thought I read once on the boards here that ECM had to see some crankshaft position first, before issuing fire @ the plugs; this would mean, if correct, that it WOULD have exhibited the same behavior at the dealer, when new.

Does anyone know DEFINITIVELY the answer here?

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[Kevin]

I thought I read once on the boards here that ECM had to see some crankshaft position first, before issuing fire @ the plugs; this would mean, if correct, that it WOULD have exhibited the same behavior at the dealer, when new.
this is what I've always heard to be the case also.

[BigJohn]

Never noticed!
Mine starts right up with a good battery.

[QB93Z]

It could be because the Crankshaft has to rotate until the Ignition Module gets a signal from the Crankshaft Position Sensor so it can determine the correct ignition timing.

Jim

[RyanChappel]

with new Accel injectors and a good (batt-tender maintained)charge, has to crank a couple seconds to fire...and I'm always thrilled it did...

[We Gone]

It could be because the Crankshaft has to rotate until the Ignition Module gets a signal from the Crankshaft Position Sensor so it can determine the correct ignition timing.

Jim

This is what I have read also crank needs to make one complete revolution, but it may also have something to do with were the sensor is at shut down.

[Fully Vetted]

It could just be in my head but I've noticed it seems to fire quicker when I turn on the ignition and wait a couple of secs before engaging the starter.

[USAZR1]

It could just be in my head but I've noticed it seems to fire quicker when I turn on the ignition and wait a couple of secs before engaging the starter.


I've noticed this,too.

[BigJohn]

Try starting my 32!

[Fully Vetted]

My Dad's '31 Model A starts so fast we had a standing challenge: If you can engage the starter at all and it not start he would buy dinner.

He never bought dinner....

[Tony Davila]

I believe there is a start delay built in in the PCM so that oil pressure builds before fire up. Helps with chain rattle.

I might be wrong.........maybe..... I had two different tunes in my Z and both started different with one longer than the other.

Just sayin..:)

[efnfast]

My car used to bark to life when I hit the starter. After I did injectors and starter, amongst other things, now it cranks. I read somewhere there was a 4 second delay build in.

[Pete]

I believe there is a start delay built in in the PCM so that oil pressure builds before fire up. Helps with chain rattle.

I might be wrong.........maybe..... I had two different tunes in my Z and both started different with one longer than the other.

Just sayin..:)


I also think something to do with Oil Pressure Sensor the one for ECM.

Mine used to start right up,after i changed out the sensor now cranks
a while before she fires up.

Oh well.
Pete

[Hog]

Fuel pump has to build pressure? Would explain an engine that fires quicker if you leave the key in the RUN position for a couple seconds before continuing on to the CRANK position.

There should also be a switch somewhere that will shut down the fuel pump(s) with a loss of oil pressure. Makes accident scenes much safer rather than having the pump continueing to pump fuel through a busted supply line.

I'm curious what would happen if you turn the key, the pump primes for a few seconds, then will shut off. If you turn the engine over manually(not using starter/key), will the pump turn back on? If the pump energizes again, the crank reluctor/sensor is involved. The L31 engines will energize the pump twice for every crank revolution. I can grab the front crank pulley from underneath, not sure this is possible on a Vette?

The ZR-1 era Testarrossa's take a while to fire as well.

[Hog]

Fuel pump has to build pressure? Would explain an engine that fires quicker if you leave the key in the RUN position for a couple seconds before continuing on to the CRANK position.

There should also be a switch somewhere that will shut down the fuel pump(s) with a loss of oil pressure. Makes accident scenes much safer rather than having the pump continuing to pump fuel through a busted supply line.

I'm curious what would happen if you turn the key, the pump primes for a few seconds, then will shut off. If you turn the engine over manually(not using starter/key), will the pump turn back on? If the pump energizes again, the crank reluctor/sensor is involved. The L31 engines will energize the pump twice for every crank revolution. I can grab the front crank pulley from underneath, not sure this is possible on a Vette?

The ZR-1 era Testarossa's take a while to fire as well.

[Roadster]

It could just be in my head but I've noticed it seems to fire quicker when I turn on the ignition and wait a couple of secs before engaging the starter.

I've noticed this,too.

That is the way I learned to start my 82, turn the key to the on position during first start-up and after the pump primes (2 seconds) start the engine, fires right up. On restarts it is instant, I also learned that giving it a little fuel especially in cold weather, it will fire up without the engine cranking.
Also on the 82 CFI, the ECM needs to see oil pressure of 4 psi before the engine will start. I would imagine our ZR-1s have a parameter in our ECMs very similar to the 82 ECM.

[Schrade]

Looks like NO ONE knows for sure?

I always wait until FP shuts off before pulling trigger.

Fuel pump has to build pressure? Would explain an engine that fires quicker if you leave the key in the RUN position for a couple seconds before continuing on to the CRANK position.

There should also be a switch somewhere that will shut down the fuel pump(s) with a loss of oil pressure. Makes accident scenes much safer rather than having the pump continueing to pump fuel through a busted supply line.

I'm curious what would happen if you turn the key, the pump primes for a few seconds, then will shut off. If you turn the engine over manually(not using starter/key), will the pump turn back on? If the pump energizes again, the crank reluctor/sensor is involved. The L31 engines will energize the pump twice for every crank revolution. I can grab the front crank pulley from underneath, not sure this is possible on a Vette?

The ZR-1 era Testarrossa's take a while to fire as well.

[BigJohn]

I was told by my dealer when I first got the car to turn on the ignition, then wait six seconds before starting.

[Mystic ZR-1]

I was told by my dealer when I first got the car to turn on the ignition, then wait six seconds before starting.

Who told you that Tom Q or Will? ;)
Colchester?

[BigJohn]

Who told you that Tom Q or Will? ;)
Colchester?


Jimmy!

:neutral:



YES!!!

[badbob326]

I got my 1991 new, the start thing always be there. It seems the longer they sit the longer it takes.

[Made in USA]

Mine starts within 2 seconds tops. After reading the thread about the vapor canister, I just got a new one and am going to change it this weekend. We'll see if it changes anything.

[badbob326]

I also have a 90 DRM 600 it the same with the starting and no canister. It's just a ZR1 thing. Just do not over heat the starter it will be ok.

[Paul Workman]

I've always let the fuel pumps run until they quiet before rolling the starter.

When the 90 has been sitting for a week or more, it's a "Mississippi-one, Mississippi-two, Mississippi-three - aZOOM! But, after running some that day, it seems to fire anywhere between 1-2 seconds, if not before.

Ami's 91 Z, after passing through Pete's Mystery Garage, never seems to wait more than a second - IF THAT - before TURQ MONSTER roars to life.

Worth mentioning? I had a couple backfires on my 90, back when I first got it. But, later I read here to hold the starter ON for about half a second after it starts. Since I've been letting the pumps reach pressure AND holding the starter on a tad after it fires, I've never had a backfire since, IIRC. (Now that I went and said that, just watch it sneeze and blow all the hoses off!:p)

[Hog]

Does the LT5 use a "wasted spark" ignition, or an ignition that fires the plug both during the compression stroke AND the exhaust stroke, or whenenever the piston is near TDC?

The reason I ask is because GM's other DOHC V8 the Northstar 4.6 liter V8 did use a "wasted spark" and my 300hp L37 Northstar would also require some extra cranking time before it started, even after letting the intake pump perform its pre programmed cycle when te ekey is in the run position, before turning further to crank the engine.

[Fully Vetted]

Strangest thing happened yesterday. I went to start it and decided to not wait at all. I just turned the key all the way and BAM! it started immediately. And it had been sitting for several days. Strange...

[8cam]

I simply turn the key like a normal car, and mine fires almost instantly...like a normal car. In fact I had no idea there was a "start thing." Most of the time when I hear long start times, I suspect low fuel pressure. My car has had almost all fuel components replaced, and it clearly does not lose fuel pressure for a long time. Maybe this is just something that has happened over time? In any case it does not sound normal.