1991 coupe , I put in Bosch 3 injectors ,a new fuel pump, new plugs ( a/c delco platinums which I just took out and replaced with a/c delco standard plugs ) the fuel pressure is 42 lbs and drops to 39 when running , when I take vacume hose off regulator pressure goes up to around 50 . Once it starts it runs fine except for a little stumble if you punch it if you ease into the throttle no stumble . After it has been cold started it starts fine 1 second of cranking . The problem is the cold start it take 10 attempts at least the there is a little puff of white smoke that clears right up . Seems other guys have had similar problems from the Bosch 3's what can I do ?

 

call FIC?

 

Turn the headlights on & then disconnect the battery negative or positive cable...
Wait a few minutes.. .
Reconnect the battery cable...
Turn the headlights off...
Start your Corvette without touching the gas pedal.......
And let it warm up fully till the main cooling fan(s) come on & turn off automatic...
Then drive your Vette away as you normally do in town & on the highway for at least 20 minutes driving time.....
You reset all the BLM's.
Block memory cells in the ECM reset to baseline & to your own driving style.
Your Corvette should drive & run better afterwards.
Start up easier also.

Good thing you have 50 psi fuel pressure.

I run 57 psi with my Bosch 3's.

Another topic I won't get into in depth no more on C4 tech main page.

 

Try cranking for 1-2 seconds, let off, key again and it should lite up faster. For whatever reason it takes the B-III several crankshaft cycles to pulse. The inj gets reference from the distributer telling the inj that the engine IS running and to continue fuel pulse. For some reason the B-III do not spray as liberally as the old stock inj, or they require a stronger signal...not sure which. I have tested and see pressure in the system that holds, I see the inj signals thru a noid lite, but it still wants to crank over longer when cold. Any start attempt after that until stone cold again is instant. The B-III have a different nozzel than the stock inj, and I suspect that they do not drip or bleed down as the stock inj did, so they have to cycle a couple times to get enough spray in the intake port to lite a fire..
Knowing that the inj does NOT actually spray at or in the cylinder or in the open intake valve, just toward the intake, the valve is not necessarily open as the fuel is sprayed since C4 systems are mostly bank fired. Later sequencial multiport EFI was timed with intake opening but that did little for power or economy in C4s.. Just a bump in efficiency.

 

Long crank = fuel pump leakdown see how long your pressure holds after shutdown.

 

My recently installed Bosch IIIs fire up instantly and have no pulse issues at all. Jon will check yours if you want. The problem is then elsewhere. The injectors are the end of the chain.

Driveability issues are usually ignition or fuel. Elimination of each possible problem component is the best procedure, and the FSM has a great flow chart for any symptom. It could be as simple as a cracked wire or as bad as leaking head gasket or cracked head (white smoke).

 

my bosch III's fire instantly cold. 10 attempts?!!

if we assume leakage it should be measurable, some plugs should be wet. if throttle is WOT at first start, that should eliminate the rich/flooded condition.

didn't see any diagnosis on ignition, which is possibly/likely the hesitation -unless we conclude that the injecrors are both leaking and not firing. tain't likely. retarded spark caused by ecm/ign module or base timing can cause what you describe.

if you suspect injs, follow the advice to call FIC.

 

If you punch it, If you ease into the throttle? Really? WTF?

Puff of white smoke? That's an indication of impending head gasket failure. Antifreeze burns white.

I'm not sure your problem is "similar". Any chance you didn't correctly diagnose a problem before throwing B3 injectors at it?

Have you done a pressure test on the cylinders, fuel line, and the radiator?

 

GREGG, I would take "white smoke" with the disclaimer that a puff of oil from valve guides looks white, esp if inside the car. more white than black or blue, from my experience with my 90. by the time you see it, it's gone.

 

White,
yank the heads.

 

Fixed the extended crank problem . It was the coolant temp sensor , replaced it and now it fires right up cold or hot .Bosch 3's work great !

 

so much for the idea that all "white" smoke is coolant. my experience is that a puff of white at start up occasionally is from valve guides.

that small puff wasn't part of your problem, as you discovered.

maybe pull the heads to be sure.