Bahhh !! Cranks but won't start.

[tonylong]

I thought I read recently, either in this forum or one of the others, that all 8 injectors fire at once, not right bank, left bank as many of us thought previously. :confused

Can someone confirm this?

Jim S.

I'd hope that each injector fires only when needed. I'd like to know for sure too.

 

[tonylong]

Update (the plot thickens)
Fuel pressure is good hot or cold.
There is spark, replaced all plugs, cap and rotor.
There is signal at each injector.
No gas odor.
Removed and replaced all gas, old stuff smelled odd, kinda "weak". Mechanic thought might have too much ethanol.
Refilled with ethanol-free gas. (I hadn't known there was a place in town that had that. Seems I was the only one that didn't know, Duh).

Will start so so when sitting for a while (coupla hours), runs rough, and quits when somewhat warm - 130+.
Will then crank but not restart.
If I squirt "starting fluid" (ether I think) into the intake air tube it will start but soon dies.

Next step is to pull injectors and see what's in there.

Bahhhh squared. At least I got thru the summer top-down weather OK. Now I've got until April to play with the problem, in an unheated garage.

 

[tonylong]

If it turns out to be injectors, should I look into replacing them with Ford injectors? I remember reading here that they were better and cheaper than GM. Since my local dealer closed I don't have a good source for discounted GM parts now.

 

[gmjunkie]

Sorry Guys,there batch fired!! Left 1,3,5,7 Right 2,4,6,8!

 

[bill5674]

thanks junk ,was hoping you could back me up on that.it is startiing to sound more like injecters to me now.sorry can`t give advice on the fords ,heard soome guys run them,but i put gm back in mine...bill

 

[tonylong]

Sorry Guys,there batch fired!! Left 1,3,5,7 Right 2,4,6,8!

OK just to clarify - do you mean that the entire left bank is fired, then the entire right? If so, then is there any advantage to this as opposed to just firing the whole lot at once? It would simplify the computer's logic. Just shoot 'em all, every rev. Let each valve suck in what it needs. Kinda just maintains a constant fuel/air presence throughout the manifold. Like carburetors used to do.
Sounds like my kinda plan: shoot em all, let God sort it out.

 

[gmjunkie]

OK just to clarify - do you mean that the entire left bank is fired, then the entire right? If so, then is there any advantage to this as opposed to just firing the whole lot at once? It would simplify the computer's logic. Just shoot 'em all, every rev. Let each valve suck in what it needs. Kinda just maintains a constant fuel/air presence throughout the manifold. Like carburetors used to do.
Sounds like my kinda plan: shoot em all, let God sort it out.

Each injector shoots 2 times every revolution,I guess it's so the fuel can vaporize better,and the ECM can adjust the air fuel ratio more evenly!! And while I'm thinking about it,have you checked the Inj 1 and Inj 2 fuses in the panel at the right end of the dash?? If 1 of them is bad or corroded and not getting a good connection,It will make it run rough as hell and not start so good!!

 

[tonylong]

Each injector shoots 2 times every revolution,I guess it's so the fuel can vaporize better,and the ECM can adjust the air fuel ratio more evenly!! And while I'm thinking about it,have you checked the Inj 1 and Inj 2 fuses in the panel at the right end of the dash?? If 1 of them is bad or corroded and not getting a good connection,It will make it run rough as hell and not start so good!!

Ooooh excellent idea junk. It's easy too. Just my kinda job. Idiot-proof. Well maybe. I could still drop the fuse into some inaccessible spot where it will rattle and drive me more nutz.

 

[91 Black Convertible]

found it...

O.K. I found the thread in that other Corvette Forum that talked about this subject and here is a quote from it.

...interesting however, tpi's from gm fire all 8 at once contrary to popular belief. The 2 fuses are for the load but the grounds for all 8 are common. Here's an excerpt from gm performance. I was always under the same impression untill I put on two noid lights on the oppisite banks.
"Most early EFI systems were batch-fire systems where the ECM fired all eight injectors simultaneously. Usually batch-fire systems fire the injectors once per engine revolution. This way, the injectors could be sized small enough to be more easily controlled at idle. Later, sequential EFI systems were refined to fire an injector a few degrees before the intake valve opened. Generally, sequential injection offers more precise fuel control at the price of increased complexity. But on production engines, the benefits are more in the area of emissions and driveability than in performance"...


So, does anyone know for sure? What can we use as the ultimate source in this case?

Inquiring minds want to know...


Jim S.

 

[tonylong]

Nother update:
Per Junk's idea. I removed the 2 injector fuses. They looked good and so did the entire fuse panel area. No corrosion or dirt. I polished the fuse tabs and replaced them.
She started and ran good. I let her run awhile, popped the throttle linkage, she revved up and kept running smoothly.
After a few minutes, when the temp hit 100+, i shut her down, Wouldn't restart. Cranky, but no run. Hmmmm.
Went to inspect the local Pub, and Pubesses for about 2 hours. Came back. Started up fine. Smoothly purring.
Pulled the 10 A fuse, she slowed and stumbled a little, replaced the fuse, back to purring. Pulled the 20 A fuse, Whooaaa didn't like that at all, bad stumbling,nearly stalled out, replaced fuse, back to purring. Revved up decently. Shut her down, no restart. Cranks, no run.
Double Hmmmm. Noticed the exhaust less smokey, too.
No fuel smell. Haven't actually tried running on the road when she's purring. I'll try that next, around the block just in case I gotta walk home again. Maybe run to the Pub, it's nearby. Ask the Pubess her ideas on this.
Can't hurt.
I'd take a shot at pulling an injector if I can see how to disconnect the wire cap, and if I can just remove it without messing with the manifold or other stuff.
I don't know what to look for, but what the heck. I'm bored and willing to try.
The mechanic can't get to it until next week. He want to pull injectors and maybe flush them. I'm still thinking bad gas is the cause.
I found out I can call the PA Dep't of Agriculture to learn about testing of gas. We'll see.
[[[ End Transmission ]]]

 

[John Robinson]

Check This

You said that you were able to get it to start by spraying fuel into it. The one thing you have not checked is the TPS. I don't know for sure on your model but on my 93 the TPS tells the ECM what the throttle opening is and the ECM then responds with the right fuel amount to the injectors. If the TPS is breaking down with heat then the ECM will sense a no need for fuel and will shut it down. It may also think that the engine is flooded and shut the fuel off so the engine can be cleared out. In that case the moment it has fire it restarts the fuel to the injectors when you have it in a not start cycle after running for a while try spraying fuel into it and if it starts and runs replace the TPS.

 

[tonylong]

You said that you were able to get it to start by spraying fuel into it. The one thing you have not checked is the TPS. I don't know for sure on your model but on my 93 the TPS tells the ECM what the throttle opening is and the ECM then responds with the right fuel amount to the injectors. If the TPS is breaking down with heat then the ECM will sense a no need for fuel and will shut it down. It may also think that the engine is flooded and shut the fuel off so the engine can be cleared out. In that case the moment it has fire it restarts the fuel to the injectors when you have it in a not start cycle after running for a while try spraying fuel into it and if it starts and runs replace the TPS.

I believe my 89 ECM works the same same way as yours.
I was advised to check the TPS and MAF.
Is there a way to check the TPS itself? Where the heck is it? I have lotsa time, and VOM. If I can get to it I'll check it. thanks.

 

[onedef92]

Sounds like it could be a bad Ignition Control Module (ICM).

Have you removed it and had it bench-tested, too? They can test ICMs at NAPA, AutoZone, etc.

My car did the same thing when my ICM went without warning, resulting in the crank, no-start condition you're describing.

 

[John Robinson]

TPS

On my 93 You check the voltage between the Blue and Black wire with the key on and the throttle closed it should read around .40 to .50 volts then as you open the throttle the voltage should climb up until at WOT it is reading somewhere from 4.0 to 5.0 Volts ( rule of thumb it should be approximately 10 times the reading at WOT then it was at closed throttle.

I used some straight pins to push through the wires and then used alligator clips to fasten my voltmeter to the pins. I would suggest you get the smallest pins or needles you can to push through the wire because they are thin and you do not want to damage any wires inside the insulation.

 

[tonylong]

On my 93 You check the voltage between the Blue and Black wire with the key on and the throttle closed it should read around .40 to .50 volts then as you open the throttle the voltage should climb up until at WOT it is reading somewhere from 4.0 to 5.0 Volts ( rule of thumb it should be approximately 10 times the reading at WOT then it was at closed throttle.

I used some straight pins to push through the wires and then used alligator clips to fasten my voltmeter to the pins. I would suggest you get the smallest pins or needles you can to push through the wire because they are thin and you do not want to damage any wires inside the insulation.

Aha !! Another Idiot-proof test I can do. thank you

 

[John Robinson]

Aha !! Another Idiot-proof test I can do. thank you

That's the nicest thing anybody has said about me in a long time thank you

 

[tonylong]

Update. Very interrrestink.
If I wait a coupla yours, she'll start right up and idle just fine. No stumbling, or roughness. As she warms up, temp 100 say, then she'll stumble, POP, etc, exhaust gets a little smoky. She won't then restart, crank, but not run.
waiting a coupla hours - same thing.
I don't want to pull the injectors and cost me up to $1,000 if it's not likely to be the problem. I don't think that injectors would work cold if they're clogged or bad. Any opinions on this? I don't know much about injections systems, I'm a carburetor guy. I'm just being simplistic and thinking "broke is broke".
Need feedback here.
(BTW I haven't checked out the TPS yet, I need to find the VOM first GOK where it is).

 

[southbay]

No need to spend $1000 we can clean your injectors for $15 per injector, or you can purchase a set of the "new style" Bosch Designlll injectors. We have them for $150.00 per set. We have sold hundreds of them to corvette ownere and we have gotten fantastic feedback on them! www.southbayfuelinjectors.com

 

[tonylong]

No need to spend $1000 we can clean your injectors for $15 per injector, or you can purchase a set of the "new style" Bosch Designlll injectors. We have them for $150.00 per set. We have sold hundreds of them to corvette ownere and we have gotten fantastic feedback on them! www.southbayfuelinjectors.com

My estimate included labor to remove/reinstall the injectors. I believe it requires removal of the manifold, that's where the labor comes in. I'm estimating high.

 

[southbay]

Before you pull your injectors, check your Water and air temp sensor. Most likely the H2O sensor.