Thumper33

For lack of knowing what else to do, I made a few movies and experimented a little. This first movie is what it always sounds like when I try to start it. You might want to right click and save. The first one is about 7 MB, and the 2nd one is about 12MB.

http://www.offroadtoystore.com/pictu...engine-run.avi

I was monkeying around and thought... I wonder what would happen if I try to start it w/o the ETC module plugged in. So crazy enough, after I unplug it, it will run a little longer before it dies. Here is a movie of that...

http://www.offroadtoystore.com/pictu...ngine-run2.avi

I figured I'd also go take some pictures of those three vacuum ports so you can double check that I'm thinking of the same three... I'll get those pictures shortly.

mullenh

iTrader: (1)

if it is not the vat what did you use for a fuel pressure regulator? oil pressure sender installed? any check engine lites? codes?

Thumper33

Here are those vacuum port pictures...







and one more just for giggles..

Thumper33

Would the engine turn itself off if it wasn't getting oil pressure?

Thumper33

for a fuel pressure regulator, I used the 2000 corvette regulator/return setup.

I haven't installed the oil pressure sender for my gauges yet. Would the engine turn itself off if it wasn't getting pressure?

There are no codes in the computer right now.

I haven't looked at the engine check light. I expect it to come on after the engine dies right?

Speartech

iTrader: (14)

Oil pressure doesn't have any affect on running or not.

The check engine light should come on with key on, and remain on while cranking, until the engine starts.

You might make sure that cranking rpm continues to register on an extended crank. Maybe unplug the coil pack connectors and crank the engine for about 10-15 seconds and confirm that your laptop reads cranking rpm the entire time (hopefully your software is good engough to give real time data).

You may also want to take out a spark plug so that you can observe spark while cranking. Remove plug, hook plug wire back up, run ground wire from spark plug threads to engine block. Also on the same cylinder unhook injector plug and hook a small light buld to the plug. Then have someone crank the engine while you watch the spark plug and light bulb. This will require two people obviously; one to turn the key while you watch. Have them keep cranking and not let off even though it starts briefly and then dies. Then when it dies while they are still cranking, you can observe what goes away; fuel, spark, or both. This may tell alot about what is happening.

They make tools (spark tester and noid light) to check this:


......but you can improvise with stuff around the house.

Thumper33

New Update. I hooked up a noid light. The light flashes two or three times and then stops. On the cycles that it runs a long time, it flashes like it should for 4 or 5 seconds, and then it dies as the noid light stops flashing.

Either...

1.) The computer is telling it to turn off...

2.) There is a drop in voltage that is making the computer stop telling it to fire.

Those are the only two options.

So far, I've tested my voltage lines to makes sure they never lose voltage, but that was only with a test light. I'm going to now test with a volt meter and see if that tells me anything different.

I also have a spark tester, but I'm waiting for a buddy to come over to help me with that one. I can't see the spark from inside the cabin.

Thumper33

Lets talk about the crankshaft position sensor. Is it possible that this would be bad but isn't throwing a code? Maybe it doesn't need that signal to start since it starts right away, but then sees that it doen't have this signal so it kills the motor?

Also, I'm still puzzled by the engine's occasional ability to run for 4 to 5 seconds. If I try it over and over, then it will only run for 1 second. But it seems if I unplug something and plug it back in, or let it sit for a while, it'll run for 4 or 5 seconds before it dies. That HAS to be a clue.

Thumper33

Just to try to eliminate one more thing, I ran a 10 gauge wire from my battery, straight to both of the ignition wires. I also put in another ground wire to make sure that it wasn't a grounding problem. It didn't make any difference.

mullenh

iTrader: (1)

hang in there guy we will get an answer for you. i will try to remember to ask the guys at the shop next week

Thumper33

I finally got to test spark. The spark does NOT stop when the engine dies. As long as I crank it, it will keep sparking. I didn't expect to see that actually. Does that tell us anything more?

So the fuel injectors stop firing, but spark does NOT.

ls1stang

iTrader: (38)

I noticed in your pics that you don't have a pcv, where is the vac. line for that connected to. I'm not sure if that has anything to do with it.

Jamie

Thumper33

ummm... I guess I'm running this engine as I got it. Where would that go? I don't know what that would do to immediately stop the engine, but maybe it's something to think about.

bczee

iTrader: (12)

You appear to have the hose.. on pic #1, it is laying on top of the intake.. it goes to a tube that Y's, one side goes to the back side of the valve cover on the passenger side, The other runs up front to the PCV and into the TB on the passenger side.. In pc #2.. it looks like it make be connected or running from the TB ok.. you can see it just below the right fuel rail.
No sure how much of a vacuum leak it would cause. but it would be one !... (I can try unplugging mind tomorrow.. unless someone know or can do it before I do)

mullenh

iTrader: (1)

i think you are thinking of an f-body 2000 ls1 they changed it on the vette

Thumper33

bczee - I looked over that hose and the Y. Everything looks okay there, although they're not the tightest seals they do look like they seal. I'd be interesed if someone would unplug that from their running motor to see if it dies. I suppose I could try to plug mine to see if that does anything. Would that hurt the engine if I tried to do that?

ghettocruiser

iTrader: (17)

So the injector noid light stops flashing right as the engine dies...? Ide say it sounds like the PCM is cutting power to the injectors.

What else besides VATS would shut down the injectors shortly after firing? Is the vette PCM looking for some other signal that the f-body PCM doesnt require??

I remember someone else on the boards using a vette setup having strange problems that the f-body guys werent having.

Its just so weird that it fires and runs the engine over at speartech. Darn LS1 gremlins...

Justin

mullenh

iTrader: (1)

i think you are on to some thing and it does involve the vat. go tto go into the computer and disable something however he did say that it would run the test motor so ?? now what..........? i am going to have to ask some one

please spec out exactly what you did for fuel pump, corvette regulator, and the return line. and does the fuel pump stay on ? can you hear it?

ghettocruiser

iTrader: (17)

Yeah I cant say its VATS related...because John did the programming and knows whats up. Plus it runs the darn test motor.
$10 says its some silly sensor that the computer wants to see that isnt getting a good connection or something. Or one of the thin wires that make up the engine harness has a small crack in it or something. I hate tracking this sort of stuff down. I dont have a huge scan tool that can pinpoint a problem with an individual circuit or sensor.
I just cant think of anything else that would shut down injector power like that after only running for a second or two. The thing isnt really running long enough for the PCM to check sensors and realize there is a problem...

Justin

Thumper33

I dawned on me that although I have the engine grounded to the battery, and the body grounded as well, I don't have the frame grounded directly. Not sure what that would have to do with the engine, but I'm brainstorming here.

Also, Is it possible that a sensor can be bad and not throw a code? Like maybe my Cam position sensor, or Crank Position sensor is bad but it's just not throwing a code? I'm tempted to try replacing those two sensors. I don't know how fun those are to replace though. They don't 'look like easy work.