Okay an update on my no-start condition:
I no longer have a no spark condition. I'm getting spark at the coil and the wires, but the car will not stay running. It starts and makes an attempt at idle and then cuts out. I hooked a fuel pressure gauge and I have normal pressure at pump activation (47 psi, then when it shuts off I have 42ish psi). The pressure will hold for quite some time. When I start the car, it runs until the fuel pressure drops out and the car shuts off-seemingly from lack of fuel? No wetness or coolant around the opti, no reason to think it's been contaminated with water, changed approx 5k ago. Suggestions on what to do next?
-Dave'
96 LT4, Procharger

 

Fuel filter? A pinch is a fuel line somewhere?

RACE ON!!!

 

If it was the filter, how could it charge to 47 to begin with? I'm just asking I am lost on this fuel system business at this point.
-dave

 

Pressure requires little to no flow. If there is a restriction in the filter or line, the demand, of the running engine, may exceed the supply, causing the pressure to drop. It could be a super weak fuel pump, too.

RACE ON!!!

 

Oh! that makes sense. I've got holy big injectors too so now I could see how the fuel could be consumed too fast if it wasn't getting there in time. Any suggestions on diagnosing filter or pump flow?
-Dave

P.S. is there an avatar for downed cars? 11 sec. club is mighty misleading at the moment, I'm pretty sure the tow truck might be able to go across in 30 sec. with my car on the back

 

It must be a fuel problem if it's not holding steady pressure with the motor running. It'll be a bit less with the vac line hooked up and at lower rpm, since the regulator is vac operated, more vac, less fuel pressure.

There are several things that have been touched on. Fuel filter, fuel line obstruction (like a pinched line), the sock on the fuel pickup clogged with debris, the fuel pump dying off, etc.

The first thing I would do is check the fuel lines and make sure they don't look damaged. They run from the fuel rails down and along the frame rail under the pass side of the car (at least on the earlier cars, but I don't think that changed). Then change out the filter, which would be a good idea anyhow if you haven't done it in a while.

But, my guess would be the fuel pump. Mine got harder and harder to start as it died, and eventually it wouldn't start the car. It would pressurize the rails, but not hold the pressure under any kind of load. When the car would no longer start, I could turn the key on a few times to charge the rails and it would start for a second or two, then cut off.

Good news is that a fuel pump is pretty easy on a C4. Took me 30 min taking my time when I did it. It's also not too expensive. I think an oem replacement from napa was around 50 bucks and they had a new strainer (the sock looking thing on the pickup) in stock, which was a few dollars. You may or may not need a new gasket and the rubber piece that goes around the gas cap. I didn't need either and mine had a disgusting number of miles on the odometer and was 16 years old at the time.

I think there's a tech tip here on how to do it.

Chris

 

Allright, the psuedo-good news and the bad.
Changed the filter, changed the fuel pump. Car started up and run just fine. Let it run for about ten minutes. shut it down. Repeated this a couple of times while I was cleaning up thinking my project was done. Now I'm back to square one. The problem resurfaced when I took my fuel pressure gauge off the rail and reinstalled the autometer hook-up for the in car gauge(the gauge has been pegging out at 100, haven't started to fix that yet). I can't see any reason why the automete hook-up would be causing any of the problems. Anyone have an idea on what to check out next?
To review:
-Spark confirmed
-Too few pulses on IC module trouble code present -> I believe this is because my FAST computer now controls injector pulses and low resolution timing.
-Low manifold pressure trouble code present. I have a supercharger so I am guessing the vacum is setting this code.
-Car when running idled hesitantly and ran like total crap when I turned on the A/C (Like about to die)
-Replaced fuel filter and fuel pump, rehooked up lines and confirmed fuel pressure with analog gauge off of schrader valve.
-No fuel leaks seem to be present.
-Black smoke(very very rich) from tailpipes.
-Did not get a chance to test drive when car was running.

Thanks guys, I swear any of you who come around my area are entitled to all the frosty beverages you can drink.
-Dave

 

Unhook the fuel gauge and put the cap back on the fuel rail and see if it starts and runs again. If it does then you obviously have a fuel leak in the gauge system that is bleeding off your pressure.

 

Rehooked up the fuel pressure analog gauge. I'm getting the exact same symptoms I did before changing the filter and pump . So what would be next? there is no fuel leak that I can find, nor restriction. Had the car running again and now it's dead . I pinched off the return line and the pressure shot way up, like pegged the gauge at 100 up, but still the fuel pressure bled off until the car shut off. grrrr
-dave

 

Just a thought but try unhooking the vacume line to the regulator and see if it stays running. The only two thing I can think of is that the FPR is screwing up when vacuum is applied or that the FP is not getting power from the fuel pump relay after the first initial signal of the ECM (Think it is like 5 seconds or so). The other check is to hook a test lead up to the FP relay and just let the pump run and see if that solves the problem if it does start checking wiring.

 

Ok, now you need to unhook both fuel lines at the engine, the filter and back at the tank. Blow compressed air through them (high pressure!) and see if anything comes out of them. Next you'll need to remove the pump/sender assembly and check the lines on it for obstructions.

 

Any chance your VATS system is active and killing the fuel enable signal to the PCM. If that happens it will start and die.

 

Okay, I''ve determined (I think) that the fuel pump is not running once the car is started. It is charging the lines before start, but once the engine is on, it does not run. I verified this by pulling the liscense plate, gas filler door and listening for the pump, once the engine is on it is not running. If it was VATS, wouldn't the car not even crank over? Is there a way to run a wire to the pump that turns it on once the key is on? I thought I heard of someone doing that, but I'm not sure which one to jump.
-Dave

 

which wire is the fuel pump hot wire while the engine is running?
-Dave

 

Greetings. Just an update on my progress.
She's running again, though so rich I think I need to not drive around open flames ;-). The immediate problem creating the start then stall condition was a scotch adapter(you know the plastic thingies that bite into two wires to put them on the same circuit) had created an open to the fuel pump while the ignition was on. The engine was being starved for fuel because the fuel pump could not supply gas because it wasn't on. After much fretting over which wires were for what, I discovered that at some point I had an inline fuel pump to boost the pressure for my supercharged/stroked engine. I bought the car after the pump had previously been removed and this was the case for the scotch adapter being on the hot wire for the fuel pump.
As an answer to those who are concerned about their fuel pumps not meeting the demand of additional horsepower-my fuel pump is supplying nearly 52 psi at idle of pressure and 47 psi at full boost/wot. I have 42# injectors and the stock AC delco pump seems to keep up with demand with no issues.
Thank you to all who offered their advice to me. I really appreciate it. I'm now battling shut-down issues after a hard dash, but I think I will troubleshoot other threads before creating a new one since this seems to have happened to others before.
-dave

 

At leat one problem is down, I am sure you wil get the rest

 

Thanks for the encouragment. I really hope someday my brain will have information that is useful to others on this site. I'm new to the corvette world and the last car I built with this much hp was carb and didn't have any stinking computers :-).