84 won't start

[hdcwagsvette]

The other day I went out to start my 84 corvette and it cranks but won't start. I know it has plenty of fuel (3/4 tank) and spark. I thought for the hell of it let me top off the fuel and see if it starts. After adding 5gals it started right up. I went to the gas station to be sure the tank was full and it only took 1/2 a gallon. Fuel pump and filter are new. What is the problem? Can the fuel sending unit go bad or is the ECM not detecting there is fuel in the tank?

 

[Hot Rod Roy]

It's probably just a coincidence it started after adding the fuel, since you weren't out of gas. So it will probably do the same thing again some time. Back to basics (when it does it again): Fuel injectors putting out a fuel spray? (TBI makes this an easy test) Spark? Ignition timing?

 

[vetteoz]

. Fuel pump and filter are new. is the ECM not detecting there is fuel in the tank?

ECM "detects" nothing ; it runs the pump
Sender is for gauges only.
Can you hear pump run with part tank?
Check fuel pressure at rail when it won't start.
Maybe you screwed something up when you installed new pump?
A leak possiblely that gets covered when tank is full?

 

[hdcwagsvette]

Guess you are right, just a coincidence because now it won't start again. There is no fuel spray and no spark. The manual says to hook up a test light across the injector harness connector and see if the light blinks. It did not. I also pulled the hyper tech chip and put the factory chip back in thinking that could be the problem and it was not. Now its looking like the ECM or the distributor.

 

[vetteoz]

Any codes?
Possibly a bad connection /ground somewhere

 

[hdcwagsvette]

A couple years ago when it was acting up it had a code 32 that we cleared, then it had nothing. I haven't checked it this time, will check tomorrow.

 

[hdcwagsvette]

Went after the cheapest possibility first, (the ignition module) which has seemed to do the trick. The car has started every time since I replaced it. I'll keep my fingers crossed.