Ok, I have a 1971 Nova that i have swapped a TPI system into it runs a speed density setup and is stock except for the headers. I have been driving the car for about a year now and this is the first time it has done something like this. so hear goes.
The car started fine and as i drove it it started to have a skip to it. and was running rough all around. i drove it home and pulled into the shop and shut it down and tried to restart but it would only turn over.
Spark is good, fuel pressure is good, but i do have a leak as the pressure dropped rather quick ( down to 10 or 15lbs in 20 min).
I pulled the intake apart to check and make sure the injectors were not leaking and they are not. i also just turned the engine over to see if they would fire and got nothing???
I have power at all of the injectors on both terminals in the clips themselves? i thought you were only suppose to have power on one side and not the other?? i also turned the engine over with a test light hooked to the injector connectors and got a dim light? I also checked the injectors themselves and found that they would work when i would power them up myslef?
I know that these systems give problems with the injectors so it would not suprise me if i need to replace them. im just confused as to why they would work individually but, i can not seem to get the computer to control them, maybe they are just clogged and i can't hear them openining over the engin turning?
Also should i see a bim light when hooking the test light up to the connectors or should it be nice and bright? im wondering if the computer could be going out or possible bad ground?
Thanks in advance

 

Hi, dim light could be a bad ground, however it also could be something with distributor components affecting the injection pulses, however you mention you get a drop in reading on your pressure gauge for fuel. If the injectors arnt leaking, and you pull the vacuum hose to Pressure regulator and dont smell gas in the line,, Then most likely it could be a failed connection to the fuel pump in the tank itself. Typically these cars have a pulsator after the fuel pump then the hard lines to the filer then to the rails. IF that pulsator is a little loose it will back flow into the tank. The pulsator is a slip on, WHy would GM use slip on, on highpressure line<I have no idea. Typically this can be mistaken as a bad check valve in the fuel pump, so typically people swap the pump and ditch the pulsator for the include neoprene hose included with the pump and that seem to fix the problem, however it really only needed the hose. People tend to use self-adjusting clamps on the hose, screw clamps, and high pressure fuel clamp. I recommend the high pressure clamp that require a special tool to crimp permanently. The same clamps can be found on the return hose for the powersteering pump. If you get a lot of pressure when you open your gas cap and smell gas really bad afterwards, it might just be the slip on pulsator that slipped off and is misting gas through the pin hole leak and building pressure, mucho. If that happened it would explain your problem youre having but to drop the tank is a hassle. Theres ways on testing the pressure regulator and the fuel pump check valve. If i remember il post it. Theres somebody out there that knows. update: i think i remember now, to test the pressure regulator, put a hand vacuum pump tester and check to leak down meaning the diapram is bad. to test check valve, put a clamp on the return line by the tank and prime the pump by turn key on. it should sky rocket and drop. This isnt advice, just what i did to diagnose and solve my leak down issue.

 

Sounds like your ignition module took a dump. Bring it to Auto Zone and have it tested.

 

I go for ignition module as well... you need to have a couple on hand at all times.. when I drove my bird, I would have the stock ignition module and a stock coil, just in case I had ignition problems... my backup coil saved me once as it just stalled for no reason... ended up being a lose cable... which I ended up diagnosing at home a few blocks away...

 

Both terminals of the injectors WILL show positive voltage all the time when not being commanded on by the ecm. They are turned on by a pulsed ground if I remember right. The 12v positive on one terminal will travel thru the injector windings to the other terminal if not grounded. Also the injector driver holds the ground side at a positive voltage when not pulsing.
On a side note you should typically not probe an ecm input or output with a normal 12V test light. You should use a high impedance probe made for ecm testing. A normal test light will allow too much current to flow thru the ecm which most likely damage that circuit. You could also use a Noid light made specifically for injector testing. It's possible a short duration test light might not damage the ecm.
If you have VATS still enabled you might check that, this will prevent your injectors from firing. If I'm wrong on any of this someone please step in. This is all from past experience that I believe to be accurate. Also make sure your timing is where it should be.