BlackHawk23

Ive been having this problem the past couple of days with my car. Its been very hard to start, sometimes taking up to 8 tries to get it running. When it finally does start, it shakes like hell and knocks like its missing horribly. I can give it some gas for about 30 seconds, it shakes more and then it clears up and runs fine until the next time i go to start it. The car does this whether its hot or cold. Any good pointers of where to start? Should i check for injector pulse? Or would it more likely be ignition? Open for any good ideas!

cnorton

...or, a clogged fuel filter, weak fuel pump related issue. One of our LT1 cars developed the same problem and it required a new pump.

c

BlackHawk23

Is there a good way to test for a weak fuel pump? I dont have a whole lot of test equipment here.... If i can find a fuel pressure tester, how much pressure should i have at the rail? Thanks

Injuneer

First thing to do is check your fuel pressure. If it leaks down too quickly, it may cause hard starting. Hook of the pressure test gauge to the Schrader valve, and see what the pressure is when the pump primes (~40psi). Then see how fast the pressure leaks down. If it drops too fast, you may have leaky injectors, a faulty check valve in the fuel pump, or a faulty fuel pressure regualtor.

BlackHawk23

Ok, i checked fuel pressure. It had about 45 psi when the pump primed the system, then dropped to 42 psi. Running pressure is 35 psi. The strange thing is that i could only get a couple injectors to flash the noid light. A couple of them would work sometimes, and not work sometimes. I definately dont have all 8 pulsing. Could this be a bad ground somewhere, or maybe a module?

Injuneer

If you have an injector (or several) that aren't firing, you should be getting DTC 18 for injector electric circuit problems.

Check the fuses for the injectors - there are two, each supplying 4 injectors (not all on the same bank). With the key on, check for +12V at the pink wire in each injector harness plug. Pull the plugs off the injectors and check the resistance of each injector. Should be in the range of 12-15ohms.

Odd that it clears up and runs fine eventually, with several injectors not firing.

BlackHawk23

Im not getting any mil lamp, but dont have a scanner to check codes. I checked for voltage at each injector koeo and i have between 11.5v and 11.8v at each pink wire. Resistance at each injector is 12.5 to 12.8 ohms. How can i check the control side? Where is the pcm grounded? Could i have a bad ground somewhere?

BlackHawk23

So i checked for injector pulse again today, and noticed something i didnt notice yesterday. When i unplug each injector, and plug in the noid light, it wont start flashing for about 30 seconds. Is this normal? I got the car to run today, and if i shut it down, it may or may not start back up. Im so confused! Think i may have a problem with my pcm?

BlackHawk23

Are there any other tests i can run on this car without having a scanner or a scope? Im trying to figure out if i have an issue with the pcm, or something in the wiring. I really need to have this car back on the road but cant afford to start throwing parts at it. Where can i go from here?