nmay

I have no power/ pulse to my injectors. it all started with a head gasket leak. I tore everything off all the way down to the block to make sure to replace all top end gaskets.
In the process i decided to change the distributor, coil, plugs and wires, distributor modular, oil sending unit, fuel pump, fuel filter, tps sensor, ecm, fuel pump relay, radiator and i know there are other things that are not coming to mind but iv pretty much rebuilt this whole car.

iv got everything working all the way up to the injectors. The car wants to start with starter fluid. my fuel pressure holds at 42. i used a noid light to test the injector harness pulse and none of them work besides the cold start injector. Please help.

Mishawaka

Check for injector signal at the computer. There may be a break in a wire or plug not completely pushed in.

nmay

how do i check for injector signal?

Mishawaka

If I recall correctly, you can check with a test light at the ecm, you will need to find out which pin or pins it is on on the computer. Since you mention a ninth injector you must have an early C$ with an L98. I'm not very familiar with them since Ive only owned an LT1 so I could be wrong on the test procedure. If no signal at the ecm, I would probably check all wiring. An FSM would be very helpful right now.

nmay

i just bought a new ecm so it should be working correctly. what is an fsm?

64Scout

FSM=Factory Service Manual

Tuned port should have power from the fuse box to the injectors, and the ECM grounds them. You can unplug the injectors and probe them for power, checking for ground is a little more involved.

C6_Racer_X

With starter fluid, the engine should actually start and run for a second or two. If you keep spraying starting fluid, it should continue to run. If it's running relatively normal for a second or two on starting fluid, then it's getting spark at least. If it sputters and doesn't actually run for a second or two, it's likely you're not getting spark either.

If it doesn't actually run, check to see if you have spark. You can pull one plug and set it on a solid bare metal ground (with the spark plug wire still connected) and watch for a spark as someone cranks the thing.

Injectors should have power on one wire whenever the key is in the "run" position (the position when you normally drive). The ignition coil should have power as well with the key in the "run" position. The PCM provides the ground signal to the injectors (and the coil).

If you're not getting either spark or fuel, that's most likely a crank position sensor/cam position sensor issue. I don't have wiring diagrams for your year, so I'm not entirely sure which of those is present and/or critical. The factory service manual would be very helpful for that diagnosis. I would look it up, but my source for that information has dramatically changed their website, and I haven't found my way around there yet.

If you're getting spark but no fuel, then there are other issues. On many GM engines, the spark is controlled/timed by the crank position sensor and the injectors are controlled/timed by the cam position sensor, so again, checking sensors would be an early step. I'm not sure if your injectors are sequenced with the valves at low loads/low speeds, or if they are gang fired under all conditions. GM engines with "sequential" injection usually time the injectors with the cam position sensor (often that sensor is in the distributor, if a distributor is present).

All my information here is general from years of experience with "not your GM engine." Anyone with specific information from a factory service manual for your specific model/year or more specific experience with your engine is probably more correct.

nmay

okay, i checked for power at the fuse box. im getting power to both injector fuses when i plug a noid light in the fuse spots. i checked ecm to make sure it was plugged in tight. it was. i traced down all the wires i can get to and even some that are hard to get to and i see no shorts or cuts or anything. im still not getting any poer to the injectors

nmay

i also found the ground to the injectors. its connected to the block on the driverside toward the firewall and they were all hooked up good

3D-Aircrew

It's worth a try to plug the original ECM because ECMs can be DOA.

Check the fuse to the ECM too and check codes ... make sure you have 12's

nmay

i bought the new ecm because of this problem. what ever it is, i dont think its the computer itself. shoukd i try buying a third ecm? maybe the one i bought is broke? ill check the fuse to ecm in morning and let you know how it does. What code reader do i need for this car? none of my local parts store offer one for my car

desertmike1

Without the proper FSM, this might be your next best bet for troubleshooting.. again, a FSM and a good Scan Tool makes life much ease yer.

http://www.corvettebuyers.com/c4vettes/l98.htm

I'd look closely at both your oil pressure sender, and the TPS followed by the Distributor..

64Scout

What kind of "noid light" ate you using? When I think of a noid light I think of a light that plugs in to the injector harness and you can watch it flash when the injector should fire. I would suggest a "logic probe" which is like a test light but has two wires and two lights, and tells you whether you are probing a hot or a ground.

I was going to tell you that was wrong, but I had to double-check before I posted, and have to admit I was wrong about the injectors being fed a constant 12v. http://chevythunder.com/fuel%20injection%20ecm%20pinouts.htm

nmay

i changed both oil pressure sender and throttle position sensor already. My oil pressure hold good at 4 and i didnt test the new tps but i assume it works. should i buy a new one again? the fsm isnt helping me to much. ill find a scan tool somewhere and see where that leads me

nmay

yes, i was using my noid light for the injectors to test the power at the fuse box. ill look into the logic probe

aklim

Not sure I agree with Grumpy on that part. Going with what he says, you should not get any oil pressure with the sensor disconnected and therefore it should not start. IIRC, I have disconnected the sensor and gotten a start so.....

nmay

my oil presure sensor is new and working properly. my dash is telling 4psi so thats not my problem

aklim

The oil pressure sensor, AFAIK, is a backup so it isn't an issue.

aklim

It's weird that you are getting no power to the injectors. Try this. One end of the DVOM to the negative and probe both pins. IIRC, they are constantly hot and the ECM grounds it to cause it to fire.

desertmike1

I would back probe the TPS and either verify or adjust for the .54 voltage signal at the idle position. According to the Blue sheet an appreciably Higher voltage is determined by the ECM as an engine flood condition and will turn Off the injectors.

Which FSM do you have; the factory manual or a cheaper version Haynes type of manual.