injectors not pulsing with my FAST

[iroctt]

Ok
We put the car back together after repainting the engine bay and now the car won't start not even trying to start. I have the fast b2b wide band ECM and we didn't have my laptop with us but we were able to determine spark is good and fuel sytem is working fine and the computer is telling the fuel pump to turn on but we pulled one of the injector plugs of and there is power to the injector but the FAST computer is not grounding the injectors so no pulsing. I will be going back out to hook my laptop up and see if It can tell me anything. I made no changes and have been running the car for 2 years. One note is I did have a bad ground wire of the msd 6a box that was not grounding due to new paint. My electric guy seems to think the bad ground may have back fed into the fast box and burnt out the injector drivers and thats why the computer won't ground out the injectors and let them work. Electronic are not my area so I'am relaing what my mechanic and I found today and he is very good but never messed with anything but factory computers. We also pulled a plug after cranking and its bone dry. Any thoughts would be helpfull

 

[iroctt]

Hooked up my laptop everything seems to be working. My tps jumps up when you floor it. Is there something I can look at while I'am cranking the car to see what the injectors are doing. All I know for sure is the computer is not grounding out the injectors at the connector to the injectors itself and so the injectors are not opening up and spraying fuel, hence no start.

 

[Craig Smith]

Perhaps there is a ground issue, especially since the engine compartment has just been painted. However, I am fairly certain that your injector drivers are still OK. They are essentially indestructible so you have that going for you.

Out of curiousity, how are you determining that the outputs are not switching to ground? Also, where are the main ground wires in the harness connected to? Pins Y1, Y2, and Y3...

 

[iroctt]

The main harness goes to the battery in the back of the car and is grounded back there on the frame. The only two ground wires under the hood have been grounded down to medal and we checked them they are grounded now, one is a ground of the msd box and the other is a ground from the factory wire harness. My mechanic pulled one of the injectors wires of and tested it and got power to it but said when I crank the engine over its not grounding out from the computer and therefore the injector is not pulsating. We also pulled a plug and it was bone dry after cranking. Does the harness conector at the ecm marked with y1 y2 y3 I can double check those tommorow.

 

[HighPSI]

What is your TPS when cranking? If it's over 80% the injectors aren't gonna fire.

Hey Craig!!!

 

[iroctt]

I will check my tps while cranking tonight. Anything else I should look at?

 

[iroctt]

I talked with a tech guy at fast today. He said check my relay on the harness it controls the injectors and 02 sensor. He also said look at your rpm signal under cranking. The car is in the dark outside so all I did was crank it and my tps is fine about 18 during cranking and goes up when you floor the gas so thats fine but this is what I found
HR RPM 0
RPM 0
scaled RPM 0


I will just replace the relay tommorow since I don't know how to test it.

 

[HighPSI]

The relay provides power to the injectors. Based on your first post, yours is fine. If you don't have rpm when cranking, then you found your problem. I would look at whatever you are using for a crank signal (HEI or crank trigger?)

 

[iroctt]

I have the factory HEI
The car does have spark does the hei also control injectors

 

[Otto J]

I have the factory HEI
The car does have spark does the hei also control injectors

If your running HEI with the module in the distributor then yes
The pick up and module setup both spark and injector firing,Im pretty sure
SO either dist isnt plugged in or module could have went bad

 

[iroctt]

Thats interesting because sunday my mechanic said he thought the ignition module was bad and that it also ran the injectors so I went to advance auto and got a new one and when I picked it up the sales man made a point to tell me its not returnable ounce I buy it as if to imply some guys just replace sensors untill the car runs. Maybe He sold me a bad ignition module? It wouldn't be the first time I bought a new generic senor that was junk. I will get a new GM sensor and hopefully that will do the trick.

 

[Otto J]

Does the car have spark? I had a factory ecm trans am tpi that the distributor wasnt grounding well and had problems, If i moved the dist whle cranking it fired,ended up being a ground prob with the dist housing

 

[Craig Smith]

Good to see you found the problem.

Before you spend more money on it, I would like to recommend that you closely inspect the wiring to the distributor. Since it failed after being pulled apart and reassembled, it's possible that a pin is backing out of a connector or something of that sort. If you feel pretty good about the wiring, then the module is definitely the next suspect.

This is a tricky thing about the HEI ignition system. Even if the control signal from the module isn't getting to the computer, it will still make spark during cranking. However, the lack of a reference signal to the computer, as you are finding out, means there won't be an injector control signal and this is often perceived as an injector or fuel system problem.

Let us know how this turns out...

 

[iroctt]

Yes it has excellent spark. I will check the pins on the connectors and then replace the module again. I may have to wate till the weekend but I will let you know what I found.

 

[Otto J]

Where are you located?

 

[iroctt]

central PA
state college aka penn state university

 

[iroctt]

Fixed it
One of the 4 wires that goes to the ignition module came apart so thats why there was no rpm signal to the fast.
So I fixed it and car runs fine almost. After a day of running the car no issues I drive it down the road and it dies suddenly like some one pulled the plug. Well sure enough I have no fuel or rpm signal from my FAST again. Well it is either another bad wire in the 4 going to the ignition module or a bad ignition module or a bad distributor. Well wiring is fine and I have a extra accel ICM and its ok so I guess I will pull the distributor and replace it its the only thing left