What makes fuel injectors not work?!!!

[KillaCam]

I have spark but the engine just cranks and the injectors are not spraying, thyre getting fuel but not spraying it ....I have a 85 e.... What's wrong!?

[ttrousdell]

you have pressurized fuel at the rail? The ecu determines when and how long they stay open. The rail pressure determine how much comes out. I doubt all 4/6 could have become clogged at the same time

[DÌEGØ]

make sure ur getting power to them

[KillaCam]

Just got it to run... Turns out to be a bad relay that I replaced that made my fuel pump not work then the injectors wouldn't fire because not enough pressure

[KillaCam]

up!! it wont start again....idk what it is now....i changed the out side fuel pump for a junk yard one and it got the car to start and then i got the intake one to work with some rigging and after that it wouldnt start...its getting fuel to the rail and everything...the relay works and idk how to test if im getting power to them...enlighten me please on how to do that.

[jlevie]

Throw a gauge on and see what the pressure in the rail is.

[lennon]

Yes, check the fuel pressure first.

To check for power, turn the ignition on to run. Both pins of the injector plugs on the harness should have 12v. The DME pulses ground to one of these 2 pins when it wants to fire the injector. If you have proper pressure, and 12v at the injectors, get a noid light set to see if the DME is pulsing ground when cranking. The light will flash. Using a test light or multimeter won't work. Advanced auto loans these around here, if not, they are cheap.

[KillaCam]

Sure....let's say it's not getting power what could be the problem?
Let's say there isn't enough pressure...would a fuel filter cause that?

[KillaCam]

up im getting power to the injects and im sure i have some sort of pressure..idk whats going on! could a sensor keep them from firing?

[ttrousdell]

Is your rail pressure about 45psi? A bad cps would prevent injectors from firing, the pump from working and no spark. However you claim that you have pressure so that might rule that out. All engine sensors(tps, temp, maf, ivc,O2) send a varying voltage signal to the ecu which then processes the input voltage from the sensors. The ecu then sends a signal to actuators (fuel injectors) and changes its pulse width(duration its open). From my experiences a fault or no signal from any one of these sensors (tps, temp, maf, ivc,O2) will cause a shitty running engine but it will start.

[KillaCam]

cankshaft position sensors aren't on early eta's could the sensors on the trans keep the injectors from firing ?

[ttrousdell]

The flywheel sensor functions the same way and will cause the same symptoms as a bad cps. Essentially it is a crank sensor because the flywheel is mounted to the crank.

[KillaCam]

I think it might be that.. I'll change them now and let u know

[KillaCam]

Son of a bitch.... I had them hooked up backwards .....The cps

[ttrousdell]

Good to hear. Its usually the simple shit.