No fuel injector pulse!

[spyderGT]

I'll get right to it...

Went to crank my car....only spins over. I am getting an excellent spark from my 6AL box, but my fuel injectors aren't pulsing correctly.

I took a for noide light and checked the pulse with that, it is VERY dim.

Anyone have any suggestions as to what my be my problem?

 

[jrichker]

A Noid light available from Autozone, is one way to test the injector wiring. I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles. Cheap if you have the stuff laying around, and works good too.

There are two 10 pin connectors at the back of the upper manifold, one of them has all 8 injector connections. Pull them apart and check for damage. Clean the connector pins and sockets with electrical contact cleaner or non-inflammable brake parts cleaner (same stuff as electrical cleaner in a bigger can). Scrape the pins with an exacto knife and use a jeweler's screwdriver to scrape the inside of the pins. One of the pins is the +12 volt supply to the injectors. Each injector should ohm out at about 13 ohms +\- 1.5 ohms.

Remember that the computer supplies a ground path for the injectors. The power for the injectors comes through the ECC relay located on top of the computer. They have power to them any time the ignition is on. The computer turns on the ground and completes the circuit, making the injectors fire.

Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on. No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold). If the connections are clean & tight, check the ECC relay mounted above the computer. You may need some midget hands to get to it.

See http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for some wiring diagrams that will be helpful

 

[spyderGT]

Thanks for the idea rich.

I checked the power connection, looks like a good 12 signal from the red wire on each injector.

Now as for the computer supplying the ground signal to the injector, it looks as if it's comming from pin20 on the computer. That pin is tied directly to ground. In other words, I think the computer sources ground from pin20 and supplys it to the injector. Hopefully your idea about the soapy water will help me out :-D

Thanks again

 

[jrichker]

Thanks for the idea rich.

I checked the power connection, looks like a good 12 signal from the red wire on each injector.

Now as for the computer supplying the ground signal to the injector, it looks as if it's comming from pin20 on the computer. That pin is tied directly to ground. In other words, I think the computer sources ground from pin20 and supplys it to the injector. Hopefully your idea about the soapy water will help me out :-D

Thanks again

Pin 20 is the case ground. Power ground for the computer is pins 40 & 60. The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. It uses a barrel type quick disconnect connector inline with the battery ground pigtail. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-90 wiring

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif