jrichter / electical gurus help

[bcd]

car wont start self test so i decided to check continuity. The black wire was the only one that i found connection on. think it was 46 (cant remember though). The other two (17 and probably 48) had no connection between the computer plug and the self test plugs. after finding this i tried to start self test by the wires just above the computer. so i shorted 46 and 48 then put the meter between 17 and the battery positive. when i turned the key on the fuel pump would prime twice (which is abnormal), click a few times then nothing. no needle sweeps. any ideas?

 

[bcd]

somebody has got to have some idea

 

[jrichker]

I understand that the engine runs, but you cannot pull codes, is that correct?

 

[bcd]

thats affirmative. i drove 30 miles to the court house yesterday ran like crap for a couple miles ran like a dream the rest of the way. when i got in the car to come back ran good for a couple of miles then ran like crap the rest of the way home. it runs but cant pull codes

 

[jrichker]

car wont start self test so i decided to check continuity. The black wire was the only one that i found connection on. think it was 46 (cant remember though). The other two (17 and probably 48) had no connection between the computer plug and the self test plugs. after finding this i tried to start self test by the wires just above the computer. so i shorted 46 and 48 then put the meter between 17 and the battery positive. when i turned the key on the fuel pump would prime twice (which is abnormal), click a few times then nothing. no needle sweeps. any ideas?

If you back probed the connections at the computer connector with the ignition switch on, what you did should have started the computer to dump the codes. There are only three possiblites why it wouldn't work.
1.) More than 1.5 ohms between the black/white wire and battery ground.
2.) One or more of your back probed connections wasn't making good contact.
3.) The computer is toast.

While you are checking out the wiring, check the computer power ground. The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery. It is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire. The wire goes into the harness at the starter solenoid.

 

[HISSIN50]

In addition to Jrichker's wise post, here is some more info.

Good luck.

 

[bcd]

the battery is in the trunk and is grounded to the body on the underside of the body. would that cause it. i am toying with the idea of swapping the computers but want to figure out why its missing first i just wanted self test to tell me that. when i get home i will make sure all of the former ground wires are grounded good. where is that cylinder you were talking about

 

[HISSIN50]

where is that cylinder you were talking about

If you find the neg battery cable where it attaches to the inner-fender, you will see that the computer ground attaches to the same location (bolt). if you trace this wire upstream a few inches, you will see what looks like an inline glass fuse holder. This is the cylinder JR is talking about. I know because he and The User were able to answer this for me some time ago (I thought it was a fuse holder of sorts, which made no sense on a ground connection).

 

[bcd]

i am going to check my computer ground this weekend. i dont really have time to work on the car during the week unless i do it with a flashlight.

 

[bcd]

i am thinking of replacing the wires between my computer and the self test connecters. do the split off anywhere?

 

[jrichker]

Check it out...

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 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

Diagram courtesy of Tmoss & Stang&2birds

AutoZone wiring diagrams

http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs

 

[bcd]

looks like i better just find the break and fix it. thanks though