Ive got some updates on my non-running mustang situation

N8Miller · Oct 11, 2005

Ok, i finally found the volt meter and used it for a few minutes to trouble shoot what jrichker/rick91gt/grn91lx/daggar and staff has helped me with.
anyway, heres what i got:

*still no fuel pump priming
*13.3 volts at starter selinoid
*.3 volts at fuel injectors
*.2 volts at red/blue (maybe black?) wire on FP relay
*0 volts in pink/blue wire on FP relay

interia switch:
*.3 volts in red/blue wire
*.0 volts in solid red wire

fusable links:
all had 13.0volts in both ends of them

where do i go from here???

edit: right now i am leaning toward the eec relay?!?!?!

jrichker · Oct 11, 2005

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

The ECC relay is on top of the computer. The computer is located under the passenger side kick panel. Some of the wiring may be difficult to get to, and require some bends and kinks in your body that it isn't used to.

ECC power feed
Locate the ECC relay in the above diagram. Look for 12 volts on the black/orange wire that feeds it, no 12 volts and the fuse link is bad. If the 12 volts is present, the ECC relay is either bad or is not energizing.

ECC relay control voltage
Look for 12 volts on the red/Lt green wire. No 12 volts here, and the fuse link for this wire is bad or you have a broken wire. The same fuse link feeds the red/lt green wire on the ignition coil, so look for 12 volts here too. If you find it at the coil and not at the relay, the red/lt green wire is broken somewhere.

ECC relay control ground and computer power ground
With power off, measure the resistance between the black/lt green wire on the ECC relay and battery ground you should see less than 1 ohm. More that that is a bad connection or broken wire.

tmoss · Oct 12, 2005

Yep, sounds like the EEC relay - assuming the key was on for those tests.

Make sure you have 13.3v at the orange/light blue wire on the fuel pump relay too.

ram360 · Oct 12, 2005

nate, I've had that problem before. Fuel pump wouldn't prime turned out my eec was bad. Put in a new one, problem fixed. Hopefully you get away lucky w/ just a new relay.

N8Miller · Oct 12, 2005

bernie, when you say eec, do you mean the relay? when we doing that inspection?

tmoss: all of those tests where done with the key on.

tmoss · Oct 12, 2005

ram360 said:
nate, I've had that problem before. Fuel pump wouldn't prime turned out my eec was bad. Put in a new one, problem fixed. Hopefully you get away lucky w/ just a new relay.

A bad EEC transistor will keep the pump from priming, but the injector power comes through the EEC relay and he has no volts to the injectors.

N8Miller · Oct 12, 2005

tmoss said:
A bad EEC transistor will keep the pump from priming, but the injector power comes through the EEC relay and he has no volts to the injectors.

whats a transistor vs. the relay?

jrichker · Oct 12, 2005

N8Miller said:
whats a transistor vs. the relay?

A transistor is soldered in place inside the computer. In your case, I would not consider it a user replaceable part.

The relay(s) are all outside the computer and plug into sockets in the wiring harness. They are all user replaceable parts. You pull the old relay out, make sure the new one is the same part number and then plug the new one in the socket. You might want to inspect the socket and wiring for corrosion, overheating and other damage while replacing the relay.

RsStanG1987 · Oct 12, 2005

N8Miller said:
bernie, when you say eec, do you mean the relay? when we doing that inspection?

tmoss: all of those tests where done with the key on.

He replaced the whole computer. - Dave

tmoss · Oct 12, 2005

I've often thought that if the fuel pump transistor was the only thing that failed on my EEC, I'd supply the pump ground through a relay slaved to the ignition switch "on" position.

emagdnim · Oct 12, 2005

tmoss said:
I've often thought that if the fuel pump transistor was the only thing that failed on my EEC, I'd supply the pump ground through a relay slaved to the ignition switch "on" position.

Would that not be potentially dangerous in a accident situation?

tmoss · Oct 12, 2005

No, because the inertia switch is still used to power the pump

N8Miller · Oct 12, 2005

Update!!!!

on the dist. module:

red/grn: 13 volt
red/dark blue: 0 volts

all key on.

tmoss · Oct 12, 2005

N8Miller said:
on the dist. module:

red/grn: 13 volt
red/dark blue: 0 volts

all key on.

That's good. The red/blue only has 13volts in crank key position.

Aliate X · Oct 12, 2005

okay please tell me why he has said his fuel pump is not priming and nobody has said his fuel pump is bad......

If your car cranks and you have spark, but your fuel pump doesnt prime, its obviously the fuel pump. I must be missing something, why has nobody pointed out the fuel pump?

tmoss · Oct 12, 2005

Because his pump CANNOT be getting voltage or the injectors would have some voltage too. Maybe the pump is bad, but he can't know htat till he gets power to it. Study some diagrams.

Aliate X · Oct 12, 2005

Cut the wires going to the pump and see if you can get the pump to work by an external electrical source.

jrichker · Oct 12, 2005

Aliate X said:
Cut the wires going to the pump and see if you can get the pump to work by an external electrical source.

Bad idea. start with the ECC wiring & relay. No power to or past the ECC relay, no power to the computer, injectors or fuel pump relay.

Diagram courtsey of Tmoss & Stang&2birds. See http://www.veryuseful.com/mustang/tech/engine/ for more good stuff.

N8Miller · Oct 12, 2005

ok guys, put it in laymans (sp?).... you think that its the eec relay? or the wiring?

tmoss · Oct 12, 2005

tmoss said:
Yep, sounds like the EEC relay

You are reading these responses right Nate?

Ive got some updates on my non-running mustang situation

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