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Discussion Starter #1
Long story short, I am on my second engine, it is a 91GT 5.0L Stock. I have a computer from an 89 Stang. I have wired everything up according the Ford Motorsport Stuff.
Quick rundown:
Brown Connector #31
W/R to the oil pressure dash gauge.
R/G crank & run
W/P 12V crank only
R/LB 12V crank only
T/Y Not used (for tach, I don't have no stinking tach)
P/Pk or R/W water temp gauge
G/P or GR Not used (for manual tranny/neutral safety switch)
P/Y Not used (for manual tranny/neutral safety switch)

Green Connector
G/Y run only
DG/Y Inertia switch
PK/G Check engine light then to crank & run. When I wired the light I put a 500 ohm resistor in parallel with it, should I have put the resistor in? And I used a little light from radio shack.

Now symptoms:
I turn key, starter turns, but I don't here pump running. So, I bypass check safety switch and now the pump gets 12v when I first turn the key on, then immediately turns down to 6v which isn't enough to make the pump work. I attempted bypassing that and giving the pump 12v directly while I cranked the engine and nada.
I double checked all connections and made sure all the wires above were getting the proper voltage and hooked to the proper stuff.

I do not have any of the A/C stuff hooked up because I don't have A/C and I don't have the A/C relay in either. Does this make a difference?

I have the Ford Fuel Injection book and am reading through it and attempted to do the quick test with my voltmeter, but my volmeter is digital and just went from .1 to .4 back and forth with only about a second between. I don't know what the hell that means. Any ideas?

I have the ground on the computer grounded to the dash and I check the resistance and there isn't any resistance. I also have the ground on the wiring harness, which is connector #26 on Figure 2 of the Main Harness diagram in the Ford Motorsport Diagram.

Thanks for bearing with me, but I am at wits end and need help.
Jason
 

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My suggestion, since this seems to be an ongoing problem you are having, is to go to one of te large mustang boards and post this exact post. Try www.corral.net as it is really the largest one out there, and pretty good with the tech. Just be as detailed as possible.
Hope you get it fixed.
Phil
 

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diiulio said:
When I wired the light I put a 500 ohm resistor in parallel with it, should I have put the resistor in? And I used a little light from radio shack.

Now symptoms:
I turn key, starter turns, but I don't here pump running. So, I bypass check safety switch and now the pump gets 12v when I first turn the key on, then immediately turns down to 6v which isn't enough to make the pump work. I attempted bypassing that and giving the pump 12v directly while I cranked the engine and nada.

Thanks for bearing with me, but I am at wits end and need help.
Jason
What's the point of the 500 ohm resistor? If it is in parallel with the bulb, then it won't do anything; if it is in series with the filament, then the bulb won't light.

If you put 12V directly on the pump when it is disconnected from the rest of the fuel system ahnd wiring and it still won't run, then either the pump is bad or it has a bad ground.
 

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Ok, so your only problem is the fuel Pump? Do what pinhead said and run 12 bolts to it direct. Just use an inline fuse, and go from the battery to the pump. If the pump doens't work then, its fawked up. Make sure your pump ground is good.
I am finishing the 5.0 in my tj rightnow, and just have the fuel pump wired to a toggle switch. I'm using a low pressure external that feeds to a high pressure external.
Your wirings look correct as far as I can see.
If you want, I can scan some diagrams and send them to you, but I won't be able to do that until monday.
Josh
Also, check your injectors. They fire when grounded.
 

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Discussion Starter #5
When I put 12v to the pump it works and when I turn the key the engine turns over, but does not start.

I don't think the fuel pump is the problem.

I think the problem is electrical.

Why does the pump get 12v instantly, but then die down to 6v when wired off the computer?

Could the EEC power relay be bad? If this is bad, what are the symptoms?

Do I need the A/C open throttle cut off relay?

Can I get away with the speed sensor not hooked up?

Wiring the resistor in parallel I have found in two sources: Chris Waterman's site (5.0 into YJ) and the other on a mustangs guy site that frequents corral.net. He has diagrams and that is how it is shown. That is why I did it. Do you think I should take the resistor out?
 

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is it a FMS harness?

I have 3 computers, one the fuel pump does not turn on, one the check engine light doesn't come on, and the third.. works

The one that works is a A9S

The computers ARE different..
 

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Discussion Starter #7
It's an A9L computer that I got off one of the stang sites. Is there any other way to test it other than trial and error?
 

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dont know if this will help or not. I worked on a little bronco once with a no start condition. After hours of dicking with all the normal checks found a note in a service manual that said to unplug all 3-wire sensors one at a time and try to start engine. Turned out to be a egr sensor , unplugged it and motor started. dont know how this stopped the injectors from working but replaced sensor and everything worked. Just a thought , good luck!
 

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diiulio said:
It's an A9L computer that I got off one of the stang sites. Is there any other way to test it other than trial and error?
I'd rule out the computer first, find someone with a mustang or something. Is it a ford motorsports harness? The wiring IS different
 

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my 5.0 just wouldn't start one day and had spark had fuel and i couldn't figure it out.... it turns out that there was a relay that wasn't getting switch so i got a new relay didn't fix the problem, so i hot wired the relay..... perfect runs great, the relay i'm talkin about is not far after the harness comes out of the firewall check that .... it MIGHT be it.... it happend to me....
 

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I'm a little rusty, so my advice is probably worth what you paid for it.

I don't think you need the "WOT" AC relay. All it does is kill the voltage to the AC clutch, when you mash the gas pedal. But install one any, cause it's easy!

Check the EEC relay(next to the computer) and fuel pump relay. There should be a larger wire with 12 volts constantly, and then another larger wire that gets 12v when you crank(fuel pump), or crank and run (eec relay). If these relays aren't being triggered, you have to investigate, WHY. Could be a bad connection that isn't sending a full 12 volts, you could have a resistor upstream, or it could be a bad relay. Since you know you have problems here, I would get this working correctly first, and then move on.

I recently pulled my Mustang motor and replaced it with a Explorer motor. Went to start it up and it would not fire. WTF! After calming down :) I realized I used my spare distributor in this motor, since the explorer only came with the little stubby thing. Swapped distributors and the motor fired right up! :)
The TFI on the spare distributor worked fine when I used to run it, but maybe it's been bouncing around the tool box too long.

Good luck,
 

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Discussion Starter #12
oh sh*t, the wiring is different?!!

Yup, I have a stock harness that I wired like the FMS one. I will have to go back to my drawings I guess, unless someone know what is different?

I am thinking if it isn't the wiring diff then I agree with it could be the relays or sensors.

I'll work on it tonight after work.

Keep the comments coming please!
Jason
 

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Discussion Starter #13
I keep fogetting to add the WEIRD part.

The run wire to the green connector somehow causes the blinker indicator sound to sound! Even though the blinker is not on, and when I turn the blinker to either side the sound still works. If I disconnect the run wire from the computer then the blinker sound goes away.

What is up with that.
 

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I would check the EEC relay, mine was messed up and had the same thing you are stating. If you are using the FMS harness it will not use the same relay as the fuel pump they are differant..good luck
Dave
 

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Thats a relay being energized.

I swapped an 87 5.0 into a 64 Falcon.I had all the same problems.Turned out to be a bad EEC relay.It would test good with a test light, but couldn't pass the required current.Try bypassing it for a test.
 

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You do know that you could buy a NEW harness, that goes with the easy to follow directions, from SouthWest Ford (800) 256-7933 for $200...........right?
 

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Discussion Starter #17
Yes, I know I can buy the harness, but if I can figure this out within a few days, then I would rather figure it out over the $200. I am a cheap b#stard if I can figure it out. The harness I have is in great shape, just I don't know if I wired it wrong. If I can't figure it out by Monday I probably will just shell out the $200, but not without a fight.
 

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keep in mind there are a few things that send signals to the ECU to tell it when to run the fuel pump. when you turn the key on it runs the fuel pump for 1 second to prime the fuel rail then it shuts off. after that it needs a signal when you turn the key to crank, if you are not getting this signal it wont start. after it starts (after 700 rpm) the distributer (TPI) sends the signal to the ecu to run the fuel pump. i had all sorts of trouble and after hot wiring the fuel pump (using a 12v battery charger), i verified the engine would start and run. then went after the wiring. turned out to be a bad fuel pump relay (which was brand new from ford). the fuel pump relay and the ECU relay are interchangeable.

also on the ecu test port there is a wire that if grounded will run the fuel pump constantly. i think its the grey wire but im not sure with out looking.

do you still have the inertia switch? make sure it is not tripped.

You stated you do not have the neutral safety switch but you must jump the wires or the signal wil not get to the ECU thus no fuel pump....

i also have had ecu trouble. the first ecu came with the donor vehicle from an automatic. when i went from bank fired to mass air i had to switch. a friend gave me an ecu (also fron an automatic) he had removed and it worked fine for a few weeks then quit. i asked him why he changed it and he said it would mysteriously quit and then would work. well with this new info i bought a brand new one and all problems were solved.

those are all the issues i had when doing the conversion and hopefully help you eliminate some areas..... good luck
 

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Discussion Starter #19
FINALLY! Yesterday that b#tch lighted right up. I checked, there was no fuel to the engine. So, as I am bending new lines because I think it is blocked, I realize I have the supply and return lines mixed. Yes, it was that simple. When I originally hooked em up I kept checking them and re-checking them, but I must have mixed em up. After that, I turned the key and bam! the nice roar of a 5.0 with no exhaust! Sweet. After that the beer started flowing even though it was 10AM. Didn't get much done after that. Got to make up for it today.

Thanks everybody who helped.

I do have to say, the FMS catalog is right on the money with all the wiring, just follow that and you should be all set. In the end I did not alter anything from what that says. It was just around ten wires being hooked up. No need to spend the 200 for the FMS wiring harness.

Just make sure your pressure line is getting gas.

:beer:
Thanks again,
Jason
 

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FYI I have ONE wire in the grey plug and ONE wire in the Black plug, then the green plug wires and fuel relay - that is IT!
I added the speed sensor (2 wires to the black) and passed smog. The 5.0 has to be the easiest engine to wire out there..
 
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