1990 5.0 GT Mustang Fuel help - MustangForums.com

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Old 05-07-2013, 01:22 AM   #1
Shane 5.0
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Join Date: Nov 2012
Location: British Columbia
Posts: 20
Default 1990 5.0 GT Mustang Fuel help

Ok so a month or so ago I started losing power in the mustang, wasn't sure why, it would kinda jerk up hills, and 3k+ RPM it just wouldn't pull like it used to, especially up hills and such.

On two occasions over the last while the car completely died, once at a red light, and another time after sitting idle for 10 minutes, just shut right off, no fuel getting to where it needed to, nothing, would turn and turn and turn but wouldn't start. On both occasions I finally got it started and carried on, knowing that at some point I'd have to replace something.

The last couple weeks the car started sounding different, the fuel pump on one or two occasions was humming very loudly, and the overall sound of the motor just seemed off, it didn't like any high RPM or heavy pedaling.

Two days ago when I turned the key to start it I noticed the humming of the fuel pump was gone, and as such the car would turn and turn and turn but would not get any fuel.

Gotta be the fuel pump I thought... well two sets of tools and 5 and a half hours later in my drive way in 30+ degree weather I got it all changed. I turned the key, the pump was humming all good like it should, but once again, it turned and turned and turned, nothing...

I shot o2 sensor cleaner into the intact with a friend and it would catch just abit but than die as soon as there was nothing left to ignite... it also shot out two fireballs which my friend lost some hair to... so I've had enough of that...

So I just don't know what's up... its like its just not getting and fuel in the engine, I don't know what else it could be....

Recent things fixed/added:

Refurbished T5 transmission about 2 months ago
Starter is only 1.5 years old
brand new Carter fuel pump.
Put new copper plugs in it about 5 months ago
Fuel filter was changed two months ago
Oil change isn't even up yet

Perhaps its the wires? I haven't changed those out since I got the car a couple years back...

There's abit of oil by the top right of the engine, (like dark dirt, not running/runny( hoping its not the head gasket.

Only other thing I can think of is perhaps the fuel injectors?

I don't know what else to do/try.

I'm an electrical apprentice in school and don't have abunch of money to have it worked on at the shop, although I just dropped two hundred bucks on a fuel pump that was probably just fine besides the fact the "working" humming stopped, so maybe it needed to be replaced.

Is there any kind of pumping or something I have to do with the fuel lines when I change the pump? maybe there's air trapped in the lines or something?

Please help me out/give me some idea's if you can Mustang community, I am really stumped and broke.

I appreciate your time,

Also wanted to add that the last couple weeks it was back firing abit here and there, not enough to be really noticeable, but once in awhile where I was like "whoa that's not normal."

Last edited by Shane 5.0; 05-07-2013 at 01:25 AM. Reason: Addition
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Old 05-07-2013, 08:31 PM   #2
Join Date: Mar 2013
Location: california
Posts: 20

I know u said u replaced the fuel filter a month or two ago but i would pull that out and check it. Pull it and blow through it the opposite way the fuel goes. If u got low on gas the pump my have picked up some debris and sent it to the filter. Also clean out ur tps and ur iac. I know all about being broke so i couldnt buy all new sensors either. I cleaned mine with carb cleaner. And dont be shy with the carb cleaner either. Might work for u or it might not but thats where i would start. Also maybe pull ur o2 sensors and see what the look like. I think i bought some bosch o2 sensors for like 15 or 18 bucks a peice and the new filter cant be more then 10 or 15 bucks. Hope this helps good luck
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Old 05-08-2013, 01:26 AM   #3
Shane 5.0
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Join Date: Nov 2012
Location: British Columbia
Posts: 20

Yea I cleaned the sensors as part of trying to get it to go, they're so sensitive on the mustang I clean them about every month.

I got a continuity tester and was trying to test the spark plug wires but nothing is showing anything. I put it on the main metal cap that goes to the distributor and tried to turn it over and the light bulb didn't light up, not sure if it's just how I'm testing to or if that's the problem...

Also, if for some reason I hooked the pump up backwards, how would I know? would it still hum at all?

The mechanical instructor at my university said that there's a black cap on my fuel rail I can take off and depress, and fuel should come out when I turn the key on (as it primes it) but I can't find this dam cap to check that, not sure where that would be exactly.

Frustrating the hell out of me, the continuity tester lights up when I have the ground clip on the frame and on the positive, so I'm sure its working.

Any other idea's? when I disconnected the old pump I took the red off first, cut it, spliced it, and but it on the new pump while the black was still on so I wouldn't put it on backwards. However in retrospec the NEW pump had two connectors of different sizes, when I took the red off I put the smaller connector on it, than hooked it into the only spot on the pump it would fit, than the black wire on the larger connector, and hooked that up, perhaps I put the wrong connectors on the wires than hooked them up backwards?

Any idea's?

Thanks allot,
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Old 05-10-2013, 10:05 PM   #4
Shane 5.0
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Join Date: Nov 2012
Location: British Columbia
Posts: 20

Turns out the fuel pump was installed backwards, could hear the bubbling and the fuel coming out of the rails was really low pressure.

Thanks for the help
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