Fuel Issues

Steve-Oh · Nov 9, 2011

Being as there are no more threads in here anymore I couldn't really search for this one BUT here it goes...

Problem: Fuel pump with not prime when the key is turned on. My immediate thoughts were relays, fuses and the inertia switch but unfortunately they all checked out fine. I've also considered whether or not it could be the PATS key. From my understanding when that key doesn't work the motor won't even crank but his car turns over but doesn't fire obviously. So my last thought is replacing the fuel pump in the car. Given the online directions I've read it doesn't seem too bad.

With all that being said my next question is this. Hypothetically if all else fails and the problem ends up being the fuel pump, should I replace it with a 255lph pump as opposed to a factory one? The reason I ask is because the motor has been rebuilt to a 5.0 stroker and nothing else has been upgraded besides the bottom end. With that being said, if I do upgrade the pump would injectors also be a must or can I get away without doing them?

In the end I'm really just trying to get this car alive again for my friend so he doesn't have to sell it "as is" which wouldn't yield much money. The car is really nice but he's lost interest in it and has moved on.

Musturd · Nov 9, 2011

No you don't need to upgra the injectors too. But I would go with the bigger pump if you gotta replace the pump anyways

CC'S95GT · Nov 10, 2011

5.0 or 4.6?5.0- look at the dizzy being faulty.4.6- Have you tried to pull codes? Have you reset the inertia sw in the trunk?If the cam or crank position sensors are not working I would think the computer would prevent the car from firing.How much fuel comes out when you press the schader vlv on the fuel rail?

Mustang Mark · Nov 10, 2011

If its a PATS problem, on 96-98 it will start and run for a little over a second then shut off. On 99+ it will not start at all. Just spray some starting fluid in the sum bitch and see if it will run.

ttocs · Nov 10, 2011

if you EVER plan on doing anymore to the car then go for the bigger pump. I just upgraded mine this week after a HCI swap and a tune where my tuner said that the 24 lb injectors were running lean in higher rpms. On a side not I am amazed at the difference in drivability and power since doing it, it was definitly the choke point holding my motor back. Now it pulls like crazy over 3k and will still run perfectly fine at 12-1400 rpms where it use to be surging.

94GTstanger · Nov 10, 2011

I would def upgrade the pump...it will most certainly help throttle response. Do NOT need to upgrade injectors till you start nearing higher actual HP numbers. Prob after 250 at the wheels or superchargers.

Steve-Oh · Nov 10, 2011

CC'S95GT said:
5.0 or 4.6?5.0- look at the dizzy being faulty.4.6- Have you tried to pull codes? Have you reset the inertia sw in the trunk?If the cam or crank position sensors are not working I would think the computer would prevent the car from firing.How much fuel comes out when you press the schader vlv on the fuel rail?

4.6 DOHC. Yup inertia switch is fine, no codes. I didn't think of the crank sensor, def a possibility. Zero fuel comes out of the schrader, pump will not prime / come on at all.

Steve-Oh · Nov 10, 2011

ttocs said:
if you EVER plan on doing anymore to the car then go for the bigger pump. I just upgraded mine this week after a HCI swap and a tune where my tuner said that the 24 lb injectors were running lean in higher rpms. On a side not I am amazed at the difference in drivability and power since doing it, it was definitly the choke point holding my motor back. Now it pulls like crazy over 3k and will still run perfectly fine at 12-1400 rpms where it use to be surging.

Like stated its my buddies car and I'm just trying to get it running so it can be sold. An aftermarket pump seems easier to get a hold of then a factory at this point. Just being cautious as it's not my car and I'm not too good with this sort of thing.

I'm sort of going about this the wrong way by just replacing parts but it's really the only method I have right now as I'm limited on time with this.

ttocs · Nov 10, 2011

just out of curiosity, when you checked the fuses did you check EVERY fuse under the dash and the hood or did you just try and pick the one you thought that the manual said? If you have not checked every fuse take the 2 mins it takes to do so. I have always done this and then when one was bad if I had time I would look up what the manual said it pertained to and most of the time it had nothing to do with the problem at hand.

castine917 · Nov 10, 2011

Have you checked for power going into pump before replacing it? Should be simple to test with a test light and rear end in the air. step 5 on this link. http://www.ehow.com/how_7740204_test-pump-1999-ford-mustang.html

Steve-Oh · Nov 12, 2011

ttocs said:
just out of curiosity, when you checked the fuses did you check EVERY fuse under the dash and the hood or did you just try and pick the one you thought that the manual said? If you have not checked every fuse take the 2 mins it takes to do so. I have always done this and then when one was bad if I had time I would look up what the manual said it pertained to and most of the time it had nothing to do with the problem at hand.

I wouldn't say I checked EVERY one but I did look at about 75% of them all.

Steve-Oh · Nov 12, 2011

castine917 said:
Have you checked for power going into pump before replacing it? Should be simple to test with a test light and rear end in the air. step 5 on this link. http://www.ehow.com/how_7740204_test-pump-1999-ford-mustang.html

I will do this before I install it.

Steve-Oh · Nov 12, 2011

Regardless though even if I replace the pump and it still doesn't work then at least I have an upgraded pump in there for when it does run. Those pumps aren't expensive.

ttocs · Nov 12, 2011

it only takes 2 mins to pull and check each one or run a meter over the top of them. I would not recomend replacing anything until you are 100% sure on the fuses..........

Steve-Oh · Nov 12, 2011

Copy that!

framda · Nov 12, 2011

I'm sort of going about this the wrong way by just replacing parts but it's really the only method I have right now as I'm limited on time with this.[/QUOTE said:
Checking all of the fuses takes less time than checking the price of a new fuel pump. Do yourself a favor and go through the flow chart from beginning until you reach the correct answer.