96 cobra breaks up under WOT

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Pedrothecobra

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ok so the voltage is there, its just getting lost somewhere. While your checking the fuel pump power at the ccrm see if you can find the power wires for it and see what its voltage is. If the ccrm is only getting 11v, it can't sent the pump 13.
good point. ill probably dig into it on sunday
 

Buffalo5Spd

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Thirty years ago or so I read an article about Buick Grand Nationals and a trick to get more umph outta the Fuel Pump. It’s called a hot-wire kit. The long and short of it is running a wire directly from the Alternator output to the Fuel Pump thus giving the pump the most power available with as little voltage loss as possible. I haven’t heard of this being done on a Mustang, however it seems reasonable to me that it would help if the problem is in the “hot-side” wiring. Obviously you need to upgrade the ground also to eliminate the bottleneck there. This would be more effective if the in tank wiring is upgraded as well but be mindful that it is a specialized wire in the tank and wiring though the fuel pump bulkhead is a pain.
 

ttocs

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Thirty years ago or so I read an article about Buick Grand Nationals and a trick to get more umph outta the Fuel Pump. It’s called a hot-wire kit. The long and short of it is running a wire directly from the Alternator output to the Fuel Pump thus giving the pump the most power available with as little voltage loss as possible. I haven’t heard of this being done on a Mustang, however it seems reasonable to me that it would help if the problem is in the “hot-side” wiring. Obviously you need to upgrade the ground also to eliminate the bottleneck there. This would be more effective if the in tank wiring is upgraded as well but be mindful that it is a specialized wire in the tank and wiring though the fuel pump bulkhead is a pain.
specialized wire?
 

joe65

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Just a wag but I had a car that had a cut out issue that drove me nuts tracking down and it ended up being a bad cable at the battery. Just a thought
 

D3VST8R96GT

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Just a wag but I had a car that had a cut out issue that drove me nuts tracking down and it ended up being a bad cable at the battery. Just a thought
Good ole dumb dumb wound, bit me a couple times. Its my first place to start now hahaha "grounds/negative cable clean tight and not corroded" followed by "car has PLENTY of fuel" lmao
 

ttocs

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a resistor is made to either drop the voltage or for current driven purposes so I can't say I would recommend removing it unless your installing a new relay/circuit (with a fuse) to drive it.
 
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Pedrothecobra

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Yea problem is I can’t find a replacement without goin on eBay. I’m getting 11.5 at the pump and my pressure starts to drop when I’m getting into it. Like the pump can’t keep up with the demand
 

07GtS197

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If it is the pump not being able to keep up then it’s a pump issue and not a wiring issue. How much boost are you making and on what pump?
 
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Pedrothecobra

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Yea problem is I can’t find a replacement without goin on eBay. I’m getting 11.5 at the pump and my pressure starts to drop when I’m getting into it. Like the pump can’t keep up with the demand
If it is the pump not being able to keep up then it’s a pump issue and not a wiring issue. How much boost are you making and on what pump?
my pressure is at 36lbs at idle and it goes up to 45-5-0 when I ease into the throttle. The pump is new. I have 13.8 into the resistor and 11.5 coming out so I’m losing roughly 2v to my pump.
 

07GtS197

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Yeah but what brand is it? Also you said your alternator output is 13.5v, is that what it’s putting out at wide open throttle? I’m no electrical engineer so take this with a grain of salt but I don’t think your voltage drop is too much. All circuits will have valtage drop because of resistance in the wire itself and heat. It’s a big issue with the crown vic guys because their headlights don’t use relays. I’m leaning more towards your alternator isn’t keeping up at higher engine speeds. I still wouldn’t rule out bad splices or anything around the pump just in case.
 
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Pedrothecobra

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is that resistor in the ccrm?
No the resistor is mounted up under the passenger fender right after the CCRM. So from what I’ve found I could have a bad fuel pump relay. There is another relay that opens and closes depending on rpm which takes the resistor out of play at higher rpms. Now I’m not sure if it’s the relay in the CCRM or one behind the glove box possibly. I’m going to do more research before I make another move.
 
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Pedrothecobra

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Yeah but what brand is it? Also you said your alternator output is 13.5v, is that what it’s putting out at wide open throttle? I’m no electrical engineer so take this with a grain of salt but I don’t think your voltage drop is too much. All circuits will have valtage drop because of resistance in the wire itself and heat. It’s a big issue with the crown vic guys because their headlights don’t use relays. I’m leaning more towards your alternator isn’t keeping up at higher engine speeds. I still wouldn’t rule out bad splices or anything around the pump just in case.
So the alternator output is higher usually around 14.2 I was just using 13.5 as an average. And I am dropping about .3v from the battery to the CCRM then another.2v out of the CCRM to the resistor. But I may have found something with the fuel pump relay. I’m trying to track down more info on it now
 

ttocs

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it could just be a bad connection at the resistor. I would get your eyes on it and see if it looks bad/corroded or worn out and it could be as simple as a quick touch with a soldering iron to fix. While your there it would also allow you to confirm that it is the problem or not with a quick test of the voltmeter.
 
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Pedrothecobra

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Yea I checked the connection it’s fine the resistor is also fine. I’m leaning towards a relay but I’ve hit a wall for the day lol. I’ll be back out in the garage tomorrow after work
 

lwarrior1016

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I thought only the 98’s had a relay behind the glove box?

Either way, the resistor and second relay is made to make the pump sort of a two speed setup. If the relay is not energized, it sends power through the resistor to reduce voltage. If the relay is tripped, it takes the resistor out of the circuit and sends full voltage to the pump.

If you really believe your issue is voltage at the pump, run a wire from the battery hot and send full volts to the pump (with a big enough wire, and only temporarily). Then drive the car with the normal power circuit out of the equation.

It is a return system so having the pump full speed will be no problem.
 
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Pedrothecobra

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I thought only the 98’s had a relay behind the glove box?

Either way, the resistor and second relay is made to make the pump sort of a two speed setup. If the relay is not energized, it sends power through the resistor to reduce voltage. If the relay is tripped, it takes the resistor out of the circuit and sends full voltage to the pump.

If you really believe your issue is voltage at the pump, run a wire from the battery hot and send full volts to the pump (with a big enough wire, and only temporarily). Then drive the car with the normal power circuit out of the equation.

It is a return system so having the pump full speed will be no problem.
Yea I was thinking about doing that. I have a relay coming
 

ttocs

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you can pull it out and test it. Put 12v on pins 85/86 and it should click. When it does pins 87 and 30 should be common.
 

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