YJ with 5.0 swap. idles just fine but dies under throttle

[olivedrabcj7]

A friend of mine has swapped a fuel injected 5.0 into his YJ and everything is hooked up, it will fire up and idle just fine but once you give it gas, it dies. Weve narrowed it down to a fuel delivery problem. Im thinking its because he is using the ford fuel pump. We have the fuel pump just wired directly to 12 volt switched power. could this be the problem?

 

[DementedXJ]

the wiring sounds fine how it is. Did you put a fuel pressure guage on it to see what happens while it is running or when it dies?? what is the motor out of? what computer is he using??

 

[olivedrabcj7]

we didnt have a fuel guage to test it. Im thinking its the pressure regulator even though its new. The motor and computer are out of a 91 mustang GT. Right now the only exhaust on it is manifolds and straight pipes. no mufflers or cats.

 

[RedHeep]

Electronic ignition?

Does the timing advance when you increase the rpms?

 

[goodburbon]

Can you accelerate it very slowly or does any throttle at all kill it?

 

[olivedrabcj7]

yes electronic ignition. we havent checked the timing on acceleration. it doesnt matter how you throttle it but once it gets to about 1200 rpm's it acts like somebody switched the fuel pump off. if you just floor the throttle from idle it will choke out at the same place as slowly increasing throttle. Im thinking its something to do with the fuel pressure regulator.

 

[goodburbon]

When you say he was using the ford fuel pump, its one for FI 5.0's? Is he using the stock YJ fuel line? Is the line clear of any debris or rust? if the line sat empty for very long it could have scaled up, if it sat with fuel in it for a long time it could have gummed up. Both of which would lead to a drop in volume available at the correct pressure.

A fuel pressure gauge would tell you much.hasta

 

[Oatmeal]

You might check the TPS as well--------Hans