92 400 wont run when warmed up

[Matt300ZXT]

So I might be getting a sweet deal on a friend's 400 if I can figure out the problem with it. If this is a common problem and is discussed elsewhere, if someone can link me, or give me the name of the problem, I'll be more than happy to search it.

It's a 92 400, had the motor swapped with a lower mileage JDM engine. Ran fine until the week before my friend got it. Since it's been acting up, the alternator, distributor caps, rotor buttons, plugs, wires, and battery have been replaced.

He said what it's doing is it starts up perfect and runs until the engine warms up, then he said you can hear the fuel pump get louder, and quieter, then it spark knocks and cuts off, or if you cut it off. Also says it won't crank until the car cools back off. He said he has a friend that's pretty good with the Toyotas and Lexus cars and did an ECU bypass on it, and it still acts funny, so he thinks pretty much it is the fuel pressure regulator.

If anyone can shed some light I'll be more than happy to take the help, or ask some ?s to help get some details ironed out.

 

[cribbj]

I've never fooled with a stock UZ, (both of mine are modified) but it sounds like a weak fuel pump, or as you say, perhaps the FPR is acting up. Can you check the fuel pressure at the rail and see if it's holding OK?

 

[Matt300ZXT]

I'll pass the info to him...I was thinking pump myself. Would hate to pick the car up and not be able to diagnose it at all. Would be great if it was something super simple. My pump has 190k on it and running strong, his actual body has way less and if it's the pump, then maybe I am just lucky

 

[sideshow]

toyota must be makign a fortune on 1uz dizzy caps and rotors hehehhehe
everytime theres a prob most people change these
ive never seen a std fuel press reg fail

ive had pumps go noisey because of half blocked pump or old pump or low on fuel
or even when return fuel is not getting back but since this is a std car and not been touched its probably the fuel pump
you can have a 20k fuel pump fail it all depends if he picked up a bad batch of fuel

you could even have a blocked gauze on the end of the pump
so i would pull [pump assembly out and just double check and even get tank flushed clean so it doesnt happen again

one way to know if its pump is like others said put a gauge on it plus run a wire from the fuel pump + to the + battery and make pump get constant power
this way u will know its not the wiring if it still fails

 

[Matt300ZXT]

I'm beginning to lean fully towards a bad pump myself. The guy who had it before him isn't the greatest with cars, kinda cheaps out on things...he's the guy that'd cut his stock springs to get that slammed look rather than just buying the lowering springs. I wouldn't put it past him to have been putting the absolute cheapest gas in town in his car just to save a few pennies.

If I can work out a deal, the first thing is the pump's coming out and I'm inspecting the innards of the tank. Thanks for the info guys.