Runs with return line off??

[Stadick_shock]

Okay, a little background information: It's an 85 turbo with T-tops. I bought it for $2500 a couple months ago and has been running fine. Then, about two months ago I was doing a little bit of a pull and I believe it was around 3000rpm in third gear when the car lost power and shut off.
Now here's the weird part: it only starts and idles with the fuel return line disconnected from the fpr. So far, I have replaced the fpr, fuel filter, fuel pump, spark plugs, spark plug wires, the ENTIRE distributor, and have blown air through the fuel lines. I took it to a shop to see if they could find something and they said it had fuel, spark, timing was correct, and that it's compression is almost perfect.
Now, I assume it's something electrical or a sensor because the wiring looks pretty atrocious and a lot of things are disconnected. I'm at a complete loss and I desperately need assistance, so any ideas would be a great help. Thanks guys.

[evildky]

And no cgas is coming out of the fpr? The FPR is located at the front of the engine. The fuel return line hooks comes from the bottom of the FPR there are 2 fuel lines one from each side of the intake then a vac reference that goes to the intake plenum. Are you missing the fuel return hose or maybe just the vac reference line? If the vac reference line is off it will cause rich idle, if the vac port on the plenum is open it will cause a lean condition and likely all sorts of idle issues

[Stadick_shock]

Hey, thanks for the reply!

And no, fuel gushes out of the fpr when I disconnect the return line and only then will the car run. Also, the vacuum line on the top is connected. I'm thinking now it's either wiring or the injectors. The return line deal is a real curveball. Haha

[evildky]

Well if there is no fuel coming out of the fpr it's either stuck shut which is unlikely especially since it's new or the fuel pump isn't making enough pressure to overcome the internal spring which could be the pump the wiring or the relay, you said you replaced the pump so I'd go for that relay.

[Stadick_shock]

There IS fuel coming out though.

[evildky]

Injectors don't all die at the same time. I'm gonna theorise that the disconnected return hose allows the rail pressure to drop a few psi enough to keep it from flooding itself out because it likely has a bad CHTS or CHTS pigtail.

[Stadick_shock]

Hmm that sounds possible. I'll stop by the parts store and see the cost. If it's cheap, I'll just straight up replace it.

[Stadick_shock]

Looking into it, it does sound like it could be the problem. Do you know any reputable vendors that would sell the sensor?

[evildky]

Last I knew it was a nissan only part, courtesy parts will likely have the best price on the sensor and the pigtail.