1989 D21 Rough Idle

[PullinWrenches]

Hello all,

Recently for no apparent reason engine started running rough at idle, a bit better at higher RPM. Changed all ignition (was due anyway) did not help. No codes.

Seemed to me to be running too rich, could see a bit of fuel puddling on top of the butterfly plate in the carb. Could not see any fuel running from the FPR into the throttle body from the FPR "vacuum hose (is that REALLY a vacuum hose, or just a vent line???)", began to wonder if the FPR was stuck shut (too much fuel pressure).

I unplugged the fuel pump relay and it started up and idled nicely... as it began to sputter (running out of fuel) I would plug the relay in enough to give it a shot of fuel. I could keep it running nicely by "blipping" the relay in and out. When I plug the fuel pump relay back in and leave it idles very rough.

 

Conclusion: Either the FPR is sending too much pressure to the injector or the injector cannot handle the factory ~35 psig any more? I cannot find these Fuel Pressure Regulators anywhere.

 

Not sure what to do, maybe time to get rid of the truck if I can get it running well, maybe a aftermarket FPR is the best route. Damn I have always loved these trucks, but parts are more and more made our of UNOBTAINIUM.

 

If I go weber and dive in the biggest issue seems to be distributor advance? Worried that unplugging the ECU from all carb circuits will put the ECU into limp home mode or something.

 

Would be nice to have a zero electronics motor. Just not sure

 

Any wisdom would be much appreciated.

[datzenmike]

There's two injectors and two throttle plates. Was the puddling on one or both?

[PullinWrenches]

Thank you Mike,

This truck appears to have only a single injector/throttle plate, see photo.

 

When I look at the fuel line set up it does seem a bit odd, appears to supply full pressure to the TBI and then return fuel to the tank to hold the fuel pressure set point.

I spliced a tee into the fuel line and connected my highly accurate harbor fright gauge to it which read ~39 psig.

 

This might indicate the return spring inside the injector might be weak or there is junk in there? Cannot close the injector in between pulses from the ECU?

 

Looking on line a bit I cannot find that injector... ~sigh.

 

Not sure what to do, the truck only has ~120k miles or so, I use it on the farm

 

Thank you again for any input.

 

https://u.pcloud.link/publink/show?code=kZct8NVZx771sB0pFdjJsWkD2xMHm743CSDy

[Crashtd420]

Not sure how much your looking to spend but it seem you might be able to get at the dealer....

You didn't say what motor?

This is an oem online parts store I like.. once you know the part number you can check the local dealership and see if they have it...

https://www.nissanpartsdeal.com/oem-nissan-hardbody_pickup_d21-fuel_injector.html

 

Other option is to use a rebuild service through rockauto or directly with a place that rebuilds them..

 

https://www.rockauto.com/en/catalog/nissan,1989,d21+pickup,2.4l+l4,1210903,fuel+&+air,fuel+injector,6224

 

 

[PullinWrenches]

Thank you all for your help, I just listed it as is on CL, sold in 45 minutes! I need a farm truck, not a hobby, but what a great truck other than the weak emissions stuff.