Nsd90 wont fire

[dlr123]

I have a nissan nsd90a tldi that has been sitting for 2 yrs. i have replaced the fuel pumps and sent the fuel injectors out to be cleaned. I also replaced the reed valves in the compressor. I have 70 psi on air side and 70 psi on fuel side. But the engine wont fire. If i spray starting fluid in the intake it will fire and run till that starting fluid is burned. So it acts lime the fuel is not getting thru the injectors to the engine. I checked the air injector resistances and they are fine. It has fresh fuel and filter and hoses. Any ideas what i need to check now?

 

[pvanv]

Those pressures are really low. Chase that first. There should be a 10 psi differential fuel to air, so check the regulators.

 

[dlr123]

I checked the air pressures again by pinching off the air hose going from the rail to the exhaust. After a few cranks it fired and ran for a minute or so but didnt run well. Air regulator? Is there anywhere else to check

thanks for the help

 

[pvanv]

Using your Factory service manual as a guide (forget the aftermarket manuals), go through the fuel and air systems.

 

[dlr123]

I have been using the manual but not much luck. No codes. My local technician shop closed or i would take it to them. Another shop 1 hr away is where i bought some parts but i heard the guy on the phone asking tohatsu service line what 3 blinking lights meant. I knew the answer to that so I'm not sure i trust him to do higher level troubleshooting

 

[pvanv]

Indeed. That's kind of like the "check engine" on modern cars. But Tohatsu will guide the tech through troubleshooting.

Your pressures need to be up around 90, and there should be a 10 psi difference between fuel and air. Get that right, and you may be OK.

 

[dlr123]

Thanks again. I will keep plugging

 

[pvanv]

Air 80 psi, fuel 90. +/- 6 psi.

If both are low, and the pressures slowly drop when the key is OFF, then check the air regulator (use shop air). If regulator pops off in spec, the air filter or hose is probably restricted, or the compressor needs attention. If the air regulator pops off below spec, you need a new air regulator. If the compressor is suspect, you can run the motor on shop air over 100 psi.

If the pressures do not drop off, you have a possible air leak, compressor line, reed, or gasket... Air injector leak or o-ring leak.

If air pressure is in spec, and the fuel is NOT 10 psi higher (same as air), the fuel system is malfunctioning. If so, does the FFP come on for a few seconds when the key is turned ON, and fuel pressure goes up 5 to 10 PSI, and then falling off?

If yes, pump is working... if the pressure does not come up 5 or 10 PSI, the regulator is suspect, or there is a restriction either before or after the FFP... possible high pressure filter restriction.

If no, check voltage to the FFP connector. If 12v for about 2 seconds after key turned ON, the FFP may be stuck; if not, check wiring, ECU pin, and fuses. The ECU sends ground to activate the FFP.

When checking the fuel & air pressure on TLDI engines, remember if both pressures are low then the air system is the problem. If only the fuel pressure is low then the fuel system is the problem.