Nissan Repair: 91 300ZX Slow Starting, fuel pressure regulator, vacuum leaks

Question
Thanks for the quick reply.  I'm not smelling any gas and have no visible leaks.  Is there a common area to look for vacuum leaks on this vehicle?
-------------------------------------------
The text above is a follow-up to ...

-----Question-----
I have a 91 300ZX 2+2,  200K miles, which is slow to start (5+ seconds) after sitting a long time.  After short stops, cars starts right up.  Once running, car runs fine so I'm assuming I'm loosing fuel pressure while it sits.  Replaced fuel pressure regulator.. no change.  I would appreciate any ideas... Fuel pump?  Thanks
-----Answer-----
Hi Red,

Fuel pump could be the culprit. A line leak or vacuum issue is more likely in that year.

Answer
I was answering this trying to help with the cause of what causes low fuel pressure. But if the car runs fine at all rpm's it's probably not the fuel pressure issue. Here is the service procedure that Nissan has:

Classification:
EC96-004

Reference:
NTB96-032

Date:
April 17, 1996

ENGINE CRANKS, BUT WILL NOT START OR IS HARD TO START

APPLIED VEHICLE:
All

SERVICE INFORMATION

This bulletin has been developed to address complaints of an engine which cranks over normally, but is difficult to start or will not start at all.

1. Connect CONSULT. If the vehicle you are working with is not CONSULT compatible, connect a tachometer (digital readout if possible).

2. Start the engine (the accelerator may have to be opened and/or the fuel pump fuse removed during cranking to get the engine to start), and warm it to operating temperature.

Note :
If the engine will not start after performing the above procedure, clean and dry the spark plugs, and attempt to start the engine again.

3. Run the engine at 2000 rpm (no load) for two minutes. Then shut the engine off.

4. Check the oil level and correct if necessary (between the "L" and "H" marks on the dipstick). If the oil level is overfull and has a gasoline odor, change the oil and filter before performing this procedure. If the crankcase is overfull with oil, idle speed adjustment may be affected.

5. Disconnect the throttle position sensor (TPS) connector. Now re-start the engine.

Note :
When the engine is in this condition (TPS disconnected), the IACV-AAC valve and the ignition timing are held in a "fixed" position, and the idle speed is called "base idle." If the engine stalls with the TPS disconnected, the base idle speed is adjusted too low. Temporarily increase the base idle speed by turning the adjusting screw on the IACV-AAC valve until the engine will idle.

Note :
On 1989-1994 Maxima's (J30) with VG30E engine the IACV-AAC valve is a "stepper motor" type valve. To set base idle on these vehicles, set the ECCS ECM mode screw fully "clockwise". This will close the IACV-AAC valve completely to allow base idle speed adjustment. Return the ECCS ECM mode screw fully counter-clockwise after setting the base idle (see step 9).

6. Rev the engine 2-3 times to 2000-3000 rpm, then allow it to idle (all accessories "off").

7. Check the ignition timing with a timing light and adjust it to specification (if necessary).

8. If the vehicle is not CONSULT compatible, monitor the idle speed using the tachometer connected in step 1. If using CONSULT, perform the following procedure:

Monitor the idle speed (CMPS^RPM) on the CONSULT screen.

9. Check the idle rpm and adjust to specification (if necessary) using the screw on the IACV-AAC valve.


A pic was here with a graph. This medium does not allow pics. Sorry.



 



The table shows ignition timing and base idle speed for some models.

If the model or model year you are working on is not listed, refer to the appropriate service manual (EF &) EC section, and perform the "IDLE SPEED/IGNITION TIMING/IDLE MIXTURE RATIO INSPECTION" procedure.

10. Turn the engine off, and re-connect the TPS.


NOTE: To obtain an accurate fuel pressure reading the engine must by running. Basic fuel pump operation can be verified in a no start condition by observing gauge reading while cranking engine. Fuel pressure should be approximately 43 psi (299 kPa).

On 300ZX models, relieve fuel system pressure as follows:
Disconnect fuel pump relay, which is located behind the lefthand side kick panel.
Start and run engine until it stalls.
Try to start engine two or three more times to ensure that fuel pressure is released.
Turn ignition switch off and reconnect fuel pump relay.