Does not start when hot

Hi,

Is the check engine light staying on when the engine runs? Also, your description sounds like low fuel pressure or a crankshaft position sensor, but I see you replaced both. Do you have access to a live data scanner? Is there any smoke from the exhaust?

Since you have already replaced parts for the most common problems, I need you to check for either engine vacuum leaks, a plugged catalytic converter, or if you have a live data scanner, check for both diagnostic trouble codes and let me know what the long term and short term fuel trims are when the engine is warm.

Here are a few links you may find helpful:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Also, if you haven't already, reconfirm fuel pressure to make sure it is within spec. Here is a link that shows in general how that is done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Here are the directions specific to your vehicle along with the manufacturer's specs. The attached pic correlates with these directions.

_________________________

1996 Nissan-Datsun Truck Pathfinder 4WD V6-3.3L (VG33E)
Component Tests and General Diagnostics
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pressure Testing and Inspection Component Tests and General Diagnostics
COMPONENT TESTS AND GENERAL DIAGNOSTICS
Fuel Pressure Check
-When reconnecting fuel line, always use new clamps.
-Make sure that clamp screw does not contact adjacent parts.
-Use a torque driver to tighten clamps.
-Use Pressure Gauge to check fuel pressure.
-Do not perform fuel pressure check with system operating. Fuel pressure gauge may indicate false readings.

pic 1

1. Release fuel pressure to zero.
2. Disconnect fuel hose between fuel filter and fuel tube (engine side).
3. Install pressure gauge between fuel filter and fuel tube.
4. Start engine and check for fuel leakage.
5. Read the indication of fuel pressure gauge.

At idling:
With vacuum hose connected -
Approximately 235 kPa (2.4 kg/cm2, 34 psi)
With vacuum hose disconnected -
Approximately 294 kPa (3.0 kg/cm2, 43 psi)

If results are unsatisfactory, perform Fuel Pressure Regulator Check.

_________________________________

Since it fails to start when warm, I suspect it is an electrical issue, but without trouble codes, we have to check one thing at a time. So, if you can scan the computer, let me know what you find. Here is a quick video showing how it is done:

https://youtu.be/YV3TRZwer8k

I realize most people don't own a scanner, but if the vehicle is safe to drive, most parts stores will do it free of charge.

Let me know what you find or if you have other questions. Also, let me know if the timing belt has ever been replaced.

Take care,
Joe

Even though you replace the fuel pump we need to start with checking fuel pressure at the rail.

This sounds like a fuel issue but if you have good fuel pressure then we can move onto other things but we need to eliminate that first.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

The things that are pointing me there are the issue when you accelerate but if you give slow steady accelerator, it is fine. This is a sign that it is starved of fuel but when given steady throttle it can build the pressure.

It could also be a sensor issue but again we can get to this once we eliminate the fuel issue.

https://www.2carpros.com/articles/engine-has-low-power-output