Start up issue after the car has been driven 5 minutes

[bdrs]

Hi there,
I have a weird issue on my NSX and maybe some people here can help me defining where it comes from.

So, when the car is cold or warm (like after being driven for 30 min or more), I don't really have any issue starting the car.
I put the contact on, hear some clicking then the fuel pump running and the engine starts without issue.

But if I just try to start the engine after driving for something like 5 minutes, I would have contact, hear the clicking but not hear the fuel pump.
And if I try to start the engine, it cranks but then dies. (Probably no fuel coming since I didn't hear the pump)

Any idea what could be causing this?
Thanks in advance !

 

[ftuhy]

I'd start by looking at the main relay. It could be a number of other things, but the cracked solder joint issue on that is a possibility.

Cracked solder joints are often temperature sensitive. My lab tech used to find them using a heat gun and a can of quick freeze.

 

[Old Guy]

First thing, make sure that all your electrical connections are good. You would hate to go around spending $ or € just to find a bad connection.
The electrical supply for the fuel pump is pretty simple(see the attached figure). You have 5 items in the circuit:

1. The ignition switch which provides +12v to the #2 fuse (top black/yellow wire) which supplies the pump (and other stuff)
2. The main FI relay
3. The fuel pump relay / resistor combo
4. The fuel pump
5. The ECU

If the ignition switch was the problem, I think you would have other issues (no dash indicator lights). You didn’t mention that so I will assume that is not your problem.

Probably the easiest thing to check first is the fuel pump relay resistor. By-pass the resistor (put a wire jumper from the black red to the black yellow wire). If this allows the pump to start up when it previously wouldn’t, you have a fuel pump resistor that is in some kind of weird failure mode and should be replaced.

If you eliminate the fuel pump resistor as the source, then the likely candidate is the main FI relay. If you have an electrical tester or 12v test lamp, connect it between the black/yellow wire on the fuel pump resistor and ground. Try starting the car. If the pump doesn’t start but you are getting 12v here then the problem is not the relay. When you do this test, you will need somebody to watch the tester /light while you try to start the car. If the engine doesn’t start, the ECU detects a start failure and should shut the pump off after a couple of seconds so trying to start the car and then running around to the back to check for voltage is a non-starter (pun intended). If the relay is good, you will get 12v for a couple of seconds (if the engine doesn’t run) or continuously (if the engine does run). If you are uncomfortable with electrical test procedures I suggest substitution with a new relay is the easiest way to go.

If it is not the resistor or main relay, the remaining options are painful / expensive. If this problem just started recently, it is possible that your fuel pump could be in its end of life mode. Sometimes the pump dies completely; but, sometimes pump start-up will become hit or miss before dying completely . If this problem has been going on for an extended period of time (a month or two), then the fuel pump should have died by now and is likely not the problem. That leaves you with the ECU; however, in my limited experience, ECU failure is a really low probability event.

 

[BATMANs]

I had similar symptoms that was the main relay (easy parts to access and replace from the rear panel behind the seats.

http://www.nsxprime.com/wiki/Main_Relay

http://www.nsxprime.com/forum/showthread.php/55874-Fixed-my-PGMFI-main-relay!!!!

 

[bdrs]

thanks for the detailed troubleshooting.
I also thought that if the pump itself had an issue, I would have had other issues than that by now.

I will run the checks and keep you posted!