Electrical Issue or Vacuum Leak?

[shingo]

Hey all, first off sorry if this question has been answered and I just didn't find the right thread. I have searched a bunch of forums/google/yahoo/etc. and I always come up empty handed.

Car is a 1991 Nissan 240sx AT>MT swap still using the #25 AT ECU (unsure if motor was swapped or is the original but it is a DOHC KA24DE)


Car USED to turn over and idle/run in limp mode etc. with MAF unplugged but when MAF is plugged back in the car dies AND the dash lights don't turn off. The car would also turn over every once and a while with the MAF plugged in, but would idle roughly for a few seconds then bog down and die (and dash lights would stay on) When the MAF was unplugged and started/shut off the dash lights would turn off, most of the time. A few times the MAF would need to be plugged in, then unplugged for the car to start and shut off with the dash lights turning off.

Did some research here and there, removed the intake to check for any kind of vacuum leaks, let the car idle in limp mode and listened for vacuum leaks but couldn't find any. Checked MAF voltage, it's fine. Cleaned MAF connecter and MAF (MAF connecter is a 3 pin and MAF is a 4 pin, don't think this means anything but I thought I better post it anyway) unplugged the purple/blue wires on the IACV. Checked random wire connections, etc. all was alright. Also tried to unplug/reset the ECU and nothing.

When we connected put the ECU back in and put the intake back after checking around the car won't start at all now.

Fuel filter is brand new, 02 sensor is disconnected and car needs a new knock sensor and coolant temp. sensor but according to other forums/friends those wouldn't be the reason why the car wouldn't run/now won't start.

Other things I am going to try are a new wiring harness, new ECU, but if those might not the reason why I will hold off on spending the money to buy them.

Sorry if this all sounds confusing but I don't really know any other way to explain it. Thank you!

[shingo]

Update:

Bought a new wire harness and ECU.

The wire harness is cut here and there and when we removed the globe box to get better access we noticed a bunch of wires cut, also the new wire harness has a connector on the ECU side that the wire harness on the car now doesn't have.

Car IS getting fuel, spark.

[PapaSmurf2k3]

A bad coolant temp sensor absolutely can cause a car to not start. It'll give it too much fuel.
You need to determine if you're getting too much fuel, or too little fuel (or if your timing is way off).

If you crank the car and it doesn't start, pull the fuel pump fuse. Try starting it again (it may take a few extra cranks). If it fires up and runs well for a few seconds, you know you're running too rich when it has the proper amount of fuel pressure.
If you pull the fuse and it still doesn't start, try plugging it back in and doing one of these 2 things:
Pull a vacuum line and pour a little gasoline down it. It should enter your intake and help with starting.
Spray some starting fluid in the intake.

You can also pull your plugs to see if they are black with carbon (rich), or white and clean (lean).

[shingo]

We got the car to start late last night, we checked the fuel pump one more time and whoever worked on the car before us put the fuel pump back in without a clamp on one of the hoses, so the pump actually fell out, into the gas tank.

Car turns over and runs like it did before. With no MAF plugged in it will idle fine and start fine. With MAF plugged in car will start and run for a few moments, then bog down and die. Car will now actually start with the MAF plugged in so I guess that's a step forward.

Thank you for the reply!

[PapaSmurf2k3]

Sure!
Might be a good idea to reset the ECU now that the fuel pump is working properly.

[shingo]

Thank you! Reset the ecu and it starts and runs with MAF in now. One more step forward but now car is bogging and making a "pop" noise inside of the intake under throttle.

Going to check timing and TPS (according to forum searching this would be up next on the things to check)

If that doesn't help I will probably need to get a new 02 sensor, Cooling temp sensor and knock sensor?

[shingo]

She lives!! Thank you so much for your help!

[PapaSmurf2k3]

Yup, I would have said ignition and valve timing were the next things to check.

[shingo]

It actually wasn't either, check this out.



I don't know who, or why they ghetto rigged it like this. We smelt fuel but I guess it was just whatever was left in the lines. Car also needed new spark plugs.

[PapaSmurf2k3]

I'm not a huge fan of the grommet system Nissan uses to hold the fuel pumps in place. There's nothing solid. I think I zip-tied mine to the shaft when I was in there.

[shingo]

It is a little dumb but I just can't believe they didn't put something down to keep it clamped on.