# 1996 4x4 HB mystery no start. K24E



## mtne (Aug 22, 2012)

Hi, I'm at a loss here and looking for help like all the other n00bs.

It died. My wife was running errands 80 to 90 miles and stopped at her moms, stopped and wouldn't start again. No noise, rough running, other indicators of any issues. I'll note that yes she is actually good about noticing those kinds of things.

I've since bought a 2wd 96 to use with the intent of helping diagnostics. 

I've changed the cap and rotor, plugs and wires. And put in a new fuel pressure regulator.

It gave no OBDII codes.

I've swapped to the other truck to verify function the:

Both underseat computers
fuel injector rail, with pressure regulator and injectors
distributor, cap rotor

the fuel pressure is low 30psi, but not so low that is shouldn't try to start. To test this, we ran fuel lines between the trucks and cranked together. Not even an attempt to start. 

EGV functions proper under manual vacuum.

The timing and movement of the valves seems to check out fine. Nothing noticeably amiss with the valve train action.

The cylinder pressures are low, but not so low that it shouldn't try to run. cyl1 -85, 2-100, 3-100, 4-105
And I've separated the exhaust before the cat to make sure there was not a blockage.

The noticeable oddity which makes me think valves and timing is a push back through the throttle body when cranking. 

I'm at a loss. My feeling is that it should be something simple. If it were a bike I'd be looking for a failed clutch bypass switch or a kickstand safety switch.....

So what am I missing? What say the gurus?


mountain eagle
:newbie:


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## SPEEDO (Jun 9, 2003)

does it turn over? or just a click?


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## mtne (Aug 22, 2012)

SPEEDO said:


> does it turn over? or just a click?



Turns over strong with a fresh battery w/ a charge.


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## rogoman (Dec 16, 2004)

Are you getting spark at all the plugs? If you are, then the fuel injectors may not be firing; this could be caused by a bad CAS.
Other possibilities:
- Ignition timing incorrect.
- Timing chain skipped several teeth.


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## mtne (Aug 22, 2012)

We've verified spark. Checked the rotor and timing as to valve positions are in relation to when the rotor would be delivering spark. This is why we think the timing is good. Tension is good on the chain too.

Besides the fuel rail being verified on the running truck, I've pulled the rail and visually checked for injector spray.

Bad CAS=? 
something? air sensor I'm guessing?


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## ajriding (May 10, 2010)

could still be the fuel pump. Seems there is a threshold of pressure the pump has to get to before it can get through the throttle body/ or fuel injectors. Too low a pressure and no fuel will enter the cylinder. Replace fuel pump or add an electric pump with the right press inline (outside the gas tank). 
Running the tank low all the time could cause the fuel pump to over-heat as the gas in the tank is meant to keep it running cool - just for those that need to know.


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## mtne (Aug 22, 2012)

Well we hooked up the fuel rail to my other nissan and tried to test it that way. Took an extra 10' of hose to make the loop and it still didn't want to fire. I can't help but think that there is another issue, but a weak pump is adding to the problem in terms of troubleshooting.


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## smj999smj (Jan 1, 2006)

Damn! You sure do diagnostics the hard way! Always start with the basics! Air, fuel, spark, compression and timing. Personally, I think those compression readings are a bit low. When testing compression: did you install a charger on the battery...fix the throttle plate into an "open" condition...remove all plugs....perform a "dry" test followed by a "wet" test (adding a teaspoon of oil into the cylinder to see if the compression raises)? If you verified spark to the plugs and the plugs are not fouled, try spraying carb cleaner into the throttle body and see if the engine starts and runs off of the carb cleaner. If it does, you have a fuel delivery issue. Use a fuel pressure gauge to confirm proper pressure. If pressure is lower than specs, replace the pump. If fuel pressure is good, confirm power to the fuel injectors with the key "on" using a test light. If the fuel injectors have power, use a "noid" light to confirm the injectors are "firing" while cranking. If the noid light flashes, this tells you the ground circuit is good to the ECM and the ECM is pulsing the circuit to ground to "fire" the injector. A cylinder leakdown test can also be helpful as this will tell you if compression is being lost when the cylinder is at top dead center and where it's being lost (intake valve, exhaust valve, rings, head gasket). 

NOTE: Compressiont test per Nissan service manual:

Start engine and run until engine reaches operating temperature.
Turn ignition switch off.
Release fuel pressure. Refer to Technician Safety Information for fuel system pressure release procedure.
Remove all spark plugs.
Disconnect distributor coil cable.
Attach a compression tester to cylinder No. 1.
Depress accelerator pedal fully to keep throttle valve wide open.
Crank engine and record highest gauge indication.
Repeat measurement on each cylinder.
Standard compression is 192 psi, minimum pressure is 142 psi and compression difference limit between cylinders is 14 psi.
If compression in one or more cylinders is low, pour a small amount of engine oil into cylinders through spark plug holes, then retest compression.
If adding oil helps compression, then piston rings may be at fault. If adding oil does not help compression, then valves may be at fault.
If compression stays low in two cylinders that are next to each other, then cylinder head gasket may be leaking or both cylinders have valve component damage.
Repair as necessary.


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## GeoBMX4Life (Mar 25, 2010)

AT or MT...if MT...could be the clutch safety switch


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## ajriding (May 10, 2010)

correct Geobmx. Mine, manual, had a plate on the clutch pedal that pressed a button to tell computer that the clutch was pressed. The plate fell off so I can't start it without pressing the over-ride button. I could put my foot on the button I guess if needed. This also serves as a cheap anti-theft mechanism, so I have not fixed it - haha.


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## smj999smj (Jan 1, 2006)

The engine cranks, according to the post, so that would rule out a potential bad clutch switch. The big "red flag" to me is the stated compression of 85-105 psi when the standard compression spec is 192 psi with a minimum spec of 142 psi per the service manual.


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