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Troubleshooting help needed please!


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1985 Nissan 720 4x4 z24 2.4L

The engine was pulled from a '86-87 with unknown miles and ran for a couple years after being hooked up.


While out romping around in the back country my truck ended up dying on me. Everything was going fine, I had just gout out of a rough part and about 1/8th a mile later on a flat part it just cut out on acceleration, I would back off and it would idle a bit but then died. It fired up a couple minutes later, I tore out for the next 3 miles and on an uphill it died and I had to be towed out for a few miles. Got to a down hill and rode 4th gear to get the engine turning and after a bit it actually resumed acting normal. 


I started throwing parts at it:

New air filter

New NGK Iridium plugs

New wire set

New Dist Cap & Rotor

Replaced every conceivable vac hose and fuel line in the engine bay (some were sorely needing replaced)

New fuel filter

New valve cover gasket (oil was slowly leaking a bit on the engine)


I tried my hand at rebuilding the carb (with the help of an experienced friend) thinking this should help, and I messed up the idle and mix screws. Stuck it in the shop and they had their "carb guy" adjust it as best they could over a month and a half. It will idle about 1100 RPM, choke works again without being super high RPM, but now it slugs when I hit the gas coming off idle, and it will die if I hit the gas super hard. They said it was not a bad job rebuilding it, and my friend said I likely did not damage it in the rebuild, but it still has not fixed the issue. Truck died after a full warm up cycle 1/2 a block from home on a warm day. 


A month later I put a fuel pressure gauge on it and it reads 3.7psi constant regardless of cold choke, warm idle, and warm 4200 RPM. I did notice the mixture heater relay was pretty active: https://youtu.be/Wfascxlab0g


Test drove it, and all ran fine. Took it out into the back country and after loading up with wood 10 miles in on my way out I was coasting in neutral down hill with a fully warm engine after about 5 miles and it dies. Drop it in gear and it runs, neutral dies again, in gear engine runs and will backfire a bit, moreso in lower gears. https://youtu.be/ga76dkpZf34


Next on the list is:

Compression test

Check timing (based on other posts I have read each of these are suggested)


I am at a loss and need input. I would love not to have to spend $500 on a rebuilt carb, or $175 on a fuel pump just to play guessing games on how to get it fixed. 

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Fuel pressure is fine.


Idle should be around 750. Can you get this? 1,200 would indicate the idle cut is not connected or choke not shutting of or fast idle cam stuck.


How many wires on the electrical plug on the back of the carburetor???

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I have the feedback carb, 6 wires. The nice expensive one.


I have seen you mention a clicking noise  on the carb with the key on in other posts and mine does click.


The flap on the 2nd barrel is not sticking and is fully open when warm.


When I was trying to get it to 750 rpm idle it would die on me all the time. That is when I gave up and stuck it in the shop. I left the manual in the seat for them to try and get it to factory specs with the CO2 levels and whatnot described, but my guess is the guy tuned the carb by ear/feel alone. 


My buddy was concerned of sedement in the tank?


Also, intermittent fuel pump failure?


We did test the fuel relay on the passenger side of the cab and it seemed to be functioning fine.

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The front of the carb has a small round window. If gas is showing then the fuel pump and fuel pump relay are working.


The flap (choke) is actually on the primary barrel which is what the truck runs on. The secondary is closer to the valve cover and is only used at high speeds.


Sediment in the tank isn't an issue as the fuel filter will catch that.



(gotta go back to work)

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Failing fusible link?  Had a shop fix mine for fuel related problems, ran better but not best. Checked, seepage at carb butterfly swivel points on carb body  meant swivel holes ovalled. Will deal with that in the near future. Fuel pump ground bolted to fuel pump guard bracket. Welded stainless bolt to frame and grounded to that, running better.

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EGR is just a measured amount of inert gas taking up space in the cylinder. It reduces peak cylinder temperatures. There is no EGR at idle so if it is leaking in the engine wouldn't idle or idle poorly


How about checking the valve lash and the timing is 3 degrees BTDC +- 2 degrees


Check that the plug wires all go to the correct plug. The cap is labeled.  Firing order is 1342  in a counter clockwise direction.

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  • 2 weeks later...

All plug wires match the dist cap label on both the ignition and exhaust sides.


Timing was at 2 BTDC, so I adjusted it to somewhere in the woods of 3 to 3.75 BTDC. Based on my cleaning efforts for the timing gauge and the dist cap adjustment bolts it has not been changed in years (means that the shop that had my truck for 1.5 mo.s didn't check/adjust it either, which seems odd given the concept that the customer is paying you for a diagnostic and fix, thankfully they didn't charge me in the end, though it makes me question the extent of actual work they put into fixing it).


Compression test up next when I can get a buddy to help.

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  • 2 months later...

Well, haven't gotten to the compression test, but that may have just been the right fixes I needed. I have driven it out for a couple loads of wood in 4x4 country and no more issues really. Still have a slight chug when hitting the gas on occasion (mostly in 1st gear, or after coasting in neutral) but as long as I don't try to get on it like it is my WRX she is running consistently ok. I know all the fixes were necessary but the last key must have been the timing. I am still shocked that being 1.5ish btdc off on the timing would cause an issue like that. Didn't want to dissappear off the thread without providing one last update.  I will be back if it starts to act up again though 😉

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  • 2 months later...

Update. Idle cut solenoid is on the fritz.


Last trip into the woods and the idle coming out of gear was 2100 and taking 30+ seconds to creep down to 1000ish on the trip in. On the way out all was normal.


Yesterday, the solenoid stopped clicking all together and had to tow it home. I jiggled wires around the fuel relay and all over the carb in case of bad connection,  nothing.


Checked the fuses by the pedals, all ok. 


Suggestions? Can I replace just the solenoid? 


I am wondering if I have to scrap this carb for a new one, but with it being the California plug $450 is a bit of a headache.  Is there a easy way to just use the other cheaper non Cali carb?

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The idle cut solenoid would not stop you from driving it. It would cause it to not idle if not working but if in gear driving or if you keep revved up you could get home. If in town just turn the idle speed above 1,200 and the idle cut would have little to no effect if not working.

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Usually I hear the ticking time bomb, but that is not happening right now. 


No fuel in bowl, went to the fuel relay under passanger side dash and started trying to see what had power using this diagram: https://axleaddict.com/auto-repair/The-Datsun-and-Nissan-Pickup-Fuel-Pump-Relay-What-the-Haynes-Automotive-Repair-Manual-Wont-Tell-You


Took the voltmeter cable and jumpered the fuel pump to fuse terminals, got fuel in the bowl and truck started but with jumper removed the fuel pump stopped and truck died a few moments later.


This being said I am guessing the fuel relay is the issue, and needs replaced? 

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Think I got it, soldered the chip at the points on that site I posted and truck turned right over!


Going for a test drive, but I am pretty sure that was the trick! I will post if it acts up again though 😉


Even though I did a bench test on this 6 months ago and it looked ok, I am guessing it was on its last legs. Makes me wonder if this was the major kicker in the original problem I was having when I posted here...

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