STALLING, BUT NOT ALL THE TIME.

[drb5721]

So after a head rebuild, new carb mounting gaskets, new fuel pump and filter, I have an issue that has gotten better but is not resolved. If I start the truck it will run all day with no issues. If i drive it for a distance of about 10 miles, it wants to stall out. Fires right back up basically no problem. Its not every trip like this though. And to make it more interesting, it may do it on the first trip, then after it stalls and starts back up, i can drive straight back, and it may or may not do it again. Not sure what I really need to check. Runs fantastic otherwise. 

[banzai510(hainz)]

soon as it does it ck for spark. or look down carb and pump the gas and see if the accell pump squirts gas.

 

feel  the coil if HOT

[Doctor510]

Fuel filter?

[datzenmike]

So after a head rebuild, new carb mounting gaskets, new fuel pump and filter.... 

 

 

 

It tries to stall while driving, or stalls when you try to idle it?

 

Next time it stalls turn the key off right away, then look at the round window on the front of the carb. Can you see the gas level???? If yes it's not a fuel delivery problem.

[Dolomite]

Which vehicle?

Also, remember one of Gato’s favorite rules of thumb: when you think it’s fuel, check spark and vice versa. It sounds odd but it has a nasty habit of being true. My recent issue that seemed like fuel starvation was timing related.

[flatcat19]

This guys issue sounds fuel related.

 

 

Check coil to see if hot/burned out. Check cap and rotor for burn marks. Check ignition wires for arcing. Check for loose wires at all connections in ignition system.

[datzenmike]

Which vehicle?

Also, remember one of Gato’s favorite rules of thumb: when you think it’s fuel, check spark and vice versa. It sounds odd but it has a nasty habit of being true. My recent issue that seemed like fuel starvation was timing related.

 

 If I start the truck it will run all day with no issues.

 

 Z22 or Z24

 

Why was the pump replaced??????

 

Was it quitting like this before the pump change?????

 

Do you still have the old one????

 

 

 

Again, next time it quits, turn key off so an intermittent electric fuel pump can't re-fill the carb and fool you. If carb is empty it's fuel delivery problem. If full it's not.

[drb5721]

81 720 with the z22 engine. Fuel pump was replaced because i was having an issue where the truck would run ok at idle but with any power demand would lurch and i sould have to feather and pat the throttle to keep it running and moving. Found intake leaks from a bad intake gasket and the carb mounting gaskets. Replaced both. No change.

When it died again i sat cranking for 15 seconds...nothing. 15 more....nothing. Cycle the key and pump and it finally fired. This pointed to fuel delivery. No more lurching and such. The stalling occurred with both pumps. Nowhere near as often with this one. The stalling isnt consistent in regards to if it will do it. Today, for instance...drove 6 miles to a stop, no issues. 4 more, stalled, 24 more to work nothing at first until i gave it a slight throttle blip to move forward as our gate opened then it wanted to die. Does it with or without brake pedal being depressed. I'm going to check ignition timing again while I'm figuring this out.

[banzai510(hainz)]

accell pump bad inconsisitant?  see if gas squirting when you cycle the gas

[datzenmike]

The pump doesn't supply gas on demand. It only keeps the carb full. You can shut the pump off and drive several blocks on it with a full carb. This is why it stalled with both pumps, because the problem isn't the pump.

 

But... could be the filter or blockage in a line or the float set too low causing the carburetor to drain and run out even though the pump is working.

 

 

First idle the truck then shit off and look at the sight glass on the front of the carb. Gas should show at the half way point. Does it? If not, the float is not set properly to maintain the correct height.

 

If fuel level is correct...

The next time it stalls, shut off as fast as you can and safely pull over. Realize that the time it take to stop, the pump can refill the carb and spoil this test, so get the ignition OFF ASAP to preserve the results. Now look at the sight glass on the front of the carb.... got gas?????

 

If not showing any gas there is a blockage or float problem. Possibly the screen at the fuel inlet is blocked.

If full there is no fuel delivery problem.

[KELMO]

Not a 720 guy here but, does this have an electric fuel pump?  Could it be the fuel pump relay if so?

 

 

Scratch all that, I just checked and the relay does not apply until NOV 1982.

 

 

Keep moving, nothing to see here.

[mainer311]

My guess is fuel delivery. My roadster used to do this all the time, especially on long climbing hills. I ended up restoring the gas tank and no longer have problems like that any more.

 

Change your fuel filter, and check the banjo inlet screen if it has one. They are still available from Nissan.

 

If there is sediment in your fuel lines, you can blow it back into the tank with a compressor set on low pressure. Take the gas cap off first though. 

[racerx]

Yep..how does ur filter look?

[drb5721]

The filter before the pump was just replaced. It still looks fine. I do not see any significant deposits from debris or anything like that. Also, when I redid the carb gaskets, I did check the filter at the banjo bolt, clean as a whistle. The unit is a rebuilt unit put on prior to me purchasing by a shop not far from me. This was a year or so ago. But I can't say I have a lot of faith in them. I found the Repair Order from the replacement and the customer complained that the truck ran great but smoked ALOT! So they suggested a carb. Truck wasn't really driven much after that and had a blown head gasket when I bought it. 

 

To make matters even more fun, the new pump took a crap on me this morning. Truck shut off, and after stopping, I could not hear it pumping. Got out and check the wires and still no go. Fuses checked good. Even swapped some around. Glad I kept the old pump just in case. Got a ride to the house, grabbed the old one, and slapped it in and drove it back to the house. No oddities like before with the old pump and lurching. Drove great just kept stalling when coming to a stop. Going to go have the other pump swapped out because of the warranty and see what occurs. 

 

Seems my initial issue was something to do with the bowl style filter pre-pump. However, still chasing the stalling problem. I am thinking I may have the ignition timing off some. A few times today, when trying to start it after stalling, the truck was having a hard time spinning over, like a cylinder was firing too soon or something. After a pump or two of the throttle, it fired off and would run until I had to stop again. 

 

Drove my s13 to work today as I ran out of time to mess with it.

[mainer311]

I don't know a whole lot about the Z engines, but it takes an awful lot of timing retard to make the older R and L engines stall. If it's advanced beyond TDC at all, there is just no way it would stall at idle due to timing.

 

I'm assuming you re-timed it after the head rebuild. 

[drb5721]

I guess in theory, timing could be a bit on the retard side and the issue could be a bit of vapor locking as the fuel in the cylinder isnt being ignited...either way, gonna check that and confirm it. 

[datzenmike]

Vapor lock is gas boiling in the lines or the fuel bowl of the carb on extremely hot days. Fuel in the cylinder will be a vapor but retarded timing will still ignite it.

[drb5721]

Got it to stall in the driveway last night. Fuel can be seen up to the dot on the sight glass. Ignition was cut as truck died. Seems like an idle air problem.

[datzenmike]

So this never happens while driving along, only when idling? or at a stop?

[drb5721]

Yes. Only when coming to a stop or at idle. The pump thay died while driving has a lifetime warranty so grabbed another. Just took it for a drive and it did fantastic excelt when making a very slow u turn. Did die when turning steering wheel to full lock. Fired right back up.

 

On another note, noticed the oil pump has a very slight leak. Ugh.

[datzenmike]

Probably the crank seal dripping and the fan flows it back. Might also be the valve cover. Power wash or rinse the oil pump off with carb cleaner and let dry. Now watch to see where it comes from

[drb5721]

The new warranty replacement pump has done pretty decent over the past few days. I have gone around 200 miles on it and the only stalling i have got it to do is when making hard turns in a parking lot. I am pretty certain my oil leak is coming from the oil pump itself, not the crank seal as everything else looks dry. Very small drip here and there. I also think the pump isn't pumping hard enough as on initial start up there is a good bit of clattering and such for the first 4 to 5 seconds then tends to fade away. Once engine is good and warm the noise never occurs again until the next start up. Either pump or a bad timing chain tensioner which would suck given I just replaced it when doing the head gasket.

[noramost]

The factory elect pump has a second fuel filter inside it if your are running OE. The carb throttle shaft wares out and sucks air every 80k, usual symptom is idles to fast and you have to wick the throttle to get it to come down. Your charcoal canister is the vent for your gas tank, remember 5lbs fuel pressure and 5lbs vacuum =  0. When it stalls pull your gas cap, should push not suck

[G8KeaPoR]

Mine did that and it progressively got worse till it wouldn’t start. The coil was only outputting 8v on trigger. It was an msd and like all msd’s it was junk from the moment it was made lol.