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521 Acts funny when Hot


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hello every one, i know its been awhile.

 

i've been having some problems with C.L.DRAGGER. it has a smooth idles and it runs like a bat out hell in cooler weather but once its 100+ out and tends to cut out or sputter, so to keep it from dying i pump the gas a few times. and it likes to diesel when i turn off and it doesn't over heat either.

 

I NEED HELP Please :confused:

 

this is what i'm running in the datsun, its L20B

 

Weber dgv 32/36 no choke

Pertronics ignitor

new fuel pump

new coil with resister

newer cap and rotor

new ngk

BPR6EGP

the timing is at ??

 

i have a dune buggie style gas tank with non vented cap instead of the original tank. i don't if this might be the problem.

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Carb should have an anti dieseling or idle cut solenoid. Try holding the brake on in gear while letting the clutch out as you turn the motor off. Ggzilla is right. The L20Bs had a return line to the tank so cool fuel is constantly circulated past the carb.

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Not sure about the heat issue but the one time i had a dieseling problem i just started running 91 octane gas instead of 87. Might sound like bullshit but it worked for me. I had the same carb, didn't know about the anti-dieseling mechanism that Mike is speaking of at that time.

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open chamber heads will diesel. thats why Hithachi(carbs) put on a anti dieseling selinoid.

Most Weber 32/36 to not come with them unless you have the option of the selinoid(bigger main jet port or just order qa 32/36 DGEV-IC.

 

as for the pertronix makesure you ordered a point coil(range of 1.2 to 1.6 ohms should be about good) and use the stock ballast resisitor. EZer just feel if COIL is HOT. If not I dont think its the prpolem unless the Pertrnix is on the edge of not working.Assumeing the faster you go the more current draw in the system

 

als ck for looseness of the distributor bushing. see if the dizzy shaft has alot of wear(side to side movmt) , it could also wear out the magnet ring.

 

 

maybe at half tank en the gas tank and see what happens. if it still does this.

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If you don't have a return line, it is likely the fuel is getting too hot.

I have the same problem on hot days with my dual SUs, it was running fine when I get to the stoplight, and it idles fine at the stoplight, but when I start out it starts missing till I get into second or third, then it smooths out till the next stoplight.

I do have a return line, but my fuel bowls are separate from the carbs, so they quite likely are boiling.

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Do you guys have the heatshields for the twin SU-type carburetors? If not the exhaust manifold will overheat them.

 

I have a stock undamaged heatshield, but I am running a header also.

It hasn't been a bad enough issue for me to take any extreme measures yet, so I leave it alone, it only happens on really hot days, which seem to be on the decline in the PNW, it's almost july and it is still freaking cold.

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The hard fuel line from the pump has the return built into it, not the carb. You could get one from any L20B motor..... finding a way to return the fuel to the the tank is something else.

 

Try running without the hood on. If the problem goes away it must be trapped radiant heat from the exhaust.

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******i have a dune buggie style gas tank with non vented cap instead of the original tank. i don't if this might be the problem. ********

 

The non-vented tank is worrisome........crack the cap and see if that helps as it's likely a prob.

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Problem using the hard-line L20B return in a 521 is it isn't plumbed for it- there's no main return back to the tank. Webers REALLY don't like having no return, or at least not without a fuel pressure regulator if using a L20B fuel pump (which are higher volume than the L16/L18 pumps). But the pressure regulator makes vapor lock even more of an issue since the fuel tends to sit in the lines longer.

 

Some 521s had a vapor line running to the original air cleaner as part of the evaporative emissions system, which could be used as a return, but it would have to plumb separately into the tank. You would HAVE to have a vented fuel cap at that point. Unless the tank has a separate vent already. You have to have some sort of vent or the pump will pull vacuum and not pull any more fuel.

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MY 521 I dont have these proplems. I have no retun on any of my 510s and 521 and never had a proplem.

I see you have a 620 style pump. since the inlet is in a different spot that how I can tell. But I dont see what it would vapor lock,

 

Try another gas cap but ai have agerneric locking cap and have had no proplems.

 

521 tanks can get dirty since the fuel filler hose is in the wheel whell. make sure noting is plugging the line.

<aybe it does it less with a full tank. Maybe soemthin in tank?

 

the desieling is normal with a L20 and a weber DGV unless you have a idle cutoff selinoid installed and most DGVs the selinoid will not fit. Only certain models. On stock Hitachis has a idle cutoff with a 12volt wire(i think blu)

Try to run super gas. and right when you turn off the key press the pedal down to open up the butterfly to decrease the vacuum. Its a learned techniq.

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I believe Napa has a smaller type 5151(oil filter)I Know for a fact) or soemthing close to that. alot really to chose from as its a common thread type size

Napa uses Wix filters or Puralator. those are better than the Frams.

 

i think Penzoil PZ1 is smaller also

 

 

On 521s I alwasy ck the filter ,cut them open and ck the idle jet for cleanlness.

alwasy retime and ck the mixture. I can do this a few times till I get it right also

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The Nissan filter isn't "much smaller". The Nissan one for the L-series is exactly the same size as a PH8A.

 

Filter- you can't go slimmer without going remote since the gasket ring is on the outside edge. Well, close to. I suppose there might be a filter with that thread pitch and only externally as large as the gasket surface. You can go shorter, there are ones out there. While I don't use the PH8A (because it's a FRAM) I di use the WIX equivalent (51515). The original Nissan filter for the L-series is exactly the same size as it. There's a shorter one that was standard on some NAPS-Z engines *81-86 720, perhaps) that was the same diameter but shorter from the factory and works, but I prefer the bigger can.

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I see you have a non stock intake. Does it have the water passages in it? Without the passages it can get hot from the nearby exhaust.

 

Also try wrapping the exposed metal fuel line all the way to the carb with some insulating tape or foam pipe wrap.

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the oil filter is a mobile 1 i just dont remember the number its the same size as the ph8a, i'm gonna try to find one thats at least 1/4" thinner.

 

yeah its a Offenhauser intake, i was planning to install a street performance Holley 2-barrel 350cfm with an adapter to see it out performs the weber, i wanted to run a single sidedraft carb but its expensive.

i need to check the carb again but it idles like if it have Fuel Injection but the vaper lock does happen at 4th and 5th gear.

 

whats normal rpm when in 5th gear i'm around going 75 - 80 mph. i'm at 3750 - 3900 rpm in my truck. i dont have a speedo cable an i'm running a 5 speed z tranny i just don't know which one i have. can you guys tell by the shifter?

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yeah its a Offenhauser intake, i was planning to install a street performance Holley 2-barrel 350cfm with an adapter to see it out performs the weber, i wanted to run a single sidedraft carb but its expensive.

i need to check the carb again but it idles like if it have Fuel Injection but the vaper lock does happen at 4th and 5th gear.

 

whats normal rpm when in 5th gear i'm around going 75 - 80 mph. i'm at 3750 - 3900 rpm in my truck. i dont have a speedo cable an i'm running a 5 speed z tranny i just don't know which one i have. can you guys tell by the shifter?

 

 

I'm asking if there is a water line coming out of the intake and connected to one coming out of the thermostat housing.

 

All 4 and 5 speeds rev the same in 4th gear. If the tranny is installed rev it to an even RPM number like 3K and shift into 5th and see how much it drops. From this the overdrive ratio could be worked out and the tranny identified. Knowing what it is out of won't really change much.

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