Weber and vaporlock Z-22?

[slemers]

I drove my 720 today in the 95 degree heat today and as I attempted to back up my driveway the truck died. Initially I thought I stalled it but when I attempted a restart it wouldn't take any throttle.

I let it cool off for 10 minutes or so and it ran normally. I drove the truck about 2-3 miles and it died again. After another 10 minutes, the truck started and I drove it back home only to have it die in the driveway again. Is there any thermal protection on the fuel pump? As I turned the key thru off to start the truck I didn't hear the fuel pump running. The accelerator pump didn't seem to being pumping fuel. 

Vapor Lock?  After letting it cool off, As I turned the key the pump was working normally.

 

I have a 32/36 Weber installed, once the truck cooled down it ran normally until it died again.

After the temperature cooled down, I drove the truck and all is well once again.

Any thoughts?

 

Thanks,

Slemers

[spottedog]

Do you have the factory fuel return line? I had a vapor lock issue, put a return line the po removed, fixed the problem.

The fuel running from the carb inlet then back to the tank through a calibrated orifice cools the fuel, and makes life easier for the pump.

 

(I don't know if the napz engines had a return line)

[nerdistmonk]

My z24i truck has a return (it was fuel injected though), i went to a weber 32/36, i bought a fuel filter for a 79' jeep cj and hooked the return line to it. (it came with the extra port on it for a return line)

[720life]

Yeah it is pretty important to have the return line hooked up, it does help cool the fuel.

Do you still have the heat shield that goes under the carb to block heat from the ex. mani?

That may be be some of the issue as well...

[slemers]

Do you have the factory fuel return line? I had a vapor lock issue, put a return line the po removed, fixed the problem.

The fuel running from the carb inlet then back to the tank through a calibrated orifice cools the fuel, and makes life easier for the pump.

 

(I don't know if the napz engines had a return line)

I kept the stock fuel lines when I did the Webber install. So yes, it does still have the return line.

[slemers]

Yeah it is pretty important to have the return line hooked up, it does help cool the fuel.

Do you still have the heat shield that goes under the carb to block heat from the ex. mani?

That may be be some of the issue as well...

I'll take a look and see if a heatshield is installed. My fuel line runs up the right side of engine and then between the head and the intake manifold. If i don't have one maybe I can fab something up.

[720life]

I myself don't have the heat shield installed cause I forgot to put it back on but I have yet to have any probs with it myself.

 

 

There have been a few members on here that had to go back and install it cause the gas was boiling the gas out of the carb and flooding the engine.

Sounds like you've got a Z motor, but I can take a oic of my heatshield if you need. Its for my l20b so itll be different then what you need but may give you an idea.

 

I know its only a heatshield, but pics always help when trying to figure something out IMO 

[slemers]

A photo would be great, I have think I have some suitable material that may work. All I have to do is find my tin snips, they are around here someplace.....

Today it was only in the low nineties it ran fine without any issues.

[720life]

Spaced on the pic man Ill get one first thing in the AM

[datzenmike]

Yeah it is pretty important to have the return line hooked up, it does help cool the fuel.

Do you still have the heat shield that goes under the carb to block heat from the ex. mani?

That may be be some of the issue as well...

.

Yours is an '80-... the only year that the L20B was used. It has intake and exhaust on the same side and could use a heat shield. His is a cross flow Z22 motor with intake on one side and exhaust on the other so shield not needed... but this shows you're thinking.

[720life]

.

Yours is an '80-... the only year that the L20B was used. It has intake and exhaust on the same side and could use a heat shield. His is a cross flow Z22 motor with intake on one side and exhaust on the other so shield not needed... but this shows you're thinking.

 

 

 

...uhh...duh...geeze... IDK about myself sometimes.   :blush:

Apparently not thinking about it ALL though lol

 

 

I had an 81 with a z22 so I SHOULD know intake and exhaust are not on the same side.

Most of the 720s Ive had were 80s so they had the L20 in them.

Its just what Im used to seeing in the 720 lol

[720life]

So I guess theres no use of a pic of something you don't need then huh slemers?

[slemers]

I like Oic's as much as anyone, but I guess Datzenmike is correct. I certainly had a vapor lock problem though. Luckily it doesn't get into the high nineties around here to often.

[Bagged620bulletside]

That's weird I have the same setup as you and I daily my truck everyday is Texas summer heat and Have never had this issue.

[slemers]

Strange, Maybe my electric fuel pump is weak? It's been running ok the last few days. I don't notice any diffference in the sound when the pump runs prior to starting.

I have been driving my other car to work this won't be a problem until my daughter goes back to school in the fall.

[datzenmike]

There's a fuel filter between it and the tank and there's one in the pump base that twists off.

[slemers]

I have a new filter between the pump and the tank but haven't looked at the one on the pump itself. Are these still available?

[datzenmike]

Not from Nissan I think but seem to remember something about a VW part number.

 

Any way the Nissan number is 16404-28530  so you can cross reference it to purolator or something

[slemers]

Thanks, I'll do some research and see what I can come up with.

[elmerfudpucker]

I had a similar issues but it was the fusible link was loose the first time, then the ignition module in the dizzy acted up...then it died. Watch the module, it is expensive as hell $300+, try to source it from Ebay if you need one around $40.