Keyboard Air Duster Used to Cool Fuel Rail

[jas280z]

I was wondering if anyone had ever thought of using one of those pressurized keyboard dusters on their fuel rail when experiencing vapor lock to try to cool it? I have been trying to think of something to use, because it is no fun sitting in the parking lot waiting 15 minutes with the hood open for it to cool down. I thought of a CO2 fire extinguisher, but those can get expensive and probably wouldn't last very long. I know that the propellant that comes out of the dusters is very cold, so cold that if you hold it upside down and spray it will freeze just about anything. The only problem I can think of is it may not be safe to leave in the car on hot days, kind of defeating the purpose. And police may frown upon it being in the car since it has other less than legal uses. I will also have to find the non-flammable version. Any thoughts?

 

Apologies if this is a double post, I tried to post this today before work and couldn't find my post when I got home. I think I forgot to hit the post button .

[cygnusx1]

You can just get a cooling fan, controller, and ductwork from a 280ZX.  It's ugly but it works.

[v8wannabe2]

I wouldn't do it, the sudden and dramatic temperature changes may crack something.

[RTz]

Your problem is not vapor lock.

[jc052685]

I was gonna say does EFI even have the ability to vapor lock on a return style system?

[jas280z]

I know it is not vapor lock per say, but it is a heat problem that is related to the fuel delivery, I haven't heard any term to describe it and vapor lock seems to be the closest thing. I am fairly certain this is the reason why Nissan installed the blower fan on 280zx's. And I wouldn't try to instantly cool the rail, just a couple quick spurts from 8-10 inches away to get some forced convection to cool the rail a bit. If worse comes to worse I may end up having to install one of those blower fans, I just don't like their looks.

[jc052685]

The blower fan is to keep the injectors cool(er). Not for any other reason. They just wanted the injectors to last a little longer. You need to look deeper into your problem.

[jas280z]

I finally found a definitive answer (TonyD answer) on the purpose of the fan, as well as describing the problem I am looking to solve:

 

"Exactly the conditions it was made to combat! There is a period from around 5 minutes after you do a hot-shutdown (in warm weather, above say 85 and running on the highway) to about 12 minutes where no matter what they tried, Nissan could not prevent the formation of vapor in the rail due to pressure rise, and FPR venting it back to the tank. Initially it starts with the fuel expanding and venting, then pressure drops and it flashes... The S30's with EFI does this, and it's the reason the S130's have a priming pulse, as well as the cooler on them. In JDM, they had a vehicles with plastic valve covers to combat heat transmission in un-vented hood engine compartments like the Cedric, Leopard, Gloria, Laurel, etc...

 

Timer criteria is coolant temp above something like 215F, and as mentioned no longer than about 15 minutes of runtime after shutdown.

 

It may turn on some time after shutdown as well, should the temperature rise to the point it gets triggered, but in any case it will not start after being 'ignition off' for 15 minutes no matter what happens.

 

One thing you can do to forestall the hard-starting is simply change the 'priming pulse' for your Fuel Pump---make it run for 10-15 seconds to take that heat out of the rail and get fluid petrol up there, it may be stumbly after the start, but it is FAR better than trying to crnak and bleed that vapor out of the rail using the normal pulse and cranking/cranking/cranking.

 

I've noticed it's exacerbated of course in hotter weather, but also as your tank level goes down. Ever do a fuel temperature reading when you go highway driving with less than a 1/4 tank of gas? Scary how hot it will get!

 

Yeah, I know, I got WAAAY too much time on my hands to be checking crap like that out of simple idle curiosity. What can I say? I'm diseased! "

 

 

Here is a link to the post to which I am referring, in case anyone would like to read it in context. http://forums.hybridz.org/index.php?/topic/68780-what-is-this-part-in-the-engine-bay/page__pid__648324#entry648324

[Zmanco]

What EMS are you using?

 

I find that after the engine heat soaks it's hard to get a reasonable mixture for the first minute or so. This was a mild occasional issue when I ran NA, and now that there's the additional heat of the turbo it happens often. I've added the factory blower with a manual switch which I just turn on when I run into a store. It helps a little but not as much as I'd like. Before that I tried a manual override for the fuel pump. My theory was that the fuel in the rail was very hot and hence less dense which leaned the engine out until cooler fuel circulated through it. But that made absolutely no difference. My theory now is that the real culprit is the heat soak of the injectors themselves and that it takes a minute or two of fuel passing through them to cool down and hence for the amount of fuel they are injecting to be accurate again.

 

To combat this I've extended the ASE (after start enrichment) time with some extra fuel via Megasquirt when the coolant is over 195F and this has helped a lot.

 

If you're running with an aftermarket EMS I would suggest you can probably solve this via tuning for hot starts.

[FlatBlack]

Daniel,

 

What fuel rail do you use?

 

I keep hearing about vapor lock/hot start issues, and I have never had that problem. I think I should, as I'm running no heat shield, a non-webbed shaved mani, and a turbo.

 

My N/A L28 Turbo has a Pallnet-style o-ring rail made out of aluminium fuel stock [compliments of XNKE], using Denso INP-008 injectors. I wonder if it can dissipate heat better, which is staving off the hot start issues? I've always thought my car should do this as compared to other Zs. I'm also running an electric fan.

 

Previously I lived in Baton Rouge, Louisiana, now I live in Arkansas - it gets up to the mid-90s + regularly during the summer.

 

If the rail itself is preventing the hot start issues, maybe converting will help others.

Edited July 8, 2010 by FlatBlack

[cygnusx1]

I'm not saying there isn't another way to bandaid the problem but Nissan engineers knew what they were doing....fuel rail blower, hood vents, and heat shields.  Also make darn sure your fuel rail holds pressure after shutdown for at least 45 minutes.  There is a check valve on the fuel pump exit.

 

 

 

 

To the OP.  What symptoms are you having?  We all missed the fact that you didn't include any symptoms in your post. Rough running? No startup? Long cranking? 

Edited July 8, 2010 by cygnusx1

[Zmanco]

Daniel,

 

What fuel rail do you use?

 

I'm still using the stock fuel rail. I also have the webbed intake manifold with the factory heat shield between it and the exhaust manifold. I'll pick up on what Dave said and add that the solution is a combination of things, probably not any one silver bullet.

 

And just to be clear, I have no problems starting after a heat soak now that I add more fuel. As RTz said, it's not likely a vapor lock problem, and if the OP is using an aftermarket EMS, he should be able to tune around this.

[jas280z]

I am fairly certain in my diagnosis of it being the infamous heat/fuel problem (again I know vapor lock is not the correct term, but I haven't seen an actual name for the problem), which is why I didn't post symptoms. The main purpose of my post was to see if anyone had used compressed gas to cool the affected areas. My symptoms are that the car will not restart after it has been sitting for 5-15 minutes on VERY hot days. After it cools a bit it will start right up. It does keep pressure for several hours, although I have been planning on replacing the check valve. Unfortunately I am running the stock ECU, haven't had time to mess around with getting MS, trying to get it ready for the summer first.

[Tony D]

My symptoms are that the car will not restart after it has been sitting for 5-15 minutes on VERY hot days. ... It does keep pressure for several hours, although I have been planning on replacing the check valve.

 

No, it does not. You are TOTALLY missing my description on what is happening.

You show pressure but what you have in there is fuel which has changed state. That gasseous fuel does NOTHING to start the car when you crank it. It needs liquid fuel, not gasseous vapors. And those little millisecond pulses will not get those bubbles out. And those superheated injectors will do their thing to keep liquid fuel flashing to gas for a little while as well. See, in the dead-headed injector, fuel can not FLOW THROUGH THEM! So any gas trapped in there has to be displaced. Gas compresses but since it's at the same pressure as the regulated fuel, it doesn't go anywhere.

 

The FINAL solution to the problem was side-feed injectors. You don't see the issue in cars with that style injector, because the fuel is ocntinually flowing THROUGH the injector OVER the body and cooling it, instead of simply being pushed in the back-end and being let shoot out the front!

 

Your gauge shows pressure, but it's not FUEL thats' in there registering. It's boiling petrol with the FPR bleeding the displaced petrol out of the rail and back to the tank.

 

Wrap the rail properly, isolate it properly from heat, and you will not have this issue. Priming pulse will take care of 99.999% of the starting problem. Just bypass your 's' terminal with a spring loaded switch so you can 'crank' the car for a couple seconds without the starter turning. 3 to 5 seconds usually does it. This is VERY simple to fix, and not that big a deal. You don't need to spray freon or R134 or whatever whiz-bang Hydrocarbon they are selling these days. You just need to circulate the fuel out of the rail and then live with a slight stumble on startup.

 

I mean, how often does this really happen? Filling a tank of gas takes longer than the time period, so no issue there. Doing a splash-n-dash might exacerbate it.

 

If it was 'vapor lock' it would happen when running. And in the S30 and S130's as long as the engine is idling, and fuel is flowing, there is no gasseous bubble formation. It's only after it stops and fuel cooling flow stops that the temp can rise above 200F and cause an issue.

[T-Bone028]

Jas280Z, Just an idea, I've been thinking about buying some of this stuff and wrapping my fuel lines:

 

http://www.summitracing.com/parts/THE-14035/

 

Basically a velcro style heat insulator that should be a cheap and easy install. Perhaps it will help with the problem you are describing.

[jas280z]

I hear what you are saying Tony, I probably should have worded that better. I realize that the pressure reading on my gauge will have little value in diagnosis of the problem, as fuel can leak back and the vapor will keep it at a constant pressure (kind of like a capacitor in a fluid system I suppose). I was trying to say that under normal circumstances (cooler days when this heat problem is not encountered) my fuel pressure will stay ~30lbs for at least several hours, although it is almost always at 0 by the next morning. Therefore I do believe the check valve could be allowing the lines to slowly lose pressure and I will look into replacing it as soon as I get that far.

 

I will definitely look into extending the priming pulses as well, it made sense to me that getting the pump flowing would help move the boiled fuel out and cool down the system. As I was sitting in a parking lot the other day I was wishing my 280z had the system like my dad's 280zx where the pump will turn on for a few seconds to get the fuel flowing when the key is turned to the "on" position.

 

And it doesn't happen very often, we are just experiencing the hottest weather in Buffalo in 3 years, as is much of the North East. But normally we are not exactly known for our sweltering conditions.

[jas280z]

T-Bone, the only problem I can see with that is it appears to be designed as a radiant insulation, it appears quite thin. I know in my Heat Transfer class last semester the Prof said that sufficiently thin layers of insulation can actually increase thermal conductivity due to convection. It may actually exacerbate the problem.

[cygnusx1]

Actually pressure in the rail will raise the flash point of the fuel and will help.  Without pressure in the rail your tendency to vapor lock is far greater.  I wrapped my log style fuel rail and offset the heat issues by about 15 minutes.  Still all the same symptoms, only 15 minutes longer to happen.  Of course the heat off the turbo doesn't help.

[jasper]

I work on the newest stuff all day long. Toyota.

 

There are NO complaints of hot start problems!!!!

 

Funny thing is........there are no injector fans, and, for the last few years, they run a RETURNLESS fuel system.

 

Some cars use plastic injectors,some use metal, and some use plastic, or metal intake manifolds.

I do not know what fuel pressure they run,(because there has not been a problem !)

I remember early Saturn radiator cooling fans didn't come on until 227 degrees F. Later models were 221 degrees F. NO problems.

From my experience, newer cars run hotter than older cars. So ....I'm also a bit perplexed

I understand, and tend to agree with Tony D, but what I see with NEW cars tends to shoot some holes in some of his therories.

I'm am personaly a bit baffled

Edited July 9, 2010 by jasper

[jas280z]

If I am understanding the theories presented correctly it would seem to me that newer cars fuel systems are working properly and don't allow pressure to bleed back into the tank out of the line. Keeping the liquid fuel at said pressure should make it much more resistant to vaporizing, as the vapor would need to expand and there is no area in which it can expand. In 25 years these cars may experience the same problems. Or not, their components may have benefited from the shortcomings of previous systems and not be as prone to failure.