Hot-start issue with EFI - who has it, who doesn't

[Zed Head]

So the summary might be that you had one instance of the car not starting at all, and whatever the problem was went away? But since then it's been starting fine. You are essentially all stock, including injectors, except for headers.

So, headers might be a simple one component solution to the problem. Possibly due to reduced heat-holding mass by the injector bodies.

Thanks for reporting back. Things will get clear, piece-by-piece. At least there will be a few potential solution paths to try for anyone that can't stand it anymore.

For the record, my 14mm, o-ring, 1990, high impedance 4 hole valve injectors on a straight-shot aluminum fuel rail haven't had a problem and it's been up in the 90's and high 80's on a regular basis here. Odds are it's just the aluminum rail and its extra fuel volume dissipating heat, as the fuel vaporizes from the injectors and recools in the rail (Fastwoman's heat-pipe theory).

[S30Driver]

Up until recently, I occasionally suffered from the classic hot start issue.

Since I had both manifolds off to replace the gasket, had my main heatshield plated with chromex, coated the stock exhaust manifold, I have had no problems. And it has been consistently hot here for the last 6 weeks.

Stock injectors with Pallnet aluminum rail, stock exhaust, chromex heatshield.

FWIW

[Zed Head]

Thanks for the addition to the thread. The math seems to be leading to the conclusion that the typical Pallnet style aluminum rail (AN -6 size bore), with stock heat shielding, could solve the hot start problem alone. Heat dissipation is the key.

Just summarizing, for anyone looking for the simplest, and probably cheapest overall solution. You can get the rails with barbs, and could even get an extra port for the CSV, keeping all of the stock functions and most of the parts. Headers and/or new injectors are probably not necessary to get rid of the problem.

[BackDoorz]

Update ...

 

After working on my brakes for awhile, I am back on the road again using Ethanol-free gas. So far I have had no "hot-start" issues. After saying that, it has been cold here in NC (more so than usual). I have not driven my car as much since it has turned cold (maybe burned 2 tanks?). I guess the real test will be this summer. I will try to update again. Meanwhile ... "Happy Motoring".

[S30Driver]

Thanks for the update, interested to see what effect the gas has.

[Crazy477280Z]

My 77 has stock intake and fuel rail but I do run headers. I go through this heat soak also. Ime not sure what kind\size injectors Ime running. It doesnt affect it to the pointof a no start situation though. I can shut it off while hot,and if I start it again within 30 or so minutes, it runs rough,but it will clear up if I run it about 3000 RPM for no less than 30 seconds, and no longer than a minute. It was worse until I installed the headers,but I havent got rid of problem completely yet. sounds like I may have to do an injector swap to get it to entirely vanish,depending on where all this info leads. Just thought Ide throw my 2 cents in if it helps add to whole picture.

[Zed Head]

I think that the aluminum fuel rail is the key.  Lots of fuel volume to boil and condense, to bring the heat up to the rail to be dispersed.

 

I'd been thinking about posting in my other thread recently.  I got a tank of gas a little while ago that caused bad heat soak.  Ran through it and refilled, and it diminished, now it's almost gone.  The winter fuel has to be a big factor.

[Crazy477280Z]

Yep, I think that has alot to do with it also.Ive got a friend that owns a Z wrecking yard of a sorts in Beavercreek, Ore. and he made a fuel rail out of long, rectangular piece of aluminum stock he had laying around because of same issue,and he hasnt had a problem since, even running stock exhaust manifold..

[Zed Head]

I've had the hot start issue come back recently, pretty bad.  Everything engine-wise is essentially the same as when the problem was fixed originally.  Might be fuel, might be my junkyard 0280150901 injectors going bad.  Might be some other odd thing.  My rail holds pressure, the weather hasn't been that warm.  Not getting what's going on.  Just filled up with a different brand of fuel from a different station, took a long drive to blend the fuel, and still have it. 

 

Anybody in the Pacific Northwest having similar problems?  Many gas stations are supplied from the same big tank farms.  Just checking before I start dinking around with the engine.

[Zed Head]

Found an interesting article on fuel blends by season, with a nice chart linked.  Butane!  Looks like June is when things change, from 9 to 7.8 RVP.  Might rig up another cooling device in the meantime.  Also looks like I should avoid Washington gasoline at all times in the summer, along with certain OR counties.

 

Might explain why some people never get the problem, and others get it only sometimes.  Plus, from what I've read, some formulation components are loosely controlled.   Maybe there's extra butane in some batches of fuel.

 

 http://www.theoildrum.com/node/1776

 

http://www.epa.gov/otaq/regs/fuels/420b05012.pdf  (from the article - 2005)

 

And the web site with the latest revision (1/26/2015 as of this psot) - http://www.epa.gov/oms/fuels/gasolinefuels/volatility/standards.htm

 

Here's another EPA article on basic blends.  There's an oxygenation program also, from October to March.

 

http://www.epa.gov/oms/fuels/gasolinefuels/index.htm

 

Actually, all of these are linked at the top of the EPA page.  There's even one on water separation, which EuroDat may have linked already.  

 

It's not just gas.

 

http://epa.gov/otaq/regs/fuels/rfg/waterphs.pdf

Edited April 6, 2015 by Zed Head

[Zed Head]

Re-reviewing previous research and found a note from the pros (Chrysler Corporation, Fiat) about "heat soak".  Doesn't really give any new ideas, although retrying old ones might be worthwhile, but nice to know that the injector fuel vaporization theory has some big company backing.  Too bad though, that the problem still exists.  Maybe why fuel system pressures are getting higher, up in the 50's and 60's now, I think.

 

http://www.wjjeeps.com/tsb/tsb_wj_1803103.pdf

[Mark Maras]

Great info. I've been curious about the gas blending for a long time & the effects on engines. After reading the links I'm concerned about my son's RX7. The negative effects on lubrication in a 2-cycle, as well as a 4- cycle, engine are worth looking into further.

Thanks

Mark