Fuel injection hot idle-revisited

[Ed Jennings]

I had been having the usual hot restart/rough run problem on my 62 and got a lot of advice regarding insulating the spider/fuel meter from the engine heat etc. I have also tried a number of flavors of name brand gasoline with no noticable change with any of them. It seems the last few times I have driven the car that the problem is growing worse. It is now to the point that the car will start to surge at idle after it has been driven long enough to get hot and then allowed to idle for a couple of minuets, such as at a traffic light. Before, it only occured after a hot restart and then once it cleared up I was good to go until the next restart. When the car is first started and warmed up, it runs perfectly until the first hot start. Very, very frustrating.
Is there a brand of gas anyone has used that seems to do better?
Any other suggestions? I was going to try using the earlier model gasket that covers the area underneath the plenum, but John DeG. advised me that it would not fit without significantly modifing the plumbing.
I have a very strong desire to keep this old fuelie a fuelie, but I gotta be able to drive it!
If you have no suggestions, sympathy might help.

[Duke W.]

Re: Fuel injection hot idle-revisited

I still question if it's really a fuel issue. Modern gasolines have lower vapor pressure than in the sixties to combat evaporative emissions.

As an experiment, run the fuel to empty, then siphon the tank and add five gallons of 100 octane avgas from your local general aviation airport. Avgas typically has lower vapor pressure than road fuels so as not to cause vapor lock problems at altitude.

It might also be a little tougher to cold start due to the lower vapor pressure, but if it cures the hot restart problem, then vapor pressure is probably the issue. If not, I suspect it's something else.

Duke

[Ed Jennings]

Re: Fuel injection hot idle-revisited

Any idea what the something else might be? It's got to be heat related, and almost got to be something to do with the fuel. I didn't mention this in the post, but in the summer when we have EPA mandated "reformulated gas" the problem does not seem to be so severe.

[Duke W.]

Re: Fuel injection hot idle-revisited

Nah, I'm just (scientifically) grabbing at straws Ed. The avgas test might be beneficial to get another data point to verify or deny the vapor pressure issue.

Summer gasoline blends have lower vapor pressure than winter blends. It really doens't have anything to do with RFG. Winter blend vapor pressures are established based on starting in cold weather, but if you have a hot spell (it was 75 here in Redondo Beach, today) it can cause some percolation problems.

Duke

[Ed Jennings]

Re: Fuel injection hot idle-revisited

I guess I should have included that temps here have been generally in the 50's to mid 60's when I was experiencing the problems.

[Paul E. Young]

Re: Fuel injection hot idle-revisited

Ed, I once had a problem with the check valve inside my spider sticking on hot restart. I had Brian Futo help me take it out and clean it and it was quite an extensive job. I wonder if you could borrow someone elses spider and try that. It seemed like mine would be swollen and stick closed for a while but I think the contaminates were doing that. How about trying some fuel injector cleaner like BG 44k put out by southwest grease in Wichita? Are your injector nozzles clean? Some times that makes it act rich too if it has contaminents int the injector screens. I would agree with the others that you should check everything else first. Have you done a bench test as per manuel? If it is spraying correctly it should not have anything in the injectors. Good luck. Paul P.S. Don't give up on these units. They are great and run pretty much trouble free.

[Ed Jennings]

Re: Fuel injection hot idle-revisited

I doubt there is anything wrong with the unit. It was freshly restored by John DeGregory within the last two years and only has run a couple of thousand miles. Until the hot dile situation cuts in the engine runs perfectly. If there were an injector problem it would run poorly all the time.

[George J.]

Re: Fuel injection hot idle-revisited

Ed,

I had similar problems with my '65 unit. Mine would also change behavior from cold to hot. It sounds to me like some sort of vacuum leak. I finally took the whole unit apart and rebuilt it. Many helicoils and sheets of sandpaper on the surface plate later it was much better. The last thing that was wrong was the fact that the tach was reading 200-300 rpm high at idle. Check it with an electronic device if you haven't already. Good luck and don't give up,

George Jerome Jr. #31887

[Dale Pearman]

Re: Fuel injection hot idle-revisited *NM*

[Dale Pearman]

Re: Fuel injection hot idle-revisited

I encountered NO problems whatsoever in using a 1959 full gasket under the dog-house of my 1962 FI. No plumbing alterations were needed. I also use a Longwood fuel line insulator kit on my spider. All this on an aluminum engine block with aluminum heads. Aluminum radiates heat like gang busters and my engine compartment was always hot!

Dale

[Ed Jennings]

Re: Fuel injection hot idle-revisited

Dale, it looks like the vacuum line that runs from the air meter under the plenum to the fuel meter is below the plane that the gasket would sit in, but if you say it will work,I'll order one. Where did you get the material to insulate the spider?

[Dale Pearman]

Re: Fuel injection hot idle-revisited

Any of the hot rod racing aftermarket houses carry fuel line insulation.

Consider the air in that vacuum line running to the control diaphragm. There is no inlet source of air at the control diaphragm. Therefore that trapped air is subject to heat influence. The universal gas law of physics governs here. PV=nrT where P is the pressure, (vacuum) less than atmospheric, V is volume remaing constant (inside of the tube) and T is temperature. It would therefore stand to reason that the control diaphram, regulating fuel flow, is sensitive to the temperature of the air inside the tube. All the more reason to remove the tube as far from heat as possible AND insulate this tube as well.

Dale.

[Ed Jennings]

Re: Fuel injection hot idle-revisited

Makes perfect sense. Now at least I have a plan. Thanks! BTW, I drove the car around a little this afternoon in 45 deg temp. Ran like a top. Rough idled for about 10 sec after a hot restart. I can live with that, but I'd hate it to be 45 deg or less all the time.

[Dale Pearman]

Trouble Fee INDEED

I once went for a 7,327 mile drive in one sitting in my 62 fuelie. I carried tools, a spare pump drive cable, and a rebuild kit. (and a sleeping bag)

Started in Spearfish, SD, then Sturgis for the bike rally, then Mt. Rushmore, Yellowstone, the Dianaseurs, Montana mountains, Banff Park in Canada, Port Ludlow, Washington, Vancouver Island, Oregon Dunes, Grant's Pass, Redwoods, Big Sur, Golden Gate and San Fransisco, Los Angeles (bought another 1962 there), Tiajuna, Mexico, across Mexico on Rte 2, Douglas Arizona, New Orleans and then back to Tennessee. Visited many Corvette friends along the way. Too many to mention.

Fuel unit gave me NO trouble whatsoever and GREAT gas milage. Fuel injection systems are a LOT simpler than a carburetor and more reliable.

Dale.

[Dale Pearman]

I Can't Resist This

Just pump the accelerator pedal a few times before a hot start. See what happens then.

Dale.