Gary 65

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Need Fuelie help. I have owned a 1965 FI coupe for 41 years, and have rebuilt the unit numerous times over the years. It has always run great. I removed the unit in February to install a new high pressure pump seal. Well, I decided to go through the unit. I have taken it off and on three times. It just does not run smoothly. Idle speed is 1100RPM and surges while at idle from 1100 to 1300 or 1400 and back down to 1100. There are no leaks and the nozzle spray test was perfect. Any ideas?

jim lockwood

More information would be helpful.

When you "went through the unit", what did you do? What did you replace? What did you NOT replace?

If you used a rebuild kit, who supplied it? (It matters.)

What effect does turning the idle fuel control have? What effect does turning the idle speed screw have?

Is it running rich?

Any sound of air whistling, like a big ol' air leak?

Jim

wmf62

there are only 2 diaphragms, power and main. if the power is holding steady, then i would tend to suspect a main metering diaphragm leak?
Bill

Chuck Gongloff

How old was the kit you used? Old rubber deteoriorates. Old paper/fiber gaskets shrink and won't seal.

Were the surfaces where the main control diaphragm mounts pretty flat or were they warped? Warpage of the lid >>>>air leaks.

Chuck

63Corvette

AND are you running it with race gas, or with pump gasahol (10% ethanol)?

Gary 65

Thnks for the further inquiry questions. Here is some more information. When I went through the unit, I rebuilt the fuel and air meters. New seals and diaphrams. The kit that I used was fresh and came from Jim Thorpe in Iowa. The air meter mating surface to the plenum, and the two diaphram surfaces were sanded with 1000 grit on a granite slab. The engine exhaust seems rich. Adjusting the air/fuel mixture screw will kill the engine if adjusted too far in. I have it set at 1 1/2 turns out. I put a new set of plugs in it. I am using pump gas.

jim lockwood

These two statements tend to contradict each other. Generally, if you can kill the engine by screwing the idle fuel screw all the way in, the engine isn't idling rich.

However, putting that aside, for an overly rich condition, check all of the following:

1. Ensure that, when the engine is idling, the ratio lever is positioned on the forward (economy) stop screw.

2. Ensure the cold enrichment (or "choke" as most call it) is turning off.

3. Ensure the idle fuel bypass solenoid valve is NOT continuously powered after the engine starts. It should be open ONLY during engine cranking.

Jim

wmf62

the idle mixture acts just like in a carb, so your 1-1/2 turns is about right. IF you are not getting a surge at cruise you MIGHT try backing off the economy stop screw but be very careful to count the turns in case you need to reset it back.
Bill

Gary 65

Thank you Bill, Chuck, and Jim for your replies to my question about the fuel unit that won't idle. I have checked all of your suggestions. Everthing checks out. When I (manually) accelerate slowly, there seems to be a hesitation, then the engine takes off and accelerates normally.
Gary

jim lockwood

What was your procedure/criteria for adjusting the Economy and Power stop screws?

Similarly, what was your procedure/criteria for adjusting the Enrichment Diaphragm rod?

If the combination of these three is adjusted improperly, you'll get hesitation.

One other thought.... You said you put in a Thorpe rebuild kit. Who supplied the main diaphragm you REMOVED when you went through the unit?

Jim

wmf62

a thought... if you still have the old diaphragms, and they are OK, put them back in and see what happens
Bill

Gary 65

Thanks Bill and Jim for getting back to me. You asked about my criteria for setting the power and lean stops. The ratio lever just leaves the power stop moving toward the lean stop at three inches of vacumn, and at six inches of vacumn the ratio lever is equi-distance from the lean and power stops. the ratio lever arrives at the lean stop at nine inches of vacumn. I will look to see if I still have the main control diaphram and reinstall it. Thanks guys.
Gary

jim lockwood

Gary, this is a fine procedure for adjusting the enrichment diaphragm but ONLY after the positions of the two stop screws have been correctly set.

How did you determine the adjustments for the two stop screws? You must set these FIRST.


Who made the old diaphragm??????

If you don't know, then how about posting a clear picture of it?

Jim

Gary 65

Jim,
I did not pre-adjust the two stop screws. I moved them in order to get the vacumn numbers the way that I wrote before. I do not remember ever seeing any stop screw adjusting specs in any of the articles or manuals that I have. Do you have any info that you would share?
Gary

wmf62

messing with the stop screws is what causes novices to screw up the system; it's definitely one of those "if it ain't broke, don't fix it" things.

i never messed with the stop screws except to lean out the economy stop til i got a lean surge at cruise and then richened it til it went away.

the best way nowadays would be with an O2 sensor and use it to set the air/fuel ratios
Bill

jim lockwood

Gary,

The procedure you followed is incorrect.

You must make these adjustments in this order:

1. Adjust the idle controls so the engine will remain running. Don't worry about optimizing them at this point.

2. Adjust the Economy Stop for approximately 15:1 air/fuel mixture at cruising hiway speeds AND under road-load conditions. Best to use a wide-band O2 sensor and air/fuel gauge. If these are not available, use Bill's procedure.

3. Adjust the Power Stop for approximately 12.5:1 air/fuel mixture under wide open throttle conditions. If you used Bill's procedure for adjusting the Economy Stop, you can make a very crude Power Stop adjustment by setting it to be about 1/2" from the Economy Stop.

4. Adjust the LENGTH of the enrichment diaphragm rod such that the ratio lever is just touching the Economy Stop at a vacuum level of 7" Hg.

5. Adjust the idle speed and idle fuel screws for proper engine idle speed and best idle quality.

Make these adjustments in the above order, and your FI unit will behave properly.

Jim

ghall

Jim,
I am trying to gain some knowledge on these fi units to try to get an idea of whats going on with my dads car. Before i started a whole thread, i figured i would use the search function and check some things out. I would just like to say your responses are fantastic and very helpful

My first question at this point is how do i ensure the cold enrichment is turning off?

Thanks,

Geoff

jim lockwood

Geoff,

If the fast idle cam completely clears the fast idle screw (as can be seen in the lower left of the photo below), then the choke has turned off.



Jim

ghall

Jim,
Thanks for the reply.
The fast idle cam is clearing the screw after running for a couple of minutes(temp is 60 outside).
The problem i am having is a high idle. To start the car, i press acc. all the way down and release, car starts and idles about 1800, there is no change in engine rpm when cam clears the screw. It starts out idling high and never goes down.
Just wondering if you any thoughts or ideas to try.
Thanks for your help,

Geoff

Engine vac. is 19in@1800 rpm. I will look for a vac. leak

jim lockwood

Geoff,

Have you checked the adjustment of the screw that controls normal engine idle?

This screw is also on the air meter, but on the firewall side, 180 degrees around from the fast idle screw. Look for a spring loaded screw the head of which faces upward.

Try adjusting this screw counter clockwise and note whether the engine speed comes down. If it does, adjust it for an idle in the 800 - 900 RPM range.

Jim