hard to start when hot

[jim]

83 wagon, rebuilt motor, rebuilt non-feedback carb w/ computer still in the loop, TFI.
For 5000 miles it started great and ran great.  Then it suddenly got hard to start.  At first it started without
closing the choke or pumping the accelerator.  Now it takes a few pumps when cold but still starts pretty well.
When hot it's really hard to start.  I can't tell whether it's starved or flooded.  Each pump puts gas in the carb.   Sometimes I get it started by pumping and sometimes by treating it as flooded.   I have had to jump it.
Once started it runs great again.  I had been concerned that it didn't seem to idle and would stall at lights but the last time I drove it I just let it do its thing and it didn't stall.   Sometimes it seem to idle very fast.
Thereverendbill has said he'll help me do the computer bypass test at the meet in Sept.
What do you think?

[GRONK]

Sounds like a vacuum lead on the intake or timing is off.  If you have a non-feedback carb you MUST bypass te computer N U T T E R B Y P A S S

[txjeeptx]

I agree with Gronk completely - you have to bypass the computer completely to use a non-feedback carb, otherwise the computer does weird things to the ignition timing while its trying to figure out where the carb went(missing some inputs it needs to handle the ignition).

[jim]

I suspected it was the computer but it ran perfectly for 5000 miles.
It pulled 21-22 lbs vacuum the last time I checked.  I do plan to do it again.

[BenM]

Make sure your choke isn't hanging up, and that the electric wire is getting current. It is switched with oil pressure, so you have to be running.

I might be inclined to pull the top off the carb and double-check the float and make sure that you didn't get any gunk in the bowl or in the idle tubes. If you search for BBD idle tubes you'll find instructions for cleaning them out and even modifying them with a drill to make sure that they don't clog.

[jim]

I have tried to check the idle tubes.   They seem to be OK.  I'm not sure about the choke.  I'll have to check that wire, after I find it and find out how to check it.  I also plan to check the vacuum again.
Once upon a time the float did hang and it would flood until I found that problem.
This carb has about 6000 miles on it.
It will be a few days.  I've been replacing the interior rear trim and a bumper corner and the rear filler between the bumper and body.  One or two more evenings should see that project completed.

[ammachine390]

To check the choke circuit, put one lead of voltmeter to the choke wire, and the other to a good ground. When the engine is running, there should be 12 volts at wire.

[jim]

Thanks to both of you.

[vangremlin]

Make sure your choke isn't hanging up, and that the electric wire is getting current. It is switched with oil pressure, so you have to be running.

BenM, can you give a few more details on the electric wire to the choke and how it is wired?  About a month ago I discovered there was no power going to the choke, which explained the dieseling that was going on.  After looking through the wiring diagrams, it wasn't obvious how to trace the wires, so I just ran a new one.  The car runs great now.  The plot thickens because a few months ago I added a mechanical oil pressure gauge, removed the idiot light sensor and obviously disconnected that wire.  So if the power for the choke is somehow switched with oil pressure, that might explain my problem.  Thanks!

[Jurjen]

That is easy enough.
There is a yellow/black on the pressure swith wire coming from the ignition key and going to the pressure switch with +12V with ignition on.
This +12V is switched to the blue wire as soon as there is oil pressure, this blue wire is operating the automatic choke element.

[vangremlin]

Thanks Jurjen.  That explains a lot!

[rollguy]

That is easy enough.
There is a yellow/black on the pressure swith wire coming from the ignition key and going to the pressure switch with +12V with ignition on.
This +12V is switched to the blue wire as soon as there is oil pressure, this blue wire is operating the automatic choke element.

This may help me find out why my oil light does not work.   I do not want to pull the instrument cluster to check the bulb, so checking it at the switch might be easier.   I looked at the switch today and saw more than one wire, and wondered why so many. Now I know.   Which wire is for the oil light?   I assume it would not be the yellow/black, or the blue.

[jim]

I checked the voltage at the choke wire and it has 13.9.
The choke was full open when hot, though it took longer than I expected for it to open all the way.
It pulls 18-20" vacuum.  However, I tested it another place with the ac on and it was some less.
Where is the best place to test vacuum?

[GRONK]

The manifold port that is shared w/ your brake booster port.

[Jurjen]

This may help me find out why my oil light does not work.

There are three wires: the Y/BK and the dark BL are for the choke heater (AWG 14 wires).
There is a light blue one that is thinner (AWG20) and that is for the oil pressure light.
You can ground that contact with a piece of wire and then the oil light should come on.
If it does, the oil pressure switch is faulty.
This part of the oil pressure switch is a normally closed contact, it opens as soon as there is oil pressure and the light will go off.