Mike Romain

Ok....

I can fill in some ideas or guesses below...

Chris Roat wrote:
>
> Hi,
>
> First, two questions on the Carter BBD carb solenoid for a
> '85 CJ-7:

The solenoid on a BBD carb is there in case you have an automatic or air
conditioning. This solenoid has an electrical and vacuum connection and
steps up the idle when the AC comes on or drive is selected.

It is located on the front drivers side of the carb.


Below you are talking about a stepper motor, not a solenoid.

>
> Should square waves be seen at all 4 inputs during correct
> operation? Is the frequency low enough to notice jitter on
> a volt meter, or should I use a 'scope?

I don't know the pulse width or speed, but it will be a 12 volt spike I
'believe'. I have never taken a meter to that end of things so don't
know if a DMM is fast enough to see it. Maybe try a logic probe that
shows CMOS or TTL pulses? (likely just TTL being that old)

>
> Are the two metering pins controlled by the solenoid
> connected? To check for a jam, I was able to move the pin
> you can see using a screw driver. Did I do damage and
> unsynch the two pins so they are now at different depths?

No the two pins are set into a plate. If one moves the other has to
move. If only one moves, the fiber board plate inside the stepper body
would be broken.

>
> And then a question on a mysterious conenector:
>
> After some recent work, I've now discorved that I have a
> female two-pin connnector floating free back between the
> valve cover and the carb. It comes out of the main wiring
> harness on the firewall and has a red wire going to one
> socket and two brown wires crimped together in the other
> socket. Where does this connector plug into!!! I've lost
> it's mate.

Be thankful you have 'lost' it's mate.

That used to go to the PCV shutoff solenoid which was a bad design and
recalled at one point, or the TSB said to just toss it in the garbage
and replace it with a plain 'T' fitting.

If you want to find out if the stepper motor is functioning, start the
engine, warm it up and watch the pins in the carb while doing this.
They should move. Then unplug the O2 sensor and watch to see if the
pins move.

A dead O2 sensor will stop the stepper from moving. The computer just
puts the stepper motor into 'limp home' mode and keeps it there.

You can also heat up the engine and disconnect the O2 sensor, then put
the DMM from the sensor plug to ground to check for pulses coming out of
the (unplugged) sensor.

You should see a flicker on the meter that goes from something like .2V
to .8V with the engine hot. Depending on how 'good' or fast the meter
is, you might just see a flicker, but a pulse is what you are looking
for.

If the pins appear to be pushed all the way into the carb, and the O2
sensor has pulses, then I would next check the charcoal canister purge
valve for integrity. If blown, it causes a lean situation that forces
the stepper into full rich (pins all the way into the carb body) to try
and compensate.

To test this, trace the PCV line to the back of the carb. There you
should find a T fitting or that stupid solenoid shutoff for the PCV.
Trace the other line from the T to the top of the charcoal canister down
under the washer bottle. At idle, pinch this line to the canister
closed. If the idle changes, the canister is dead.

Hope some of this helps.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Chris Roat

*** Today, Mike Romain allegedly wrote ***

>Below you are talking about a stepper motor, not a solenoid.

Oops. You're right... I meant stepper motor.

>If you want to find out if the stepper motor is functioning, start the
>engine, warm it up and watch the pins in the carb while doing this.
>They should move. Then unplug the O2 sensor and watch to see if the
>pins move.

Yep. This is what I'm after. The stepper motor seems to
get "stuck" every once and a while... this morning it was
working on the drive to work. So who knows what is
happening. One of the computer inputs (CTS, TAC, O2) must
be flaky.

In a non-Nutter stock setup, the vacuum advance comes from
the manifold vacuum, right? I reversed the Nutter for the
moment for other reasons, and I'm trying to set everything
straight again... 9 degrees advance at 1600 RPM with no
vacuum advance? When I let it idle and then reconnect the
manifold vacuum, I get a huge advance and the engine starts
idling at 1400. This seems like intro tune-up, but what is
the expected advance at idle with everything connected??

Thanks for the help,
Chris

L.W.(=?iso-8859-1?Q?=DFill?=) Hughes III

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Chris Roat wrote:
>
> Yep. This is what I'm after. The stepper motor seems to
> get "stuck" every once and a while... this morning it was
> working on the drive to work. So who knows what is
> happening. One of the computer inputs (CTS, TAC, O2) must
> be flaky.
>
> In a non-Nutter stock setup, the vacuum advance comes from
> the manifold vacuum, right? I reversed the Nutter for the
> moment for other reasons, and I'm trying to set everything
> straight again... 9 degrees advance at 1600 RPM with no
> vacuum advance? When I let it idle and then reconnect the
> manifold vacuum, I get a huge advance and the engine starts
> idling at 1400. This seems like intro tune-up, but what is
> the expected advance at idle with everything connected??
>
> Thanks for the help,
> Chris

Mike Romain

Chris Roat wrote:
>
> *** Today, Mike Romain allegedly wrote ***
>
> >Below you are talking about a stepper motor, not a solenoid.
>
> Oops. You're right... I meant stepper motor.
>
> >If you want to find out if the stepper motor is functioning, start the
> >engine, warm it up and watch the pins in the carb while doing this.
> >They should move. Then unplug the O2 sensor and watch to see if the
> >pins move.
>
> Yep. This is what I'm after. The stepper motor seems to
> get "stuck" every once and a while... this morning it was
> working on the drive to work. So who knows what is
> happening. One of the computer inputs (CTS, TAC, O2) must
> be flaky.

I would be cleaning all of the connections on all the sensors with WD40
or some other contact cleaner.


>
> In a non-Nutter stock setup, the vacuum advance comes from
> the manifold vacuum, right? I reversed the Nutter for the
> moment for other reasons, and I'm trying to set everything
> straight again... 9 degrees advance at 1600 RPM with no
> vacuum advance?

It should say on a sticker under the hood. That sounds right, with the
vacuum line blocked too eh.


When I let it idle and then reconnect the
> manifold vacuum, I get a huge advance and the engine starts
> idling at 1400. This seems like intro tune-up, but what is
> the expected advance at idle with everything connected??

I see a couple things first off. At 1400 you are getting both
mechanical and vacuum advance. It should mellow out when you set the
idle speed back to 750 rpm.

What was your curb idle before you plugged in the vacuum advance?

What was the advance at idle with the vacuum line still off and
plugged??

Was/is the advance steady on the mark with the vacuum line still off and
plugged at curb idle or was/is it jumpy?

Does it always come back exactly the same after a shot of gas?

Jumpy can imply a sticky advance plate or broken spring inside the
distributor. It can also imply the foam pad under the rotor hasn't been
oiled in a long time. This keeps the mechanical advance and physical
parts lubed as the distributor post is a sleeve at the top for the
advance plate.

Also a big jump in rpm can imply a blown vacuum advance diaphragm. I
would put a line on it and suck to see if it leaks.

I have never set one up the way you are doing it, so I don't know what
the 'normal' jump is.

I always seem to be tuning the engines up for the added 'off road'
performance, not detuning them for that POS Ford smog computer. ;-)

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Chris Roat

Thanks Mike for the pointers. I cleaned off some
connections, but the computer still seems to come on/off at
will.

>I see a couple things first off. At 1400 you are getting both
>mechanical and vacuum advance. It should mellow out when you set the
>idle speed back to 750 rpm.
>
>What was your curb idle before you plugged in the vacuum advance?

Like 1400! It wouldn't come down to 750. :( Maybe the
throttle plates aren't seating all the way... I don't know.

>What was the advance at idle with the vacuum line still off and
>plugged??

It dropped to 700ish and the computer kicked in for a few
moments opening the pulse-air valves. (Hmmm... was I
supposed to disconnect those wires first?)

>Was/is the advance steady on the mark with the vacuum line still off and
>plugged at curb idle or was/is it jumpy?

Seems stable to within a degree or two.

>Does it always come back exactly the same after a shot of gas?

Yes.

>Also a big jump in rpm can imply a blown vacuum advance diaphragm. I
>would put a line on it and suck to see if it leaks.

Nope. Solid. Tested the EGR, too, since I was in a testy
mood... and it was leaky! Plugged the EGR line for now, but
gotta go spend that $70, unless someone knows a good way to
repair it.

>I have never set one up the way you are doing it, so I don't know what
>the 'normal' jump is.
>
>I always seem to be tuning the engines up for the added 'off road'
>performance, not detuning them for that POS Ford smog computer. ;-)

I hear ya.

I also checked that out the mechanical advance and it seemed
to be maxed out around 1500 RPM. It was at 26 at that speed
w/o vacuum advance. My guess was that the mechanical
advance springs were weak and the advance was going too
quickly. In the end, I backed off the advance to 10 at idle
with the manifold vacuum on the distributor, and the RPM
dropped to 1000. I adjusted the screws so that the O2
sensor was reading around 0.4-0.7, since the computer seemed
to quit by this point and the stepper wasn't moving. Seems
to drive fine.

I've never been inside a distributor... is replacing the
springs an easy job (say, compared to rebuilding a carb)?
How much they going to run me when I call the parts shop
tomorrow?

Thanks Mike,
Chris

Mike Romain

You have a major vacuum leak.

Is the carb loose? They are sneaky and come loose lots after being put
back on.

And yes, your springs on the advance are worn out or one is broke, they
shouldn't top out the timing until 2300 or so, but that is a different
issue sort of...

The timing advance should 'just' be starting at the 1600 timing set, not
finished.

The parts are, umm, 'easy' to replace depending on the part. Getting
the thing apart can be a chore, you need a book for the right
directions. Not many parts, just they are 'on' there.

You need to be able to stall it out with the idle speed screw unscrewed,
if not, you have a 'big' vacuum leak and nothing will set right.

Mike

Chris Roat wrote:
>
> Thanks Mike for the pointers. I cleaned off some
> connections, but the computer still seems to come on/off at
> will.
>
> >I see a couple things first off. At 1400 you are getting both
> >mechanical and vacuum advance. It should mellow out when you set the
> >idle speed back to 750 rpm.
> >
> >What was your curb idle before you plugged in the vacuum advance?
>
> Like 1400! It wouldn't come down to 750. :( Maybe the
> throttle plates aren't seating all the way... I don't know.
>
> >What was the advance at idle with the vacuum line still off and
> >plugged??
>
> It dropped to 700ish and the computer kicked in for a few
> moments opening the pulse-air valves. (Hmmm... was I
> supposed to disconnect those wires first?)
>
> >Was/is the advance steady on the mark with the vacuum line still off and
> >plugged at curb idle or was/is it jumpy?
>
> Seems stable to within a degree or two.
>
> >Does it always come back exactly the same after a shot of gas?
>
> Yes.
>
> >Also a big jump in rpm can imply a blown vacuum advance diaphragm. I
> >would put a line on it and suck to see if it leaks.
>
> Nope. Solid. Tested the EGR, too, since I was in a testy
> mood... and it was leaky! Plugged the EGR line for now, but
> gotta go spend that $70, unless someone knows a good way to
> repair it.
>
> >I have never set one up the way you are doing it, so I don't know what
> >the 'normal' jump is.
> >
> >I always seem to be tuning the engines up for the added 'off road'
> >performance, not detuning them for that POS Ford smog computer. ;-)
>
> I hear ya.
>
> I also checked that out the mechanical advance and it seemed
> to be maxed out around 1500 RPM. It was at 26 at that speed
> w/o vacuum advance. My guess was that the mechanical
> advance springs were weak and the advance was going too
> quickly. In the end, I backed off the advance to 10 at idle
> with the manifold vacuum on the distributor, and the RPM
> dropped to 1000. I adjusted the screws so that the O2
> sensor was reading around 0.4-0.7, since the computer seemed
> to quit by this point and the stepper wasn't moving. Seems
> to drive fine.
>
> I've never been inside a distributor... is replacing the
> springs an easy job (say, compared to rebuilding a carb)?
> How much they going to run me when I call the parts shop
> tomorrow?
>
> Thanks Mike,
> Chris