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Re: Help on carb solenoid & connector

Ok....

I can fill >

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
Reply to
Mike Romain
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*** Today, Mike Romain allegedly wrote ***

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

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

Reply to
Chris Roat

Reply to
L.W.(ßill)

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

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

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
Reply to
Mike Romain

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

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

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?)

Seems stable to within a degree or two.

Yes.

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 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

Reply to
Chris Roat

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:

Reply to
Mike Romain

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