IcemanG17

Well my flappy died.....bummer...but it explains the sudden "flat" feeling in the middle of the powerband....

So how long will it take to replace it? I'm thinking 4-5 hours?

dr bob

So what died? Miti-Vac on the actuator hose from the solenoid should help diagnose. Also-- Frequently, users accidentally swap the two hoses on the solenoid, and that doesn't work so well. You need the port that swaps to atmosphere to be towards the the flappy actuator. I don't have a pucture handy, unfortunately.

Charley B

<http://www.tower-mt.com/pics/davids_gt/Flapectomy-1/gallery.html>

the flyin' scotsman

The vac hose that connects directly to the flappy is on the LH side of the solenoid as viewd from the front of the car.

The vac supply comes directly from the splitter near the brake booster. That line connects to the top of the solenoid.

As doc Bob said apply vac to the hose to the flappy and see if it holds vacuum; also remove the rubber cap in the middle of the intake and you should see the shaft turn when applying vac if alls good. With the engine running you should see 18-20Hg of vac coming from the splitter.

If all the vac stuff is good perhaps the solenoid is shot or is not receiving its signal?

IcemanG17

This is the line I checked....the black one that goes to the flappy...not the gray one that comes from the 4 way T by the brake booster..... whats odd is it was totally Zero, wouldn't build up at all like it was an open line...but when I pulled on it it felt attached?

Bill Ball

If that hose is still attached to the flappy vacuum pod, then it's diaphragm blew. Cap off the vacuum source in the meantime.

ZEUS+

Just replaced my actuator 2 weeks ago, did not hold vacuum. Took about 2.5 hours to replace along with a breather hose. Put vacuum gauge on solenoid port to actuator. The vacuum port on the bottom of solenoid is the supply, port on side goes to actuator. Start engine and you will briefly see vacuum, also when you rev eng past 4500 rpm. This tests vacuum supply, solenoid and LH signal.

worf928

Brian, your vac lines to the solenoid are swapped. The port on the solenoid pointing UP is the switched vacuum that needs to be connected to the flappy actuator. Don't believe me though - test the solenoid with your hand pump attached and see for yourself. With the lines reversed a working flappy will close, but will not open when vacuum is released by the solenoid.

But, if the black line doesn't hold vacuum from your pump then the diaphragm in the flappy actuator is toast too.

StratfordShark

Malcolm and Dave C who are 928 gurus have given opposite advice about the connections to the flappy solenoid!

Which is correct? The OP's photo shows connections as per Malcolm's advice i.e. supply from splitter to top of solenoid.

WallyP

1) Crank engine and check lines for vacuum. The one with vacuum is the supply.
2) Check other line to ensure that it will hold vacuum. If you remove the rubber cap you should see the shaft turn as you apply vacuum.
3) Apply vacuum to solenoid ports. One should hold vacuum, and should have the supply line attached. The other should not hold vacuum, and should have the actuator line attached.

ZEUS+

Dave and Malcolm are both correct. The lines are crossed and the port to actuator is on the side. The supply is on the bottom and actuator feed is on the side. The top of solenoid has the connector and vent cap next to each other.
http://members.rennlist.com/v1uhoh/underthe.htm

worf928

This is precisely why I suggested Brian test the ports himself. That way he doesn't have to (mis)place faith.

Wally's directions are spot on.

With a hand pump gauge, the supply port will hold vacuum when the solenoid is in its nominal unswitched state and pass vacuum when the solenoid is switched.

The other port will not hold vacuum from the pump when the solenoid is in its nominal state.

With some test leads you can hook up the solenoid to the jump post and switch it on or off as you desire. If your vacuum reservoir is evacuated, your check valve is good and the supply line is hooked to the correct solenoid port, your hand pump connected to the other port will show a vacuum spike and release when you momentarily hit the solenoid with 12v.

If you end up switching lines back and forth on the solenoid, before each test you'll need to run the motor for a minute or two to ensure that the vacuum reservoir is evacuated before you test.

Alternatively, if you can safely prop your pump gauge in a place where you can see it from the passenger compartment you can use the normal motor-start test cycle to cycle the solenoid.

I can post pictures of my '91 in its undisturbed-from-the-factory state that are the reverse. But, pictures, while worth a thousand words, don't have to be correct.

the flyin' scotsman

Dave is correct, my apologies Brian I was going from feeble memory.

Attached pic is of my car and the flappy works well:

worf928

Oooohh.. Pretty. Blue vacuum line. Where'dya get it? And does it come in black or red or yellow?

the flyin' scotsman

I got the vac line from Roger (928sRus) when doing the intake R&R.

I believe he can get all colours and if asked nice can obtain speciality polka dot