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How to change the diaphragm? - Pool & Spa

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What diaphragm are talking about?
Pool/Spa pumps don't have a diaphragm.

Posted on Apr 04, 2015

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Changed diaphragm, mower only running for short periods

did you put the diaphragm back on the right side of the gasket so that it covers the holes in the plate
( the diaphragm has to sit flush on the holes with the gasket on top)

May 08, 2016 | Garden

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Chainsaw only starts without the air filter, and is a new air filter

did the saw have this problem before changing this stuff or did it occur after you chained all these components?
Sounds like the gasket and fuel diaphragm are reversed. Gasket against the carb, Diaphragm then cover

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How to change float switch on hoshizaki ice machine ?

take the front and top cover off from the top look down and you can see the reservoir there is a black piece on top with two wires going in to it. turn it to remove it. You can test it by starting the ice machine and turning the float up side down. If water continues to flow you may have a bad diaphragm in your water valve. You can replace the diaphragm with a Phillips screw drive. Just be very careful when you lift the stem that goes in the solenoid make sure you pull the diaphragm with it as well. there is a spring it the stem that will fly out and it runs fast and hides well. look at the diaphragm's hole if it looks worn replace it before the float switch.

Jun 13, 2014 | Hoshizaki Freezer Commercial Ice Machines...

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What is a Peavey 44XT Diaphragm Kit for

If you've never replaced a tweeter diaphragm, then maybe you should seek out someone local who has. These guys are a bit fragile and misalignment can turn it into garbage. On the other side of this discussion...overpowering speakers blows tweeters 1st because their voice coil windings are so small, and are more easily damaged. Re-examine your PA setup and adjustments or you'll find yourself back on the phone ordering more diaphragms.

May 28, 2014 | Peavey Audio Players & Recorders

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The rear passenger side speaker seems to vibrate and the sound quality is bad

One of the most common problem with car door speakers are damage due to water entry. Remove the door pads and inspect the speaker for diaphragm damage. Especially if its a paper cone diaphragm it absorbs moisture and looses its rigidity, which will lead to muffled sound due to lack of high frequency response. If you are replacing them change to a new generation polypropylene diaphragm type, they last longer because they are immune to water splashes and heat.

Jul 06, 2011 | Car Audio & Video

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I had the hydraulic clutch and master cylinder in my 89 ford f-150 changed now even with the clutch to the floor the truck still moves and will only go in gear when the motor is off, If the motor is...

You can leave it out but the fluid will become contaminated from stuff getting in past the cap. You should be able to get the right replacement, if not you may be able to fold or cut the existing one and secure it with a zip-tie or wire to 'shrink' it while still keeping it sealed up. What the diaphragm does is allow for expansion/contraction within the reservoir without letting outside air into the fluid.

Apr 11, 2017 | 1989 Ford F 150

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Check engine light is on and when checked it pulls a malfunction code (code P1494) leak detection switch or mechanical failure. Is it still under warranty under the emissions? It is a 2001 Jeep Grand...

First off, a model year 2001, its possible still covered under the 5 year/50,000 mile emissions warranty. That's federal law. So you should not have had to pay a penny for that repair since the Leak Detection Pump is an emission control device.

As is the Charcoal Canister. If that is bad there should be no charge for repair or replacement. I hope you saved the receipts because I think they owe you a bunch of money. If they give you an argument about it, call Chrysler and they will take care of it.

Now, are you ready to learn more about the Leak Detection Pump then you will ever need to know? Good! Here it is!

Leak Detection Pump (LDP) Operation And Diagnosis:
* P0442-Evap Leak Monitor 0.040" Leak Detected
* P0455-Evap Leak Monitor Large Leak Detected
* P0456-Evap Leak Monitor 0.020" Leak Detected
* P1486-Evap Leak Monitor Pinched Hose Found
* P1494-Leak Detection Pump SW Or Mechanical Fault
* P1495-Leak Detection Pump Solenoid Circuit

The evaporative emission system is designed to prevent the escape of fuel vapors from the fuel system. Leaks in the system, even small ones, can allow fuel vapors to escape into the atmosphere.

Government regulations (remember I said that?) require on-board testing to make sure that the evaporative (EVAP) system is functioning properly. The leak detection system tests for EVAP system leaks and blockage. It also performs self-diagnostics.

During self-diagnostics, the Powertrain Control Module (PCM) first checks the Leak Detection Pump (LDP) for electrical and mechanical faults. If the first checks pass, the PCM then uses the LDP to seal the vent valve and pump air into the system to pressurize it.

If a leak is present, the PCM will continue pumping the LDP to replace the air that leaks out. The PCM determines the size of the leak based on how fast/long it must pump the LDP as it tries to maintain pressure in the system.

EVAP Leak Detection System Components:
Service Port: Used with special tools like the Miller Evaporative Emissions Leak Detector (EELD) to test for leaks in the system.

EVAP Purge Solenoid: The PCM uses the EVAP purge solenoid to control purging of excess fuel vapors stored in the EVAP canister. It remains closed during leak testing to prevent loss of pressure.

EVAP Canister The EVAP canister stores fuel vapors from the fuel tank for purging. EVAP Purge Orifice: Limits purge volume.

EVAP System Air Filter: Provides air to the LDP for pressurizing the system. It filters out dirt while allowing a vent to atmosphere for the EVAP system.

Leak Detection Pump (LDP) Components:
The main purpose of the LDP is to pressurize the fuel system for leak checking. It closes the EVAP system vent to atmospheric pressure so the system can be pressurized for leak testing. The diaphragm is powered by engine vacuum. It pumps air into the EVAP system to develop a pressure of about 7.5' H20(1/4) psi. A reed switch in the LDP allows the PCM to monitor the position of the LDP diaphragm. The PCM uses the reed switch input to monitor how fast the LDP is pumping air into the EVAP system. This allows detection of leaks and blockage.

The LDP assembly consists of several parts. The solenoid is controlled by the PCM, and it connects the upper pump cavity to either engine vacuum or atmospheric pressure. A vent valve closes the EVAP system to atmosphere, sealing the system during leak testing. The pump section of the LDP consists of a diaphragm that moves up and down to bring air in through the air filter and inlet check valve, and pump it out through an outlet check valve into the EVAP system.

The diaphragm is pulled up by engine vacuum, and pushed down by spring pressure, as the LDP solenoid turns on and off. The LDP also has a magnetic reed switch to signal diaphragm position to the PCM. When the diaphragm is down, the switch is closed, which sends a 12 V (system voltage) signal to the PCM. When the diaphragm is up, the switch is open, and there is no voltage sent to the PCM. This allows the PCM to monitor LDP pumping action as it turns the LDP solenoid on and off.

LDP At Rest (Not Powered):
When the LDP is at rest (no electrical/vacuum) the diaphragm is allowed to drop down if the internal (EVAP system) pressure is not greater than the return spring. The LDP solenoid blocks the engine vacuum port and opens the atmospheric pressure port connected through the EVAP system air filter. The vent valve is held open by the diaphragm. This allows the canister to see atmospheric pressure.

Diaphragm Upward Movement:
When the PCM energizes the LDP solenoid, the solenoid blocks the atmospheric port leading through the EVAP air filter and at the same time opens the engine vacuum port to the pump cavity above the diaphragm. The diaphragm moves upward when vacuum above the diaphragm exceeds spring force. This upward movement closes the vent valve. It also causes low pressure below the diaphragm, unseating the inlet check valve and allowing air in from the EVAP air filter. When the diaphragm completes its upward movement, the LDP reed switch turns from closed to open.

Diaphragm Downward Movement:
based on reed switch input, the PCM de-energizes the LDP solenoid, causing it to block the vacuum port, and open the atmospheric port. This connects the upper pump cavity to atmosphere through the EVAP air filter. The spring is now able to push the diaphragm down. The downward movement of the diaphragm closes the inlet check valve and opens the outlet check valve pumping air into the evaporative system. The LDP reed switch turns from open to closed, allowing the PGM to monitor LDP pumping (diaphragm up/down) activity. During the pumping mode, the diaphragm will not move down far enough to open the vent valve.

The pumping cycle is repeated as the solenoid is turned on and off. When the evaporative system begins to pressurize, the pressure on the bottom of the diaphragm will begin to oppose the spring pressure, slowing the pumping action. The PCM watches the time from when the solenoid is de-energized, until the diaphragm drops down far enough for the reed switch to change from opened to closed. If the reed switch changes too quickly, a leak may be indicated. The longer it takes the reed switch to change state, the tighter the evaporative system is sealed. If the system pressurizes too quickly, a restriction somewhere in the EVAP system may be indicated.

Pumping Action:
During portions of this test, the PCM uses the reed switch to monitor diaphragm movement. The solenoid is only turned on by the PCM after the reed switch changes from open to closed, indicating that the diaphragm has moved down. At other times during the test, the PCM will rapidly cycle the LDP solenoid on and off to quickly pressurize the system. During rapid cycling, the diaphragm will not move enough to change the reed switch state. In the state of rapid cycling, the PCM will use a fixed time interval to cycle the solenoid.
The Charcoal Canister

EVAP/Purge Solenoid:
The duty cycle EVAP canister purge solenoid (DCP) regulates the rate of vapor flow from the EVAP canister to the intake manifold. The Powertrain Control Module (PCM) operates the solenoid.

During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged. The PCM de-energizes the solenoid during open loop operation.

The engine enters closed loop operation after it reaches a specified temperature and the time delay ends. During closed loop operation, the PCM cycles (energizes and de-energizes) the solenoid 5 or 10 times per second , depending upon operating conditions. The PCM varies the vapor flow rate by changing solenoid pulse width. Pulse width is the amount of time that the solenoid is energized. The PCM adjusts solenoid pulse width based on engine operating condition.

Vapor Canister:
A maintenance free, EVAP canister is used on all vehicles. The EVAP canister is filled with granules of an activated carbon mixture. Fuel vapors entering the EVAP canister are absorbed by the charcoal granules.

Fuel tank pressure vents into the EVAP canister. Fuel vapors are temporarily held in the canister until they can be drawn into the intake manifold. The duty cycle EVAP canister purge solenoid allows the EVAP canister to be purged at predetermined times and at certain engine operating conditions.

Hope this helps.

Dec 14, 2010 | 2001 Jeep Grand Cherokee

1 Answer

My 2001 heritage softail is starting to spit a little is , there a fuel fitler on this bike , and if so how do you find and change it

There is a strainer on the petcock inside the tank. It's more like screen and only keeps trash the size of boulders out of the carb, anything smaller passes right through.

With your bike being an '01 model, I would suspect the accelerator pump diaphragm. Over the years, the rubber coating comes off and the accelerator pump doesn't work quite as good as it used to. On the left side of the carb, there is a rod that moves down everytime you twist the throttle grip. If there is gasoline or the tell tale signs of fuel leakage around the hole that this rod goes into, this indicates a leaking diaphragm. To see this, you must remove the air cleaner cover, the filter element, and the backing plate for the air cleaner. Turn off the fuel at the petcock.

To change the diaphragm, I would suggest removing the entire float bowl. Remove the four screws that holds it on, lower it, take it off the bike. Empty the bowl and turn it upside down. There will be two screws left in the bottom of the bowl. These hold the accelerator pump cover on. Remove the screws and there will be a spring and a diaphragm beneath the cover. The diaphragm has a ridge around the outer edge. This ridge goes into a groove in the float bowl. Put the new diaphragm in position, put the sping on top of it and reinstall the cover. Turn the bowl over and make sure there is no trash in the bowl and reinstall it on the carb making sure you get the accelerator pump push rod back into the hole it goes into.

There is one other thing that may be giving you a problem. On your bike, I think it came from the factory with a vacuum operated petcock. These are notorious for giving problems. The diaphragms in them develop leaks and don't open the fuel petcock as they should. I think you can buy a replacement diaphragm for it as well from the Harley dealer. Remove the petcock from the tank, make sure you drain the tank first. Clean the screen I told you about and on the backside of the petcock, there are four screws. Remove the screws, the cover comes off and under it is a diaphragm and a spring. Replace the diaphragm, the spring and the screws. Reinstall the petcock.

I hope this helps, Good Luck.

Apr 14, 2010 | 2000 Harley Davidson FLSTC Heritage...

1 Answer


Section 03-04A: Fuel Charging and Controls—2.0L 1995 Contour/Mystique Workshop Manual DESCRIPTION AND OPERATION Fuel Pressure Regulator The fuel pressure regulator (9C968):
  • Is mounted to the fuel injection supply manifold (9F792) downstream of the fuel injectors (9F593) .
  • Regulates the fuel pressure supplied to the fuel injectors .
  • Is a diaphragm-operated relief valve in which one side of the diaphragm senses fuel pressure and the other side is subjected to intake manifold vacuum. Nominal fuel pressure is established by a spring preload applied to the diaphragm.
  • Balances one side of the diaphragm with manifold pressure to maintain a constant fuel pressure drop across the fuel injectors .
  • Bypasses and returns excess fuel to the fuel tank (9002) .

Fuel Pressure Regulator


Item Part Number Description 1 — Engine Vacuum Reference Tube (Part of 9C968) 2 — Ball Seat (Part of 9C968) 3 — Spring (Part of 9C968) 4 — Upper Housing (Part of 9C968) 5 — Diaphragm (Part of 9C968) 6 — Lower Housing (Part of 9C968) 7 — Fuel Outlet (Return) Tube (Part of 9C968) 8 — Fuel Inlet (Supply) Tube (Part of 9C968) 9 — O-Ring Grooves (Part of 9C968) 10 — Mounting Plate (Part of 9C968) 11 — Fuel Filter Screen (Part of 9C968) 12 — Spring Seat (Part of 9C968) 13 — Valve Assembly (Part of 9C968) 2010&c18=modelyear&c35=wsm%2cfuel%20pressure%20regulator%2cssp%2c03-04a%2cdescription%20and%20operation&s=1600x900&c=32&j=1.3&v=y&k=y&bw=1171&bh=582&ct=lan&hp=n&[aqe]

Apr 06, 2010 | 1995 Ford Explorer

1 Answer

How to change the hf unit?

a new diaphragm can be fitted into the original driver and the speaker will be like brand new. first you must determine if you have the older RCF version (M44TI) or the newer Mackie versions (0008093). There is only one RCF diaphragm that will work for this repair and they are scarce. There are both authentic and aftermarket Mackie diaphragm options and both work very well.

Jun 15, 2009 | Mackie SRM-450 System

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