AFC Diaphragm 3013811 — Small Part, Big Control For Cummins PT Fuel Systems

On a big Cummins K-series or N-series engine, the AFC (Air Fuel Control) housing is the "bouncer" at the door: it decides how much fuel is allowed in when boost is low. At the heart of that housing is the AFC diaphragm 3013811. When the diaphragm hardens, cracks or loses flexibility, you'll see it in the real world as extra smoke off-idle, lazy turbo spool and inconsistent rack travel.

The reference 3013811 is an OEM Cummins diaphragm used primarily on non-certified 19 L K-series engines (K19 and related K-series PT fuel pumps) and other heavy-duty Cummins applications. Aftermarket catalogs describe it as an AFC / PT fuel pump air-fuel control diaphragm for Cummins K19, K38, K50 and other large-bore PT systems used in trucks, buses, construction and marine machinery

 

 

Inside a PT fuel pump's AFC housing, this diaphragm connects boost pressure on one side and a spring/lever system on the other. In service, it:

Limits fuel at low boost to keep smoke under control and prevent over-fueling

Progressively allows more rack travel as turbo boost builds

Helps maintain a cleaner torque curve and protects pistons and turbo from excess heat

When the 3013811 diaphragm is torn, oil-soaked or stiff, the housing can no longer "read" boost correctly. Shops see this as:

Excess black smoke on take-off

Slow turbo spool and a flat spot before the engine "comes on song"

Inconsistent rack position and fuel rate at the same boost level

Replacing the diaphragm returns the AFC to its original calibration window, often transforming driveability with a part that fits in your hand

 

 

Suppliers and OEM-style manufacturers specify the 3013811 diaphragm with the following characteristics:

Material: Oil- and fuel-resistant black rubber bellows/diaphragm, designed to survive diesel vapour and crankcas 

Application: "Solenoid/AFC diaphragm" for Cummins K-series engines and PT fuel systems 

Function: Air-fuel control membrane in PT fuel pump AFC housing, regulating fuel flow for consistent engine performanceS 

OEM references:

Cummins 3013811

Often cross-listed with 214147 and an orange version 3013811S in some catalogs 

Because it's a flexible part, quality rubber and the correct thickness profile are critical; reputable aftermarket producers highlight controlled thickness (~0.03") and form to match the original movement range

 

 

You can confidently position AFC diaphragm 3013811 for:

Cummins K-series engines – K19, K38, K50 non-certified 19 L K engines in heavy trucks and off-highway equipment 

Commercial trucks & buses – multiple listings describe it as a diaphragm for commercial truck fuel systems and heavy-duty 

Construction & mining machinery – wheel loaders, dozers, road rollers and excavators from brands such as SHANTUI that use Cummins K-series power 

You'll also see it mentioned alongside PT fuel pump repair kits for air-fuel control housings, where it's supplied with spiders, springs and gaskets

 

 

Although it's a small part, installing the 3013811 AFC diaphragm correctly makes a big difference:

Diagnose the symptom
Look for excessive low-boost smoke, poor response, or evidence of fuel/oil contamination in the AFC cap. Confirm that linkages and boost lines are free before blaming the diaphragm.

Remove and inspect
Pull the AFC cover, mark spring and lever positions, and gently lift out the old diaphragm. Cracks around the outer ring or stiff, glossy rubber are strong indicators it's past its best.

Fit the new diaphragm
Place the new 3013811 membrane so the centre button locates correctly in the spider or pushrod. Make sure the outer edge sits flat in the groove-no pinches or twists 

Reassemble and adjust
Reinstall springs and caps to the original setting. For tuning work, follow the pump or engine manual to avoid excessive pre-load that could over-fuel under low boost.

Prove the result
After installation, check for cleaner launch, reduced smoke and more consistent boost-to-fuel relationship during a short road or dyno test.

 

 

Based on real listings and search behaviour, you can mix in:

"AFC diaphragm 3013811 for Cummins K19 / K38 / K50" 

"PT fuel pump air fuel control diaphragm 3013811 

"Cummins 3013811 solenoid diaphragm for K series engines

 

 

 

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