Improve Diagnostic Skills By Listening Better

Tech Tip: No Start in Cold Weather Due to No Weep Hole

Protect Your Fuel Tank and Pump With Delphi Technologies 

Improve Diagnostic Skills By Listening Better

Tech Tip: No Start in Cold Weather Due to No Weep Hole

Protect Your Fuel Tank and Pump With Delphi Technologies 

Service Advisors: Customer Satisfaction Starts With Communication

This webinar is part of "AAPEX Repair Shop HQ Webinar Series: An 8-Part Webinar Series." Sponsored by AAPEX.

Your first encounter with a customer is a lasting one – are your service advisors’ communication skills up to the task? We’ll outline the top tips to ensure that every conversation on the phone, in person and via text helps set the appointment, confirm the service request, complete the payment, and confirm any follow-up service requirements.

Speakers Doug Kaufman, Editor, ShopOwner

Underhood Service targets repair shops that derive 50 percent or more of their revenue from the service and repair of under-the-hood systems. The expanding amount of knowledge and capital needed to keep up with technological advances has led these shop owners to concentrate on underhood systems, while also offering preventive maintenance services on most major vehicle systems. By subscribing, you’ll receive the ShopOwner digital edition magazine (12 times/year) featuring articles from Underhood Service and the Underhood Service eNewsletter (twice weekly). Access to digital editions, contests, news, and more are ready for you today!

Underhood Service targets repair shops that derive 50 percent or more of their revenue from the service and repair of under-the-hood systems. The expanding amount of knowledge and capital needed to keep up with technological advances has led these shop owners to concentrate on underhood systems, while also offering preventive maintenance services on most major vehicle systems. By subscribing, you’ll receive the ShopOwner digital edition magazine (12 times/year) featuring articles from Underhood Service and the Underhood Service eNewsletter (twice weekly). Access to digital editions, contests, news, and more are ready for you today!

ByUnderhood Service Staff Writers on Feb 25, 2022

High underhood temps, increased power demands and vibration can damage alternators or starters. Sponsored by ACDelco.

Don’t settle for “almost” - it matters where the engine is manufactured or remanufactured. Sponsored by ACDelco.

Brake pads are thoroughly developed to produce the best result. This video is sponsored by ZF Aftermarket.

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The AFM activation and deactivation are controlled by the Valve Lifter Oil Manifold or VLOM.

The experts at Melling have noticed an increase in the issues surrounding the replacement of deactivation lifters in GM LS engines with Active Fuel Management (AFM). After installing new lifters, the original issue may not have been corrected. Most lifters returned for analysis are found to be good, with most lifter faults being caused by oil pressure issues or control issues. 

The AFM activation and deactivation are controlled by the Valve Lifter Oil Manifold or VLOM. The VLOM consists of four electronically operated solenoids and is bolted to the top of the engine block beneath the intake manifold assembly. Its job is to direct the flow of pressurized engine oil to the active fuel management intake and exhaust valve lifters. 

The VLOM applies pressurized oil to the AFM lifters when cylinder deactivation is requested and shuts off that supply of oil to reactivate those cylinders. Cylinder activation and deactivation are both supposed to occur on the base circle of the cam lobe, making the transition from four- to eight- cylinder mode unnoticeable to the driver.  

To control contamination, a small replaceable oil filter is located in the VLOM inlet oil passageway. The AFM oil pressure relief valve regulates the oil supplied to the VLOM and is located in the oil pan near the oil filter housing. The AFM system has an operating range from 27 psi to 66 psi of oil pressure. At higher engine speeds, the high side of this operating range is controlled by the AFM oil pressure relief valve. At low engine speeds, the low side of the operating range will depend on the engine’s ability to produce oil pressure using the flow of oil from the oil pump. 

The AFM lifter bores in these engines have a spec of 0.843-0.844, and the deactivation lifters require 22 psi of pressure to release the locking pins. Taking these two things into consideration, a lifter bore that is even slightly worn could bleed off enough oil pressure to prevent the lifter from unlocking. 

In addition, it has been reported that it is common to find the VLOM oil filter plugged and needing replacement on high-mileage engines with misfire fault codes. Melling has received AFM DEAC lifters back for warranty claims where the lifter has been stuck compressed. 

This condition can be caused by the VLOM commanding activation or deactivation at the wrong point in the cam’s rotation, either in the ramp or at the lobe peak. 

Any time an engine has failed AFM lifters, the lifter guides must be replaced, the lifter bores must be measured, and the VLOM must also be tested for proper operation or replaced. Additionally, the VLOM oil filter must also be replaced.

Courtesy of Melling, www.melling.com 

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