ACS Engine Primer 10920

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Part# 05-19920
MFR Model# 10920


Formerly manufactured by Gerdes Products, this primer has an anodized, all aluminum body and an engraved aluminum knob. The inlet and outlet ports are located on the sides of the pump and both are 5/16-24 male thread fitting. Overall length is 3-5/8 and weight is 3.5 oz. New manufacture. Current inlet and outlet locations were changed from original design on 10-27-16.

Made in USA

Note: 2 O-Rings are used per primer. For overhaul, customer will need quantity 2 of 05-19920. See Accessories.
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Looks like a quality product. I didnt have a chance to run fuel through it before Spruce asked for a review. NOTE: the square protrusion may require alteration for replacement of older primer. I had to make room for this on on my Corben BabyAce.

Tango L Verified Purchase


August 22, 2023

Was compelled to buy this product due to having an earlier design of same which failed in service due to known fault. Hope this one proves more reliable.

John T Verified Purchase


September 28, 2021

Worked out perfectly. Identical swap out for the primer that was in my J3.

Mark R
July 30, 2020

Nice quality primer with a positive lock. Installed this unit on my experimental Super Cub using the standard 1/8 fittings off the old primer. Works perfect and I really like the locking design.

Allen R
September 8, 2017

It works and the OEM Essex (aka Kohler) K2403 is no longer available new. The CRITICAL thing everyone needs to do is read the Technical Drawing pdf that is listed in blue on the Aircraft Spruce product page. The operation of this locking mechanism is very different from the OEM ESSEX primers push it in and twist a little. Failure to follow the ASY locking directions will cause a siphoning of fuel from the primer lines into the carburetor while flying that will cause the engine to run rich and foul the spark plugs. The original ASY technical drawing did not have these directions! Only four stars for not highlighting this critical difference better.

Gary J
April 6, 2023

Looks like good quality, but could not use because line fittings are 5/15-24 course thread. All normal primer line fittings (AN805-2) are 5/16-32 fine thread. I will be talking to ACS about a path forward.

Eagles N
June 29, 2023

It is not expensive and looks good but my primer is leaking. I have to plug the priming line to eliminate rough running.

Konstantin K
August 5, 2018

Good: It does have a positive lock, which was nice. Bad: Short stroke so doesnt move much fuel. Aluminum, so it wants to bind and gaul. Worked adequately for a couple of years, now wont draw in any fuel. Ill be removing it to re-install the old Lukenheimer primer I had replaced with this one. Disappointed for the cost.

Jeff S
July 20, 2018


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Is this ACS primer FAA approved for use in certificated aircraft?

No. This primer is not FAA Approved. It is intended for experimental aircraft use only.

Q: Does the ACS primer come furnished with o-rings?

The unit comes with o-rings already installed. Replacement o-rings are available, p/n 05-19920.

Q: Does this ACS primer twist lock in the closed position?

PER VENDOR: I'm not exactly sure what is meant by twist lock in the closed position, but I believe the answer is yes. The knob / piston assembly can be pushed in and rotated into a locked position. We have added paperwork to the 'Documents' tab on the web page on how it functions. I hope this helps.

Q: What is the overall length of this ACS Primer pump? Do you have an idea of output volume?

The total length is 3-5/8", but we do not have any documents that gives the output volume.

Q: I am replacing one on my Cub PA11, is it compatible to it?

There is not an aircraft eligibility chart for this product. It is commonly used on many aircraft. It is likely that it nis is the same product you are replacing on the Cub.

Q: What fittings will I need to connect 1/8 copper tubing to this primer unit?

These use SAE compression fittings now. The nut for the male fittings on the primer is 61SM-02.

Q: What is the maximum panel thickness that this will work with?

Approx 3/4".

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