M38 CDN L-134 willys Fuel Pump

[Lyle]

I'm installing an Airtex 9562 fuel pump with Vacuum.

Looking for any documentation and/or constructive comments.

It does not have the single port for connecting to venting system from the bell-housing to Transfer-case.

My thoughts are to install a TEE between the outflow of air from Airtex 9562 and the Check Valve connecting to the bell-housing and transfer-case.

That way the Bell-Housing and Tranfser-case will never over pressure since the cracking pressure of the check valve will be 2PSI.

[wesk]

I'm installing an Airtex 9562 fuel pump with Vacuum.
Looking for any documentation and/or constructive comments.

Review your fuel pump specs in the TM 9-8012 page 151. Calls for a pump output pressure of 4 to 5 1/4 PSI. Your new Airtex 9562 pump specs:

Mechanical Pump 9562
Airtex mechanical fuel pumps are designed to meet or exceed OEM specifications for fit and performance. Precision castings and hardened rockers help ensure a long life. Advanced polymer pump diaphragms help ensure consistent performance in multiple fuel blends.

A new fuel filter is recommended when replacing.

Product Features:

Coverage for classic, performance and non-fuel-injected vehicles.
100% factory tested: Every single pump is 100% tested throughout the entire manufacturing process for worry free, out of the box performance.

WARNING: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer, and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov

Gasket Included Y
Inlet Count 1
Inlet Type Threaded
Maximum Pressure Rate (psi) 3.75
Minimum Free Flow Rate (gph) 15 GPH @ 1000 RPM
Minimum Pressure Rate (psi) 2.5
Outlet Count 1
Outlet Size 1/4-18 NPSF
Outlet Type Threaded
Package Contents Pump & Kit
Warranty Limited 1 Year

Warranty Information:
12 Months

Do not compare well in the output pressure. The Airtex 4032 is a little better choice but uses straight tube nipples.

My thoughts are to install a TEE between the outflow of air from Airtex 9562 and the Check Valve connecting to the bell-housing and transfer-case.

Waste of time if you do not plan on deep water fording your M38. Not the best way if you do plan on fording. Vacuum side of that port is 10 to 12"
which is equivalent to 5.9 PSI when driving the jeep which is a lot higher than the 2 to 3 PSI used in the crankcase and tranny/transfer fording system. You mention a check valve. Where is this check valve that cracks open at 2 PSI.

There is a very ample supply of the correct rebuilt AC fuel pumps and the correct rebuilding kits to question any need to substitute an unqualified Airtex unit.

More discussion can be found here: http://www.willysmjeeps.com/v2/modules. ... highlight=

[Ivoryring]

I hope it's not a problem for me to reply here, but this thread seems to touch on several points for me.

Wes, you mention above that there is an ample supply of correct rebuilt AC fuel pumps, but I'm having a hard time locating one. Nothing to be found on eBay and the web sites I've checked (Midwest Military, debella, Kaiser Willys, army jeep parts) all seem to list "core charge" and/or "core required before we will send" or similar wording. Perhaps I'm overlooking something or looking in the wrong place?

For my purposes, I am planning on deep fording with my M38A1 (if I wasn't, I would just build a CJ5) - but I'm not going for museum quality and don't particularly mind substitution when it will serve functionally.

Aside from needing to make a transition from the straight tube nipples, would the Airtex 4032 work for me? I don't see a spec on the Airtex web site for vacuum... Just your reference above to 10-12" for the 9562 (if I'm reading that right).

I have a pump currently that works to pump fuel - but that doesn't mean it's actually right or outputting the correct fuel pressure or building vacuum to the correct level.

[wesk]

Nothing to be found on eBay and the web sites I've checked (Midwest Military, debella, Kaiser Willys, army jeep parts) all seem to list "core charge" and/or "core required before we will send" or similar wording.

I would think based on your remarks, that you did find a few pumps but they were more than you wished to pay and you were not happy with their core requirements. In this hobby one must either be patient and really dig around for used parts and inexpensive rebuilt parts. This means a lot of surfing the net, a lot of surfing your local salvage yards and rebuilders and a lot of car show attendance. The alternative is to dig deep in the wallet and pay!

For my purposes, I am planning on deep fording with my M38A1 (if I wasn't, I would just build a CJ5) - but I'm not going for museum quality and don't particularly mind substitution when it will serve functionally.

There is nothing wrong with this approach but when departing from stock on the jeep one must go the extra mile and research compatibility, vs cost vs endurability and performance. The only purpose of the vaccuum system is to support the vacuum operated wipers and the distributor venting system. The required specs for an acceptable amount of suction and an acceptable fuel pressure range are written in the TM's and are easy to find and easy to check with simple test equipment. You do not need a vacuum side to the fuel pump for the fording system to function. When you close the fording valves you do not use vacuum or pressure from the lower side of the dual action fuel fuel/vac pump. The fording valves close the two vents for the engine crankcase and the normal running of the engine creates the increasing internal crankcase pressure to keep the water out. The transfer and tranny are pressurized with this same crankcase pressure but it is delivered thru the center section of the fuel pump and thru the outlet fitting on the center of the fuel pump then to the top vent of the tranny/transfer. The center housing of the dual action fuel pump serves only as a tunnel allowing the crankcase pressure to find it's way to the tranny/transfer.

You'll notice if you start researching the Airtex that no one seems to list vacuum capability of the 4032. Only thing listed is fuel output at 4.0 to 5.5 Lbs at 20 GPH. The requirement for the M38 is 4.0 to 5.25 and the M38A1 4.5 to 5.0.

I see no reason an Airtex pump won't work for you. But if I were headed down your path I would have already converted to electric wipers, a single action high quality fuel pump, a set of disc brakes and a dual master cylinder. I also would have installed a plumbed axle vent system for both axles to stop water entry into them

[Ivoryring]

I would think based on your remarks, that you did find a few pumps but they were more than you wished to pay and you were not happy with their core requirements. In this hobby one must either be patient and really dig around for used parts and inexpensive rebuilt parts. This means a lot of surfing the net, a lot of surfing your local salvage yards and rebuilders and a lot of car show attendance. The alternative is to dig deep in the wallet and pay!

Your insight and experience is definitely appreciated.

I was reading that the comments about 'core required'/'core charge' as directly meaning that - a core exchange is a literal requirement. I am familiar with 'core charge' with things like batteries where it's merely a charge but a return of a bad battery isn't an actual requirement. What I didn't do is reach out to any of those vendors and see if it's a literal requirement. Since I have a currently functioning pump I have the time to keep on hunting around and/or elect to dig into the wallet.

There is nothing wrong with this approach but when departing from stock on the jeep one must go the extra mile and research compatibility, vs cost vs endurability and performance. The only purpose of the vaccuum system is to support the vacuum operated wipers and the distributor venting system. The required specs for an acceptable amount of suction and an acceptable fuel pressure range are written in the TM's and are easy to find and easy to check with simple test equipment. You do not need a vacuum side to the fuel pump for the fording system to function. When you close the fording valves you do not use vacuum or pressure from the lower side of the dual action fuel fuel/vac pump. The fording valves close the two vents for the engine crankcase and the normal running of the engine creates the increasing internal crankcase pressure to keep the water out. The transfer and tranny are pressurized with this same crankcase pressure but it is delivered thru the center section of the fuel pump and thru the outlet fitting on the center of the fuel pump then to the top vent of the tranny/transfer. The center housing of the dual action fuel pump serves only as a tunnel allowing the crankcase pressure to find it's way to the tranny/transfer.

This is very interesting and really helps me understand the system better. I've been reading through the TMs and looking at the diagrams, but have had a hard time getting a real grasp of it. Looking at the diagrams I thought that it was the bottom/vacuum half of the fuel pump that was involved with the ventilation lines for the transmission and transfer case. Now that I look again, in TM9-8015-1 pg 151 I see what you mean. Would this missing connection from the center portion of the dual action fuel pump be a portion of why you are saying the Airtex 4032 would be a poor choice?

You'll notice if you start researching the Airtex that no one seems to list vacuum capability of the 4032. Only thing listed is fuel output at 4.0 to 5.5 Lbs at 20 GPH. The requirement for the M38 is 4.0 to 5.25 and the M38A1 4.5 to 5.0.

I see no reason an Airtex pump won't work for you. But if I were headed down your path I would have already converted to electric wipers, a single action high quality fuel pump, a set of disc brakes and a dual master cylinder. I also would have installed a plumbed axle vent system for both axles to stop water entry into them

Thank you for your knowledge on this - I'm inclined toward the correct pump rather than the Airtex unit with this info.

[wesk]

Tundra,

Since I have a currently functioning pump I have the time to keep on hunting around and/or elect to dig into the wallet.

Some of the vendors only require a core deposit and wait for you to return your core to them after you make the replacement.

Would this missing connection from the center portion of the dual action fuel pump be a portion of why you are saying the Airtex 4032 would be a poor choice?

Not necessarily. If you want to ford the jeep then you need to retain the ability to pressurize the tranny/transfer cases. This can be done without a fitting equipped fuel pump. You simply redirect the Fording pressure tube to a different access point to the crankcase. Something as simple as installing a male nipple that matches the pressure tube's end fitting on the valve side cover would work.

A note on the older original M38/M38A1 fuel pumps. You should ascertain they have had the service bulletin TB 9-804-11 complied with .