M38A1 fuel filter mod

[chris vickery]

Looking for info on the typical fuel filter mod done on M38A1 jeeps. Not sure if the CF ever endorsed the use of disposable filters inline other than the in tank filter. I have seen numerous atrocities when it comes to placement, wondering if there was ever a CFTO on this? Putting a filter in place prior to the fuel pump makes sense to me.

[rob love]

Nope. And I saw certain Jeeps get new carbs again and again and again. I had a problem Jeep like that at Minto Armoury, and another in camp Dundurn, and when I tried to set the float level, realized there was a fine red sand in the bottom of the float bowl. It was rust. Best solution was to replace the tank. The stone filter was just too course to filter out the rust particles, and they would cause the needle to stick. I started to install fuel filters, but it was so close to the end of service for the M38A1s, there was no point doing a TFR.

I liked using the M151A2 filter right at the carb, but the best solution was to remove the top of the fuel pump, clean out the sediment that collected there, then cut the rubber line before the pump and install an inline filter.

You also have to remember that back then the Jeeps were only around 15 years old. Now they are 50.

[chris vickery]

One of my 1970s has a fuel filter right before the carb. An easy place to get to for replacement. I am in the process of doing new fuel lines and will be using a repro fuel line kit so I was hoping to do something that is at least semi-correct with regard to the original line routing. Is it better to install prior to the pump or prior to the carb? My carb is a fresh rebuild and I also have the new in tank filter offered by AJP and others...

[rob love]

I don't know what the micron rating is of those new filter kits.

The best place is just before the fuel pump. The reason I say this is because the particles can also unseat the little check valves in the fuel pump, causing the pump to go to idle and not pump fuel. But owing to the coarseness of the fuel pump check valves, it would have to be fairly substantial particles.

As I mentioned before, remove the top of the fuel pump (I think it is about 8 screws) and remove the fuel portion of the pump. Clean it out then re-install. Now you can install the inline filter just before the pump. The reaon you have to clean out the pump is otherwise the sediment in the pump will continue to find it's way up to the carb.

If that does happen, it will usually happen when you pull up to a stop sign. The engine will rumble a little, then drown itself. You have to get out of the truck, move the machine gun mount, lift the hood, then turn off the little tap that is on the frame just before the pump. Now crank the Jeep until it starts, then jump back out, open the tap, close the hood, move the MG arm back in place, and hit the road.

Or just install the fuel filter.

[Wayne Hingley]

Rob: it sounds like you might "know someone" who can do some quick work at a stop sign.

Good info. I have been planning to add a fuel filter also. I was hoping to find a filter that would thread on to the rubber hose connection down by the shut-off valve. Post some photos when you get yours set up Chris.

[rob love]

You can merely splice the rubber hose with a regular inline (might I suggest the clear ones) fuel filter. Or you can get fancy and install the inline filter off a 70s Ford truck (that was what the M151A2 used). It shoudl thread in to the fuel pump, although you may have to use a 1/4" m-f pipe elbow to get the direction right. I think, by memory though, that the stock flex fuel line might be too small a fitting to match up to the Ford fuel filter. I'll check when I am at work tomorrow, I stock both items there. Personally, I have usually gone with the filter at the carb and spliced one in at the pump.

[Frank v R]

the stock filters only stop boulders, I had the same problem Rob spoke of with my first A1 in the early 80's, I have a mod that I do on all the A1's I touch , I pull the rubber flex line between the shutoff and the fuel pump, bend up some new steel tubing and install a fram see through inline filter, with the rubber sections there I still have the flex needed for the engine movement in the mounts, no hacking into the original system , one of the mods that bubba really seems to like is hacking into the line between the pump and carb and having his mod hang over the exhaust manifold , fire looking for a place to happen,

[chris vickery]

Frank, I understand the concept but do you have a picture to add? Also, which Fram filer do you use?

[rob love]

I did a quick check, and the existing flex line from the frame is the correct flare size to go into the small Ford fuel filter. I may try this setup on my own M38A1 at home. A 1/4 elbow, the Ford filter, and then the flex line onto the filter. The only difficulty that I can foresee is the close proximity of the lower rad hose to the filter. I would prefer a little more clearance between the hose and the filter so as to minimize heat transfer.

[Wayne Hingley]

Im looking forward to seeing what you come up with Rob. Do you have the part number of the Ford filter?

[rob love]

Napa no is 3081 (wix 33081) . Seems to me there is a narrower version of this filter which might be perfect....I'll do some investigating.

[Wayne Hingley]

Rob, I see what you mean about a tight spot between the pump and rad hose. What about the threaded connection between the shut-off and fuel pump?

[rob love]

The filter could fit onto there, but the other end of the filter is 1/8 NPT. You would need a fitting for the back that is female 1/8NPT and the appropriate flare fitting on the other. I'll have to have a look in my weatherhead catalogue and see what is available.

[Frank v R]

Chris I'll dig up a photo of my mod and email to you , some else will need to post it to the thread, Rob I bend a loop into the mod to give the space I need,