New Fuel pump questions

Deadguy · Post by **Deadguy** » Fri Nov 01, 2013 9:03 pm

I installed a rebuilt fuel pump supplied by John at Midwest Military. Pump works great, vehicle starts up faster than ever, and in the short run around my parking lot, it seemed peppier. I used thread sealant on the fuel intake lines, but not on the vacuum line. Should I go back and use sealant on it? Also, where the vent line attaches at an elbow to the lower portion of the carb, I screwed the elbow all the way in, but could not get it to connect to the tubing adapter. It was too close to the pump body. I used thread sealant, and backed it out 360 degrees, and the connecter screwed in fine. But that makes the elbow connector not as tight where it screws in to the pump body (I can turn it by hand). Will it be fine, or do i need to figure out something else? It isn't leaking any gas, and everything seems to work fine, just want some advice before I call it a day.

Post by **wesk** » Fri Nov 01, 2013 9:28 pm

When using brass pipe thread type fittings in soft aluminum housings thread sealant is not a necessity and often causes the fittings to work loose and often results in allowing the installer to over-tightened tighten them, either of which quickly damages threads by wearing them down. Backing a fitting out one turn results in a loose fitting that when left that way will quickly start moving and wear the threads out even more. The industry accepted method of resolving the fit issues you encountered is to make sure threads are clean and dry. Substitute a new brass fitting and check alignment and positioning so you know exactly where you need to stop turning the fitting. Then tighten it gently so that you come up on it's final position slowing and do not overshoot.

When pipe threaded fittings will simply not line up correctly without severe over-tightening then select a quality hardening type thread sealer to seal the threads and lock the fitting in place.

I assume this is a typo"

Also, where the vent line attaches at an elbow to the lower portion of the carb ,

Deadguy · Post by **Deadguy** » Fri Nov 01, 2013 9:56 pm

I only used hand tools, but I did crank the elbows in the fuel pump pretty tight (so they only had like two-three threads sticking out). When I first installed the carb to fuel pump line, it was gushing gasoline, I had to reorient the elbows, and looking at where the line screwed into the carb and it had sealant, I thought I'd add some thread sealant to the pump line. At this point, what do you recommend Wes? I used liquid thread sealant, and not much. Should I go back and loosen any of the elbows, or remove the sealant? The one vent line elbow, where it connects to the lower portion of the pump, does not jiggle back and forth, but it is only hand tight, and I can unscrew it easily by hand. Should I use maybe blue thread locker in there?

Post by **wesk** » Sat Nov 02, 2013 12:00 am

The more you putz with tapered pipe threads in soft materials the worst the situation will get. If there's no danger of the gas lines loosening and leaking then leave well enough alone.

Hand tight is not adequate for any tapered pipe thread and as I said in the last post will result in a loose fitting and rapid thread wear. When you have no alternative but to leave a fitting slightly loose because of indexing and clearance then definately apply a HARDENING TYPE\ thread sealer. Not just plain thread locker.

Deadguy · Post by **Deadguy** » Sat Nov 02, 2013 2:34 am

I pulled the elbow joint, and the first few threads cross-threaded. I put it in a vise, levelly screwed in the hose fitting, pulled it out, re-inserted it into the pump, and was able to tighten it and still have the vent line go in. The cross threading was preventing it, not closeness to the pump. It makes a tight fit, but even still, I think I should replace that elbow when I can. What size is elbow do I get Wes?

Post by **wesk** » Sat Nov 02, 2013 8:15 am

The center vent line is connected to the stock M38A1 fuel pump (Which has a hand priming lever) with three fittings.

M38A1 after SN MD29295

Deadguy · Post by **Deadguy** » Sat Nov 02, 2013 10:35 am

I know, I was looking at that as I installed the new pump, and I need to order a new "H", I just need to know what size I need to get.

evanso1975 · Post by **evanso1975** » Sat Nov 02, 2013 12:56 pm

I need to order a new "H", I just need to know what size I need to get

Check out the diagram on P.67 of the ORD-9. You need a 90-degree 5/16" inverted flared tube elbow with a 1/8" male pipe end.

Deadguy · Post by **Deadguy** » Sat Nov 02, 2013 8:06 pm

I could swear that vent line on my M38A1 is bigger than 5/16th. Most of my fording lines are 5/16th, and that line looks bigger