M939A2 Adjustable return fuel check valve.

[maccus]

I am trying to make this thread more searchable. Change the title Clinto if you can come up with a better title.

There are a few threads about a problem with the return fuel check valve on the M939A2 series. The check valve is the same one used on the older Dodge Cummins 5.9 pumps. And there are a ton of articles on the net about problems with the check valve used on the early 5.9s. Causing all sorts of problems with hard starting etc.

I fear I might have that problem. So after consulting my CAT friend he suggested I look into an adjustable check valve. Here is a outfit that has one and it looks good to me. I have ordered one of the OFV020 valves and will let you know how it works after I have used it for a while.

Take a look at the web page and read the data on it and see if you think it makes sense to you..

http://www.torkteknology.com/products/TORK-TEK-CUMMINS-ADJUSTABLE-OVERFLOW-VALVE-OFV020.html

 

[SLOrazorsedge]

Nice find brother! I'll wait for your progress report and pick one up for my M932A2. Now if I could only find a source for the one-way check valve on my M936A1 NHC250 injection return line...no luck so far.

 

[plode]

I was thinking about picking one of these up.
Never saw any info about it on here, so I've hesitated...because it's $50.

 

[maccus]

Crazy..........While waiting for the adjustable check valve to get here I decided to remove the existing one and take a look at it. Looked to me like there was some crud in it. Took the brake cleaner and cleaned it out. Some crap came out. Also used a small plastic rod to push back the ball and really clean it out. Reinstalled valve. Primed and ran truck for a few miles, parked truck.

Waited about 6 days and started the truck. It started perfectly and went into a very smooth idle right off the bat. No more smoking like heck and running for a minute or so and then stopping. I do think the truck performed better with the valve working correctly. As one would expect given the function of the valve on injector pump pressure..

I would expect that when the new adjustable valve gets here tomorrow and is installed everything will be fine. I will verify that after I install the adjustable valve tomorrow.

 

[wreckerman893]

Pictures of the offending parts would be great.

 

[plode]

Crazy..........While waiting for the adjustable check valve to get here I decided to remove the existing one and take a look at it. Looked to me like there was some crud in it. Took the brake cleaner and cleaned it out. Some crap came out. Also used a small plastic rod to push back the ball and really clean it out. Reinstalled valve. Primed and ran truck for a few miles, parked truck.

Waited about 6 days and started the truck. It started perfectly and went into a very smooth idle right off the bat. No more smoking like heck and running for a minute or so and then stopping. I do think the truck performed better with the valve working correctly. As one would expect given the function of the valve on injector pump pressure..

I would expect that when the new adjustable valve gets here tomorrow and is installed everything will be fine. I will verify that after I install the adjustable valve tomorrow.

Sounds like your truck was running just like mine. Cranks and cranks and eventually lights off. And then smokes until it gets driven a bit. Has new fuel lines and filters. Good diesel. I've suspected there was an issue with the return valve, which is how I found that site selling the adjustable replacement valves as well. I might try cleaning it out tomorrow, weather depending.
Once you give it the thumbs up, I'm going to order one as well.

 

[maccus]

Richard this is the standard return check valve used in most 8.3s. There is another style but I am not sure if it was used in the military version of the 8.3. Part number for the one used in the military 8.3s is 1-417-413-047

You can see what the adjustable replacement I am going to use looks like by going to my first post in this thread and going to the web site I referenced.

 

[WillWagner]

That looks like the old style one. The newer ones don't have a ball in the end. They have a, well, bolt if you will in the end sealed with a washer. the pop of pressure is around 30 psi.

 

[maccus]

That could well be Will. As we all know Cummins is great for upgrading parts etc. When I was replacing the transfer pump on the 8.3 I came up with around 3 or so numbers for the same basic transfer pump. So I called the Cummins distributer to get the latest number.

When I was cleaning the check valve I was surprised to see how little pressure I had to put on the ball to move it a little. It will be interesting to see how much pressure it takes to push the ball on the adjustable one. It is supposed to be set at 35 I believe, at least that is what I asked for it to be set at.

 

[WillWagner]

It is actually a Bosch item

 

[maccus]

Got the adjustable check valve today. Installed it, purged air from system and ran truck for a few miles. Everything ran normally. No excessive smoke when I started it or when it was running. I will let the truck sit for a few days and start it and see how it works. Will get back to you folks in a few days with the operational condition.

 

[plode]

Just ordered myself one.

If it doesn't work...oh well, at least I tried.

 

[plode]

Installed the valve a couple of days ago. It might be slightly faster at starting, but still not as I'd expect it to be. Smoke at idle has gone away though.

 

[maccus]

It has been a week since I last shut down the truck. Started it today and after a minute or so it quit. So the check valve did not solve my problem. The check valve itself did what it was supposed to however. So the check valve is a good deal if you want to be sure to prevent back leakage at the valve point.

I have just about run out of places to look for the source of my leakage. I bought a ball valve with barbed ends and installed it in the hose that is attached to the input of the large fuel filter that is under the left front fender. Installed it. Ran the truck and after shutting it down turned off the ball valve. I hope to be able to isolate the leak area with the ball valve to either before or after the ball valve. Will cut the fuel input line distance in about half that way.

If one looks at all the connections of the fuel lines from the transfer pump to the tank (M931A2) you will see a mess of rubber and pipe connections. Way to many. I will order a CAT fuel filter and the correct adaptor to hold it. Then I will replace everything from the tank to the transfer pump. No more multi fuel line connections. Where I use this truck I do not need that very large fuel filter. And besides a spin on filter has much less of a chance to leak than that large filter. And I bet it would be much easier to find a CAT filter or its replacement when you are on the road...........NAPA etc..

Now to wait a few days and see just what the ball valve accomplishes. P.S.....A ball valve attached to a hose without other support is not a long term good deal........but is a good temp troubleshooting tool.

 

[maccus]

Well the saga continues. It has been 9 days since I last ran the truck (M931A2). Started right up and ran for about a minute or so and quit. Primed and it ran very well. So today I ran a temp 1/2 inch hose directly from the ball valve on the large filter input to the left tank (remember the M931A2s have the floor mounted tank selector). I will start the truck in 6 days or so and see what happens. That will bypass all the stuff in the line from the tank to the first fuel filter.

If I still have a problem in 6 days I will replace the fuel filter under the left front fender with a good CAT filter and run new lines from the new filter to the transfer pump. Was going to do that anyway.

If It still does not cure the problem the problem has to be from the transfer pump up the line somewhere.

When I get all done I will leave the ball valve in the input to the first filter (sort of a on/off fuel switch deal). I already have a battery ground on/off switch for the electrics on the truck. Should slow down the dumb ones if they decide to take the truck for a ride. If that does not work there is always number #4 buck

This is the filter and the mount I will be using (already have the items). I chose the mount so I could run both the input and output from the same inside location. Thus eliminating a 90 degree elbow or two. Mount will bolt right up to the existing mounting plate. Have to drill a couple of new holes but looks like that should be no problem. I will then fab a new protective cover/shield to keep the rocks from eating the new filter.

http://www.truckpartstores.com/Fuel-Filter-175-2949-P25583.aspx

http://www.amazon.com/Wix-24770-Filter-Mounting-Base/dp/B000CSGT64/ref=pd_bxgy_263_img_z

 

[silverstate55]

I know it sounds dumb, but it worked on my truck...try removing your in-tank fuel return elbow and check the drop-in return line. Mine were rubber, and they were disintegrating as well as swollen to the point that it was restricting fuel. When doing research I found that some other engines' IPs (as well as a few Cummins) would do the exact same thing when the return lines became restricted. I had steel tubing brazed to new elbows to replace the rubber ones, and I haven't had a single problem since (and I had already replaced filters & all fuel lines to eliminate air leaks).

Sounds dumb, I know (some here will say that that suits me perfectly), but it immediately solved my similar problems. Now I can let it sit for a month or two & it will fire up immediately and not lose any prime.

Thank you for keeping us updated & for the great info.

 

[maccus]

Been 7 more days since I last ran the truck. The hose directly from the input of the first fuel filter to the tank seems to have taken care of the problem. Truck started right up without any problem. So it looks like there is a problem with one of the hose/pipe connections, hose itself or the tank selector switch.

I have always been going to replace everything from the transfer pump the tank anyway. I just wanted to know for my own knowledge which part/connection was the problem. Now I know. Only parts I am waiting on are the 1/4 pipe 90 degree to 1/2 hose barb that goes directly on the input to the transfer pump. And the inline electric fuel pump I am going to add in the fuel line coming directly out of the tank. Will use the inline should I ever need to prime again. Otherwise it will just be in the line and waiting for power to be applied to it.

Here are the two parts I am waiting on. The picture of the brass 90 does not look to be dimension correct but the description looks correct. And the fuel pump is a lot cheaper than the same one advertised by a MV vendor.

http://www.amazon.mk/dp/B006PKLD4Q/ref=biss_dp_t_asn

http://www.amazon.com/Airtex-E8131-...&ie=UTF8&qid=1434591857&sr=1-1&keywords=e8131

 

[MtnSnow]

If your not always powering the electric fuel pump when running the truck you will want to make sure that fuel will flow thru it in sufficient volume when not powered.

 

[maccus]

Yep!

 

[idbankrman]

I have had this problem on 2 M939A2 trucks and still have it on a a third.. On one it was the line from the tank to the large canister filter. It was deteriorated and had small pin holes that spewed fuel when pressurized ( To pressurize the line I just took it off the canister filter and then using a water bottle full of diesel I forced the fuel into the line) . On the other it was the O ring on the top of the large canister filter. This truck also had a copper washer that was leaking air where the fuel supply line attaches to the injector pump. On the third truck the mystery continues. The third truck is an M929A2 and I have replaced the lift pump and its starts better and holds a prime much longer so I am suspecting the return fuel check valve mentioned above.