Testing Aux Fuel Pump Operation

[CapePrep]

After running the 803 for 24 hours last week during an outage, Since I was using fuel cans to refuel, I realized I needed to make sure the aux fueling procedure was working. The aux pump was running in normal run position, so had to take the sheet metal off and check it out. Disconnected the wiring harness and the pump turned off even when full. I wanted to add/remove fuel quickly to verify operation. Took my off road pump out of my tank to facilitate moving fuel back and forth. Worked perfectly! I went back and forth a few times and the pump filled and shut off and turned on as designed. Just in time for our 4th Nor'easter tomorrow!

 

[Light in the Dark]

Its a great feature... but not one to be blatantly ignored. They work great (until they don't, and the entire volume of your external tank has been pumped in and subsequently pumped out of the day tank on the genset... it happens).

 

[Bmxenbrett]

Its a good feature to test every year. Saves hand filling too.

 

[CapePrep]

You are right. Considering adding some kind of indicator light to show when aux pump is on. I can see instruments from my house and I could keep an eye on it if it is running continuously. Maybe Guy will chime in on reliability of that pump and how often he saw failures.

Its a great feature... but not one to be blatantly ignored. They work great (until they don't, and the entire volume of your external tank has been pumped in and subsequently pumped out of the day tank on the genset... it happens).

 

[Light in the Dark]

The liquid level sensor is the culprit. It has internal contacts, and a float which engages/disengages them. These can become inoperable, telling the set that its empty when its not... or the reverse, only half working (the lower limit) and as the fuel level rises, the shut off top doesn't engage, so it just keeps pumping.

 

[Bmxenbrett]

A light wouldnt help. The purpose of the pump is to transfer fuel and to start/stop at a specific fuel tank level. The only way to really properly test this is to do what the OP did.

Adding a light would only tell you that power is applied to the pump. Not that the pump is actualy pumping or turned on/off at the correct time.

 

[Guyfang]

I have only seen the unit over pump fuel three times. And I am sure that two times happened because the army uses JP8 for fuel. JP8 was not nice to the float material. Sometimes it just flat out ate up the floats. They would hang up in the "tank empty, pump fuel from aux source" mode and over fill the set. The third time was because someone hooked the wire on S1 that is supposed to be Aux fuel pump setting, to the same terminal that is for the normal fuel pump. You never notice it when the S1 is in the run position, if the cap in on the Aux fuel inlet nipple. If the pump can not get fuel, it will slow down and or completely stop. BUT, if you are in the S1 position Aux fuel, different deal. The float will NOT turn off the pump.

 

[glcaines]

I have an MEP003A genset. I use the aux fuel pump often because we are way back in the woods and have frequent power outages. When I picked up the genset, the float / switch inside the tank was burned out. I found a cheap NOS one on Ebay, which works great. Although I use the aux pump, I do have one complaint. When I use the long hose and wand that came with the genset, the tank I'm pulling from must be higher than the aux pump. If it's not higher, it won't pull the fuel through the line. At first I thought the aux pump might be faulty. I purchased a new identical pump, but it behaves the same way. There are no air leaks in the line or connections. I don't know if others have this problem or not, or even if it is a problem. Nothing in the TMs that I've seen indicate that the tank you are pulling from must be higher than the aux pump. That being said, it is not difficult for me to make sure the second tank is at the required height.

 

[Guyfang]

Your K-4, Aux solenoid may not be opening fully. They can sometimes hang up, rust, dirt and that kind of thing.

 

[Farmitall]

I have an MEP003A genset. I use the aux fuel pump often because we are way back in the woods and have frequent power outages. When I picked up the genset, the float / switch inside the tank was burned out. I found a cheap NOS one on Ebay, which works great. Although I use the aux pump, I do have one complaint. When I use the long hose and wand that came with the genset, the tank I'm pulling from must be higher than the aux pump. If it's not higher, it won't pull the fuel through the line. At first I thought the aux pump might be faulty. I purchased a new identical pump, but it behaves the same way. There are no air leaks in the line or connections. I don't know if others have this problem or not, or even if it is a problem. Nothing in the TMs that I've seen indicate that the tank you are pulling from must be higher than the aux pump. That being said, it is not difficult for me to make sure the second tank is at the required height.

Having your external fuel source mounted/situated higher than your genset is asking for a siphoning problem. The pump should lift and transport the fuel from any source at the same level or even lower(within reason) than the genset.

I would never situate a fuel source higher than the genset under any circumstances. I'd buy and use a different pump if necessary.

 

[Guyfang]

Just how much difference in hight are we talking about?

 

[glcaines]

Just how much difference in hight are we talking about?

The solenoid valve is working correctly. I found a new one on Ebay that I bought as a spare. I eventually replaced the solenoid valve with the new NOS one when I was bored one day. No difference. I tested the old one, which is now my spare, and it opens completely. The secondary fuel supply I'm pumping from must be at the same height as the pump, or higher, to pump properly. I also tested both the old aux pump and the new aux pump using electrical connections directly to the batteries. Both put out pressure on the output side, but don't have very strong suction on the intake side. They will both pull diesel fuel out of a can and lift it about 2 or 3 feet, if the line is short. Using the long suction line precludes the ability for that lift. I'm sure there is some siphoning going on when I use the aux pump with the long line. The solenoid valve stops this when it closes and hopefully it will always shut off when the tank is full. I have also by-passed the RF filter on the power connection with no effect.

 

[Chainbreaker]

I wonder if your long aux fuel line might have a pin hole, or something like that, that is allowing air to enter while under suction. If that were the case it would not have the draw necessary to suction fuel as well. I seem to recall that the aux fuel pump spec says it can lift fuel 6 ft. They must be able to at least pump fuel out of bottom of a 55 gal drum sitting on ground next to trailer mounted elevated genset.

Edit: Also, have you tried to blow out your long Aux fuel line with compressed air? It wouldn't take much obstruction (goop or whatever) in the hose to restrict flow.

 

[CapePrep]

With my very rudimentary set up when I did the test, I uncoiled my full length aux. fuel line, which I think was the first time it had been used, attached the one end to the 803, and just layed the other end in a 5 gal bucket that had fuel in it. It picked up prime within 30 seconds. I was worried about it being coiled for so long that the fabric coating and inner rubber may have a crack and leak air, but it was fine. I think Caines may have an air leak as well. The military, for the most part, isn't going to design something that should be a simple procedure and make it complicated as to have an elevated fuel source. As soon as this weather breaks I am going to fab up a port on my 275 gallon off road tank to tie the line into.

 

[glcaines]

I wonder if your long aux fuel line might have a pin hole, or something like that, that is allowing air to enter while under suction. If that were the case it would not have the draw necessary to suction fuel as well. I seem to recall that the aux fuel pump spec says it can lift fuel 6 ft. They must be able to at least pump fuel out of bottom of a 55 gal drum sitting on ground next to trailer mounted elevated genset.Edit: Also, have you tried to blow out your long Aux fuel line with compressed air? It wouldn't take much obstruction (goop or whatever) in the hose to restrict flow.

I actually pressurized the aux fuel line with compressed air at 25 PSI. I then used a spray bottle with dawn liquid dish detergent to look for leaks. I went the entire length and didn't find any leaks. The aux fuel line was obviously used before, but looks almost new. I was fortunate when I got my MEP003A that it came with a complete set of tools, most of them unused.

 

[Chainbreaker]

When you pressurized the aux fuel line did you also blow it out? It could hold pressure yet still be constricted by something lodged within the hose. Also, are all the fuel fittings both on pump (elbow) and aux fuel source in good condition with no damage to threads that might somehow allow air past those fittings. Are you hooking up aux fuel line directly to a draw tube type fitting on your aux fuel supply or dropping hose directly into to tank? Try it both ways to see if it makes any difference.

Also another thought...have you checked the Aux fuel pump's lower sediment screen to make sure it hasn't picked up any gunk/trash recently that might be restricting the filter screen?

Other than those types of potential issues...it seems a mystery why it is not drawing fuel as spec'd since you've eliminated both the valve and pump as an issue.

 

[glcaines]

When you pressurized the aux fuel line did you also blow it out? It could hold pressure yet still be constricted by something lodged within the hose. Also, are all the fuel fittings both on pump (elbow) and aux fuel source in good condition with no damage to threads that might somehow allow air past those fittings. Are you hooking up aux fuel line directly to a draw tube type fitting on your aux fuel supply or dropping hose directly into to tank? Try it both ways to see if it makes any difference.Also another thought...have you checked the Aux fuel pump's lower sediment screen to make sure it hasn't picked up any gunk/trash recently that might be restricting the filter screen?
Other than those types of potential issues...it seems a mystery why it is not drawing fuel as spec'd since you've eliminated both the valve and pump as an issue.

I did blow out the hose. It is completely unrestricted and the fittings are in good condition. I'm hooking up the aux fuel line directly to the dip or draw tube that came with it. I cleaned the sediment screens on all of the pumps. There was some trash in the other pump screens, but the aux pump that came with the genset was very clean. As I mentioned previously, I purchased a brand new FACET aux pump and have the same exact issue. The new aux pump is what is currently installed.

 

[Guyfang]

When you got the set, did it have a cap on the aux fuel inlet fitting?

 

[glcaines]

When you got the set, did it have a cap on the aux fuel inlet fitting?

Yes, and I always keep the cap on unless using the aux pump.

 

[uniquify]

I did blow out the hose. It is completely unrestricted and the fittings are in good condition. I'm hooking up the aux fuel line directly to the dip or draw tube that came with it. I cleaned the sediment screens on all of the pumps. There was some trash in the other pump screens, but the aux pump that came with the genset was very clean. As I mentioned previously, I purchased a brand new FACET aux pump and have the same exact issue. The new aux pump is what is currently installed.

Is the draw tube clean and clear? Is the line from the aux pump to the tank clear? Could there be a stuck check valve? Are you able to bench test the old/new pump using short hoses?