Stanadyne / Roosa Master Inj. Pump problems

I recently purchased a MEP-006A with a Stanadyne injector pump mounted on a Allis-Chamber 6 Cyl. engine. After going over the Gen. Set with a fine tooth comb we fired it up only to have it shut down as soon as we released the starter switch. We could hear the fuel pumps working so we tried to run it by using the battle short switch but still the same problem. After 3 days of trial and error and rerouting the fuel system we placed all of the safety systems back and and removed the check valve from the top of the injector pump and made a new fuel line and the unit fired up with no problems. It was the check valve which has a glass ball inside of it that was not allowing the fuel to fill the top of the inj. pump.
I hope this helps anyone who is having problems getting their engine running because of a fuel problem.
These check valves were widely used during the 70's and have stumped many mechanics before they narrowed it to this check valve.

I know nothing about military gen sets but I do know about AC engines. This is a common problem with Roosa Master IPs. The rubber inside the pump comes apart and stops up the check valve. Remove the timming cover (rectangle plate on side of pump with two screws) and I will bet you there will be pieces of rubber in there. It is a common shadetree fix to remove the check valve to get it to work. Your pump is comming apart inside but I've done it and had engines run for years like this.

What size engine is it? I'm guessing it's either a D262 or a 2900.

m16ty said:

I know nothing about military gen sets but I do know about AC engines. This is a common problem with Roosa Master IPs. The rubber inside the pump comes apart and stops up the check valve. Remove the timming cover (rectangle plate on side of pump with two screws) and I will bet you there will be pieces of rubber in there. It is a common shadetree fix to remove the check valve to get it to work. Your pump is comming apart inside but I've done it and had engines run for years like this.

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Thats correct. There's a rubber ring that holds the governor basket onto its drive plate. It disintigrates and contaminates the pump. If it runs this way too long it will destroy the pins on the 2 steel parts. The replacement ring is of a better material & lasts longer.

Make sure you put a new bushing in the housing while you're in the pump & epoxy it in, they're always well worn where the seals ride and you dont want a crankcase full of fuel!

One more thing, If you decide to remove the IP it's easiest to leave the shaft on the engine on ACs. Just line up the timming marks, take the mounting bolts off, and pull the IP off the shaft. As long as nobody turns the engine over while the the IP is off. To install all you have to do is line the marks back up and tighten everything back down. Just remember to replace the shaft seals and take care not to damage them when sliding the IP back over the shaft.

Hey, I was just reading your post looking for answers on why my base is filling up with fuel I have an mep-006 runs fine, but I checked the oil today and it's overful and smells like fuel.

Thanks for your tips!

Dale

washingtonmountains said:

Hey, I was just reading your post looking for answers on why my base is filling up with fuel I have an mep-006 runs fine, but I checked the oil today and it's overful and smells like fuel.

Thanks for your tips!

Dale

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I don't know which engine you have but if it has a mechanical fuel transfer pump on the side of the engine that is more than likely your problem.

I have the Allis Chalmers 3500, it has two electric fuel pumps that feed the injection pump, my first thought was that it was blowing by the rings, but a previous thread said it could be a bad seal in the IP, shouldn't be to bad of a fix.

Yes, The pump shaft seal can fail and dump fuel into the crankcase.

I have an MEP005AAS, White 6 cyc engine and a Roosa master IP. Can I rebuild/fix this myself? Does anyone have a tm for the pump and where can I get parts ? Thank you Laddie

I've taken apart a junk Roosa Master pump. From what I saw, I really don't think this is something that should be done in the home shop.

What's wrong with the pump? leaking into the crankcase or not pumping fuel. If it's leaking into the crankcase, you can replace the shaft seals without taking the pump apart. Also take the timing cover off and see if there are rubber shavings in there (this indicates a IP going down).

If it's not pumping fuel there is a shadetree fix that will fix it about 75% of the time. There is a check valve where the return line goes into the top of the pump. Either take the check valve out of the line and plumb the return directly into the IP or take a hammer and punch and knock the glass ball out of the check valve. This is not the proper way to repair a IP but most of the time it works to get you back going.

Fuel getting into crankcase at an alarming rate. When removing IP does pump shaft come off with pump or does IP come off of shaft? TM says nothing of removing timing gear when removing pump.. Thanks

That's an easy fix. Frist remove the two screw cover on the side of the IP. Under that cover will be the timing marks. Turn the engine over by hand to line the timing marks up. Then take out the IP mounting bolts and side the IP off of the shaft ( the shaft will stay with the engine).

In the middle of the shaft you will see two seals. Remove the seals and get new ones from any IP shop.

Going back is just reverse of removal. You have to be careful not to damage the seals when you slide the IP back onto the shaft. Also make sure you line the timing marks back up before you tighten the mounting bolts up.

I replaced the shaft seals,( they were shredded). Now the pump isn't gertting fuel. No power to solinoid termanals. Is there a fuse I burrned out? Thanks

Will the electric pumps run in the battle short position? It may be a case where you already have presure in the secondary tank and it's not calling for electric ones to run; start by bleeding the air off supply side of pump, then bleed each injector line at the injector. Good Luck!

Yes electric pump runs in battle short. No fuel is entering pump, I suspect the fuel shutoff in the IP is not opening. There is no voltage across terminals on IP. I can't find a scymatic for that circuit.

Where are the fuses or citcuit breakers located? I can't find them Thanks.

I'm subscribing to this one, just in case I need a reference. Picking up my PU-650b in the coming days.

I am following this thread closely as I am working on my first MEP-006a. The dc circuit breaker is located on the control panel. If the Battle Short switch works, then the breaker is closed. Check to see if you get voltage to the IP sol with the master switch in "run" and the battle short "on".

TM-5-6115-545-12 Check out page 67.

Just saw this thread involves a 6cyl allis chalmers with a db2 pump. Is this the same or simmilar that would have been used in combines or tractors? just curious as one just came into the scrap yard. any parts that might be usefull?

All the info I gave is for agriculture engines. I was just assuming that the military version is the same.

What's wrong with the engine? I'd be interested in the whole thing depending what condition it's in ( I have to think there's some reason it's at the scrap yard). If nothing else, pull the IP. I know people that will pay good money for Roosa Master IPs.