Need help with a 400D....no go on diesel

Checking out a 400D for possible purchase. Generally good condition and has been stored out the weather but hasn't run in 2 or 3 years.

The owner and I got it started on gas without more than usual minor issues, but when you switch to diesel it's not putting fuel to the injectors.

I don't have experience with these things other than reading about them.

The fuel is on at the main tank. I cracked the bottom drain on each big filter and no water came out, did that before starting. We get diesel from the filter bleeders and up to the plunger while running on gas. It comes out in a stream so it's under some amount of pressure. At first the pressure gauge on the injector pump didn't show any movement and after several tries of switching it moved a tiny bit. Tried cracking lines at injector 1 and 2 then switching and didn't have any fuel under pressure, just a few drops weeping out.

Could it have lost prime or have something sticking after sitting for a couple of years?
What is the correct procedure for bleeding and priming?

I have heard of a lot of people talk about stuck racks. I have neaver dealt with it, but I'm sure M Diesel will be along shortly.

They can't really lose prime. However, they do have a tough time bleeding out the fuel filter (the one that doesn't need to be running to bleed) without a lot of fuel in the tank.

A stuck rack is sure a posibility. They are not difficult to free if vsrnished up. Take pictures, do not force anything. SOlvent helps. Jim

It has about 1/2 to 3/4 tank of diesel and the fuel has been "on" the whole time so I wouldn't think it would lose prime but I'm in new territory on this one.

Do you have to give it throttle when you switch to diesel or is the linkage designed to give you enough on it's own? We tried moving the lever down some and then switching but no change.

A stuck rack makes sense. Can you get to it under the side cover on the pump?

Yes, you have to give it throttle in order for it to start spraying diesel. The MD or WD-9 book says this.



Do some searching on RPM. There are a lot of posts on gas starts. Hopefully you can find what you are looking for.

I'm pretty sure the "throttle" control by the steering wheel is the only control that affects diesel fuel delivery. the compression release lever does the compression, spark, gas side. So when it's working properly there is an art to switching over- you've got to push the compression release lever and give it the diesel before it stalls. in your case i think i'd start on gas, then open up the diesel "throttle" while still on gas. if the diesel fuel system is working properly, it should soon start pumping fuel which will be obvious by the cloud of smoke and rough running. as soon as that happens push the compression release lever to the diesel side and off you go.

this is all assuming the only trouble is air in the diesel fuel system.

Find out first why pressure isn't comming up to normal on the gage. With no blockage or air in fuel line from tank to pump the gage on the pump should come up to normal pressure running on gas.
Unless the primary pump on the rear of injection pump has a problem. Sometimes the primary pump drive coupling will fail or other things. You can't be sure the main pump has a problem until the primary fuel supply is working.

Thanks for replies. Messed with it this morning but did have time to make much progress. It built pressure very slowly on the gauge but not enough to be in the "run" range. Still no fuel at the injectors while running on gas.

I'm going to go ahead with the purchase as the rest is solid and it's sitting on 4 brand new tires. When I get it home I'll go through filters and such thoroughly.

(quoted from post at 08:45:07 05/09/12) Find out first why pressure isn't comming up to normal on the gage. With no blockage or air in fuel line from tank to pump the gage on the pump should come up to normal pressure running on gas.
Unless the primary pump on the rear of injection pump has a problem. Sometimes the primary pump drive coupling will fail or other things. You can't be sure the main pump has a problem until the primary fuel supply is working.

Click to expand...

Yeah that pressure part is kinda worrisome. If it builds some pressure then the gears probably are okay and most likely one of the pressure reliefs is sticking open. They look and operate much like a needle valve in a carb float bowl (only with a stiff spring to close them) and are a snug fit. A little water causes them to rust slightly and the spring wont close them after the initial opening. Usually the one in the bottom part of the primary pump is the culprit, the one in the top of the plunger body, not so much.

Also, these machines will run at light slow loads without much pressure from the primary, but I've never tested them to see how low.

Also, priming these things is way over rated. I have yet to find one that will not run up and clean itself out is a short time. That gas cycle is very effective.

To check the rack, pull the filler neck. Just two little bolts, but be careful of crud around the base. Work the throttle and look for and look for anything NOT moving. The rack gear slides horizontally, front to rear. It is usually easiest to pull the pin on the double spring thingy that moves the arm on the pump.

Looking at the books again I see the pressure relief on the primary pump, looks fairly easy to get to. The other one you mention is the fuel return check valve?

I did pull the side cover off the pump this morning but could only see the end of the rack and that didn't do me much good. Was working solo this morning and couldn't see in there and move the throttle easily. When I get a chance I'll puller the filler neck and check from there. I'll also put new filters in it anyway.

I definately have some amount of fuel flow as opening any bleeder gets me a stream of fuel, also at the top of the plunger.

(quoted from post at 11:36:42 05/09/12) Looking at the books again I see the pressure relief on the primary pump, looks fairly easy to get to. The other one you mention is the fuel return check valve?

I did pull the side cover off the pump this morning but could only see the end of the rack and that didn't do me much good. Was working solo this morning and couldn't see in there and move the throttle easily. When I get a chance I'll puller the filler neck and check from there. I'll also put new filters in it anyway.

I definately have some amount of fuel flow as opening any bleeder gets me a stream of fuel, also at the top of the plunger.

Click to expand...

Yeah they call it a check valve. It does that, but is also the main pressure regulator on a B pump. It is more of a pain to get to. Both valves do the same job, but one is just set to a higher pressure. The B pump relies on the upper valve, others on the lower primary pump valve.

You can easily check the rack motion if the side cover is off. Working the throttle will move the arm at the front of the cavity as well as the inner arm that is behind it. This bypasses all the springs except for the shoe that pushes on the inner arm.

The slow pressure rise may just be a gauge gone stiff. They do have an orifice to slow them down so they don't buzz and die from fluid vibration but it isn't that slow. Any ordinary gauge will work for testing. Many pumps are set for about 35 psi to increase lifespan. They early ones are set for a skosh over 60. I have run both and it didn't really make any difference. Controlled by the little spring, not adjustable.