Replacing injector pump on a 2000 312 BL

Ser # 8JR01751, I'm planning to replace the injector pump this winter. Where is the best source to find a replacement? Does it make more sense to rebuild? I have a skip and 2 mechanics have condemned the pump. When I start it in cold weather I get a few minutes of gray smoke. Jeff

Has injectors been checked / changed and fuel pressure tested. imo these pumps don't fail often. Unless the fuel system was contaminated ex. Lines left off. I see injectors and aerated fuel systems cause similar issues more often. No help on sourcing a pump.

Injectors were replaced about 18 months ago. I will look into having the fuel pressure tested.

Normally if that pump goes bad it will show up hard starting when at operating temp. wonder how is compression do you have blow by when you take the oil filler off running

Those pumps are aggravating to time there are marks on the gears line them up then you have to hold pump gear with a socket and ratchet if you bump the pump the gear will rotate under spring pressure

If u could post a picture of the pump, I’m certain I can help.

This is what it looks like in the Parts Manual

I have not touched one of these but.... I would sure be looking at everything else first, especially the engine. Testing compression is far easier than a pump swap. Does it use oil? Have you tried to check blowby? Valve adjust? Gray smoke only on a cold start just means it is not getting all the fuel burned. That can be many things. Does it have an intake heater?

Others here are probably more up on common failures but in my experience, a bad pump just means it is worn and internally bypassing so it can't achieve the flow needed at pressure. That usually stands out more at WOT. Maybe you are fighting a fuel supply issue that is amplified with the higher viscosity fuel in cold weather?

As to the DIY rebuild, pumps are much more precise than an engine. Component tolerance can be .0001". If you don't have the tools and experience to measure such values, it might be better to farm out, and I would sure want a pump tested before reinstalling.

OH, let me share my recent duramax experience. Truck will limp if pushed too hard, otherwise runs perfect. It was determined through testing that the desired fuel pressure at the rail is commanded to 26ksi, but I can watch actual pressure roll back to 18ksi. Some might look at the pump, until I tested the fuel return rates on some injectors. All injectors will return "a little", but mine are many times higher than the service limit. So the pump 'may' be fine and just cannot keep up with the volume demand at higher engine load PLUS all the return fuel off the injectors. I will replace injectors first because they are certainly toast, then see where I am.
Another test that I did was to command the pump to full rail pressure at idle, which makes sure the pump can even do it. It had zero issue with that.

I’ve got the same machine 100 serial numbers older , should be a Mitsubishi engine with a zexel pump on it , had my pump rebuilt runs great now . Took it to one shop they said it was within spec , replaced a spring in it and sent it back to me , 800$ bill . Machine ran the same as it did , which wasn’t right . Took it off in the winter sent it to a different shop and they rebuilt it for 1800$ runs great now . I think rebuilding would be your cheapest option if it’s needed . But I’ve got a couple questions .... what do you call a cold start ? and what’s it run like when it’s warm? .... hanco

Ok, THANKS NIGE..
It just a little 4banger Zexel in-line pump..
If you did all the diagnostic tests & everything leads u to the injection pump.. here’s how to get started..
IF your doing it yourself.. without the special tools..
Remove the side cover, 2-10mm bolts.. rotate the engine over until u SEE # 1 tappet start to rise..& STOP ( the tappet is the little gizmo below the spring..)
Now go in front of the pump (radiator side) & see if there is a access cover, if yes, remove it and LOOK for timing marks between the pump drive and another gear..
THAT will get u started..
Oh, there might also be a timing mark on the outside of the pump housing..
Snap a pic to keep as a reference when u go back together with it..
It’s usually less expensive to get your pump rebuilt..
Just google “diesel fuel injection shops near me “..
Once u get the front cover off, snap a couple of pics & post them..
We might b able to pick out the timing lines for ya..
Good luck

If you go for a rebuild send it to thepumpguysc.
He did mine and it looked and worked like a new one.

thepumpguysc said:

If you did all the diagnostic tests & everything leads u to the injection pump.. here’s how to get started..

Click to expand...

Has it actually been established yet that the FIP is the root cause of the problem..?

I haven't seen anything concrete.

I will be bringing the machine to my mechanic in a couple weeks to figure this out. I appreciate all the comments. I will keep you posted on the diagnosis. Jeff

I think you need to bear in mind that the FIP is the most expensive part of the fuel system and don’t let anyone convince you it’s the root cause of the problem until all other avenues have been exhausted.

For example has anyone measured the fuel supply pressure from the transfer pump.?
Have you drained water & sediment from the tank.? Is the tank clean inside with no sign of rust.?
Have all the heads of the fuel filters been disassembled & cleaned in case something is wedged in a small orifice somewhere.?
As above for the fuel supply lines right from the tank to the FIP.?

Sorry it has been so long but here is the update. The pump was close to catastrophic failure. They replaced it and now she runs like new. More power, idles better, like a new machine! I'm a happy guy. Jeff