Cat 274B Rough Start

[Kevin Sundquist]

I have been having this issue for the last few months. While it is not really a serious problem (it still starts and runs), I would like to fix this before I do have a big problem, or a problem at the wrong time.

My machine has about 2200hrs and is in reasonably good shape. I have done a bunch of DIY stuff on it since I bought it 5 years ago.

However, over the last winter, the starts have gotten rough. I have to rev it up to about 1200 - 1500 RPM (guessing by the sound) to keep it running for the first 15 to 20 seconds. After that, it smooths out. I do have to keep the revs up until is fully warmed up however. Revving back down too soon just brings on the rough idle, or stall, again.

I have changed the fuel filter (annually) and run fuel injector cleaner through the system. I have also pulled the small basket (about 1.5" in diameter) in the fuel pump and had to dump out a bit of debris in it. The basket stays pretty clean now.

My best guess is that it is just a matter of replacing the fuel injectors.

Does that make sense? If this does make sense, any gotcha's I should be watching for when I change them?

It looks like a straight forward job, the injectors are certainly easy to reach. But, I have never done this before so want to make sure I am going in with my eyes wide open.

P.S. I bought this machine used at auction for our small horse farm. I only put about 100 hours a year on it, but it is the best investments I have made. I want to keep this thing running forever!

 

[Kevin Sundquist]

In the interest of paying it forward, here are the notes I made when I fixed the fuel pump last year:

(Disclaimer: I am not a trained mechanic, just a DIY guy. I make no guarantees).

Replacing the fuel pump:

• The pump is mounted on the block, above and behind the oil filter. The screws that mounts it on the block are hard to get at. I had to use a short socket with a Phillips screw driver head.
• When all was said I done, I realized I did this the hard way, all I really needed to do was remove the top screw and one fuel line. I could have pulled the top off and cleaned it out with much less effort
• Once I had the pump off, I opened it up and it was full of grime. Small bits of grass and debris in the basket - probably from when I lost the fuel cap while digging (which means my fuel tank needs to be flushed).
• It had a small filter basket inside (see marked up picture below). I pulled it out and cleaned it thoroughly, and blew out the rest of the pump. Note, per my marked up picture below, the basket looks like it can go back in three different angles. Only one way works properly. Look carefully at the grooves in the bottom of the basket, one is deeper.
• I replaced the one o-ring that seals against the block just to be safe (it wasn’t showing signs of leaking, but still).
• It started up on the first turn, which it hadn’t done in 18 months

P.S.

• I really like the cat fuel pump design. It is mechanical, looks like it runs off the crank shaft, not electrical. Well thought out and should be very reliable over the long haul.
• The only parts that could really go wrong are the rubber diaphragm in the pump and the rubber seals in the two one way valves. Everything else is metal.
• If the rubber diaphragm cracks I don't think it will pump anymore. It will suck air up from the engine.
• I suppose it could allow diesel into the oil because it is “open” to the oil pan. If that was to happen, I think you should just change the oil.

UPDATE to the picture below:
The one marked-up picture below, showing "From Fuel Filter" and "To Engine" is wrong. The intake ("From") comes directly from the fuel tank. The outlet ("To") goes to the fuel filter and from there to the injectors. That is why the basket can collect debris. The fuel is unfiltered at that point.

 

[Kevin Sundquist]

BTW, the Serial number for the Rough Start problem is *CAT0247BLMTL04112*

 

[Nige]

I assume the below is the type of fuel filter/water separator you have.
Have you ever removed the filter head, then all the elbows and/or fittings (circled) from the head and cleaned out the passges inside both the fittings and the head itself.?
Also when you changed the element did you make sure that the central O-Ring didn't stay on the head and that you have inadvertently installed another one on top of it.? Or did it fall off and you installed the new element minus the O-Ring.?

 

[ThreeCW]

You will likely want to check out a few other things before considering an injector replacement. Have a look at this thread ... it provides some more detail on what Nige referred to about cleaning possible debris out of the filter head. Pay particular attention to Post 11 from "heymccall" where he shows a photo of area of potential plugging in the filter head.
https://www.heavyequipmentforums.com/threads/cat-226-fuel-problem.78929/