Operation/repair of Isuzu 2AB1 fuel primer pump

[mrmrsk]

I have a Isuzu 2AB1 and fuel priming pump that I’m not sure is working correctly. I just got this boat and the engine is running fine so far. I WANT to check the fuel filter and know how to replace it when that becomes necessary, but I’m afraid to open the fuel system for fear of not being able to reprime it.

The 2AB1, I think, has a plunger-style primer rather than the level-style. When I try to manipulate the primer (in the Triangle annotation of the attached image), it doesn’t move - seems solid - though perhaps this is because the bleed valve is still closed?

The only thing I’ve been able to move is to unscrew the top of the plunger. Perhaps that’s step 1 for operating the plunger - unlocking it? However, once loosened, that top/plunger shaft and the spring around the shaft come off completely. The end of the shaft is cut to a ball maybe for a socket.

The fact that this pops off makes it seem broken to me. Is it? Can I repair it without replacing the $168 (says google search) primer assembly?

If I needed to replace that assembly, is that difficult?

[Iron E]

The primer top (1.) should unscrew then pop up (Not the entire primer). When it pops up, it works like a little pump.
The area that I circled (2.) is your bleed. You crack the outer nut loose and unscrew the center several turns with a flathead.

OK
1. unscrew the top of the primer pump
2. Loosen bleeder nut
3. loosen center bleeder with a flathead
4. pump primer until fuel and air comes out of the bleeder
5. keep pumping until there is no air
6. tighten bleeder
7. tighten bleeder nut
8. push the pump down and tighten

[skipperpete]

G’day mrmrsk and welcome to cruisers forum. The plunger on the priming pump is a fairly common failure, not because of bad design, but because it’s often not screwed down tightly enough and when it finally unscrews completely it’s then free to move up and down with the action of the fuel in the mechanical lift pump below it and a few hours of engine time is enough to wear out the piston seal and rod. You can get a kit to repair it OR a complete new priming pump for anywhere between $10 and $30 dollars. The newer pump has no screwdown function so far easier to operate. The hex on the lower end of your existing primer pump is there to undo it.

[skipperpete]

Oh, I nearly forgot the pentagon (lid ) ….. its a breather. Your injector pump has a dipstick and a drain plug just like the engine and is sealed completely, hence the breather. ya need to change the oil from time to time as it either leaks out, gets contaminated or gets diluted by diesel fuel from worn plungers. The dipstick is visible in your photo ….but not the drain plug.

[mrmrsk]

Oh wow! Thanks. I was also gonna ask about the breather because that part just pulls right off - I think "above" the bolt hex (yours is pictured upside-down) That looks like a cheap part I can/should replace too.

Is there a good place to identify the replacement parts available for this engine?

[Iron E]

Originally Posted by mrmrsk

Oh wow! Thanks. I was also gonna ask about the breather because that part just pulls right off - I think "above" the bolt hex (yours is pictured upside-down) That looks like a cheap part I can/should replace too.

Is there a good place to identify the replacement parts available for this engine?

Don't hold me to it, but looking up 2AB1 Isuzu Diesel or 2AA1 Isuzu Diesel will get you about as close as you can get. Then use your eyeballs for the refinement. They were used in small tractors, snow blowers, etc.

[mrmrsk]

With further research, I think the "flywheel end" is opposite what I originally thought. The flywheel end tends to be near the transmission and primary output end, I think.

So what is this seeming addition that I've outlined in purple, please? I think it might not be part of the Isuzu 2AB1 precisely and I wonder if the serial number plate might be under it. I see some obvious hex bolt heads. Can I remove that and put it back on? Is there liquid in it?

[mrmrsk]

I think it might not be part of the Isuzu 2AB1 precisely and I wonder if the serial number plate might be under it. I see some obvious hex bolt heads. Can I remove that and put it back on? Is there liquid in it?

That wouldn't have been right. For others: I found the serial number finally within this new purple outline under all those additions and some flaking paint on the engine block (of course). I wouldn't have been able to find it without my bore scope.

Isuzu's only guidance on this was "Right front, top part of block." and "All directions are as viewed from the flywheel end of the engine" and I don't think this location matches the description.