CAV DPA injector pump - no fuel to injectors after bleeding

[mungus]

Any diesel gurus here? My FIAT 780 is having some post maintenance issues with its CAV DPA injector pump. Hoping someone here can help. The tractor was starting, running and stopping fine. Always ran like a clock. It has an IVECO diesel with a CAV DPA type 3342 injector pump. But recently there had been a slowly worsening drip problem on my barn floor which I traced to the pump. So I decided to reseal the pump and change the 2 filters at the same time. Easy enough, as I've successfully bled the system many times before when I had some dirty fuel problems. (long since fixed, cleaned tank, new lines, new lift pump and in line filter fitted, it's run for years since then, so I doubt that's got anything to do with this).

Anyway did all the above, after reading a CAV DPA manual and watching a couple of good YouTube videos on resealing the top cover, then afterwards all the usual filter and pump bleeding procedures were followed successfully. Lots of clean fuel coming from both filter bleeds and likewise the two little bleed screws on the pump itself produced nice strong foot long squirts of clean fuel when open. BUT the problem is I can't get ANY fuel at the injectors. Nothing, nada! I also opened one of the lines where it exits the pump. Just to see if it's at least making it that far, and again nothing...

Now as I said, this tractor ran sweetly immediately beforehand and I did everything you are supposed to. So anyone got any clues? The symptoms reminds me of one time when I tried to start it with the cut off pulled out. So that made me think is there something I've done under the cover that's got the cut off activated? That's all I can think of. The cut off hook seems like it's aligned with the little dowel on the cut off lever's shaft /cam OK, but perhaps something I did has jammed the cut off system to its OFF position. All seemed to be moving OK when I closed it all up, but who knows. I've been pretty careful and I'm quite mechanical, (see my restoration threads), just not really a diesel guy. But I'm thinking this has to be something I've done rather than a fault in the pump, and I'd be loathed to spend lots of money and delay things on a full pump rebuild when I've probably just done something dumb I can fix.

The FIAT and its IVECO engine are nice units, but to be honest the pump is not well located for on machine maintenance, being cranked over to one side a bit, so that you can't see under the cover's edge easily and that fuel keeps dribbling out when the covers off, until the pumps empty... Grrrrr!

Anyway ideas or experiences anyone?

 

[Petarmk]

Because the tractor was working before you removed the top cover, then it must be related with the stop shaft.
Maybe you have missed the hole in the stop lever under the cover and the metering valve is stuck closed, resulting with no fuel when cranking.
Please let me know what happens if you try to pull start the tractor, does it tries to fire up or not?

Regards.

 

[mungus]

Because the tractor was working before you removed the top cover, then it must be related with the stop shaft.
Maybe you have missed the hole in the stop lever under the cover and the metering valve is stuck closed, resulting with no fuel when cranking.
Please let me know what happens if you try to pull start the tractor, does it tries to fire up or not?
Regards.

On my own at the moment so can't really pull start it. However I agree it must be something to do with the stop shaft. I tried hard to ensure I got the stop cable shaft's little cam dowel into the hook / slot in the stop lever, but I guess it's possible. It is hard to tell because of the angle the pump is on this engine. But I put alignment marks on the cover and the pump to show where everything was and it felt like it clicked I to place OK and if I'm careful it feels like it's moving something inside when I move the stop arm. Really would nice if there was a wee inspection hole there to check.

However the thing is this, when that little lever with the hook is fully forward to engage the dowel, it's in the run position, not cut off. So if any thing if you miss the hole you won't be able to shut the engine off, not prevent it starting. And I note one excellent rebuild video mentions just that being the case. So my though was more like the short square shaped arm at the other end, that the little hook arm presses on when you pull to cut off, might be stuck in cut off.

Anyway I'll take the cover off again and see. Thanks for the reply.

 

[Avondale]

I just repaired my CAV DPA top cover fuel leak while it remained aboard the tractor. It is very hard to get the "hook" to set, thanks to gravity. I used a loop of thread that held the hook arm in the raised position while I fiddled the cover on, then withdrew the thread. Seems to work okay now.

 

[mungus]

Thanks for the idea. I used a smidge of light grease under the hook where the arm rests up against the cover stud bases. Did basically the same thing, but not so reliable I'm thinking. This seems to be a recurring problem on many threads and videos etc that I've seen. Almost makes you want to drill and tap and inspection hole somewhere out of the way so you can peer in and see if the arm is moving...

Did you have the same symptoms as I before you did this?

Still don't feel like that's it though, as a failure of the dowel to engage with the hook should just stop you shutting the engine off. As the governor pulls the linkage forward when you open the throttle.

 

[thepumpguysc]

Just pull the top cover & free up the metering valve.. ALWAYS, ALWAYS, ALWAYS push the shut off rod to RUN after shutting one down..

 

[mungus]

Just pull the top cover & free up the metering valve.. ALWAYS, ALWAYS, ALWAYS push the shut off rod to RUN after shutting one down..

I tried that after the first attempt. Moved it around quite a bit. And yes, I always push it run after I stop it.

Anyway after 4 failed attempts at bleeding I've now gone one step further and pulled everything off on the top platform to give it all a thorough cleaning and look over. I've got a suspicion it might be a bit more than that though. I've now had the cover off 3 times and checked freedom of motion, and that the dowel and cut off lever hook are engaged. Still the problem persists. Today I actually did remove the metering valve from the little platform under the cover, it came out easily, had no signs of corrosion etc to indicate its been sticking. So I'm starting to wonder if something has broken off inside, and that's the cause of my troubles.

Anyway just in case I've removed the timing cover from the rear of the block and the gear cover from the front of the engine in preparation for a possible pump removal and overhaul. If upon reassembly tomorrow it does bleed OK and runs, then at least I've cleaned up those covers and made sure their fasteners are all good for the future. I have a pump overhaul kit In case and just as well as it looks like my tractor had little engine maintenance before I came along. (the fuel filters I just changed out were date coded 18 years old).

I'll review the excellent CAV DPA pump rebuild video on YouTube (by "Bundy Bear"), to see how it all works inside, and then have another look at mine tomorrow. Nighttime here now. Adding a few photos so we are all on the same page.

 

[thepumpguysc]

AAAHHH.. the plot thickens.. I "think" I know what happened..
You see the spring is in the #3 hole.. When you put it back on.. the spring HAS TO BE in the center of the lever..
Or actually visa versa.. the lever HAS TO BE IN THE MIDDLE of the spring coils.. NOT on the outside of it..
Give THAT a try..

 

[mungus]

Thanks for the reply but not exactly sure what you mean.
By "lever" do you mean the govenor plate?
Or do you mean the 3 holes on the little tag that pivots off the throttle lever or the 3 holes on the govenor plate with the little pin.

Regarding the govenor plate, the 3rd hole is the correct location for the little pin that hooks the spring, on this application. I photographed it before disassembly and the FIAT factory workshop manual also clearly shows the pin (and spring) in that position.

Not 100% sure about the location of the hole for the other end of the spring (the little part that pivots off the throttle lever). I would be surprised if changing a spring position by one would completely kill the fuel flow at start up, which is what's happening. Not even a drop is coming out of the head ports. Nada.

Anyway I removed, cleaned and rebuilt the pump today, putting a reseal kit through it. Made sure everything was very clean and took my time. Following 2 manuals and the YouTube video I mentioned.
Guess what, after reinstalling and testing - no change! Grrrr.

Tomorrow I'll have another look but I have a thought. The metering valve has a slot cut into the bottom part which didn't click into anything down its hole when refitting the governor linkage, it just spins around in its hole, which makes me wonder if something isn't right. See the last photo below. So what exactly goes in that slot? I think that's the first thing to check.

The metering valve dropped in easily, it moves smoothly and freely with no resistance at all. Had a little varnish on it which I polished off but other than that was fine.

Anyway a couple more snaps, looks nice. Pity it doesn't work eh!

 

[thepumpguysc]

If you give me the COMPLETE # off the nameplate I can tell you which position the spring goes in.
3342F***
NOTHING goes in the slot on the MV.. that's the shut-off/run slot..
What I was talking about was the pivot on the throttle shaft has to go in the center of the spring.. the part that has the 3 holes has to end up in the center of the coils..