Need help with tracking down air leak in 1.9 AAZ pump

[Buji88]

Hey all,

Im at my wits end with my injection pump lol!

Likely its going to go to a rebuilder but Im super stubborn and like to fix things myself, so here's the story.

I have a 1.9 AAZ just did a fresh rebuild on the engine and been using the pump I got with the engine. Its been great up until the last few weeks.
 
I have modified the pump (keep in mind it was running great before this) with governor mod, 1.6 TD top for simpler throttle controls and better boost.

After the rebuild I did struggle with some leaks and I ended up replacing the main shaft seal, the cold start 0-rings, head seal, cover seal, throttle shaft seal. And it was fine up until this last part.

The cold start lever started leaking a river of fuel out of it. I took it off and replaced the cover with a TDI one since that's what I had, couldn't get it to run, and I realized why (TDI cover doesn't support the end of the timing piston so it basically had no timing. Fixed that and got it running. I also changed the seals on the pressure regulator (10MM plug next to fuel inlet)

This is where it's all gone sideways. I can get the engine running, but it has no power what so ever (Im doing a swap into a Suzuki Sidekick) at idle if I let out the clutch it just stalls (before it was able to get it moving). It starts fine, idles fine, revs fine but has no power whatsoever. Timing is sitting at 1.05MM. I'm getting air bubbles in the return line while it's running. I cant see any fuel leaks externally, and it always acts like the pump needs to be reprimed (lots of cranking to get it going). When it runs, it's a bit smokey grey, which I think is timing, but when you rev, it goes black. Increasing the fuel screw slightly (1/4 turn) made it easier to start but no additional power.

I haven't touched any of the seals inside the cover except for the main cover seal and throttle shaft seal. Is there anywhere it could be drawing air but not leaking fuel? With the air bubbles, it's gotta be drawing air in, but no idea at all where that might be. Or is this one of those things where you need to just change them all?

[ORCoaster]

Ahh, as I was reading down the list of symptoms I thought, there's air in the lines, which means his overall pressure at the injection site is crap.  Lots of air or even a little air makes the diesel lose its hydraulic pressure.  So instead of getting 155 bars at the injector, you might get 100.  OR less.

So yes chase the air from the crush washers on the fuel filter to the IP first.  Get new ones or look really hard at the ones you have first and see if they have scratches on them that would be letting in air.  Now, I have taken them off, heated them with a propane torch to reaneal them and put them back on with success. 

If that doesn't solve the problem then you have to look at maybe that top seal or the throttle bushing as a potential source of the air.  Like you say a real pain to have no visible leak but yet air in the system.  It is due to the fact that a vacuum will put air in more than pressure will push it out.  The vacuum on the system is from the front side of the IP. 

You might also try running it off a jug on the front end just to see if that clears up the problem.  If so you need to look at that filter to tank area for a source. 

That's my take.  Glad mine purrs like a kitten and now with the new air shocks in the back I won't be slamming every pothole in town.  And there are a bunch of them.

[fatmobile]

There are only a couple spots that will allow air to be pulled in.
 The banjo at the front of the pump, the mainshaft seal,
and the pressure regulator that you changed the seal on just before all this problem started.

 The pressure regulator compares the pressure inside the pump to pressure of the fuel coming into the pump.
 Through a passageway that goes to a spot behind the mainshaft seal,
 which continues on to the pump input, near the banjo bolt.

 If it is pulling in air at the pressure regulator, you could probably pour/spray some diesel on it and see if it gets sucked in.
 Or maybe spread some vasoline on it, see if it gets pulled in or anything changes.

I think you would have to mess up both of those o-rings to get it to pull in air at the pressure regulator.

[Buji88]

Ahh, as I was reading down the list of symptoms I thought, there's air in the lines, which means his overall pressure at the injection site is crap.  Lots of air or even a little air makes the diesel lose its hydraulic pressure.  So instead of getting 155 bars at the injector, you might get 100.  OR less.

So yes chase the air from the crush washers on the fuel filter to the IP first.  Get new ones or look really hard at the ones you have first and see if they have scratches on them that would be letting in air.  Now, I have taken them off, heated them with a propane torch to reaneal them and put them back on with success. 

If that doesn't solve the problem then you have to look at maybe that top seal or the throttle bushing as a potential source of the air.  Like you say a real pain to have no visible leak but yet air in the system.  It is due to the fact that a vacuum will put air in more than pressure will push it out.  The vacuum on the system is from the front side of the IP. 

You might also try running it off a jug on the front end just to see if that clears up the problem.  If so you need to look at that filter to tank area for a source. 

That's my take.  Glad mine purrs like a kitten and now with the new air shocks in the back I won't be slamming every pothole in town.  And there are a bunch of them.

I had a thought about this last night. In theory, if I block off the fuel inlet and the injector return, I should be able to put my vacuum tester on the outlet, and if all the seals are doing their thing, I should be able to build a bit of vacuum on it. If not I think I should be able to spray a bit of diesel on points where there are seals and see if it get sucks in.

Fuel going into the pump is perfect; no bubbles that I can see heading into the pump through my clear lines; I only get bubbles on the outlet when it is running, and when I shut it off, they do roll back to the pump, but not like when the front seal was leaking. They just mosey up to the pump over night.

Curious, if the pump is perfectly sealed, are air bubbles on the outlet line still ok? Or should it be a perfect line of fuel? I would suspect you would get some bubbling just due to the return lines from the injectors.

[Buji88]

There are only a couple spots that will allow air to be pulled in.
 The banjo at the front of the pump, the mainshaft seal,
and the pressure regulator that you changed the seal on just before all this problem started.

 The pressure regulator compares the pressure inside the pump to pressure of the fuel coming into the pump.
 Through a passageway that goes to a spot behind the mainshaft seal,
 which continues on to the pump input, near the banjo bolt.

 If it is pulling in air at the pressure regulator, you could probably pour/spray some diesel on it and see if it gets sucked in.
 Or maybe spread some vasoline on it, see if it gets pulled in or anything changes.

I think you would have to mess up both of those o-rings to get it to pull in air at the pressure regulator.

I changed the main shaft seal when I was initially having issues and it fixed it then. Im curious about the cold start lever cover because it was also leaking, I changed it, then it failed, so I wonder if its where its getting sucked in as well. I have a block off plate from a pump in my parts piles and since Im not using the cold start for my swap I wonder if that will it.

That is a great suggestion, Im borriwng your idea and Im going to block off the fuel inlet, injector return and put my vacuum tester to the outlet and see if I can bet it build some vacuum and hold it. Probably spritz some diesel on the areas that have seals and see if it gets sucked in.

I couldn't find the exact size of o-rings for the regulator so I just ended putting the ones I took out back in. We will see how it goes I guess. I also did pull a random piece of red plastic film out from the pressure regulator, I wonder if that was part of something inside?

[fatmobile]

I forgot, there is a passageway from just underneath the front timing cover to the front of the pump as well.

 I wonder if trying to put pressure on it would work as well. Maybe do both.

 You mentioned air might be coming from the injector small line too.
 It could be, I've had injectors that streamed air into the return line.
  I actually have all the small lines clear.
 One clear line on the last section heading to the pump banjo would let you see how much air is coming into the banjo from the injectors.

 So you don't have any air bubbles coming out the front of the pump when you shut it off?
 Have you put a vacuum gauge on the inlet fuel line to see how hard the pump is pulling when running?

[Buji88]

I will, caps get here tonight so I can try and see whats up with the pump.

I run clear lines between the injectors and they get bubbling a bit then eventually fill up, but I've always the injectors getting air there don't really matter since the return is just fuel that didnt get injected. But yea I get a fair amount of bubbles in the injector returns.

[fatmobile]

 That air should eventually bleed out.
 Such a small amount of fuel moves through those lines it can take a while to purge it.

[Buji88]

Well I think I figured it out....I put vacuum to it and it held good, was able to build about 15 inch on it with no drops. I tore it down to access the timing piston to check the advance and make sure it was all good. I noticed the cold start assist (the thing that runs from top of the housing down to the timing piston that has the electrical connection) had stripped badly. You could grab about 1 thread at the bottom but it won't tighten fully. I think either A) The threads were damaged at a past point, and when I took it off to change the seals on the covers (which is when all this started), I finished off the threads, or they cracked. B) I had cross-threaded it on the original install, but I didn't feel anything wrong ever retightening that banjo bolt.

But either way, you could kind of tighten it, and I suspect during running and vibration that it would be able to pull air in there. I'm also pretty sure that the chunks of threads likely ended up in the pump. I had a spare pump that wasn't turning, and I loaded it with sea foam and let it soak for a couple of days, and now it spins. I pulled the head off of it as well, and it was very serviceable looking inside, so I'm going to clean it up, fully reseal it, and, well, hopefully, that's it!

[ORCoaster]

Nice detective work guy.  Hope it gets sorted out and runs smoothly from now on.

[Buji88]

Hopefully that is it. I'm going to weld up that hole tonight so going to have it in by this weekend. There was a surprising amount of debris in the transfer pump and the vanes could move, but not well. 3/4 would shift inside the housing while turning but one just wouldn't come out at all, there is a pretty decent layer of varnish so I wonder if it also wasn't working that great and kind of starving it for fuel.

[ORCoaster]

Diesel purge soak to the rescue?  I have had vanes stick on me even after I took them out and cleaned them.  Quite the pisser as the remaining varnish sort of melts and the vane gets frozen in position again. 

[fatmobile]

 I've also had them where cleaning the vanes and getting them moving didn't mean it would run when back together.
 That's when I try a helper pump and see if I can get the RPMs up high enough to get them moving.
 Sometimes that doesn't do it either.
 But yeah, opening it up and finding even some of the vanes sticky or gummed up, that probably was one of the problems.

[Buji88]

Well the saga continues. Got it all back together and on last night, but now there is no output of the pump from the delivery valves and you can see nothing is getting pushed out the return line.

I tried priming the pump with my hand vac initially and it led to this question. Is 10 inch of vacuum to much to get fuel flowing (hand vac pump on the fuel outlet)? That feels pretty high feeding from the tank. It also holds that vacuum easily. I am starting to wonder if my filter is plugged since before all this happened, I drained a lot of fuel out of the tank by mistake, and it seems like it progressed slowly from that point.

[fatmobile]

Have you tried swapping a regular banjo bolt for the regular banjo bolt?
 10 should be enough vacuum to pull fuel through the pump.
 If it isn't, the OUT bolt might be plugged.

 If it pulls fuel with a regular/unrestricted banjo but not with the OUT bolt then that's part of the problem.