1.9TD AAZ fuel pump issues

[CaddyJim]

I currently have a 1.9TD AAZ in my MK1 caddy. Fuel Pump is filling up when turning over and hand priming but the fuel is just going down the return line and the fuel lines to the engine are dry, even after hours of bleeding. Anyway, long story short, I've now fully stripped the pump to check for issues and looking for some knowledge. Can't see anything broken or even worn, the only thing I could see that was off (to my knowledge) is the delivery valves.

Looks like there's a few washers missing from them or are there meant to be different numbers of washers of different thicknesses in each delivery valve? I'm unsure if this would affect the fuel being sent to the fuel lines but it's the only issue I've found so far... See link below for photos of what I mean.

I can't seem to find much info on these washers online and which ones are required so any help with this would be hugely appreciated!

AAZ Fuel Pump pics - Google Drive

drive.google.com

 

[KLXD]

Has it been running? Newly acquired pump? A bit of background might help.

Maybe call DFIS in Oregon. I think.

 

[CaddyJim]

Has it been running? Newly acquired pump? A bit of background might help.

Maybe call DFIS in Oregon. I think.

It was running before and no it’s an old pump as far as I know. It’s always had a fueling problem but the cars been sat for a few months and now it doesn’t seem to want to pump fuel at all!

 

[Steve Addy]

The most I can offer is to suggest that you follow the pump reseal process and see whether that gets you anywhere. At the very least you're likely to need seals for the IP which fortunately are available pretty cheaply. If you're just wanting it to run for a short period of time you might try spiking the fuel with a generous amount of ATF, that will swell the seals some and maybe bring you to a point where it will run, but if you're not getting any injection now that effort could be futile.

At any rate, this is the layout drawing and photos of the reseal process that used to be on VWdiesel.net IIRC, I managed to find it again, it was pretty good and there are good pictures.

You will need a seal kit and with that will be the washers for the delivery valves (copper washers) but not new ones for the valves internally. You should have all those original ones still I would hope.

The process is here and at one time it was also floating around as a PDF too, but I didn't find that yet.

And I believe you're in the UK right? Might be good to include that in your information.

EDIT: just looked at your pics, it looks like you've already got a kit and maybe have found the resealing process. I don't think those delivery valves are right, it looks like they aren't all the same. I would find a junk pump and pirate the valves off of it and maybe even the distributor head itself since removing the head is pretty easy.

Steve

 

[CaddyJim]

The most I can offer is to suggest that you follow the pump reseal process and see whether that gets you anywhere. At the very least you're likely to need seals for the IP which fortunately are available pretty cheaply. If you're just wanting it to run for a short period of time you might try spiking the fuel with a generous amount of ATF, that will swell the seals some and maybe bring you to a point where it will run, but if you're not getting any injection now that effort could be futile.

At any rate, this is the layout drawing and photos of the reseal process that used to be on VWdiesel.net IIRC, I managed to find it again, it was pretty good and there are good pictures.

You will need a seal kit and with that will be the washers for the delivery valves (copper washers) but not new ones for the valves internally. You should have all those original ones still I would hope.

The process is here and at one time it was also floating around as a PDF too, but I didn't find that yet.

And I believe you're in the UK right? Might be good to include that in your information.

Steve

Cheers for the advice! I have replaced all the seals and washers already as it was a good opportunity with the pump in bits. Funnily enough that’s the exact guide I used to take the pump apart, it’s the best one online by the looks of it!

Still wanting to clarify the number and size of the internal washers before putting the pump back on the car though for peace of mind.

 

[Steve Addy]

Cheers for the advice! I have replaced all the seals and washers already as it was a good opportunity with the pump in bits. Funnily enough that’s the exact guide I used to take the pump apart, it’s the best one online by the looks of it!

Still wanting to clarify the number and size of the internal washers before putting the pump back on the car though for peace of mind.

I don't know what your pump might have had for delivery valves or how many internal washers that pump had, only that it looks like your missing some stuff and that one delivery valve looks shorter.

Honestly in your case I would replace all the delivery valves if I could. Find a junk pump and pull those and see what washers it has and use those valves instead. The mismatch in what you have now could be the explanation for why you originally had fueling issues.

Steve

 

[CaddyJim]

Just a bad photo, all the delivery valves are the same length. I think you’re right, may just have to try and source a new set of them and rebuild the pump. Cheers for the help!

 

[ToddA1]

Any IP I’ve ever taken apart had the same parts in each of the DVs. Changing the DVs will change timing.

Maybe start with one washer/shim in each DV?

-Todd

 

[CaddyJim]

I’ve put it back together now with one washer in each DV and one DV with the two thinner washers (pretty much makes up the thickness of other ones) so will see what happens!

 

[burn_your_money]

Based on the first lines of your first post, I would say the stop solenoid failed or you have an “in” bolt on the “out” of the pump.

 

[ToddA1]

I don’t think the DVs were your initial issue.

You can spin it on the bench, with a drill, to see if it’s pumping. I have a feeling it will.

-Todd

 

[KLXD]

I agree. Dats why I asked the usual wujado questions.

My recollection is that they maintain pressure in the lines and act like relief valves so the injection event ends abruptly rather than taper off.

Didn't really understand it but I don't think they would cause a no start. Especially since it was running previously. Moot point now.

Hey Caddy, I assume you had the injector pipes loose while cranking at some point?

I think I'd try running it off a bottle at this point. On the bench first as Todd suggests if it isn't installed yet.

Oh, and do check the solenoid as was suggested.

 

[Steve Addy]

Undoubtedly the delivery valves would not cause a no start, that had to be either bad seals or something inside that was stuck or clogged due to sitting. I didn't mean to imply that they would, however, a DV can cause a fueling issue if there's corrosion or goop in there.

If in fact all the DV's are the same and washers are the same thickness, including the two when paired together, then it shouldn't be a problem if all the components were corrosion free. My concern about the DV's was based on the photo, which doesn't really show very well what was installed where nor what their condition was.

I bet that a reseal will improve the situation dramatically.

It takes a pretty powerful drill to spin one of these on the bench IIRC.

Steve

 

[CaddyJim]

KLXD, Sorry should have clarified before. My trouble shooting before taking the pump off was first to crank the engine over with the fuel lines cracked at the block. When I got no fuel after a while I tightened them and cracked the lines at the pump to no avail. I then took the ‘fuel in’ hose and put it in a clear can of diesel to bypass the filter etc. I could see the pump was sucking in fuel while cranking but it was just getting pushed down the fuel return hose. Pump at this point was full to the brim with fuel.
I can turn the pump over by hand on the bench and it all seems in order, don’t have access to a powerful enough drill though.
‘Burn your money’, I’ve ordered a new stop solenoid just incase and will fit that. The ‘in and out’ banjo bolts are in the right places as well if that’s what you’re meaning.

 

[Steve Addy]

BYM could be right about the solenoid, I would however test it before replacing because the inop condition (if it exists) could be ignition switch related too.

Steve

 

[KLXD]

I usually tell folks to leave the plunger out for testing if the solenoid valve is suspect but since you're working with a "mechanical" pump you'd have to find another way to shut it off once it starts. Could leave it out if all the injector pipes are loose.

I'd think just verifying voltage is there while cranking and that you can hear the plunger move when you apply 12V would be enough to exonerate it.

If I remember correctly, fueling with these is controlled only by the pedal? Did you floor it while trying to prime it to maximize the injection quantity?

 

[CaddyJim]

The wire leading to the solenoid gets power when cranking, I know that much. Good idea, I’ll have to listen for the plunger before I write it off completely. When you say priming do you mean when I’m turning the car over or hand priming it? I’ve tried holding the throttle open when cranking the engine but no joy.

 

[ToddA1]

A decent cordless drill will easily spin it on the bench. Install just the hard lines.

When you install the injectors, is when it gets tough. I use an electric drill that’s rated for 7A.

-Todd

 

[burn_your_money]

Max fuel is typically automatically delivered on these pumps at cranking RPM. However, you might get a bit more fuel with the go pedal down and boost pressure applied to the LDA assuming this pump has one. (Pictures never loaded for me). There is a lever on the pump that limits starting fuel to reduce the startup plume of exhaust. You can actually use this lever to manually shut the car off. I would not suggest moving it if it’s never moved before but since this pump is resealed there is no risk in moving it.

Edit, just found the pictures. It does have a LDA.
Regarding the missing pieces in the delivery valve assembly, are they course on the outside diameter or smooth? If smooth, they are shims and need to go back where they came from. If course, they are wear washers and you just need one in each delivery valve holder. It is extremely common for the shims/washers to get stuck on the delivery valve holder. You need to blow them out with compressed air or hit the delivery valve holder hard against a flat surface with the bottom pointed down. Be careful either way because they like to go flying.

 

[CaddyJim]

The shims/washers were all smooth so I just put one in each DV. The hose coming from the section just before the turbo elbow is joined to the fuel pump lid where the LDA is. Is that how the LDA gets pressure? That hose is connected this way as standard I believe.
I have now put the pump back on the car and timed it, filled it with fuel and turned the car over for a fair while. Pump is pulling fuel but very slowly and no fuel seen at the fuel lines yet, now confused as to what to try next!? Even advanced the pump timing slightly from 0.8mm to 0.9mm.

 

[burn_your_money]

Yes that LDA hose routing sounds correct.

I would remove the plunger from the stop solenoid and remove the injection lines and see if it squirts fuel.

 

[CaddyJim]

BYM, didn’t think to remove the plunger, will give that a shot, cheers!

 

[CaddyJim]

Update: stop solenoid plunger out and used up a whole battery (800CCA big boy) turning the car over again with no luck. Delivery valves bone dry and pump full to the brim with fuel - it shot out the fuel return bolt hole when I unscrewed it afterwards. Anyone got any other ideas?

 

[burn_your_money]

Try winding the main fuel screw in 1-2 complete turns. Are you sure you have the throttle arms indexed correctly to the throttle shaft? All the internal springs are on and not stretched out?
Remove the delivery valves and see if fuel shoots out.

 

[CaddyJim]

Yes to all those things unfortunately, had the fuel screw nearly all the way in at one point by accident for a while and now I’ve backed it off to the appropriate place so must not have made a difference. Throttle shaft/arms are at the right angle/orientation, even pre loaded it a small amount to try and help. Which internal springs are you referring to exactly? Governor spring and the springs on the governor assembly are on and seem tight. Will remove the delivery valves and see what happens!

 

[burn_your_money]

I was mainly referring to the idle spring as it’s easy to damage on disassembly but of course, all the springs are important.
You are certain that the governor ball is seated in the fuel control sleeve?

 

[CaddyJim]

The idle spring is in there and actually new because I managed to lose it when disassembling a couple months ago! If by ball, you mean the governor/throttle shaft then yes that’s seated correctly.
I have just removed the DV’s and turned the car over and to my surprise, fuel came out all of the openings! Does that mean that somehow the delivery valves are goosed? Or does it mean the pump isn’t building enough pressure to force fuel through them? I didn’t think the DV’s wouldn’t be able to block fuel flow.
cheers for the help so far also!

 

[burn_your_money]

Yes, that ball thing I was talking about is what you described.
When you had the delivery valves out, did you make sure they open and close easily?
Just to confirm, you are testing with the stop solenoid plunger removed correct?
When you had the pump apart, did you remove the control sleeve off the plunger? If you put it on backwards, I think you get issues similar to this but I’ve never seen that so it’s just theory.

In my mind, you have a few possibilities:
- Delivery valves are holding fuel back (not likely)
- head and rotor are damaged and unable to produce sufficient pressure (seems unlikely)
- Control sleeve is not sliding to proper spot to send fuel through delivery valves

If you have a helper, I would leave the pump installed and remove the top cover. Have your helper crank the car over. Using a screwdriver (or your finger) press the part of the fulcrum lever that the max fuel screw presses on. Then using your other hand move the governor back and forth and see if you can get fuel to come out of the delivery valves. This will make a pretty big mess so be ready to catch any spilled fuel. If you are successful, hook the fuel lines back onto the injectors and see if you can get it to run. If everything is assembled correctly, when you release the screwdriver holding the fulcrum lever, the car should turn off. Have your helper be ready to dump the clutch if needed or be ready to open the injection lines.

if you prefer, you can remove the fulcrum lever and just use a screwdriver to move the control collar. You will need to remove the pump head to put it back in though.

 

[CaddyJim]

The delivery valves seem to be fine and freely moving in the housing by the looks of it. Plunger from stop solenoid is still off the pump so shouldn’t be affecting it? I did remove the plunger sleeve inside the pump but I put it back on the right way round as per the guide.
Right, that’s a good idea will give that a shot and report back!

 

[CaddyJim]

Update: Had someone turn the car over whilst i pulled the governor lever with the lid off of the pump. No sign of any fuel coming out of the DV's what so ever! Any thoughts? As a last resort I found a website for a shop 'Nerings' in Latvia who seem to sell refurbished versions of these pumps in exchange for your old pump. Anyone have any experience with these guys?