Cleaning used injectors: ALH

PradoTDI

Veteran Member
Joined
Sep 25, 2020
Location
MT
TDI
1997 Jetta TDI, 1991 Toyota LandCruiser LJ78 with ALH Swap
I recently purchased a set of stock, used ALH injectors that I plan to install in place of the 0.220 injectors I currently have while I sort out some other aspects of the drivetrain/engine hardware. My question is, what is the best way to clean them? Originally I had planned to install the injectors and run a cycle of LiquiMoly Diesel Purge through them right away, but I got to wondering if I should attempt some cleaning before install. They aren't super dirty, but I don't want to run any more gunk through the fuel system than is absolutely necessary.

Current thoughts:
Soak in Seafoam, Diesel Purge or some other injector cleaner prior to install.
Run through ultrasonic cleaner (not sure this is a good idea for no.3 injector).

I welcome your input!
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
Send them out to someone who has the equipment to proper assess them and, if necessary, take them apart and rebuild them and balance them.

If ALH injectors are removed from an engine, and left to "dry out", they will be bad. They need to be stored immersed in fuel or kerosene or thin motor oil or something.

I've had to deal with this multiple times over the years... the first time I was trying to diagnose a VERY low power problem on an engine that a local dealer replaced after a different local dealer tooefed a timing belt job and mashed the valves. While the first dealer had the head off, the injectors just sat on a bench (two weeks). Then they got the engine back together, and struggled to get it running at all, finally got it running but it had low power. The owner got disgusted with them (they said "it's normal, it's only 90hp!") and took it to the second dealer. They somehow, no idea how, said the engine was no good, and replaced the whole thing. Injectors sat out again on a bench, for another two weeks. They got it back together and running, and it still had no power.

Then it got to me. Car seriously struggled to move. It maybe made 50hp at best. I checked a bunch of things, found an odd deal with the motor oil: it was clean. Like, WAY clean, like it was just poured in. This engine under normal circumstances would turn the oil black fairly quickly. That was my clue: the engine was being severely UNDERfueled. The ALH has no feedback for fuel injected post-combustion. It only knows how much the QA moves in the pump, and that the lift sensor in #3 injector is generating a signal. That's it.

I sent the injectors out, they were all barely flowing. They took them apart, cleaned the solidified gunk out of them, reset and recalibrated and balanced them, I got them back and installed and bled the system.... engine fired right up, a test drive of about 100 feet confirmed the car was fixed, and the oil was already nice jet black as usual.

I have now known what to look for if the injectors have been sitting, and I have fixed many basket cases over the years following by doing just that. And now I know to store the injectors properly if an engine will be apart for any length of time.
 

gmenounos

Vendor
Joined
Jun 26, 2003
Location
Watertown, MA, USA
TDI
'99.5 Golf GLS, '01 Jetta GLX Wagon (TDI conversion)
How does VW keep replacement injectors from drying out while they're sitting around in the warehouse? Do they fill them with some special non-evaporating fluid after their manufactured so they won't dry out?
 

Nero Morg

Top Post Dawg
Joined
Oct 19, 2017
Location
OR
TDI
2003 Jetta wagon, 2001 Jetta TDI, 2014 Passat TDI
Can't speak for vw, but with Cummins injectors, both heui, mechanical, and solenoid, they come wrapped in an oil like substance soaked paper sleeve, then in a bag, with a rubber tip on the nozzle end. Probably something similar?
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
Unused injectors that have never had fuel in them are not an issue. And yes, like most parts of that nature, have a coating of protectant and are wrapped up.
 

PradoTDI

Veteran Member
Joined
Sep 25, 2020
Location
MT
TDI
1997 Jetta TDI, 1991 Toyota LandCruiser LJ78 with ALH Swap
Good to know! I understand that rebuilding and calibration require extensive special equipment, but is there any reason that a disassembly, cleaning and reassembly wouldn't work? Unless I'm mistaken that shouldn't mess with the calibration, correct? I have rebuilt older Mercedes IDI injectors before, so I know the basics of how to handle and clean injector parts.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
The prechamber injectors are very different. They have one GIANT pintle in the middle, and the end wear is easily seen with the naked eye (the flat part around the pintle erodes away).

The direct injected engines' injectors have a series of tiny holes arranged in a pattern around a tiny dome at the end. You can see them (barely) with the naked eye, and with a magnifying glass see a little more detail, but you could never see any wear patterns in them let alone have any idea of the spray pattern and opening pressures.

Prechamber engines are also more forgiving for less-than-ideal injector health. One, because they are not nearly as precise at the amount metered in the first place, and two because any poor combustion starting event is cushioned before it gets into the cylinder. This is why they can tolerate lots of things like WVO use and what not and not have an issue, whereas a direct injected engine can and will blow-torch a hole right through a piston inside of a few seconds if an injectors starts leaking or spitting or doing something otherwise not right. Because it is literally fitted right down inside the bowl of the piston.
 
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