Air in fuel line after nozzles

I bought pp520 nozzles for my 02 alh manual. Installed them today. And it took awhile to first start it. Like there was massive air in the line. So I cracked the Injector lines and cranked it over. Tightened the lines and then cranked it for about 7-8 seconds before it started. It blew out tons of white smoke. Smelled of unburnt fuel. And I looked and could see air lines in the see through fuel line. So I let it run a few seconds and have it just a little gas and I could still see air. Mind you the engines running rough. So I check the iq and adjust it to 3.8 and it’s still having the issue. So I read some threads and some suggest bad nozzles. I also had a code for misfire in cylinder 3. So I put the old nozzles back in. Same thing. Can still see air in the clear fuel line. Wondering where to go come here.


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Go drive the car hard a few miles and work the air out of the system before you make a judgement. Everytime you have the inkector lines off, and injectors out, you introduce air back into the system.

I went out and drive the car about ten miles. Still did the same thing when I got back. I have all the pp520 nozzles in now. I felt is misfiring. Or that’s what it felt like. But got no CEL. Still air in the fuel line.


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Checking vcds. Start of inj specified is 11btdc. And actual just says 0.0. So is it not injecting fuel? I’ve cracked the lines and waited for fuel to come out then tightened the lines and still nothing.


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So I made sure each injector is getting fuel. Pressure bled the system. And I noticed today. The tach isn’t moving while I crank the car. Yesterday the tach was moving. What appeared to be around 250ish. Now today it’s not moving and I’m vcds I’m not getting an engine movement reading. So I ordered a crank sensor it’ll be here in the morning but i don’t think that’s the issue. Any other suggestions.


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jon_570 said:

I also had a code for misfire in cylinder 3. So I put the old nozzles back in. Same thing.

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I think that's your real problem, injector 3 has the sensor in it so the ecu knows what's happening. Check the wires to the plug and injector, it's likely one is actually broken.

It uses the sensor for timing and injection duration or something.

Air in the clear lone is completely normal on the ALH, only way to get rid of it is to mod the sender unit in the tank. There's a thread on it somewhere.

Seatman said:

I think that's your real problem, injector 3 has the sensor in it so the ecu knows what's happening. Check the wires to the plug and injector, it's likely one is actually broken.

It uses the sensor for timing and injection duration or something.

Air in the clear lone is completely normal on the ALH, only way to get rid of it is to mod the sender unit in the tank. There's a thread on it somewhere.

Click to expand...

The wires on injector three appear fine. No tears or rough looking area. Can I check the plug with a multimeter? Maybe check for resistance and see if it’s open.


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I will admit. When i first put the nozzles in, the #3 injector internals fell out. I followed a post on here to put it back together and i cant remember if it started after that or not. So yesterday, i had a spare #3 injector that hasnt been in a car for about 2 years and i took it apart to see where everything was. there were 2 shims swapped around in the wrong place. Could i have messed up the injector? Could i swap the nozzle to the old 3rd injector i have and would it still work?

Im also receiving a glo plug light so i know the ECu is gaining power. Still when i was in VCD there were no start of injection parameters. nothing indicating that the injectors were firing but i know the pump is pumping because when i bled the air, fuel sprayed out of the lines.

So, im thinking either the #3 injector is boogered up due to me, or theres some other stupid issue. Car ran flawless before and i only touched the injectors so it has to be something easy. Also, i had broken the Crank sensor plug but was still getting a crank reading. I am receiving my new CPS today and will plug it in to be sure thats not an issue. I guess since i have that spare injector i might as well test it and see what happens.

Send the nozzles to someone who can test and put them back together (if necessary) properly. It's not rocket science but you really do need to have them balanced and you CANNOT do that without the equipment to do so.

Genesis said:

Send the nozzles to someone who can test and put them back together (if necessary) properly. It's not rocket science but you really do need to have them balanced and you CANNOT do that without the equipment to do so.

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Thats understandable. I know they need balanced. I ran nozzles on my old tdi some years back without ever sending the injectors out for balancing. and while i may not have been getting the best performance out of them i still averaged 50mpg and for two years never had an issue. Im not say every case is like this. But, i know for sure the injector is assembled correctly now after matching it to one of my others.

So while cranking I see the iq go to 28. I can see the cold start injection percentage rise. I threw in my other cylinder 3 injector with nozzle and nothing. Still won’t start. Can I check pump timing with the engine not started. I did my timing belt about 1k miles ago and it’s been flawless ever since. Until I changed nozzles. Even throwing the stock nozzles back in does nothing.


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I have more clues. For s&gs I unhooked it from the fuel filter. And hooked it to a small bottle. After about 8 seconds of cranking it fired it. And ran crappy then shut off when the fuel ran out. When it died. It pushed a bunch of fluid back through the feed hose and looked like foam. I’m not sure what that indicates. Bad fuel filter? I just replaced it 3k miles ago.


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I got a mity vac and could not pull fuel through the return side. I pulled 25 inches of vacuum and let it sit for a few minutes and it would not pull vacuum. I also checked and made sure the fuel line from the tank was good and the filter is flowing fine as well. While holding vacuum I cracked the I hector lines loose and it still held the vacuum. Not sure if that helps or not.


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If the #3 isn't working your timing will be all over the place. No idea what the pins should read though but yeh, need that signal to tell the ecu where it's at. That's why you can't read the timing.

Seatman said:

If the #3 isn't working your timing will be all over the place. No idea what the pins should read though but yeh, need that signal to tell the ecu where it's at. That's why you can't read the timing.

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I swapped to a known good #3 injector and having the same issues. I got the vehicle to start by gravity feeding the pump. And it shut off when my rigged up bottle ran out of fuel. There’s no restrictons in the fuel supply. And I can’t vacuum bleed the pump. If I can get it to run for a few seconds again I’ll have vcds up on the timing graph to see if it’ll read.


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Bump. Any suggestions as for what to check.


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Are the return lines from the injectors O.K.? You might check to see if they are open.
When you run from a container of fluid connect 2 lines close to the pump. Inlet hose in the bottom, return line near the top of the container. You should see fuel coming back thru the return line not the inlet.

BobnOH said:

Are the return lines from the injectors O.K.? You might check to see if they are open.
When you run from a container of fluid connect 2 lines close to the pump. Inlet hose in the bottom, return line near the top of the container. You should see fuel coming back thru the return line not the inlet.

Click to expand...

I checked the return line from the ip to the filter. And the hoses on the Injectors. I did not check from the filter to the tank. But. I just can’t believe it would happen so randomly and when I install nozzles.


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I had a thought that some pump damage may have occurred by cranking it without priming, do you think that is a possibility? I did notice it ran on gravity feed, but do you have another pump to try? It should prime by putting vacuum to the port that the INJECTOR return line connects to. A damaged electrical circuit on #3 would show up on VCDS at individual injector IQ readings if you get it running. My experience is #3 overrules, doesn’t seem like your problem though. You can pull fuel by vacuum from the tank through the filter?

jmodge said:

I had a thought that some pump damage may have occurred by cranking it without priming, do you think that is a possibility? I did notice it ran on gravity feed, but do you have another pump to try? It should prime by putting vacuum to the port that the INJECTOR return line connects to. A damaged electrical circuit on #3 would show up on VCDS at individual injector IQ readings if you get it running. My experience is #3 overrules, doesn’t seem like your problem though. You can pull fuel by vacuum from the tank through the filter?

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Yes I can pull fuel easily through the filter from the tank. I don’t believe it’s a 3 injector either. I do not have another pump to try. I didn’t run the pump completely dry. Once I installed the nozzles. I cracked the Injector lines till it sprayed fuel then went from there. I’ve seen conflicting info about vacuum priming. Some say it should flow fuel from the return line where the injector return feeds to. Others say pressure bleeding should be done. Others say I need to turn the engine to specific spots to be able to vacuum bleed the system.


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The vacuum will likely hold if you crack the injector because the delivery valves in the distributor head of the pump are made like a one-way valve that holds a small amount of pressure in the injection line after an injection event.

I've always bled the pumps from the top where the injector return line goes in, and never had a problem. If, as some say, the pump has to be in a specific position then you can put the car in 5th gear, jack up one side, and rotate the tire by hand in a forward direction to turn the engine over slightly while the vacuum is applied. That may line things up in the pump better.

-Rich

Above advice should work, I have not encountered an issue priming from that port either, though I have only had to do it a few times. It can take a little while to get a good solid flow, so internal alignment may play a factor. Air in the injector lines won't bleed off by cranking alone after priming the pump. Good luck, hope it works.

I’m gonna work on it here shortly. I’ll try these ideas and post what happens


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Genesis said:

Send the nozzles (injectors) to someone who can test and put them back together (if necessary) properly. It's not rocket science but you really do need to have them balanced and you CANNOT do that without the equipment to do so.

Click to expand...

^ This. It takes very little effort to screw something up.
And that comes from someone who prides himself in doing all his own wrenching. Injectors absolutely need a trained professional with the right tools and absolute cleanliness to achieve consistent results.
....just my 2 cents.

maxmoo said:

^ This. It takes very little effort to screw something up.
And that comes from someone who prides himself in doing all his own wrenching. Injectors absolutely need a trained professional with the right tools and absolute cleanliness to achieve consistent results.
....just my 2 cents.

Click to expand...

Im guessing one of the nozzles is bad. I got the car started and it was running choppy. i let it run for a few minutes to see if it was air and it did not smooth out. So i slowly cracked each injector line while it was running and listened for the change in tone. All of them changed tone except the 4th injector. I had a spare injector body that i swapped the nozzle onto and it made no difference. So my guess would be the nozzle is bad for cylinder 4.

Glad to hear that it's at least running!
One hurdle down...

Yea. Put stock nozzles back in. Spent thirty minutes bleeding it and it fired up and ran fine. So 3 if the four nozzles I got were good. One was bad. So on to find just one pp520 nozzle


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If they are genuine PP520's then this info won't help you, but if they are "generic" .216's, you might try these out: KINTDINOZZ216K from Concept-1.com There are other places that sell them too, and by the each for less than that but I don't remember where.


I just installed a set of 4 that I had DFIS set them up, and they are running great.


Also search "NU502" from Sun Dieselsystems