P0301 cylinder 1 misfire and tandem pump?

I just want anyone with similar experience to chime in pls. So I naturally replaced my injector harness to no resolution on cylinder 1 misfire. Next step is to swap injectors to see if code follows injector, which I will do next. Also noticed my vacuum/tandem pump seems to need new gaskets. Its leaking oil. Also tried doing a diesel purge with lube moly injector cleaner but couldn't get tandem pump to suck without lift pump connected. I applied fuel from bottle with mityvac, air was removed but wouldn't start or flow. Is there any chance my tandem pump is bad and that's why #1 cylinder is not getting fuel being its farthest away? Just a long shot before I start swapping injectors etc. I read that there is place to connect gauge to test tandem pump while running and it should be 60-100 psi? Lift pump is good, I dont have a vag-com but I am going to get one now that we have 2 tdi's. This is a 2005 Jetta bew 156000 miles. Also egr is bad and needs delete or cleaning, cant even get it off without breaking to get valve cover off. When I did harness.
Thx for any leads. Going to swap injectors this weekend. I thought those injectors were fairly reliable? Everything breaks I know.

No way I'd start by swapping injectors.

I'd start with seeing what a proper scan tool tells you.

Then Ohm check each injector circuit individually at the round connector on the head (do not even need to take the valve cover off, this would have given some clue as to the integrity of the injector harness BEFORE you replaced it needlessly).

Then I'd check the compression.

Then I would check the integrity of the cam/lifters.

Swapping injectors around would be pretty far down the list. There is a seal kit you'll need, a stretch bolt for the hold down clamp, and a removal tool is very helpful, as well as a tool to clean the bore out.

Wolfganghammer said:

Also tried doing a diesel purge with lube moly injector cleaner but couldn't get tandem pump to suck without lift pump connected. Is there any chance my tandem pump is bad and that's why #1 cylinder is not getting fuel being its farthest away?

I read that there is place to connect gauge to test tandem pump while running and it should be 60-100 psi?

Click to expand...

You have to run the diesel purge "gravity feed" into the fuel lines. I don't believe it will suck. (think IV bottle at the hospital).

There is a test port on the tandem pump where you can hook up a tester. You will need a banjo fitting, and a pressure gauge/kit.

Look for a thread on fuel system/tandem pump. It has all the info you seek, pressures, what to test, volumes supplied, etc.

I agree with Oilhammer, I wouldn't be swapping injectors until I absolutely had too. (Said as a person who has pulled a few BEW injectors)

Yes that's what I get for not posting a thread first and relying on somebody else's thread saying you are a fool if you dont replace harness before dealing with injectors. Compression tester in glow plug was my next purchase. Vag-com next. Will follow your steps of troubleshooting oilhammer. Thx for advice.

Keep us posted.

I have a whole BEW engine for sale if you decide you want to swap the whole mess!

Will do.

Update, harness ohmed out good, checked all 4 cylinders compression, 460-480psi. Noticed #4 glow plug was wet with fuel? #1 is misfire code. Now going to take valve cover off and check cam lobes for obvious wear. Then to the injectors. Only thing I dont have is the new injector hold down bolt. Is it critical to replace? I know they stretch.

Cam and followers looked good no visible wear. Injector came out easy. Put new o-rings on injector. I ordered new injector hold down bolts. Bad idea to reuse one time bolts. $5 each. 33ft/lbs for rocker arm bolts. Anything I am forgetting? I also bought another rebuilt injector to use instead of swapping two of them.

I've never done TDI-PD injectors but I've done more MEUI injectors than I care to recall...
I would assume injector height needs to be set?

Did you ever verify you had adequate fuel supply pressure to the head?

Yes you are correct on injector adjustment. I have been told and read a thread on putting a banjo fitting by tandem pump to check psi. The tandem pump is suspect, will hook up a gauge to read fuel pressure. I read that it should be 15 psi at idle and 60-100 psi at higher revs.

Update, replacing injector fixed the misfire. Runs really well. I think it might have slowly clogged up. I have a lot more pep in the pedal. Thx for everyone's help, this forum is invaluable.