Tdi overfueling
- Thread starter ocnorb123
- Start date
bmali98
Veteran Member
If you have replaced your manual 10mm pump with an 11mm automatic trans pump, this could overfuel. I'm usure, but there should be a way to test ip case pressure to see if the pressure release is stuck/setup wrong. Also, while replacing the pump, there is a possibility of contamination getting into an injector and causing it to get stuck open and overfuel 1 cylinder only but there would likely more symptoms including engine imbalance.
Last edited:
No I have the automatic in the car. Also have stock injectors in the car. I've had all the sensors checked for function and everything was ok. i.e.-iat sensor,maf sensor,ambiant air sensor. The kicker to all this is that the injection pump that I purchased was used. The seller assured me that the pump was good and only had approx 150000kms. Can the pump be defective and overfuel the system. I do work @ a garage so I have access to a scanner-not the vag-com type. I should clarify that when the injection pump was replaced I was able to get somebody to time the pump with vag-com scanner. The car overfuels mostly on idle. Overfueling so much that it's dumping fuel in the crank case. My tech is stumped-and he's very good at what he does.
Rembrant
Veteran Member
Well, any used pump could be defective. Not sure where you are, but finding a used injection pump in Atlantic Canada with only 150,000 kms on it would be very unusual imho. I bought a used one that supposedly had 400,000 kms on it, and it purrs like a kitten. (I suppose if he told me it had 400k, it likely had 500k...lol).
Anyway, I always circle back to the beginning. You skipped the first chapter of your story.
When did all of this start, and why did you change the injection pump in the first place?
UhOh
Top Post Dawg
I'd be interested in the story as well!
The injector balance group (013) ought to provide a bit of insight into what's going on.
As mbali98 states, it sounds like you've got something stuck. Checking injector balance (Group 013) might give some insight: if one or two of the cylinders show up at or over spec then try swapping a couple of injectors to see if the imbalance follows or stays the same (if staying close to the same then it's like the iP that's causing it- this assumes, of course, that you don't have some other issue like a bad head valve that's slightly sticking?).
This got me to thinking... wouldn't it be wise to force fuel out of the IP before connecting to the injectors so that you purge out any old, crappy fuel and possible debris from an IP that could have been sitting around?
The injector balance group (013) ought to provide a bit of insight into what's going on.
As mbali98 states, it sounds like you've got something stuck. Checking injector balance (Group 013) might give some insight: if one or two of the cylinders show up at or over spec then try swapping a couple of injectors to see if the imbalance follows or stays the same (if staying close to the same then it's like the iP that's causing it- this assumes, of course, that you don't have some other issue like a bad head valve that's slightly sticking?).
This got me to thinking... wouldn't it be wise to force fuel out of the IP before connecting to the injectors so that you purge out any old, crappy fuel and possible debris from an IP that could have been sitting around?
KLXD
Top Post Dawg
How can it overfuel at idle? Too much fuel would increase the idle speed.
What exactly are the symptoms. Overfueling is too much fuel for the available air yielding black smoke.
What exactly are the symptoms. Overfueling is too much fuel for the available air yielding black smoke.
BobnOH
not-a-mechanic
The pressure relief valve is easy to deal with.
I'm not clear on what you mean by overfuelling. What are the symptoms? Could it be transmission related?
I'm not clear on what you mean by overfuelling. What are the symptoms? Could it be transmission related?
bmali98
Veteran Member
Having a leaking injector looks like overfueling. You will usually get a grey/black haze out of the exhaust at idle and it can get worse with rpm/load. Instead of injecting only when it's supposed to, it will dribble before and after the main intended injection. Dribbly fuel doesn't burn proper and results in smoke. Also, this can end in melted Pistons due to uncontrolled timing since there is always fuel available to ignite. It only takes a bit of crud to keep the plunger from seating properly so it's no surprise to me after a big fuel system overhaul this could happen
Ocnorb123 has new injectors after the pump was installed so this seems less likely tho.
Last edited:
UhOh
Top Post Dawg
I wouldn't think that "new injectors" could be immune from sticking due to any crud that was sitting in a used IP. I don't think one can rule out the thought (yours) that there may be an injector or two that's stuck (due to crap).
I'd check Group 013 and look for the odd one (or two) out and then swap around to see what happens.
Rembrant
Veteran Member
bmali98
Veteran Member
I agree group 013 is worth a look. From the original post I believe the injectors were replaced post injection pump replacement to cure the smoking. Could be wrong tho about the order of things. I suppose there's no reason contamination can't kill two sets of injectors.
.There's always more to the story!
We still need to know the beginning