d2audia8guy

I have a 1999 d2 a8 4.2 quattro. I recently replaced the fuel pump/filter and fuel pump relay. The car will start and drive fine however when the car is parked for longer periods of time the car will not start. I think it has something to do with low fuel pressure. When I turn the ignition on to the on position several times and try to start the engine it will start occasionally. I'm not sure if it's a fuel pressure regulator bad plugs wires etc? However I am going in for my timing belt service in about a week. Can the timing belt towards the end of its life have something to do with its intermittent starting issues? what could be the culprit?

d2audia8guy

I think the timing belt being worn out may be causing problems with the compression... Am I incorrectly understanding this?

Kneale Brownson

Timing belt isn't the problem. Could be leaky injectors.

silverd2

Sorry, but completely incorrect there...nothing to do with compression, unless the belt jumped time, which would cause misfiring all the time and timing codes.

Have run a VagCom on it? ...NOT just a simple code reader (only reads codes associated with

You are describing a likely loss of residual fuel pressure after shutting off the engine...all it takes is one tiny leak from an injector, not closing completely...you'd never see it or smell it. If it was not doing this before changing the fuel filter (almost NEVER a needed change...waste of time, money and exposing an otherwise clean system), you may have introduced just enough dirt on the clean side of the filter to cause this...doesn't take much.

I'd start by putting a bottle of Techron (PROVEN: NOT ANY OTHER BRAND...USELESS) in 1/4 to 1/2 tank of gas...Then do it again on the next 1/4 to 1/2 tank. Many posted reports of this doing the trick...if it can be cleaned, this is the ONLY stuff that actually works.

If that doesn't work, you'll need to go deeper...pull injectors, test pressure regulator, check fuel pressure and pressure bleed-down, etc...

JoePGT5S

Are you suggesting a higher concentration than suggested on the bottle? What size of bottle have you used?

Thanks.

silverd2

YES, I am.

I put 12 ounces (12 gallon treatment) in about 1/4 to 1/3 tank (5-8 gallons)...NEVER more gas than that...Why dilute it any more?

You could fill your tank with pure Techron and if it would burn, it wouldn't hurt a thing....especially to treat an existing problem (not just preventive maint), diluting it too much will only render it ineffective.

The label instructions are to make it look better than it is...but read carefully >>> 12 ounces "Treats *UP TO* 12 gallons"...Translation: Put it in LESS than 12 gallons for more effectiveness...12 gallons would be the MAXIMUM dilution without rendering it ineffective.

I've used it in high concentration on all my cars (all present and a few past) with nothing but good results.

P.S. Whatever size bottle, I always try to put 2 ounces per gallon rather than the MINUMUM of 1 per gal.

"UP TO" >>>

d2audia8guy

Hello

Prior to changing the fuel filter I had been told by a German specialist that there was a problem with my fuel sending unit. About 4 months later the fuel pump died. I replaced the fuel filter prior to the pump in case it was clogged (it had never been replaced at 188k.) I wasn't having intermittent starting issues until I replaced the fuel pump. The car will drive perfectly and idles fine, although, the car immediately shut of out of nowhere a couple times while in traffic. She starts back up no problems. What's weird is that no start issue only happens when it sits over night and loses compression? Possible fuel regular bad?? Also I recently used two bottles of "liqui moly" to clean out fuel injectors....I will get pressure tested....one last thing...when I replaced the fuel filter I accidentally cut the line...had the line repaired using a "stint"...tested for leaks....any other ideas??

JoePGT5S

Thanks for clarifying. I got excited when I read this thread and put a 20 ounce bottle in a full tank (23 gals). Next time around I'll definitely try at a higher concentration. In my case it's just preventative maintenance. Always good to hear that someone with the same car has had success with a particular brand of magic-in-a-bottle. You had me add ATP AT-205 to my Amazon wish list as well :-)

d2audia8guy

Would you recommend a leak down test?

d2audia8guy

I was able to get the car to start and let it idle. After idling for about 5 minutes the engine started shaking and sputtering. I revved the engine and when I hit the gas it chokes, when I let go of the gas it revs to higher rpms but returns to rough idle. I went to listen to the new fuel pump and it was making weird noises almost like it was malfunctioning..instead of having the quiet & constant buzzing noise... I'm going to pull my fuel sending unit back out and replace the entire unit...the pump is brand new so I can't imagine its actually malfunctioning....