'86 5K TQ don't want to start after air and fuel filter change

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Hi,
My '86 5K TQ don't want to start after an air and fuel filter change. I did get it started twice by cranking but as soon as it starts up it will die if I don't hold the gas. It drives great but dies upon
attempting to idle. It starts no problem when the car is moving and is put in gear. What could be the problem? Could it be air in the system? What is the fuel filter change procedure, does the system have to be bled afterwards? Also, before I touched the car today, when turning off the car when the engine is warm, the car won't start again for 5-8 minutes, after that it starts no problem. Though it never has any problems starting when the car is moving and is put in gear. Cold starts are immediate, though not anymore of course.
Thank you in advance for any help! cp
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It sounds like you have a vacuum leak.
Or, you may have disconnected the wires to the throttle body for the switch that controls the ISV.
No special bleeding procedure for filter changes.
Tony Current: 98.5 A4 1.8TQM Previous: four T44s '84 - '91
cp wrote:

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Vacuum leak? Are there any other tell-tale symptoms I should look for? Today, after getting back from a trip (in another car) I went to start it up after letting it sit for a couple of days and it started right up, idled fine and the problem started again a couple of minutes later.

You know, I might have nudged something. Will take a look at the factory manual what it could be.
Thank you!
cp
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Here's a Q&D vacuum leak test:
- engine idling - remove oil dipstick - engine should stumble and run poorly. Replace dipstick. - open oil filler cap - engine should die
If these conditions do not occur you have a vacuum leak that is either intermittent or being compensated for by other adjustments and needs to be coppected.
Damn, these Audi's are so much fun :-)
cp wrote:

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Ah, so this is normal, I was wondering why the car would die when the oil filler cap was removed.
My mechanic friend however checked it out and said that the fuel pump is bad, says fuel stops coming from the (losened) fuel filter connection before the car dies, ahhhhhhhhh I don't want to waste money on this!! What's a good place to get a fuel pump assembly? Here in Canada the fuel pickup, fuel pump and wire harness costs about $350USD, can't I just get the fuel pump?
cp
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Shokan usually has a $125 US fuel pump special on ebay. The pump is Pierburg and is good. I used one in a '91 100qm. Quiet and works. What more can one ask for.
Shokan increases the price if you order on the phone. Gotta use ebay. Not sure how that would work shipping to Canada.
cp wrote:

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hmmmmmm but don't I need the whole assembly with it? (fuel pick up and wires)
cp

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cp, No, you just need the pump. The wires just bolt on. There's lots written up on Audifans and (probably) Audiworld about replacing the pump - most important thing, aside from the warnings about gas fumes being dangerous/explosive/etc.etc. is that you make sure that the orientation of the connections to the pump remain unchanged - otherwise your gas gauge will stop reading when the float arm hangs up on the wires/hose. BTDT numerous times - I gave up. Cheers! Steve Sears 1987 Audi 5kTQ - fuel gauge won't read the last 1/8th of a tank 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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Hi Steve!
Always good to hear from you!
Well, my mechanic friend took a look at the car today and says that the fuel pump works fine. He took off the fuel pressure accumulator and a load of RUST came out (why is a "fuel pressure accumulator" needed?? (Couldn't they build up fuel pressure by activating the fuel pump before ignition?). Should I flush out the gas tank? Supposedly, if the "fuel pressure accumulator" was the problem then I would have trouble starting the car up after it's been sitting over night, but the car starts fine, idles OK for a couple of minutes and then dies. And THEN I have trouble starting it, though it starts no problem when thrown into gear when the car is moving. Any idear what this could be?
Thank you!
cp

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Sounds like you have a problem with the coating on the inside of the fuel tank falling off and clogging the fuel pump's intake screen. Common problem for pre '90 T44s
Check history on Audiworld T44 forum for correction: http://forums.audiworld.com/v8 /
The recommended Audi fix is to cut off the intake screen from the fuel pump and then replace the fuel filter.
cp wrote:

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Yeh, I was thinking of flushing the tank (with my mechanic friend's help of course). Is there only one filter?
Also, what could possibly go wrong with a fuel accumulator? Isn't that a relatively simple part?
Thank you Tony for your help!
cp
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Flushing tank is fine but the pealing crud will continue so cutting the screen from the fuel pump is important. Once that is done the crud will be trapped by the fuel filter in engine compartment (on Passenger side fender). You will need to change the filter more often as a result.
If the fuel accumulator check valve goes bad then you will need to crank the starter for a longer time when starting to build pressure. I am not sure but if the accumulator is completely non-functional you may have a no-start condition result.
May want to check history at Audiworld on that.
Good luck.
cp wrote:

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Yeh, took care of that.

Well, we bypassed the fuel accumulator and haven't noticed anything different, BUT the problem is SOLVED, turns out the hose from the air cleaner to the intake was severed, now there's no problem at all. It starts fine any time and idles fine. Whew! Glad I didn't have to replace anything, what a learning experience, I think I'll understand the whole fuel process soon! :-)
cp
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cp, Good to hear that you solved the problem. You might want to check all the underhood hoses for leaks as well - heat and rubber don't really get along too well. One method for checking for leaks is to make a cap for the intake, and then get a regulator and supply compressed air at a pressure at or slightly below the max boost pressure the ECU transducer will allow (say, at 1.6 bar - sorry for the units) and then listen for leaks - or have some real fun, and dump a bucket of soapy water on the engine compartment and look for bubbles - kids enjoy this method and it makes car diagnosis fun for the whole family ;-) The accumulator is, in essence, a pressure tank for the fuel system, you may liken it to a device that deals with water hammer in pipes. Although I have never dissected one, I did replace the one in my 5ktq once and it sounds like there's a large spring in there. My guess is that it cushions the pump from the rapid changes in fuel delivery. I do believe that the check valve Tony is referring to is mounted just above the pump in the tank. Good luck on understanding the fuel process.....if you really get into it, you'll realize why some have ditched the whole CIS stuff and gone with things like 034EFI and such. Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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Hi Steve!
Thank you for the info, I'll try the other diagnostics! :-)
So what's special about this CIS or 034EFI thing?
cp

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cp, CIS is what your car has now - Continuous Injection System - the injectors are open and constantly spraying, at variable rates depending on the amount of air flowing into the engine measured by the air plate - as the plate rises, there is more air flowing thru and the distributor increases the pressure to the injectors, increasing flow. The problem is that the metering plate system has a limit to the amount of air that can be measured, and so things like Mass Airflow Sensors will do a better job at measuring larger flows of air. If you look at the amount of equipment that can be replaced with, essentially, a MAF, well let's say that a big chunk of the passenger side of the engine bay is opened up, that can be filled with, say, a massive hybrid turbocharger. To see what Javad has done with the development of his Audi 80 Turbo Quattro with 034EFI (Electronic Fuel Injection - I do believe that the 034 is an Audi-ism - aka a part number prefix) - there's also Megasquirt, etc. You can find some talk on different systems on Motorgeek.com Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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ahhhhhhh! Thank you for the info, all that junk is making me love my 1966 Heckflosse benz even more! Still, for a 20 year old car, the audi IS amazing, what besides super cars could have compared to it 20 years ago? I have a review of the TQ and other cars in it's class from 20 years back and it just blows the others away. It's looks were definitely years ahead, even today it looks like a recent car, as compared to a mercedes or bmw or honda of the same vintage. Still, nothing like a good ol' benz.
cp

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Steve, is it worth it to get the K&N filter? I don't care about performance, it's got more than I need but I do a bit of mountain driving and if it helps the car breath easier....
cp
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cp, I have a K&N protecting my garage shelf from dust - it does a wonderful job at that. I had it in my 5ktq, and my 5k before that, and noticed little perf. increase, other than making the whine from the turbo more noticable (5ktq), but when I removed the filter I noticed that the metering plate and all plumbing back of the filter were coated in a thin film of oil and dirt. People with MAF's have reported that the heated wire MAF's tend to fail due to oil&dirt accumulation while using K&Ns. Someone on Audifans once posted a study conducted by a company concerned with keeping crucial computers running (think - in bunkers?)....they concluded that paper was better than air/oil. Stick with the cheap paper filters and change them regularly. Cheers! Steve Sears 1987 Audi 5kTQ - paper filter keeping dust out 1980 Audi 5k - paper filter keeping dust out 1962 and '64 Auto Union DKW Junior deLuxes - wire mesh and oil filter keeping pterodactyls out (SPAM Blocker NOTE: Remove SHOES to reply)

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:-)
hmmmmm... well.... if you've got a paypal account and the filter is good, send it over!
cp

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