Advice please - CIS K-Jet issue

urquattr085 · 25-04-20, 02:24 PM

Hi all,

I'm looking for some advice from any K-Jet experts out there please. Apologies in advance, this may be a bit lengthy.

Here's my situation (1985 Ur quattro)......

The car has always run rich, heavily smells of fuel from the exhaust, the plugs and exhaust tips are black and it's known to foul the plugs easily.

I ran fuel pressure tests and got the following results :
System pressure 88psi (6.1 bar)
Cold Control Pressure 27 psi (1.9 bar)
Warm Control Pressure 62 psi (4.3 bar)

So, System Pressure is marginally high (84psi ideally) but the high warm Control Pressure (50-54psi would be normal) should mean the car runs lean.

I've adjusted System Pressure to the required 84psi (5.8 bar)
Then stripped, cleaned & rebuilt the warm up regulator with new seals.
Cold Control Pressure adjusted to 17psi (1.2bar)
Warm Control Pressure adjusted to 54 psi (3.7 bar)

Still running rich as I expected.

Warm Control Pressure increased to 64 psi and little changed.

I've checked the following already and all seem to be working ok :

Vacuum pipes (90% replaced 2 years ago)
One-way vacuum valve (blue&black near hydraulic reservoir)
Two-way electro-magnetic solenoid valve on bulkhead
Cold start valve & thermo switch
Auxiliary air valve
Warm up regulator heater strip
Control Pressure rises with engine temperature/time as expected
Residual fuel pressure holds well, 38psi after 20 minutes.

The car generally starts fine cold, ok when warm unless you don't catch it first time. Then can need lots of cranking.

The car does consume oil (most likely turbo seals) - could this be confusing the issue and causing the "richness" ?

Should I increase the control pressure further or is there potentially something other component or influencing factor I have missed ?

I'd really appreciate any thoughts on this issue.

Don't get me wrong, the car does run ok and is perfectly useable, but it's clearly not right and I would like to improve the situation.

Many thanks in advance.
Geoff

86audicoupe · 25-04-20, 02:41 PM

Hi Geoff

I don’t claim to be an expert on K-JET but my Coupe GT is displaying similar symptoms so thought I’d reply. I’ve replaced many parts in order to try and fix this issue.

My symptoms are: rough idle, stinking of fuel and a slight ‘miss’ on idle (although you’ve got to have a good ear!). It’s fine initially on a cold start but once it’s warmed up, the idle hunts. I have the same issue with cranking it over to start it when it’s up to temperature. I fitted a distributor (including hall sender with no improvement).

Other that these symptoms, the car drives very well, no flat spots and you wouldn’t know when you’re on the open road.

I’ve given the car to my friend who is a very good mechanic and he has diagnosed the issue as the injector seals. As I’m sure you’re aware, these engines with K-JET rely on everything to do with the air/fuel mixture being correct otherwise they get quite upset! The car is going in next week to have these changed, I will let you know how I get on and if I see a significant improvement. I’ll also be having the down pipe gasket changed as this is blowing which isn’t ideal for optimum running either.

Will

urquattr085 · 25-04-20, 03:18 PM

Cheers for that Will.

I'll be interested to hear how you get on with yours thanks.
I hadn't considered injector seals, but they will be old (last done 2011 at the earliest) and are on my mental list of jobs to do.

I'm not really getting the misfire or hunting, it idles quite smoothly, but I'll probably get a set on the way & fit them as a matter of good practice, not too big a job.

Good luck getting yours sorted and keep me posted.

Thanks for the input.

jimh · 25-04-20, 04:12 PM

http://www.sealtd.net/quattro/wr%20fuel.pdf

Mine was the thermo-pneumatic valve that the vacuum pipes go to on the side of the block.
I took it off, and dipped the end in hot water on the stove until it got hot enough to snap shut.
I tested it with a MityVac and although I could hear it snap shut, it still didn't hold vacuum. I blew some solvent cleaner though it and a small chunk of dirt came out.
I heated it again and it could then hold vacuum when shut.

urquattr085 · 25-04-20, 04:49 PM

Thanks Jim,

Not tested that yet.
I found that PDF from Seal.net the other day, very useful :tup :

It did show me that my 2 vacuum hoses on this thermo-pneumatic valve were the wrong way round !
Correcting them didn't seem to make any difference so definitely worth a check tomorrow.

Cheers for contributing

Colin Aitchison · 25-04-20, 05:30 PM

Hi, not much to add, but if the engine is running rich you need to look at your engine oil to make sure it is not more petrol than oil, if the engine has been running like this for some time change the engine oil it will contaminated with petrol.

urquattr085 · 25-04-20, 06:43 PM

Quote:

Originally Posted by Colin Aitchison

Hi, not much to add, but if the engine is running rich you need to look at your engine oil to make sure it is not more petrol than oil, if the engine has been running like this for some time change the engine oil it will contaminated with petrol.

Hi Colin.

Oil & filters were changed less than 500 miles ago, will likely do it again once resolved.
It does smell a little of fuel but is still quite clean & consistency seems ok.

Thanks for the advice

mikes2 · 25-04-20, 08:10 PM

what's the CO emissions like out the back ?

It may be the mixture could be adjusted

BackintheFold · 25-04-20, 11:14 PM

Quote:

Originally Posted by mikes2

what's the CO emissions like out the back ?

It may be the mixture could be adjusted

This is the first thought I had-could it be simply the mixture is badly adjusted?

vorsprung durch technik · 26-04-20, 12:08 AM

I don't think your alone with this issue Geof, yours and another member who has the same as your version quattro has the same problem.

There was a program last night comparing the Renault 5 turbo and Ur Quattro and the blue car ( MB engine? 10v anyway)
as it went round the corner on a country lane accelerated and out came the blue smoke.
I remember yours being very rich don't remember it being smokey though!

25-04-20, 02:41 PM	#2
86audicoupe Classic Audi Pervert! Classic Audi Club Member Join Date: Dec 2007 Location: Dorset Posts: 2,182	Hi Geoff I don’t claim to be an expert on K-JET but my Coupe GT is displaying similar symptoms so thought I’d reply. I’ve replaced many parts in order to try and fix this issue. My symptoms are: rough idle, stinking of fuel and a slight ‘miss’ on idle (although you’ve got to have a good ear!). It’s fine initially on a cold start but once it’s warmed up, the idle hunts. I have the same issue with cranking it over to start it when it’s up to temperature. I fitted a distributor (including hall sender with no improvement). Other that these symptoms, the car drives very well, no flat spots and you wouldn’t know when you’re on the open road. I’ve given the car to my friend who is a very good mechanic and he has diagnosed the issue as the injector seals. As I’m sure you’re aware, these engines with K-JET rely on everything to do with the air/fuel mixture being correct otherwise they get quite upset! The car is going in next week to have these changed, I will let you know how I get on and if I see a significant improvement. I’ll also be having the down pipe gasket changed as this is blowing which isn’t ideal for optimum running either. Will Last edited by 86audicoupe; 25-04-20 at 02:44 PM.

25-04-20, 03:18 PM	#3
urquattr085 Senior Member Classic Audi Club Member Join Date: May 2016 Location: Displaced Northerner in Essex Posts: 1,528	Cheers for that Will. I'll be interested to hear how you get on with yours thanks. I hadn't considered injector seals, but they will be old (last done 2011 at the earliest) and are on my mental list of jobs to do. I'm not really getting the misfire or hunting, it idles quite smoothly, but I'll probably get a set on the way & fit them as a matter of good practice, not too big a job. Good luck getting yours sorted and keep me posted. Thanks for the input. __________________ 1985 WR quattro 2010 A6 3.0Tdi Allroad 2010 A3 1.4 tfsi Sport - Sold but still in the family 1984 80 Quattro - Sold many moons ago 1981 Coupe GT - Sold to buy above

25-04-20, 04:49 PM	#5
urquattr085 Senior Member Classic Audi Club Member Join Date: May 2016 Location: Displaced Northerner in Essex Posts: 1,528	Thanks Jim, Not tested that yet. I found that PDF from Seal.net the other day, very useful :tup : It did show me that my 2 vacuum hoses on this thermo-pneumatic valve were the wrong way round ! Correcting them didn't seem to make any difference so definitely worth a check tomorrow. Cheers for contributing __________________ 1985 WR quattro 2010 A6 3.0Tdi Allroad 2010 A3 1.4 tfsi Sport - Sold but still in the family 1984 80 Quattro - Sold many moons ago 1981 Coupe GT - Sold to buy above

25-04-20, 08:10 PM	#8
mikes2 4 ring whore! Classic Audi Club Member Join Date: Nov 2007 Location: Polmont Posts: 2,617	what's the CO emissions like out the back ? It may be the mixture could be adjusted __________________ 1991 90 quattro 20v sport 1991 90 quattro

25-04-20, 04:12 PM	#4
jimh Grown up member Classic Audi Club Member Join Date: Dec 2008 Posts: 122	http://www.sealtd.net/quattro/wr%20fuel.pdf Mine was the thermo-pneumatic valve that the vacuum pipes go to on the side of the block. I took it off, and dipped the end in hot water on the stove until it got hot enough to snap shut. I tested it with a MityVac and although I could hear it snap shut, it still didn't hold vacuum. I blew some solvent cleaner though it and a small chunk of dirt came out. I heated it again and it could then hold vacuum when shut.

25-04-20, 05:30 PM	#6
Colin Aitchison Senior Member Classic Audi Club Member Join Date: Dec 2013 Location: Back home in Tillicoultry Posts: 1,309	Hi, not much to add, but if the engine is running rich you need to look at your engine oil to make sure it is not more petrol than oil, if the engine has been running like this for some time change the engine oil it will contaminated with petrol.

26-04-20, 12:08 AM	#10
vorsprung durch technik 4 ring whore! Classic Audi Club Member Join Date: Feb 2014 Location: Near Watford. Posts: 7,753	I don't think your alone with this issue Geof, yours and another member who has the same as your version quattro has the same problem. There was a program last night comparing the Renault 5 turbo and Ur Quattro and the blue car ( MB engine? 10v anyway) as it went round the corner on a country lane accelerated and out came the blue smoke. I remember yours being very rich don't remember it being smokey though!