S1 2.8 K-Jet, anybody had this problem before?
Discussion
I am afraid I have definitely fallen out with my S1 this time, 'she' is being a right b..... What is more it is the second year on a run I have missed Glen's Barn farm run and I really love that area.
I took her out for a run in the Yorkshire Dales last weekend, not running perfectly but nevertheless enjoying the day. The imperfect running however developed into a misfire which gradually got worse (despite roadside attempts at a 'fix') and we had to nurse her home. Bit short of time during the week but I tried all the usual things, and even got lunchtime use of a gas analyser. While we had the analyser in use it appeared that the mixture went weak and inconsistent at low air flow and that the K Jet air meter was 'fluttering'. By this time I was pretty frustrated so I decided we would run it with the air filter out and see if we could watch the meter.
I found that one of the mountings on the airbox had broken and it had clearly been vibrating a bit, although not exactly 'loose'. I took the filter off to find a loose metal plate, the remains of an aluminium rivet and plenty of dust! The air valve, which has to be so precisely weighted and clean, was covered in muck! The filter however was clean and fitting correctly.
Are all our air boxes the same? Mine has (or had!)a steel plate rivetted to the back for some reason. It is held in with 5 x 3/16 pop rivets. All 5 had broken, and 3 had fallen out completely leaving 3 x 3/16 holes between the air filter and the air meter! A neat bypass of the air filter. Presumably several bits of rivet have found their way through the engine as well!
I should have taken a pic 'as found' but this pic shows the plate out of the air box, cleaned ready for reassembly.
Examining the rest of the air intake, there was plenty of dust throughout and the throttle butterfly was surrounded in a build up of gummy muck and probably wasnt working properly. I think I had better remove the plenum and the vacuum system and clean those as well. Having removed and cleaned the air meter valve in petrol I am a bit concerned that there might be some damage so I will have to get an expert to look at that...if I can find one! Anybody know a K-Jet expert within reasonable distance of Preston?
Does anybody have an airbox I could buy? Apart from the one mounting that has broken off it looks like another is well on its way.
B.....y cars!
I took her out for a run in the Yorkshire Dales last weekend, not running perfectly but nevertheless enjoying the day. The imperfect running however developed into a misfire which gradually got worse (despite roadside attempts at a 'fix') and we had to nurse her home. Bit short of time during the week but I tried all the usual things, and even got lunchtime use of a gas analyser. While we had the analyser in use it appeared that the mixture went weak and inconsistent at low air flow and that the K Jet air meter was 'fluttering'. By this time I was pretty frustrated so I decided we would run it with the air filter out and see if we could watch the meter.
I found that one of the mountings on the airbox had broken and it had clearly been vibrating a bit, although not exactly 'loose'. I took the filter off to find a loose metal plate, the remains of an aluminium rivet and plenty of dust! The air valve, which has to be so precisely weighted and clean, was covered in muck! The filter however was clean and fitting correctly.
Are all our air boxes the same? Mine has (or had!)a steel plate rivetted to the back for some reason. It is held in with 5 x 3/16 pop rivets. All 5 had broken, and 3 had fallen out completely leaving 3 x 3/16 holes between the air filter and the air meter! A neat bypass of the air filter. Presumably several bits of rivet have found their way through the engine as well!
I should have taken a pic 'as found' but this pic shows the plate out of the air box, cleaned ready for reassembly.
Examining the rest of the air intake, there was plenty of dust throughout and the throttle butterfly was surrounded in a build up of gummy muck and probably wasnt working properly. I think I had better remove the plenum and the vacuum system and clean those as well. Having removed and cleaned the air meter valve in petrol I am a bit concerned that there might be some damage so I will have to get an expert to look at that...if I can find one! Anybody know a K-Jet expert within reasonable distance of Preston?
Does anybody have an airbox I could buy? Apart from the one mounting that has broken off it looks like another is well on its way.
B.....y cars!
It is a lug on the plastic case which has broken off and I do not want to drill any more holes in the case if I can avoid it. I might have a go at plastic welding a threaded plastic block onto it.
Thanks David, I was not aware of that firm in Haydock and I will certainly follow up that lead.
Thanks David, I was not aware of that firm in Haydock and I will certainly follow up that lead.
hi guys I have been having similar issues with my S and I cannot get to the bottom off it its been going on for about 12 months now and prob like you its beginning to annoy me now I have done all the usual stuff and I have give the flow meter a good clean etc but no better I have checked all the air/vacuum pipes for leaks but cannot find anything , it runs fine when you boot it but when your cruising so to speak at various speeds it sort off hesitates pos misfire just not smooth running is this a similar issue to your problem ? I would be grateful if you come up with any more ideas I could try or the root off the cause .
thanks Dave
thanks Dave
Just a thought. On the 2.8 there is a mechanical advance/retard that is vacuum operated. I have had the diaphragm go, so the vacuum doesn't work. That would explain why it ticks over fine, but stutters under acceleration. It is easy to test. Unscrew the vacuum advance/retard unit from the dizzy housing and when you run the engine and increase the revs, you should see the plunger go in.
Hi DaveLynch, yes, the problem sounds exactly the same and like you it has been bugging me for some time. It will tick over fine and accelerate very (!) nicely but it will not run smoothly on a steady throttle irrespective of the speed.
I can see why the vacuum might be an issue, thanks for that suggestion David. The vacuum AR does seem to work but it occurs to me that if there was any fault elsewhere in the vacuum system it might not work properly at the relatively small vacuum changes that would occur at steady speed, but might work OK at high vacuum?
I dont think the air box problem could affect vacuum as it is upstream of the throttle, so it might be another red herring I just have to eliminate.
Glenrobbos S1 seems to have gone very well on the Eurotrip, perhaps we ought to impound it and dismantle it to find out why it properly! (Sorry Glen, just jealous that you can actually ENJOY yours!)
I can see why the vacuum might be an issue, thanks for that suggestion David. The vacuum AR does seem to work but it occurs to me that if there was any fault elsewhere in the vacuum system it might not work properly at the relatively small vacuum changes that would occur at steady speed, but might work OK at high vacuum?
I dont think the air box problem could affect vacuum as it is upstream of the throttle, so it might be another red herring I just have to eliminate.
Glenrobbos S1 seems to have gone very well on the Eurotrip, perhaps we ought to impound it and dismantle it to find out why it properly! (Sorry Glen, just jealous that you can actually ENJOY yours!)
Various other cars run this system - although 4 cylinder the golf does.
This system just squirts fuel in all the time to all cylinders, its how much fuel that varies in more of an analogue style as opposed to the 2.9 with solenoid injectors.
This might be worth a look
http://www.golfgtiforum.co.uk/index.php?topic=1787...
I know there was a piece in practical classics a while back when they put a 5 litre V8 from a big merc in an older smaller merc, they sent the fuel distributor away to be reconditioned - it might be worth a call to them to try and find out where it was sent. I'll have a look through my magazines to see if I still have it but I'm currently having a clear out to move house so it may have already gone.
This system just squirts fuel in all the time to all cylinders, its how much fuel that varies in more of an analogue style as opposed to the 2.9 with solenoid injectors.
This might be worth a look
http://www.golfgtiforum.co.uk/index.php?topic=1787...
I know there was a piece in practical classics a while back when they put a 5 litre V8 from a big merc in an older smaller merc, they sent the fuel distributor away to be reconditioned - it might be worth a call to them to try and find out where it was sent. I'll have a look through my magazines to see if I still have it but I'm currently having a clear out to move house so it may have already gone.
Hi Chris, there was a good link on that site you suggested for a firm who recondition K-Jet parts, they are new to me and look like a good resource. I haven't been on to them yet about costs but I thought I would just record the link here as it is almost certain to be of use to some of us S1 owners.
http://www.kmipetrolinjection.co.uk/Bosch%20K-Jetr...
http://www.kmipetrolinjection.co.uk/Bosch%20K-Jetr...
On the S1, it's all about the fuel pressures in the system, specifically the pump pressure and control pressure. If these are off, your air/fuel ratio will be off and your car will run like carp. At idle, the mixture can be adjusted with a 3mm Allen key, but at any other RPM, the control pressure is the determining factor. You can check with a gauge set, or take it to a pro. It is tedious to check and more tedious to adjust if it is out of spec.
On my S1 I had power problems that would clear up if I removed and pinched the vacuum hose from the warm-up regulator. This was confusing, but it pointed towards control pressure, so I adjusted to make it run richer and it improved a lot. I can explain more if you like, but I never used pressure gauges because I have a wideband O2 sensor that I used to get the mixture right.
I'm assuming you've got good ignition parts and your timing is right, BTW.
Cheers,
David
On my S1 I had power problems that would clear up if I removed and pinched the vacuum hose from the warm-up regulator. This was confusing, but it pointed towards control pressure, so I adjusted to make it run richer and it improved a lot. I can explain more if you like, but I never used pressure gauges because I have a wideband O2 sensor that I used to get the mixture right.
I'm assuming you've got good ignition parts and your timing is right, BTW.
Cheers,
David
Thanks Loach1, Interesting one about pinching the vacuum hose from the warm up regulator, I will check that out when she is running again. I wonder why we have that vacuum connection to the warm up regulator, it isnt there on all K-jet installations?
The ignition hasnt shown any issues on a diagnostic check, and the plugs came out a uniform, dry, chocolate colour. The exhaust gas analysis was in the right order but was fluctuating and we could not get a consistent reading.
When I have done the other jobs that I might as well do with the air system all stripped off, I am now going to arrange with a local garage for a fuel pressure test. I understand what you mean about why fuel pressure is so critical on the K-Jet.
I have had a lot of trouble with rust in the fuel and have been running a high spec Sytek in line fuel filter for some time. I have had the fuel tank renovated during the winter and the car has done very few miles since. It does occur to me that any particles that got into the pump despite the filter might have reduced its efficiency enough to drop the pressure sufficiently.
The ignition hasnt shown any issues on a diagnostic check, and the plugs came out a uniform, dry, chocolate colour. The exhaust gas analysis was in the right order but was fluctuating and we could not get a consistent reading.
When I have done the other jobs that I might as well do with the air system all stripped off, I am now going to arrange with a local garage for a fuel pressure test. I understand what you mean about why fuel pressure is so critical on the K-Jet.
I have had a lot of trouble with rust in the fuel and have been running a high spec Sytek in line fuel filter for some time. I have had the fuel tank renovated during the winter and the car has done very few miles since. It does occur to me that any particles that got into the pump despite the filter might have reduced its efficiency enough to drop the pressure sufficiently.
greymrj said:
Thanks Loach1, Interesting one about pinching the vacuum hose from the warm up regulator, I will check that out when she is running again. I wonder why we have that vacuum connection to the warm up regulator, it isnt there on all K-jet installations?
The ignition hasnt shown any issues on a diagnostic check, and the plugs came out a uniform, dry, chocolate colour. The exhaust gas analysis was in the right order but was fluctuating and we could not get a consistent reading.
When I have done the other jobs that I might as well do with the air system all stripped off, I am now going to arrange with a local garage for a fuel pressure test. I understand what you mean about why fuel pressure is so critical on the K-Jet.
I have had a lot of trouble with rust in the fuel and have been running a high spec Sytek in line fuel filter for some time. I have had the fuel tank renovated during the winter and the car has done very few miles since. It does occur to me that any particles that got into the pump despite the filter might have reduced its efficiency enough to drop the pressure sufficiently.
The vacuum line on the S1 warm-up regulator is to improve throttle response. When there is a drop in vacuum, the control pressure decreases allowing the fuel plunger to move up, richening the mixture. It's a sporty car thing I guess.The ignition hasnt shown any issues on a diagnostic check, and the plugs came out a uniform, dry, chocolate colour. The exhaust gas analysis was in the right order but was fluctuating and we could not get a consistent reading.
When I have done the other jobs that I might as well do with the air system all stripped off, I am now going to arrange with a local garage for a fuel pressure test. I understand what you mean about why fuel pressure is so critical on the K-Jet.
I have had a lot of trouble with rust in the fuel and have been running a high spec Sytek in line fuel filter for some time. I have had the fuel tank renovated during the winter and the car has done very few miles since. It does occur to me that any particles that got into the pump despite the filter might have reduced its efficiency enough to drop the pressure sufficiently.
A simple check/fix is to check the strainer on the inlet of the warm-up regulator. Remove the banjo fitting and you should see a small gauze filter, possibly with some trash caught in it. This will increase control pressure, leaning up the mixture.
When you get fuel pressure checked, make sure the mechanic knows the specs for delivery pressure and cold/warm control pressure on the Capri 2.8i. Delivery pressure is easy to check, but it's not as critical as the control pressure or the pressure after the regulator. Someone familiar with K-Jet will know all of this and how to adjust.
Your fuel filter should be after the fuel pump, but the tank should also have a strainer at the pick-up. If the strainer has failed, your fuel pump will have chewed through some rust and possibly lost performance. You'll know more after a pressure test...
The beauty of this system is that once adjusted correctly it will perform very well for years (apparently). It's a marvel of fluid dynamics and very well made.
Link
http://www.ebay.co.uk/itm/261375409928?ru=http%3A%...
Worth adding another specialist company to the list of K-Jet experts.
http://www.ebay.co.uk/itm/261375409928?ru=http%3A%...
Worth adding another specialist company to the list of K-Jet experts.
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