Bosch K Jetronic rebuild specialists (2.8 engine)
Discussion
v8s4me said:
Might have been KMI
I got a quote from KMI.......!!! 
Nearly fell off my perch! 
That is a lot of pension! 
The quote was almost 2.5 x what it cost to have two heads reconditioned (12 valves and seats refaced and ground, face to block skimmed, all four exhaust port flanges refaced, all ports cleaned out).There must be competition somewhere?
Knowledge on this system seems to vaporate quickly.
So pity if these cars can't drive as they should. The TVR is not an exception.
A friend of mine faced KJet troubles when he bought a Ferrari. Together we took the challenge to understand the system from inside-out. The real fine details of the system are not in the manuals.Then we developed our own testing and calibration methods. Crazy how some hobby can deviate, but after a couple of years we provide the best Porsche and Ferrari specialists our testing, calibration and rebuild services. Just pm me if you need some advice. (or google "bart mulder marktplaats")
regards, Bart
So pity if these cars can't drive as they should. The TVR is not an exception.
A friend of mine faced KJet troubles when he bought a Ferrari. Together we took the challenge to understand the system from inside-out. The real fine details of the system are not in the manuals.Then we developed our own testing and calibration methods. Crazy how some hobby can deviate, but after a couple of years we provide the best Porsche and Ferrari specialists our testing, calibration and rebuild services. Just pm me if you need some advice. (or google "bart mulder marktplaats")
regards, Bart
streetscreamer said:
Knowledge on this system seems to vaporate quickly.
So pity if these cars can't drive as they should. The TVR is not an exception.
A friend of mine faced KJet troubles when he bought a Ferrari. Together we took the challenge to understand the system from inside-out. The real fine details of the system are not in the manuals.Then we developed our own testing and calibration methods. Crazy how some hobby can deviate, but after a couple of years we provide the best Porsche and Ferrari specialists our testing, calibration and rebuild services. Just pm me if you need some advice. (or google "bart mulder marktplaats")
regards, Bart
Hi Bart,So pity if these cars can't drive as they should. The TVR is not an exception.
A friend of mine faced KJet troubles when he bought a Ferrari. Together we took the challenge to understand the system from inside-out. The real fine details of the system are not in the manuals.Then we developed our own testing and calibration methods. Crazy how some hobby can deviate, but after a couple of years we provide the best Porsche and Ferrari specialists our testing, calibration and rebuild services. Just pm me if you need some advice. (or google "bart mulder marktplaats")
regards, Bart
Wondering if you are still around ? I have some issues with a k-jet on a 924 race car and would be great to connect!
This guy is supposed to know his stuff on Cologne Engines.
Ric Wood Motorsport in Stockport (near Manchester).
https://ricwood.com/
Ric Wood Motorsport in Stockport (near Manchester).
https://ricwood.com/
I seem to have a slight misfire/hesitation under acceleration at about 2,000 to 2,500 RPM, whilst going up hill. The engine has had a full service, fuel pump and new cylinder heads, so everything should be working correctly regarding flow, I don't suppose anyone might know a garage or specialist in the midlands that knows what to do with the 2.8 Cologne?
Vsix and Vtec said:
I seem to have a slight misfire/hesitation under acceleration at about 2,000 to 2,500 RPM, whilst going up hill. .......
How can you be sure the problem isn't electrical or ignition timing? Have you used a timing light to check the advance is working smoothly?Vsix and Vtec said:
... The engine has had a full service, fuel pump and new cylinder heads, so everything should be working correctly regarding flow, .....
Don't count on it.Vsix and Vtec said:
... I don't suppose anyone might know a garage or specialist in the midlands that knows what to do with the 2.8 Cologne?
Beware of "specialists" 
v8s4me said:
Beware of "specialists"
My hunch is that it's something to do with the vacuum advance/retard function, as the car is perfectly well behaved at 2,000 or lower. it's just that it pulls sweetly from rest, right up until it hits either a hill or 2,500 (or both) and then microstutters its way onwards until i back the throttle off. Regrettably, although I have this hunch, I lack the kit to prove or further diagnose it, which is why I figured a K-Jet experienced company might be the safer bet than me throwing money at random fuel injection components.K-Jetronic can become really expensive when you ask the specialists to refurb any parts.
lots of so called specialists will change items, no matter if it would have been really necessary.
forums are full of reports with k-jetronics not running well...and the so called specalists will sell you new parts and at the end of the day it was something completely else.
i have gone through this several times when i still was not so skilled about the k-jetronic ... some experts told me "its the metering head, its the fuel-pump, its the fuel-pump relais....its, its, its...."
at the end of the day it was ALWAYS something simple which in most cases cost hardly anything.
the k-jetronic is an easy and simple thing....you only need to sit down, read the instrcutions and try to understand the rather un-complex system.
b4 i would invest in an expensive overhaul, i would convert to carbs.
lots of so called specialists will change items, no matter if it would have been really necessary.
forums are full of reports with k-jetronics not running well...and the so called specalists will sell you new parts and at the end of the day it was something completely else.
i have gone through this several times when i still was not so skilled about the k-jetronic ... some experts told me "its the metering head, its the fuel-pump, its the fuel-pump relais....its, its, its...."
at the end of the day it was ALWAYS something simple which in most cases cost hardly anything.
the k-jetronic is an easy and simple thing....you only need to sit down, read the instrcutions and try to understand the rather un-complex system.
b4 i would invest in an expensive overhaul, i would convert to carbs.
Edited by LLantrisant on Monday 30th January 12:55
LLantrisant said:
....the k-jetronic is an easy and simple thing....you only need to sit down, read the instructions and try to understand the rather un-complex system. b4 i would invest in an expensive overhaul, i would convert to carbs......
Agreed! 
I bought a carb and manifold for the Tasmin with the intention of converting because I'd heard the K-Jetronic was troublesome. The reality is that the system is completely bullet proof and easy to tune by adjusting the air flap in accordance with the instructions mentioned previously. With a little bit of practice it wasn't at all difficult to get the engine running very smoothly.
Despite the "Jetronic" tag it's a fundamentally mechanical system so if it works leave it alone, especially the metering head. The hot start thingy can cause problems but once again it's an easy fix.
Check out all the electrics and timing before fiddling with the fuel injection. But do check for air leaks.
Edited by v8s4me on Monday 30th January 13:38
v8s4me said:
Agreed!
I bought a carb and manifold for the Tasmin with the intention of converting because I'd heard the K-Jetronic was troublesome. The reality is that the system is completely bullet proof and easy to tune by adjusting the air flap in accordance with the instructions mentioned previously. With a little bit of practice it wasn't at all difficult to get the engine running very smoothly.
Despite the "Jetronic" tag it's a fundamentally mechanical system so if it works leave it alone, especially the metering head. The hot start thingy can cause problems but once again it's an easy fix.
Check out all the electrics and timing before fiddling with the fuel injection. But do check for air leaks.
Having done my best to diagnose via Google, it does seem the reoccurring theme is "K-Jet is bombproof 99% of the time" so I'm more than happy to spend a bit more (already spent 4k in total so a bit more won't hurt). I bought a carb and manifold for the Tasmin with the intention of converting because I'd heard the K-Jetronic was troublesome. The reality is that the system is completely bullet proof and easy to tune by adjusting the air flap in accordance with the instructions mentioned previously. With a little bit of practice it wasn't at all difficult to get the engine running very smoothly.
Despite the "Jetronic" tag it's a fundamentally mechanical system so if it works leave it alone, especially the metering head. The hot start thingy can cause problems but once again it's an easy fix.
Check out all the electrics and timing before fiddling with the fuel injection. But do check for air leaks.
Edited by v8s4me on Monday 30th January 13:38
I think I'll have to put it back into the garage where it was, and see what they say.
I wouldn't say the K Jetronic is bulletproof, it is old now and some parts will have deteriorated but, once sorted, it works very well indeed. I have had a 2.8 on K Jet for about 15 years now.
Lots has been written about the KJet. Impossible to diagnose via google but I will put a few notes down for anyone with a K Jet on their S.
1. Before touching anything try to understand how it works. The basic operation is very simple and in some ways more like a carb remote from the engine. If you cannot work out how it works then only do the most basics, trail and error is a sure way to get you tearing your hair out and bank balance dropping.
2. There is a mixture adjustment on the fuel metering head. DO NOT TOUCH IT!! If it isn't running right it is highly unlikely that the fuel metering needs adjustment. You have to find what is CAUSING the change, it will lie elsewhere. The problem that arises if you DO touch the metering, when you do find the real problem you will have a devil of a job getting the metering spot on, even if you do have access to a sophisticated gas analyser.
3 By far the most common problems are caused by air leaks, anywhere downstream of the air filter. Yes the filter! The first place to look is the airbox mountings, they are pop rivetted on. Age and corrosion, the rivets become loose or drop off, dusty air is drawn in behind the filter, dust onto the air meter changes the balance and dust affects the smoothness of operation. Seen one with a crack where it has been flexing after 2 rivets had gone. Next place to look is the air meter cover, that big 'rubber' think, they spilt underneath usually where the air leaves the meter into the pipe to the throttle. Causes some interesting effects! Sudden changes in mixture as the car accelerates as the split opens mechanically! Next is the pipe to the throttle body, is it sealed well to the air meter cover? Has the pipe itself deteriorated enough to allow air in? Is it sealed well to the throttle body? Remember the mixture metering is controlled by airflow past the air meter, if air is getting in ANYWHERE after the meter the engine will draw that air rather than through the meter and you automatically get a weak mixture.
The effects are particularly pronounced at low revs under load. If the car is hunting at low revs say in traffic, sometimes even giving that 'kangaroo' effect, then what is most likely to be happening is the air meter flap is actually 'fluttering'. Air is getting in after the meter, at low demand the air flap doesn't open, engine starts to stall, you open throttle, air flap opens suddenly and increases fuel, engine revs rise, more air leak is sucked in, goes weak, engine revs drop, air flap drops and so on.
At higher revs the demand is higher than the leak can provide so the air flap stays open, the engine runs far better but it is running weak and power is well down.
Any of this sound familiar?
4. get a garage to check the fuel pressure, if they still have the meter to test as relatively low pressures. Test at the pipe to the 7th injector into the plenum chamber, that pipe should be live all the time. Before the blue switch. Turn engine on and test. Do it a couple of times preferably at different times. Does it read the same every time. If not then suspect a problem with the regulator front passenger side of the plenum, it is fr more likely to be that than the meter head.
Run out of time for now!!
Lots has been written about the KJet. Impossible to diagnose via google but I will put a few notes down for anyone with a K Jet on their S.
1. Before touching anything try to understand how it works. The basic operation is very simple and in some ways more like a carb remote from the engine. If you cannot work out how it works then only do the most basics, trail and error is a sure way to get you tearing your hair out and bank balance dropping.
2. There is a mixture adjustment on the fuel metering head. DO NOT TOUCH IT!! If it isn't running right it is highly unlikely that the fuel metering needs adjustment. You have to find what is CAUSING the change, it will lie elsewhere. The problem that arises if you DO touch the metering, when you do find the real problem you will have a devil of a job getting the metering spot on, even if you do have access to a sophisticated gas analyser.
3 By far the most common problems are caused by air leaks, anywhere downstream of the air filter. Yes the filter! The first place to look is the airbox mountings, they are pop rivetted on. Age and corrosion, the rivets become loose or drop off, dusty air is drawn in behind the filter, dust onto the air meter changes the balance and dust affects the smoothness of operation. Seen one with a crack where it has been flexing after 2 rivets had gone. Next place to look is the air meter cover, that big 'rubber' think, they spilt underneath usually where the air leaves the meter into the pipe to the throttle. Causes some interesting effects! Sudden changes in mixture as the car accelerates as the split opens mechanically! Next is the pipe to the throttle body, is it sealed well to the air meter cover? Has the pipe itself deteriorated enough to allow air in? Is it sealed well to the throttle body? Remember the mixture metering is controlled by airflow past the air meter, if air is getting in ANYWHERE after the meter the engine will draw that air rather than through the meter and you automatically get a weak mixture.
The effects are particularly pronounced at low revs under load. If the car is hunting at low revs say in traffic, sometimes even giving that 'kangaroo' effect, then what is most likely to be happening is the air meter flap is actually 'fluttering'. Air is getting in after the meter, at low demand the air flap doesn't open, engine starts to stall, you open throttle, air flap opens suddenly and increases fuel, engine revs rise, more air leak is sucked in, goes weak, engine revs drop, air flap drops and so on.
At higher revs the demand is higher than the leak can provide so the air flap stays open, the engine runs far better but it is running weak and power is well down.
Any of this sound familiar?
4. get a garage to check the fuel pressure, if they still have the meter to test as relatively low pressures. Test at the pipe to the 7th injector into the plenum chamber, that pipe should be live all the time. Before the blue switch. Turn engine on and test. Do it a couple of times preferably at different times. Does it read the same every time. If not then suspect a problem with the regulator front passenger side of the plenum, it is fr more likely to be that than the meter head.
Run out of time for now!!
Thanks for your time, the garage haven't spoken with me recently but they did say on Monday the throttle cable broke whilst out on road test, the new one was delivered to the workshop on Wednesday, so I should get some kind of news one way or another in the coming days! I wonder is snapping/stretching cable strands caused the throttle to act in an unstable manner as the tension increased via the depression of the pedal?
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