While doing a big service on the car this problem occured.
It is a m20b20 with mechanical fuel injection.
It starts like normal, then stops like the fuel gets cut off.
It has a new fuel filter, a known good fuel pump, brand new distributor cap, recently changed timing belt, oil change with new filter about 150 kilometers ago.
It did run with for a while, then when i tried to replace the jettronic unit with another to reduce co emissions, it would not start, changed back to the old one, it would then start, but stops again after a few seconds.
I tried giving the pump constant power by brigding the contacts on the relay socket, this makes the engine run for about 5-6 seconds, but still stops.
I belive there may be another relay that stops the current from flowing to the pump, does anyone know enough about the k-jettronic mechanical system to tell me what the fault may be?
520i k-jettronic , 1982, starts but stops after 2-5 seconds.
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Threeshifter
- Posts: 704
- Joined: Feb 12, 2006
I had a VW Dasher Diesel converted to gas with a Jettronic system. I had a similar problem; the car would start but only run for 10 seconds. The car was running on the cold start injector only. The fuel pump was not grounded properly and would not run right. So, once I properly grounded the fuel pump, the car ran great.
How do you know the fuel pump it good? Have you checked the fuel pressure delivered to the fuel distributor, or by good do you mean that the pump runs?
I know that there is a circuit that incorporates the alternator into the fuel pump relay. If the alternator is not “alternating”, the fuel pump will shut off (designed to kill the motor in the event of accident).
How do you know the fuel pump it good? Have you checked the fuel pressure delivered to the fuel distributor, or by good do you mean that the pump runs?
I know that there is a circuit that incorporates the alternator into the fuel pump relay. If the alternator is not “alternating”, the fuel pump will shut off (designed to kill the motor in the event of accident).
I know that the fuel pump is good because i used to have it in this car before the problem occured, it does run smoothly without any abnormal noise, it was replaced because of the ground connection terminal was damaged, accidently stripped the bolt on connection, it is now soldered and is elektrically and mechanically solid as a rock.
I dont have a pressure gauge for measuring fuel pressure.
I will check the ground connection underenath the rear seat asap, as well as checking the alternator.
I assume this connection for the kill circuit is the wire located by the + terminal?.
Thanks for the reply.
I dont have a pressure gauge for measuring fuel pressure.
I will check the ground connection underenath the rear seat asap, as well as checking the alternator.
I assume this connection for the kill circuit is the wire located by the + terminal?.
Thanks for the reply.
how do i proceed to bleed the k-jet unit?, last time i changed it i didn't bleed the unit or anything, just bolted it on and started the car, this however was 1,5 year ago.
"distrubutor for the p/u pump" please explain p/u pump.
How would it be possible to bleed the injectors?, they all give a constant flow in a linear ratio dependant on the movement of the mass meter, i got the impression that they are constantly open or opened by pressure since they have no actuated valves like elektronic injection. (no wires there)
If the unit is filled with air that cannot escape i can see how the fuel does not come through to the injectors, but since the cold start injector does get pressure, and fuel does squirt out if i loosen the injector lines that goes to the manifold, i am not sure this is the case.
Do you believe that the automatic choke might give this fault, in my manual described as a "warmlaufregler"
"distrubutor for the p/u pump" please explain p/u pump.
How would it be possible to bleed the injectors?, they all give a constant flow in a linear ratio dependant on the movement of the mass meter, i got the impression that they are constantly open or opened by pressure since they have no actuated valves like elektronic injection. (no wires there)
If the unit is filled with air that cannot escape i can see how the fuel does not come through to the injectors, but since the cold start injector does get pressure, and fuel does squirt out if i loosen the injector lines that goes to the manifold, i am not sure this is the case.
Do you believe that the automatic choke might give this fault, in my manual described as a "warmlaufregler"
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Gene in NC
- Posts: 336
- Joined: Feb 12, 2006
- Location: Raleigh, NC
1) Had sim prob on '89 e34 525. Eliminated all wiring and control circuit probs by running fused jumpers from battery posts directly to pump. Prob was in wiring harness conn between front and rear halves. If you haven't jumped directly from b+ and b- you haven't eliminated all possibe failure points.
The direct connection stopped shop from wildly replacing expensive components left and right.
Re e28
1) Which pump is "known good"?
2) Get a FP test gauge. This won't be the last time that you'll use it.
3)Put a Walbro pump in the tank and kiss goodbye the screwing that the BMW engineering design will give you down the road.
Search on my posts "Walbro" for info on how to and peripheral issues. Notice that specd posts not threads. Lotta good info from very experienced owners.
BMW pump fails on the road and you're up ----- creek w/o a paddle. Walbro, which is not likely to fail in your cars lifetime, and any parts store will have Walbro for Mustang that any mechanic can slip in, even you or me.
The direct connection stopped shop from wildly replacing expensive components left and right.
Re e28
1) Which pump is "known good"?
2) Get a FP test gauge. This won't be the last time that you'll use it.
3)Put a Walbro pump in the tank and kiss goodbye the screwing that the BMW engineering design will give you down the road.
Search on my posts "Walbro" for info on how to and peripheral issues. Notice that specd posts not threads. Lotta good info from very experienced owners.
BMW pump fails on the road and you're up ----- creek w/o a paddle. Walbro, which is not likely to fail in your cars lifetime, and any parts store will have Walbro for Mustang that any mechanic can slip in, even you or me.
Just tested to see if the fuel pump is being cut off, it still runs while the engine stops.
Is there any circuit to cut the ignition on the car?.
I Will get myself a fp gauge, but at the moment it isnt available due to my only car registered for road use not running.
I have already ordered a new bmw pump, but how would the Walbro pump work with the accumulator system used with k-jet?, i will consider this when my economy gets better.
The engine runs for longer if i give it some throttle.
It barely starts without the cold start injector connected, but it still seems like there is something that restrains the fuel or ignition after a few seconds.
I also checked the mass meter in tje k-jet, it moves without any noticable constraints, but there is some resistance when the unit is pressurised, is this normal?.
i know that any used part probably will give me problems in the future, the only reason i am using the used pump is because i need the car to run, it is a long walk to the nearest grocery store, plus i am expecting to be called in for at least 2 job interviews, both over 100 kilometers away.
Does anyone know anything more about the bleeding of the k-jet and p/u pump, is it just releasing the bolts attaching the fuel lines at top of the unit?.
As soon as the weather clears up i should be able to test the ground plus try to directly run the pump by a fused wire from the battery leads.
Is there any circuit to cut the ignition on the car?.
I Will get myself a fp gauge, but at the moment it isnt available due to my only car registered for road use not running.
I have already ordered a new bmw pump, but how would the Walbro pump work with the accumulator system used with k-jet?, i will consider this when my economy gets better.
The engine runs for longer if i give it some throttle.
It barely starts without the cold start injector connected, but it still seems like there is something that restrains the fuel or ignition after a few seconds.
I also checked the mass meter in tje k-jet, it moves without any noticable constraints, but there is some resistance when the unit is pressurised, is this normal?.
i know that any used part probably will give me problems in the future, the only reason i am using the used pump is because i need the car to run, it is a long walk to the nearest grocery store, plus i am expecting to be called in for at least 2 job interviews, both over 100 kilometers away.
Does anyone know anything more about the bleeding of the k-jet and p/u pump, is it just releasing the bolts attaching the fuel lines at top of the unit?.
As soon as the weather clears up i should be able to test the ground plus try to directly run the pump by a fused wire from the battery leads.
Damn times 248, just tried to directly run the fuel pump, nothing new, the earthing is perfect, no resistance to the chassis, oh well, just found a perfect exuse to change to l-jet, shuld get the new pump in time for the rebuild being complete.
Have anyone tried changing from k-jet to l-jet.
It seems like a bolt on job, providing i have the whole harness,fuelrail with injectors and regulator, intake manifold with tps, brain, lmm and air cleaner box.
I want to thank everyone who has helped me so far, really appreciate every idea for finding out what is wrong with my beloved 520i.
Have anyone tried changing from k-jet to l-jet.
It seems like a bolt on job, providing i have the whole harness,fuelrail with injectors and regulator, intake manifold with tps, brain, lmm and air cleaner box.
I want to thank everyone who has helped me so far, really appreciate every idea for finding out what is wrong with my beloved 520i.
The Kjet system is self bleeding.e28stian wrote:
Does anyone know anything more about the bleeding of the k-jet and p/u pump, is it just releasing the bolts attaching the fuel lines at top of the unit?.
Don't worry so much about "bleeding" a system that does not require it when you have plenty of other things on the system to trouble shoot. Namely the diode relay(silver square one), fuel pump relay (tall black one), fuel pressure acummulator( the can looking thing next to the fuel pump), and the warm up regulator.
Trying to eliminate electricals on a mechanical (pressure) injected system is all worth about 3 seconds of your time.
The best advice would be to go to an e21 forum, http://e21.tricord.be/ , that has owners of BMW e21 323i with the same Kjet system installed. My 323i has this same fueling systen and has run longer and with less issues than any LJet or Moronic equipped BMW that I have ever owned. First step would be to tap the diode relay when the engine begins to stumble More than often the diode relays beging to fail and this will cause the fuel pump to cut out. If this is changed for a known good diode relay then the order of progression would be the fuel pump relay, the temperature time switch, warm up regulator and last would be the fuel pump which you have already eliminated.
When ever I see the K-jetronic, it reminds me of the diesel set-up, that is why I though of bleeding requirement.
If you want to goto the L-jetronic, you will have to replace the whole intake and electronics to make it work. To make the fuel pump run, just jump fuse #1 to power and that will do the trick.
If you want to goto the L-jetronic, you will have to replace the whole intake and electronics to make it work. To make the fuel pump run, just jump fuse #1 to power and that will do the trick.
Thanks again, i am just about to drive to the nearest scrapyard and get myself a complete l-jet, it looks tidier and less complicated than the k-jet with its massive amounts of hoses that all eventually go bad.
And if i am correct it is a performance upgrade, the manual says that the l-jet versions has 4 more horsepower over the k-jet.
How much would you in the rest of the world pay for this system?, when i talked to the scrapyard dealer he told me i could get it for 1500 kroner, or around 120-130 dollars.
But anyway, i better get going before the weather goes bad again.
And if i am correct it is a performance upgrade, the manual says that the l-jet versions has 4 more horsepower over the k-jet.
How much would you in the rest of the world pay for this system?, when i talked to the scrapyard dealer he told me i could get it for 1500 kroner, or around 120-130 dollars.
But anyway, i better get going before the weather goes bad again.
I wish you best of luck if you go that route, you're in for mucho hours under the hood. The L-Jet system is not a bolt on replacement for the K-Jet. Your problems started, as you wrote, after swapping parts, so somewhere along that line something went wrong. If I were you I'd continue searching until you find the problem, that 4HP performance increase really isn't worth the hassle. But that's me.
I know that i am in for many hours of work to replace the k-jet with l-jet.
I have gathered all the parts needed for the rebuild, the k-jet is laying in a box right now and i have started the conversion.
I even got a new distributor along with every other part that seemed dissimilar to the k-jet, at the time it seemed like a good deal, the salvage yard owner said that i should take All the parts i needed for the rebuild for the sum that we agreed on.
Time is not my main consern right now, as i got something to move around in, a borrowed toyota corolla, boring to drive but it does the job.
I know that the 4 hp does not sound like much, but on the other hand, there are replacements available for l-jet at most of my local bmw parts dealers, but they do not carry any k-jet parts.
And now i have the manifold and intake with all the plumbing work finished, the engine harness hooked up, the maf installed, new thermostat housing installed.
So far i have used about ten hours, including the time spent ripping out the k-jet, estimating about ten to thirty more hours before the car is up and running again.
the to do list is shortened to
-install new throttle cable
-drill hole for ecu cable in the firewall
-install ecu
-splice ecu signal wires into instrument panel harness
-install new fuel pump, remove accumulator used with k-jet.
-reserve ten hours for cursing and fixing things that dont work
-fine tuning and adjusting the ignition
I have gathered all the parts needed for the rebuild, the k-jet is laying in a box right now and i have started the conversion.
I even got a new distributor along with every other part that seemed dissimilar to the k-jet, at the time it seemed like a good deal, the salvage yard owner said that i should take All the parts i needed for the rebuild for the sum that we agreed on.
Time is not my main consern right now, as i got something to move around in, a borrowed toyota corolla, boring to drive but it does the job.
I know that the 4 hp does not sound like much, but on the other hand, there are replacements available for l-jet at most of my local bmw parts dealers, but they do not carry any k-jet parts.
And now i have the manifold and intake with all the plumbing work finished, the engine harness hooked up, the maf installed, new thermostat housing installed.
So far i have used about ten hours, including the time spent ripping out the k-jet, estimating about ten to thirty more hours before the car is up and running again.
the to do list is shortened to
-install new throttle cable
-drill hole for ecu cable in the firewall
-install ecu
-splice ecu signal wires into instrument panel harness
-install new fuel pump, remove accumulator used with k-jet.
-reserve ten hours for cursing and fixing things that dont work
-fine tuning and adjusting the ignition
IT`S ALIVE IT`S ALIVE
And now the car is officially driven by l-jetted engine, only some minor adjustments to go before it is ready for the road.
to eric_v , it was a bolt on, just a lot of bolts , and not as bad as i expected labourwise, the only thing that needed some cutting and splicing was the instrumentpanels connection to the ecu, sacrificed a spare harness to get the connector.
I have done a lot more for far less gain than 4 hp, try fine sanding the inside or a m30 manifold only to read that a mirror polish is not needed on the intake because of the fluid dynamics of air, now that was a lot of hours.
I have used less time rebuilding to l-jet than trying to make the k-jet work. , if i didnt know better i would almost say i knew what i am doing
And now the car is officially driven by l-jetted engine, only some minor adjustments to go before it is ready for the road.
to eric_v , it was a bolt on, just a lot of bolts
, and not as bad as i expected labourwise, the only thing that needed some cutting and splicing was the instrumentpanels connection to the ecu, sacrificed a spare harness to get the connector.I have done a lot more for far less gain than 4 hp, try fine sanding the inside or a m30 manifold only to read that a mirror polish is not needed on the intake because of the fluid dynamics of air, now that was a lot of hours.
I have used less time rebuilding to l-jet than trying to make the k-jet work.
, if i didnt know better i would almost say i knew what i am doing It's not a bolt on, in terms of pop the hood and a few hours later you're on your way again. Most people don't bother because it's too much work or they won't compromise the car's originality. I guess in the end, anything is possible and a "bolt on" if you just put enough time in it.
Anyway, great you got it up and running again.
Anyway, great you got it up and running again.
Thanks, it is great to her it start up and keep running, its been over two weeks without that now. , and i do believe that it runs smoother, something i`ve missed with the k-jet 
I guess i take my definitions quite litteraly, if it isn`t bolt on, it is weld or drill and then bolt on
Iv`e always been stubborn about technical things and usually get things to works even if my methods seems improbable or impractical to some other people, anyhow it is the result that matters.
Originality is great, no argument there, as long as it works. I have not seen another e28 520i with k-jet, exerpt for my parts car, i guess it was reserved for the first years of the e28 520i from 82 to 84.
, and i do believe that it runs smoother, something i`ve missed with the k-jet I guess i take my definitions quite litteraly, if it isn`t bolt on, it is weld or drill and then bolt on
Iv`e always been stubborn about technical things and usually get things to works even if my methods seems improbable or impractical to some other people, anyhow it is the result that matters.
Originality is great, no argument there, as long as it works. I have not seen another e28 520i with k-jet, exerpt for my parts car, i guess it was reserved for the first years of the e28 520i from 82 to 84.
Me neither. I'm from Europe myself (The Netherlands) and the only well known K-Jet injected car was the E21 323i, a car that I had the pleasure of owning myself. You guessed right, the first series of the 520i were fitted with a mechanical K-jet system until September 1983, when they changed over to the L-jet system. I worked at a BMW dealership at that time and never saw one. They must be extremely rare these days.e28stian wrote: I have not seen another e28 520i with k-jet, exerpt for my parts car, i guess it was reserved for the first years of the e28 520i from 82 to 84.
Good job and enjoy your ride.
Good thing i`ve got lots of spares, overheating problem solved with another thermostat.
Engine now has a nice induction growl near the intake that wasnt there before , i guess that comes from the Ramair filter and the less restrictive intake system.
Only thing left now is installing a new temprature sensor for the aftermarket temprature gauge, since the old one is broke, and i cannot seem to find what is wrong with it.
And then for a thorough test trip, to test what is called the yehaaa zone (wide open throttle mode).
Actualle found a l-jet faq somewhere that described the wot mode of the tps as the yeehaa zone
Engine now has a nice induction growl near the intake that wasnt there before
, i guess that comes from the Ramair filter and the less restrictive intake system.Only thing left now is installing a new temprature sensor for the aftermarket temprature gauge, since the old one is broke, and i cannot seem to find what is wrong with it.
And then for a thorough test trip, to test what is called the yehaaa zone (wide open throttle mode).
Actualle found a l-jet faq somewhere that described the wot mode of the tps as the yeehaa zone