CIS questions
10-23-2009, 01:01 AM
#1
Burning Brakes
Thread Starter
CIS questions
You guys have been my CIS go-to because you're a bit, shall we say more hands-on, than Mercedes guys. I'm running K-jet (no O2) with a UTCIS-PT.
Two questions:
1 - is there some way that CIS compensates for ambient temp? It seems that with the colder weather I've had to lean it out a bit (well, not make it lean, but turn the adjustment under the air filter housing counter clockwise to make it more lean to restore it to being proper).
2 - are long hot starts typically the accumulator? The lines are empty on hot starts, but the injectors don't leak down.
Two questions:
1 - is there some way that CIS compensates for ambient temp? It seems that with the colder weather I've had to lean it out a bit (well, not make it lean, but turn the adjustment under the air filter housing counter clockwise to make it more lean to restore it to being proper).
2 - are long hot starts typically the accumulator? The lines are empty on hot starts, but the injectors don't leak down.
10-23-2009, 01:30 AM
#2
Nordschleife Master
1) The Aux Air Valve and WUR both have temperature sensors. Maybe it's the way your UTCIS thing is operating. Or maybe the Aux Air Valve is never heating up. That'd keep the cold start injector ON.
2) Long? How long? It seems that the different CIS systems each control the fuel pump differently. Some run it when the engine goes ON and then stop. Some only run the pump while it's cranking. If you can make it hum be turing the engine ON then do that a bunch of times and see if it starts. I'd also stick a timing light on it to verify that it's sparking when hot. Does it smell of gas? Or fire right up with some starting fluid? If it was the accumulator I'd think it would be worse after long sits. There's also may be a check valve at the pump.
2) Long? How long? It seems that the different CIS systems each control the fuel pump differently. Some run it when the engine goes ON and then stop. Some only run the pump while it's cranking. If you can make it hum be turing the engine ON then do that a bunch of times and see if it starts. I'd also stick a timing light on it to verify that it's sparking when hot. Does it smell of gas? Or fire right up with some starting fluid? If it was the accumulator I'd think it would be worse after long sits. There's also may be a check valve at the pump.
10-23-2009, 08:43 AM
#4
Burning Brakes
Thread Starter
2) Long? How long? It seems that the different CIS systems each control the fuel pump differently. Some run it when the engine goes ON and then stop. Some only run the pump while it's cranking. If you can make it hum be turing the engine ON then do that a bunch of times and see if it starts. I'd also stick a timing light on it to verify that it's sparking when hot. Does it smell of gas? Or fire right up with some starting fluid? If it was the accumulator I'd think it would be worse after long sits. There's also may be a check valve at the pump.
No smell of gas. Haven't tried the starting fluid.
10-23-2009, 09:53 AM
#5
The auxillary air valve adds more air for a cold start idle. It doesn't affect the A/F mixture. How does the UTCIS affect the control pressure during warmup mode? Is it adjustable? The A/F adjustment should always be made on a warm engine then adjust the control pressure for cold starts. To lean the cold start A/F mixture, increase control pressure. Reducing the control pressure richens the cold A/F mixture.
Concerning the leakdown/hotstart problem, check your accumulator for leakage. There will be a plug or return hose at the top center of the mounted accumulator. Remove the plug/hose and check for the presence of fuel which would indicate a broken diaphram. If dry, and none of your injectors are leaking, the culprit is most likely the check valve at the fuel pump.
Dennis
Concerning the leakdown/hotstart problem, check your accumulator for leakage. There will be a plug or return hose at the top center of the mounted accumulator. Remove the plug/hose and check for the presence of fuel which would indicate a broken diaphram. If dry, and none of your injectors are leaking, the culprit is most likely the check valve at the fuel pump.
Dennis
10-23-2009, 10:43 AM
#6
Burning Brakes
Thread Starter
Oh, by aux air valve you guys mean cold start valve. Yeah, that's fine, I'm familiar with that and it works.
During warmup mode the UTCIS has a chart with ambient temp in the engine bay at start (it's a bit more complicated actually, but this is basically what it detects) corresponding to a given control pressure in 4F increments. How long it stays in warm up mode depends on what temp it detected when you started the car (for instance, if ambient temp is 60F it stays in warm up mode for 110 seconds, if it's 72F i's 80 seconds) and during the warm up period the control pressure slowly increases according to the slope of the various control pressures set for each of the 4F increment starting temps.
Once out of warmup mode, it goes to "run" mode. In "run" mode control pressure is set according to rpm and manifold vacuum in 250rpm and 0.1bar increments (this allows you to map it so you can get lumpy cams to work well with CIS).
All the control pressure settings are done electronically and custom set, i.e. they don't change except for rpm and manifold vacuum as programmed.
When I say now that it's colder I've had to lean it out a bit, I mean with the cold weather, using the same control pressure settings and CO adjustment screw position I was using in hot weather, on a fully warmed up engine, the mixture is too rich.
During warmup mode the UTCIS has a chart with ambient temp in the engine bay at start (it's a bit more complicated actually, but this is basically what it detects) corresponding to a given control pressure in 4F increments. How long it stays in warm up mode depends on what temp it detected when you started the car (for instance, if ambient temp is 60F it stays in warm up mode for 110 seconds, if it's 72F i's 80 seconds) and during the warm up period the control pressure slowly increases according to the slope of the various control pressures set for each of the 4F increment starting temps.
Once out of warmup mode, it goes to "run" mode. In "run" mode control pressure is set according to rpm and manifold vacuum in 250rpm and 0.1bar increments (this allows you to map it so you can get lumpy cams to work well with CIS).
All the control pressure settings are done electronically and custom set, i.e. they don't change except for rpm and manifold vacuum as programmed.
When I say now that it's colder I've had to lean it out a bit, I mean with the cold weather, using the same control pressure settings and CO adjustment screw position I was using in hot weather, on a fully warmed up engine, the mixture is too rich.
10-23-2009, 11:05 AM
#7
Nordschleife Master
Trending Topics
10-23-2009, 11:40 AM
#8
Oh, by aux air valve you guys mean cold start valve. Yeah, that's fine, I'm familiar with that and it works.
During warmup mode the UTCIS has a chart with ambient temp in the engine bay at start (it's a bit more complicated actually, but this is basically what it detects) corresponding to a given control pressure in 4F increments. How long it stays in warm up mode depends on what temp it detected when you started the car (for instance, if ambient temp is 60F it stays in warm up mode for 110 seconds, if it's 72F i's 80 seconds) and during the warm up period the control pressure slowly increases according to the slope of the various control pressures set for each of the 4F increment starting temps.
Once out of warmup mode, it goes to "run" mode. In "run" mode control pressure is set according to rpm and manifold vacuum in 250rpm and 0.1bar increments (this allows you to map it so you can get lumpy cams to work well with CIS).
All the control pressure settings are done electronically and custom set, i.e. they don't change except for rpm and manifold vacuum as programmed.
When I say now that it's colder I've had to lean it out a bit, I mean with the cold weather, using the same control pressure settings and CO adjustment screw position I was using in hot weather, on a fully warmed up engine, the mixture is too rich.
During warmup mode the UTCIS has a chart with ambient temp in the engine bay at start (it's a bit more complicated actually, but this is basically what it detects) corresponding to a given control pressure in 4F increments. How long it stays in warm up mode depends on what temp it detected when you started the car (for instance, if ambient temp is 60F it stays in warm up mode for 110 seconds, if it's 72F i's 80 seconds) and during the warm up period the control pressure slowly increases according to the slope of the various control pressures set for each of the 4F increment starting temps.
Once out of warmup mode, it goes to "run" mode. In "run" mode control pressure is set according to rpm and manifold vacuum in 250rpm and 0.1bar increments (this allows you to map it so you can get lumpy cams to work well with CIS).
All the control pressure settings are done electronically and custom set, i.e. they don't change except for rpm and manifold vacuum as programmed.
When I say now that it's colder I've had to lean it out a bit, I mean with the cold weather, using the same control pressure settings and CO adjustment screw position I was using in hot weather, on a fully warmed up engine, the mixture is too rich.
Dennis
10-23-2009, 07:00 PM
#9
Burning Brakes
Thread Starter
If the system is working correctly, you should not have to adjust the A/F based upon temps. Another possible contributor to both of your problems could be a leaking cold start valve. Try unplugging it (warm engine) to see if it solves the leakdown and rich running problems.
Dennis
Dennis
BTW, I can test the temperature-relationship - lately we've been having hot mid-days and cold nights, and yes, the same setup that is good during the day is too rich at night.
For the record, when I say too rich I mean like 0.3-0.4 richer AFR.
Unfortunately, by the time I got back in and took care of all the stuff that was waiting for me, it already started to get dark. I'm going to check the things suggested here soon, hopefully tomorrow.
10-24-2009, 11:29 AM
#10
Yes, the CIS system compensates for air density and altitude without adjustment. Since the UTCIS replaced the WUR, there should be a temp input to compensate during cold starts. Is it internal like the WUR or is there another input source to adjust for engine temps?
Dennis
Dennis
10-24-2009, 11:58 AM
#11
Burning Brakes
Thread Starter
The cold start compensation input is internal, though I'm not sure if it's in the unit that replaces the warm up regulator or in the computer box. Either way, it's internal. However, the temp input has no impact on the "run" mode after warmup. I don't know if the same is true for the WUR or not.
10-24-2009, 12:05 PM
#12
Nordschleife Master
The stock WUR will stay cooler with cold air temps but the hot engine and internal heater should bring it up to temo eventually. It's hard to really quantify how that thing is behaving.
You may also have a sub-system that varies the fuel pressure to the WUR for cold temps. It's sparsely documented and uses a temp sensor in the coolant. That enrichens the mixture at cold temps by lowering the pressure to the WUR.
