Post Number: 87
|Posted on Tuesday, 13 December, 2022 - 06:49:
1986 SZ Spirit 14,618 KJet w/ L FI
In studying about my cold start issue I find several videos on other cars (VW Golf for instance) that have a tap for a dwell meter connection into the Lamda fuel valve to set the cycle ratio at apprpx 50%
I can't find any reference in the available RR manuals for any such electrical tap
Anyone know of one or even set the Lamda valve this way?
Post Number: 2543
|Posted on Monday, 19 December, 2022 - 22:02:
Procedure is most important
How did you arrive at a cold start issue,what are the type symptoms
What was the live data ie C/O H/C hot and cold.
From my failing memory the RR K Jetronic has the timer cold start module.
Starting from cold is never a problem it is usually when warm!
Post Number: 88
|Posted on Wednesday, 21 December, 2022 - 07:07:
Actually I may have mislead on my post
I have a cold start issue I'm working on BUT at the same time I came across many references to using a standard dwell meter to set the cycle rate of the Lamda pressure controller on Bosch KJetronic w/ L fuel injection systems. The two items were actually separate issues
I was just posing the question as to whether or not anyone knew of setting the Lanmda cycle rate by using a dwell meter
I have come to find that those vehicles that do (NOT Rolls) utilize pins 17 and 16 on the control unit for the dwell meter hookup. Rolls has no connection on pin 17 so a little wiring job is at hand to make this work without the special tools Rolls requires.
Post Number: 2547
|Posted on Friday, 23 December, 2022 - 08:11:
Maybe this thread should be put in Idler Chatter.
Need more details on the VW car, ie model year etc.
can then give you all the failings of what you may do with a little wiring job!!!!.
Post Number: 4158
|Posted on Saturday, 24 December, 2022 - 10:21:
This thread is in the right place - it certainly doesn't rate as "Idler Chatter" as far as I am concerned as it relates to a technical issue.
Post Number: 89
|Posted on Sunday, 25 December, 2022 - 09:12:
More to add-
Upon further investigation and learning it seems while a dwell meter is and can be used with pins 16 / 17 to measure cycle time of the Lamda valve a more accurate measurement is acquired by using a meter with Hz % on the scale. maybe not enough of a gain in accuracy to be very meaningful but just more accurate as we are looking for a 50% cycle duty time with a cyclic variance of @ 2-3% either way
Also to add there is mention of (in RR literature)
for the 86 and later USA SZs (or w/Lamda FI) several regional WURs around the world all for the same basic Bosch FI system. Not surprisingly, the one specified for California delivery (stringent emissions) retails for $2000 USD and all the others are around $300, There is even one designed for USA 49 state rules but for high altitude vehicles. I would love to fond one of those as I live at high altitude.
Seems most any of them would work fine on our Bosch FI systems IF emissions weren't an issue
Remember they set the cold to warm mixture ratio (like a choke on a carb car) AND indirectly affect the final hot ratio by way of the "regulated" pressure they put out. Most WURs set the regulated pressure at around 3.5 BAR but the high altitude one goes to 4.0 BAR as a high setting thereby leaning the mixture for high altitude driving above what the small aneroid diaphragm does in the bottom of the normal WUR
Hope this helps in understanding our Bosch injection systems
More as I learn more.
Post Number: 90
|Posted on Sunday, 25 December, 2022 - 09:24:
To answer Patrick above-
My issue has been very rich running upon cold start (10c and above) to the point of emitting black smoke out the tail pipe much like having a carb choke stuck closed. Once warmed up fully it drives OK but still rich as mileage is low (9-10 MPG USA).
Upon checking fuel pressures yesterday (after my gages arrived) I find that my fuel pump will not reach 5.0 to 5.5 BAR system pressure (valve closed on test rig) nor will it reach required cold regulated pressure (.7 BAR) or hot regulated pressure (only 2.3 BAR) SO my first actions need to be change the fuel filter and then recheck unregulated pressure to see if the pump is good or bad. That will be done after the holidays.
Post Number: 2548
|Posted on Monday, 26 December, 2022 - 02:00:
David thanks, you are correct as I though we were going on to the VW cars.
Cliff,You may be right however the fuel accumulator could well be at fault.
When they fail it is the hot starting and rich running that becomes a pain.
If the accumulator and pump etc is ok then the thermal time switch that switches off the cold start injector could have failed.
The cold starting is a different set up that always start instantly.
To test fuel filter do a flow test on the pump from memory should be about 3 to 3.5 pints per minute.
Fuel pump pressure test from memory is carried out with the engine cranking mode.
Post Number: 91
|Posted on Monday, 26 December, 2022 - 15:08:
Yes the accumulator seems OK as it keeps pressure after shutting off the pump BUT it will also be checked when I get it lifted next week for the fuel filter change(FF is original to car 86) Never a hot starting issue.
Pump flow test will also be done at that time back at the FF outlet to be sure flow is good there too.
I will be disconnecting the cold start injector plug next time I start the car to se if that is the issue with very rich mixture after start.
Like I mentioned above I'm low on both initial and regulated pressures so I think my first stop is to check the pump output and change the filter.
The saga continues