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Does anyone know the proper dwell angle for the FI Trigger points in the distributor? In other words, through how many degrees of rotation of the distributor shaft should the point be in contact?
My assumption is that the when the points are closed the injectors are injecting, so as the cam blocks wear on these, increasing the dwell angle, it would tend to make things richer. Or maybe they just cause the control box to send a single pulse, regardless of how long they're closed, and the dwell angle is unimportant as long as the points are functioning.
Please enlighten me.
(I've had this car since 2001. The PO had it blueprinted and put a performance cam in it to go with a big bore kit. Car runs spectacularly, has for 40+K, but I had a devil of a time in the beginning. The only way i could get it to run manageably was to substitute a 140 control box, but I still have richness problems and a slight hesitation transitioning from idle. I've tried to get the head off to change the cam, but the head bolts are really frozen in place (half inch breaker bar and six-foot pipe frozen), and I really don't want to snap several of them off in the block. Besides, it runs so well when it's run hard. Problem is, I prefer not to drive that way most of the time.)
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Thanks. I'm enlightened. Thank you, gentleman. Guess that's to the source of my issue.
As to the transition problem, I've been all over the TPS and idle adjustment (My third d-jet car).
Actually, when i got the car and was struggling to get it to idle properly, i found that the throttle plate screws had worked loose (fortunately had't been sucked into the engine) and the plate wasn't seating properly. But, fixing that I still had a situation where coming off run the idle would not settle, but drop precipitously, almost to a stall, and then come back up to the proper setting. No matter what I tired, i couldn't correct this. Had an old 142 control box sitting around and put that in and it solved that problem (but not the transition problem), so, naturally, I bought a brand new control box. But it went back to the RPMs dropping precipitously. Over the years I've fooled with MPS adjustments...I have any number of those units to fiddle with, and I can get it to transition fine, but it runs incredibly rich. I'm not skilled enough or instrumented enough to be able to make ideal adjustments to the MPS (that would probably help the problem).
Would love to put in a MegaSquirt and be done with this, but, again, that's beyond my ken, at least the intellectually and computer programming part. Wish i could find someone in my area with experience who could guide me through the process. Or, at the very least, be able to get the damn head off and replace the cam...that's something I've done back in the old soft-lobe days.
As I say, if you drive the car the way a car with a hot cam is supposed to be driven, there are zero problems. But that just doesn't match my
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My again fuzzy recollection of the Djet is that there is a fuel cut circuit when you lift the throttle. I think there is a contact which closes when the throttle switch is going closed which operates that fuel cut circuit. I know you checked the operation of the throttle switch; but, the operation of that particular switch is something that you might want to give a second look at. I think it is supposed to go open just before total closure or at total closure. Maybe the sequence of operation for that contact is a little off.
Fuel cut on trailing throttle can be interesting on the B20E. I had my Megasquirt set up to radically cut fuel delivery when lifting the throttle. Made the car an absolute pain to drive smoothly. I think I have raised the fuel delivery on closing throttle to something like 70 - 80% which makes driving in heavy traffic a little nicer.
Using Megasquirt to replace the D jet isn't too bad if you are prepared to take the time to read through the official Megasquirt documentation and figure out how the thing works. It is definitely not plug and play and its best to avoid trying to transplant somebody else's solution. A lot of the web threads touting their MS implementations tend to gloss over the problems.
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The fuel cutoff is for '70 and '71 only, above ~1700 RPM when the TPS signals that the throttle is closed. Below that speed it should have no effect.
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180 degrees of distributor rotation, and they alternate. In other words, when one of the points is closed, the other is open.
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It has been a while since I did much with the D jet system (I switched my 142 E to Megasquirt); however, the duration of the injector pulse width is not determined by the trigger contact dwell, it is determined by the analog circuits in the control box. The trigger contacts just initiate the injector pulse and provide an RPM signal to the control box. The Djet is a speed x density FI system so the RPM signal is probably more critical than the timing signal. My extremely fuzzy recollection was that the pulse initiates on trigger contacts going open (positive going signal); but, it could just as easily be set to trigger on contacts going closed (negative going signal). I would have to dig out the old schematics that I found for the Djet to be sure.
If the contact blocks are wearing down, it will be altering the point in the engine cycle that injection occurs; however, the D jet is a batch fire system so injector timing (as opposed to injector pulse duration) is not particularly critical. As long as you are getting distinct open and close indication on the two contacts as the distributor shaft is rotated the trigger contacts are not the source of your problems.
As I noted, I am getting fuzzy on Djet operation; however, any time you are having trouble around idle and transitions around idle, my recollection is that you should check both the set-up and operation of the throttle switch and the set up of the idle. I remember that a lot of people screw up the Djet by using the throttle stop screw to set idle speed rather than the air by-pass screw under the manifold. If you have not done it already, you should get the shop manual and check out the very specific procedure for adjusting idle speed, setting the throttle switch and checking the operation of the throttle switch. The operation of the throttle switch on the Djet is not like the throttle position sensor on modern FI systems.
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Dave B,
What 142 Guy enlightens you to do.
You can find innumerable Bosch D-Jet manuals as installed on Volvos and other makes.
A search on Google helps you to find both scanned PDFs and web pages replete with useful information on D-Jetronic.
http://www.volvotips.com/index.php/p1800/volvo-p1800-service-manual/
http://www.swedishbricks.net/faq/fidjet.html
http://www.vclassics.com/archive/efi.htm
If the D-Jetronic controller box is original, along with wiring, you may want to closely verify the engine controller wire harness, certainly connectors and grounds. A 46-year wold Bosch D-Jetronic controller box (you list a 1970 Volvo P 1800) may also enjoy a restore. Replacing capacitors and other components inside the controller box may be a good restoration, after you've got the rest of the system tuned and good to go.
Hope that helps you get started.
Sort of would like a 164 e with D-Jetronic, or a newer engine control system.
Thanks,
Duffed.
--
Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful Comedian & Comedic Actor North America in Perpetuity
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