FAQs about D-jetronic

This page could be found on the Internet for several years but suddenly disappeared. Since we think it contains some useful information we have put a copy of it here on our website. 164 Club of Sweden, January 15, 2001.

  • Is it the atmosphere sensor?
  • How can I test my injectors?
  • D-jetronic problem solver.
  • Is the manifold pressure sensor adjustable?
  • How can I test a FI for leakage?
  • Working with p-channels.

  • Is it the atmosphere sensor?

    Date: Mon, 16 Nov 92 14:14:16 -0500
    From: bw738@cleveland.Freenet.Edu (Ed Wetherell)
    To: hwiegman@EW0099.ASTRO.GE.COM
    Subject: Re: D-jet system

    although the atmosphere sensor probably has something to do with it, the following i will quote from workshop manual 28, Bosch, Electronically controlled Fuel Injection for Volvo 1800e, 142/144 Grand Luxe..'The throttle valve switch futs off the fuel supply when coastingin gear at a speed over 1700 rev/min. If, when coasting in gear the speed drpos to 1000 rev/min, the fuel supplyu is switched on again so that a smooth change-over to idling operation is guaranteed. When the engine is cold, the speed limits are raised by approximately 300 rev/min to equalize the higher frictional resistance.'

    i would expect that the atm sensor determines if the 'in gear' condition is met, but i would expect the same opperation if you put the clutch in..

    my modification will involve replacing the atm sensor with a microprocessor and a few additional sensors. The atm sensor modifies the base pulse wave for the injectors with respect to load. The atm sensor is a transformer with a varriable core that produces this change. my experience with the atm sensors shows that they are the primary component of the injection system that determines the load richness and a few other things. they have 3 distince adjustments and ther are 3 different models (maybe more) that were fitted on B20 engines.. they are prone to leaks and are easily messed up by mechanics that claim they can adjust them so emissions requirements can be met.. these sensors cannot be adjusted without an oscilloscope and a function generator and tha vacuum pump (obviously)

    my plan eliminates the atm sensor a uses a microprocessor to to the waveform adjustment. this will provide a more accurate adjustment of the wave w/respect to load and if a lamda sensor is included, better economy and emissions control..

    using the sme microprocessor i hope eventually to replace the bosch box completely.. agreed this is a huge task, but i don't believe that it is that difficult given overall simplicity of the existing system..

    my problem at the moment involvoes the lamda sensor as discussed in my previous posting, the sensor is giving strange readings. i have analysed the probst information and another article from car design and technology.. i understand the voltages that should be present under varing condtions of combustion.. i am just wondering if i have something wrong w/ my car or if the lamda sensor is not giving accurate readings.. i would expect to see low voltages if the sensor was not hot enough and the same if my DMM was loading the sensor too much. i have checked the obvious things and wanted the collective oppinion of the net on the lamda workings and possibel problems with my car..

    thanks for your interest and help..

    hope i didn't ramble on too long about my problem, i am just frustrated..


    Date: Tue, 23 Mar 93 12:35:53 -0500
    From: bw738@cleveland.Freenet.Edu (Ed Wetherell)
    To: wiegman@orion
    Subject: mysteries of d-jet

    gonna love this one, about 90% of my problems were the throttle position switch! i swapped on one i had lying around and things changed drastically for the better. both units are of equal age and both are grooved on the acceleration path. both check out the same and both are spottlessly clean. i have no clue why some of my probs were effected because they occur over most of the throttle range and would even happen with the position switch disconnected!! as you probably know, the position switch is not necessary for base function, just for quicker acceleration and smoother return to idle. anyway, i suggest you swap yours out if you have another handy.. looks like they might be bad and your average work w/ a DMM wont pick it up.. i am going to put the old one back on to be sure that the position switch was really the fault, but i am beginning to wonder how much witchcraft hans and gunter used when creating this monster!! or is uncle olaf pissed at me??


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    How can I test my injectors?

    Subject: testing injectors (was: 164E Fuel Economy Problem)
    To: volvo-net@me.rochester.edu (volvo-net)
    Date: Mon, 18 Nov 91 13:05:12 CST
    From: volvo@zaphod.b15.ingr.com (M Palmer)

    Then one day <Michael Mahler> said:
    >Subject: 164E Fuel Economy Problem
    > Your best bet is to pull each injector in turn and fire
    > them up. I've done this on my B21 by putting a rubber stopper
    > in the injector's hole and then starting the engine on three
    > cylinders, with the one I'm testing pointing into
    > a 1 liter Coke bottle. This is NOT a Volvo reccomended procedure
    > and you do so at your own risk. Vaporized gasoline ain't
    > orange juice.

    NOTE: (this is my disclaimer) vaporized gasoline is very dangerous and highly explosive. Be extremely cautious. Use a jar or bottle to collect the spray, and rags to clean up with immediately. Don't do in your garage, especially if you have a gas water heater, kerosene heater, or any other source of ignition nearby. This especially includes smoking.

    A comment on this testing procedure. You must be cautious that the stopper you use on the injector port cannot get sucked into the manifold. This happened to me the first time I tried this procedure last summer, and I had to take the head off to get the offending piece out. This was quite a bit of needless work that I could have avoided with just a little more forethought.

    Michael G. Palmer | claimer dis:
    ether: volvo@zaphod.b15.ingr.com | In no way speaking for Intergraph, Corp.

    Subject: Re: testing injectors (was: 164E Fuel Economy Problem)
    To: volvo-net@me.rochester.edu (volvo-net)
    Date: Tue, 19 Nov 91 8:12:13 CST
    From: volvo@zaphod.b15.ingr.com (M Palmer)


    I am posting this to the net since it may be of general interest.

    Then one day <Alec Isaacson> said:

    >In regards to testing the injectors. . . Why not just do what the manual
    >says and test the resistance between the pins (my Haynes Guide says it
    >should be 2.4 Ohms at 70 degrees F).

    On the CI (continuous injection) systems, there are no electromechanical interupters in the injectors. The injectors are only nozzles to atomize fuel, and fuel quantity is controlled by varying the flow in the air-fuel control unit and the fuel distributor.

    Also, this test in the Haynes manual doesn't test the spray pattern or flow, both important things for you injectors. The spray pattern should be a fine atomized mist in a cone shape, with no streamers or large drops.

    > -Alec D. Isaacson
    > AI4CPHYW @ miamiu.acs.muohio.edu
    > isaacson @ rogue.acs.muohio.edu (NeXt Mail)
    > Miami University, Oxford, OH

    Michael G. Palmer | claimer dis:
    ether: volvo@zaphod.b15.ingr.com | In no way speaking for Intergraph, Corp.

    Date: Wed, 20 Nov 91 17:05:41 EST
    From: Alec Isaacson <AI4CPHYW@miamiu.acs.muohio.edu>
    Subject: Re: 164E Fuel Economy Problem
    To: "Herman L. N. Wiegman" <wiegman@orion>

    You said that article mentioned putting 12 volts across the injectors? Everything I read says that is DEATH to the injectors. They are designed for 3, not 12 volts.

    Alec D. Isaacson
    AI4CPHYW @ miamiu.acs.muohio.edu
    isaacson @ rogue.acs.muohio.edu (NeXt Mail)
    Miami University, Oxford, OH
    In the dark, the innocent can't see.-Melissa Etheridge

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    D-jetronic problem solver.

    Date: Mon, 9 Dec 91 09:32:28 EST
    From: wiegman (Herman L. N. Wiegman)
    To: AI4CPHYW@miamiu.acs.muohio.edu
    Subject: D-jetronic problem solver

    Alec, [D-jet in early Volvos]

    just this weekend I picked up a Volvo FI Fault Tracking book at the VSA Membership Meeting. The little booklet was published by VSA a few years back and is a logic step by step guide.

    the punch line? the temperature (coolant) sensor has a dynamic effect on the Fuel mixture. The coolant temp sensor and the thermal timer are both located near the first cylinder intake runner and water pump connections (i'm sure you've mapped out half the motor by now). the sensor should read between 2100 and 3100 ohms on a cold engine. The thermal timer should only have an effect on realy cold days.

    the guide says for "Low Fuel Milage"...

    1) check spark plugs and compression.
    2) check timing advance.
    3) check for leaky fuel lines.
    4) check for propper operating temperature (thermostat) ( a faulty one causes a cold running condition and that makes the car run in "cold" mode all the time).
    5) check temperature sensor.
    6) check fuel pressure (30psi) and leaky injectors.
    7) check for blocked air filter
    8) sticking injectors or pressure sensor (air?), warn cam shaft, faulty control box.
    9) trade car in for new one (just kidding).

    best 'o luck


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    Is the manifold pressure sensor adjustable?

    From: w2iy@hoqax.att.com
    Date: Thu, 25 Mar 93 14:29 EST
    To: att!orion.crd.ge.com!wiegman (Herman L. N. Wiegman)
    Subject: Re: D-jet manifold sensor

    Herm and Jeff,

    If it's coming from a temp sensor, it's almost surely the coolant temp sensor, not the air temp sensor (as Herm rightly pointed out). Yes, it could be the manifold pressure sensor, and yes, contrary to what Bosch would like you to believe, it is adjustable. Herm, in fact the purpose of our 4/24 gathering is to watch me and Perry put a scope on the injector leads and watch the pulse width change as we adjust the pressure sensor). Grind off the epoxy seal covering the coverplate screw. Unscrew the coverplate screw (big slot). Inside you'll see a much smaller screw slot. This is the adjustment. If memory serves, clockwise is leaner, CCW is richer. And it's very sensitive - an 1/8 of a turn can make a noticeable difference.


    PS to Herm - what's the DSP stand for?

    Forwarded message"

    Date: Thu, 25 Mar 93 14:01:01 EST
    From: wiegman@orion.crd.ge.com (Herman L. N. Wiegman)
    To: w2iy@hoqax.att.com
    Subject: Re: D-jetronic (was fuel filters/Oxy-fuels)

    Jeff and Mike,

    >The car [164] still has a problem of running very, I mean VERY rich. Since all the temp gauges and wire check out I suspect the manifold pressure sensor. Have you every had the richness problem ?

    no, but perhaps other's have... I think that teh temp sensor does highly effect the mixture.. the air temp has less of an effect. If you have the VSA trouble shooting guide, it will step you through a very nice map to find if different components are shot..

    Mike, have you heard of this rich running problem? could be that the manifold pressure sensor is on it's way out.. there should be two resistive windings at the terminals of the sensor... pins #1 and 4 should read 300 Ohms, and pins #2 and 3 should read 90 Ohms .. these should be isolated from each other.. Meg Ohm or more..

    is your fuel pressure set ok? could be that the original stalling prob caused someone to crank up hte fuel pressure.. it should be about 31psi after the regulator.. also check to see if the ground wires for the motor and fuel injectors are good. These may cause injector run on..

    see if the spray pattern is good and if the injectors leak.. the fuel consumption problem could be one injector or the cold start injector..I think that three drips a minute is ok for the D-jet injctrs.


    Herman L.N. Wiegman -> wiegman@orion.crd.ge.com
    General Electric - Corporate R&D, Schenectady NY
    - the Flying Dutchman in the DSP Swedish Brick -

    From: w2iy@hoqax.att.com
    Date: Mon, 18 Jan 93 14:43 EST
    To: att!orion.crd.ge.com!wiegman (Herman L. N. Wiegman)
    Subject: RE: manifold pressure sensor

    Herm, it's been my experience thqat the air temp sensor is very reliable. I have been able to adjust the manifold pressure sensor. Brian Woodbury (whom I see occasionally) and I are thinking about one day in the spring getting out the old o'scope and seeing if we can calibrate the sensor by looking at the injector pulse width as a function of the adjustment. Will probably write it up for the paper if we get it to work. But I'm no longer terrified by changing the adjustment on it. It may be worth a try: clockwise is leaner, CCW is richer. What I've been doing is leaning it down until it runs prroly and then backing it off about 1/8 to 1/4 turn. Seems to do OK for the beast has been sprightly.

    Wiper post seals are OK and my drain tubes are open. The water in the rear floor(!) must be coming in thru the door???? Aargh!


    From: w2iy@hoqax.att.com
    Date: Wed, 29 Jul 92 10:11 EDT
    To: att!uunet.uu.net!island!ocracoke.island.COM!bob@crdgw1.ge.com
    Subject: Re: D-jet Manifold pressure sensing

    Bob Malecki had 2 questions on his new 1800ES:

    1) The toggle switch down and to the left under the fusebox is - get this - a dimmer for the overdrive and hibeam telltales. You can adjust the brightness of these two lamps to either of two positions: UP, in which case the overdrive telltale is blindingly bright and the hibeam telltale is all but invisible, and down, in which case the overdrive telltale is moderately blindingly bright and the hibeam telltale is even more invisible.

    2) The car may be running a bit too rich (have you tracked gas mileage?) If so, try t following:

    a)Center the idle mixture adjustment on the FI control box (in the passenger footwell);

    b)Remove the epoxy seal (sharp knife usually works) to expost the protective cover on the manifold pressure sensor. Remove the protective cover (large screwdriver), exposing the adjustment screw. Warm the car and insert a CO meter in the tailpipe. Then adjust the pressure sensor (CW is leaner, CCW is richer) for about 1.5 to 2%


    If the obvious things haven't worked, this may help. Also do you know about Volvo Sports America, the club for 1800 owners? Bimonthly magazine will have leads on parts, tech tips, etc etc. |Also, I have a few things left over from a '71 E that I'm parting out. Call or write for info.


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    How can I test a FI for leakage?

    Date: Tue, 12 Jan 93 21:30:23 EST
    From: Alec Isaacson <AI4CPHYW@miamiu.acs.muohio.edu>
    Subject: fuel injector leaks? D-jet
    To: Richard Loken <tech@cs.athabascau.ca>, Volvo Owners
    Mailing list <swedishbricks@me.rochester.edu>

    And we're off with the Alec D. Isaacson Memorial First Post for '93 . . .

    To test a FI for leakage the best thing to do is to actually pull it from the injector port, "hot wire" the fuel pump and watch the tip of the injector. Of course, common sense dictates that one NOT point the tip at ones face or at anything that even remotely has the chance of igniting a potential gas leak. My Haynes guide (for my '72 164E w/ D-jetronic) lists the proper procedure for the above and tells how to hot wire the pump (all you do is apply +12V to a wire and that runs the fuel pump with the engine off.) I figure others will have the same.

    While you have the injectors out, you could run a fuel system pressure check as well. Disconnect the cold start valve and put a pressure gauge in its place (I have an old OEM oil pressure gauge that I use). Run the fuel pump for a moment (watching for leaks and taking proper precautions as listed above) and then watch the gauge, it should hold the proper pressure for a minute or so. Excessively high or low pressure could indicate a pump or pressure regulator problem. See your car's specs for proper FI pressure levels.

    Finally, you can test the injector by applying voltage to it. DO NOT APPLY 12 VOLTS !!!!!!! The injector will fry and (at least in the case of my 164) you'll be out about $50. 3 volts does it for my injectors, and you look for a fine cone shaped pattern with no big droplets in it. Again be aware that you are spraying gasoline, it is best to put the injector in a coke bottle or something to catch the spray. Remember, this is how your car sprays gas into the cylinders just prior to IGNITION, Volvo paid someone big bucks to figure how to make that ignition easy, and the gas doesn't care that its not in a cylinder being ignited by a spark plug.

    If the tip of the injector leaks (i.e. during the pressure test drops of gas fall from the bottom of the injector or during a pattern test the flow doesn't cut off sharply) the injector has to be replaced. There are seals around the injector and port to prevent "extra" air from getting into the cylinders, but there are none within the injectors.

    As a side note, I have an "extra" air problem that causes engine race and/or non-operation. Thus, I have been in after all the seals and stuff after determining that the injectors are O.K. by the above procedures. BTW: Extra air is air that does not come past whatever your car uses as an air sensor (mine has a pressure sensor, some of the newer Volvos have the infamous air mass meter). Because the air is not accounted for, the air/fuel ratio is off and the car doesn't work right.

    If you really want to become a FI system expert (as I seem to have been forced to become by my brick) try Probst's _Bosch_Fuel_Injection_and_Engine_Management (ISBN: 0-8376-0300-5) it is a complete, definitive work with all kinds of troubleshooting stuff.

    Hope this helps. Got questions or comments, let me know.

    DISCLAIMER: If you aren't sure about what you are doing, don't try this stuff, one of you out there once said "Gasoline ain't orange juice." and he's right.

    -Alec D. Isaacson
    AI4CPHYW @ miamiu.acs.muohio.edu
    isaacson @ rogue.acs.muohio.edu (NeXt Mail)
    Miami University, Oxford, OH

    "Gully Foyle is my name and Terra is my nation. Deep space is my dwelling place, the stars my destination." -A. Bester

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    Working with p-channels.

    Date: Wed, 28 Apr 93 11:05:46 -0400
    From: bw738@cleveland.Freenet.Edu (Ed Wetherell)
    To: wiegman@orion
    Subject: fun w/ FET's

    well, finally got the p-channels.. and after some wiring troubles got the thing working.. initial test show _no_ significant performance increase. being a completely untuned driver, i am not surprised.. i have to figure the correct hold level and maybe tweek the peak time (~250uS now) up a little.. found a cool parts store near me.. got the 9521's for $1 ea and the digikey price is ~$2.50.. i was happy..besides, it real close to where i am working.. big bonus!

    keep you posted


    Date: Thu, 29 Apr 93 11:25:06 -0400
    From: bw738@cleveland.Freenet.Edu (Ed Wetherell)
    To: wiegman@orion
    Subject: Re: fun w/ FET's

    after a little tweeking, they work much better..i think it can get better yet, but ill have to play round.. the on time is about 1.6 mS still slow, but i think it ill work. off time is down around .6 mS - more than adequite, at least for now.. the hold voltage is about 1v and the peak is for 500uS

    i'm a little reluctant to increas the peak time much more..i'v gotta look at the current to be sure, but im not sure how much more will be safe for the injectors over extended periods of time..

    should that circuit be able to handle 2 injectors in parallel?

    my guess is yes, although peak time and hold voltage might need adjusting again.. your thoughts?

    >>for $1 ea and the digikey price is ~$2.50.
    >so I'm not the only one to think that Digikey is a rip off.. I built
    >a Class A audio Amp and I spent $8.xx on some TO-3 cans from IRF...
    >ouch.. but they do deal in small quantities..

    that $2.50 is still $10 less than the other parts places locally that had it!! i about fell over when the guy said 12.35..the n-channel was in the $2 range so i figured the same for the p, oh well..

    ill keep you informed of any changes..


    Date: Fri, 30 Apr 93 11:37:15 -0400
    From: bw738@cleveland.Freenet.Edu (Ed Wetherell)
    To: wiegman@orion
    Subject: Re: fun w/ FET's

    >sounds like a decent driver.. have you looked at the voltage waveforms?

    yes, they look ok. 13.8 (~) volt spike that decays to about 13.5 (~) by the end of the pulse, followed by the 1 volt hold, and a sharp negative turn off spike that decays to near 0v in about 1.5 ms maybe less..

    >You may not have enough decoupling (big caps) at teh 14V supply..or you

    the supply im using is a r-shack 12v supply that i had around. i slapped a 28000uF across the output + whatever is inside. it might not be putting aout as much current as i need, but I have to check that out..

    >a driver up here and whip my scope on it and current probe. that might be a good idea. when i put a 1ohm in series w/ the injector wasnt ffiring real well, but the waveform said that the hold current was about .4 A and the peak is at least 1a although it looks more like .8 decaying to .6 before the .4 hold.. ill have to work w/ that a bit more.. i'm gonna change the drive voltage to 14v. the drivers seem to put out about 10v..

    >assuming the voltage supply is stiff (both the 14volt and the 1Volt) the
    >driver should be able to supply two or three injectors. The switches (both
    >N and P channel are limited in the amount of current that they can supply..
    >I think the pulse current capability is in the 10 Amp range.. so i don't
    >think any adjustment is necessary when paralleling the injectors. both of them
    >will see the same voltage excitation and will probably fire at the same time.

    ok.. ill have fun w/ it this weekend.. see if fi can come up w/a stronger 14 v supply.. im sure i have something around here that will work w/o resorting to a car battery sitting next to my computer..as if coffee spills werent enough trouble...

    have a good weekend


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