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I'm about ready to give up on D-Jet & I've been a professional wrench for 30+ yrs! The problem only asserts itself after heating up, usually after at least 10 mi. The injection drops out 2cyls [#s 2&4]. I have a DVOM that can measure pulse width [which is .79 ms at idle] & duty cycle for the trigger points [which is 49-51% untill it heats up sufficently to start the problem]. Running on 2 cyls in traffic sucks! I've replace the trigger points, substituted a used ecm,isolated the injection from the ignition, isolated both inj. & ign. from the ign. switch,swapped out the pressure sensor,replaced the injectors, cleaned all the grounds, replaced the connectors at the trigger points, replaced the coil [Bosch blue], & swapped out the Pertronix ign. for points. I've tested the pulse width at the injectors & at the ecm terminals & the same for the trigger points. The problem was occaisional untill the warmer weather, now it's a real pain. If I raise the hood it will take longer to occur. Voltage to & from the inj. relay & the fuel pump relay is good. The relays don't seem to be overheated. When the injectors drop out the trigger point duty cycle also goes haywire, fluctuating wildly from 0-99 & anything in between. So... any ideas guys?
Mike M.
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Sounds to me like the problem is your carburettors... Lack thereof, that is. I know that ain't the proper fix, but damn...it'll get you on the road.
Best of luck with it!
-Matt
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-Matt '70 145s, '65 1800s, '66 122s wagon, others inc. '53 XK120 FHC
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Given all the bits which you have substituted didn't help, I'd suspect a wiring fault.
Check resistance between the terminals on the plug at the triggering points and their corresponding pin on the ecm. Centre pin on the plug is 12, left pin (looking from above with plug installed in distributor) should be 21, right 22.
Check that the connectors in the plug for the points are firmly fixed in the plug body. Sometimes the little tang which holds them in place doesn't, then the connector pushes back into the plug and can cause a crappy connection. This happened to me with the temperature sensor in a cis system on a 760. Connector pushed back into the plug enough to cause resistance across the connection yet still maintain a partial connection. Sent the ecu into spasms. Took a while to figure out because when the plug was pulled from the sensor the connector moved back into its proper position inside the plug.
Also check wiring between ecm and injectors 2 & 4. Injector no 2 has pin 6 at the ecm, injector no 4 has pin 5. Pins 27 and 31 at the injectors go to earth.
I've also experienced a condition where the cam on the distributo shaft wears in such a way that if one of the trigger point gaps is small, it can cause one set of points to fire twice per revolution. This has the effect of making 2 cylinders run disgustingly rich and the engine runs like crap. Doesn't sound like this is probable in your case though.
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I pushed all the connectors in with a probe to be sure 'cause that happened on one of the injector connectors, so that probably eliminates that. I removed the 3-wire connector block & replaced the connectors individually with gold plated spade connectors [marking position first tobe sure of correct placement] You may be on to something with the worn cam though since one side of the signal completely goes away & then the other side goes goofy. But why the heat factor? Point gaps on those points are well nigh impossible to check. Thanks.
Mike M.
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It is possible (but not particularly easy) to check the points gap. Remove the point assembly and wedge a thin piece of something (a piece of old feeler gauge of suitable thickness is ideal) between the underside of the moving section of each of the points and the body of the assembly so that when the points are pushed open by the cam they stay there and don't return under the spring tension. Re fit assemblt. Rotate carnkshaft a couple of turns using a wrench on the crank pulley bolt. Remove trigger points. Note gap. Fiddly and time cosuming method but reasonably accurate.
I wonder if it is possible that the diameter of the cam expands enough when it heats up to cause the problem. Like Chris said, remove the distributor and stick it in the oven, then see what happens.
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I have found it easier in the past to remove the whole distributor (remove the bolt from the engine block, not the clamp bolt that you loosen for ignition timing adjustment) and using an ohm meter at the workbench, verify you have ~180 closed and ~180 open on each set of trigger points. It's not "terribly" critical. Get it in the ball park.
With the failure you're experiencing, I'd then put the distributor in your oven and take it up about 150 and check it with an ohm meter again. That should pretty well determine if the problem is inside the distributor or not.
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Make sure the wires and connections are in good shape around the Fuel Pump and Injection relays - as I recall they sit side-by-side under the hood, over one of the inner wheel wells.
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Sounds like maybe a marginal electrical wire where impedence increases beyond working threshold due to heat. Check/clean that big central grounding point on the intake manifold for all those little white wires.
ALso maybe a worn lobe for the trigger points. 2&4 failure sure points thataway. You might have to tweak the trigger points. AFAIK it's impossible to get a good visual of them opening and closing, If you check the dwell on them, although that's not used in the EFI, it might indicate which side is iffy.
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the above is the best idea so far, IMO
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I agree with the wiring scenario, though I've cleaned the ground connector twice. I may try to separate the wires & ground them individually next. The only problem with this is that the injectors are fired from the positive side I think, judging from the wiring diagram & there's no positive signal coming from the ecm to the injectors directly at the ecm. The only other thing I can think of is a relay drawing too much current & depriving the ecm of full voltage. I once had a fuel pump relay on an Audi that caused poor spark from the coil by drawing too much current. Anybody ever experience that on an ecm? Thanks.
Mike M.
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Pull the cover off the big ECU connector and have a look at the solder on the wire/pin connections. Your symptoms could be explained by fractured solder -- that can be very heat sensitive.
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I had already looked at the solder joints inside the ecm- looked OK,plus I substituted the other ecm while it was doing it & there was no change in symptoms. I'll check again just to be sure. Thanks
Mike M.
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Mike, I meant the joints inside the connector, not the ECU. The connector cover pulls back and lets you access where the wires meet the pins.
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I've got the gray cover removed to expose the white plastic 24 pin ecm connector & I've got the white plastic guard removed so I can access the wires & the pins. So far no luck on the connections, but I'll keep trying! Thanks again.
Mike M.
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Good thought. It might even be the fuel pump or some other major load causing low voltage. I remember my '73 stuttering when the fuel pump was iffy, and I thought it was low pressure. I replaced the fuel pump and it cleared up. I realize now that it may have been excess load sapping the ignition.
Fan belt tight?
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I agree with the wiring scenario, though I've cleaned the ground connector twice. I may try to separate the wires & ground them individually next. The only problem with this is that the injectors are fired from the positive side I think, judging from the wiring diagram & there's no positive signal coming from the ecm to the injectors directly at the ecm. The only other thing I can think of is a relay drawing too much current & depriving the ecm of full voltage. I once had a fuel pump relay on an Audi that caused poor spark from the coil by drawing too much current. Anybody ever experience that on an ecm? Thanks.
Mike M.
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posted by
someone claiming to be joris
on
Thu Apr 29 01:38 CST 2004 [ RELATED]
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How about a broken wire inside the harness?
The injectors are triggered in pairs, although I'm not sure 2 & 4 are fired together. But if so, and replacing both the ECU and the injectors did not help, I'd look at the wire that connects both. I know next to nothing of the D-jet, but electrical wires are among the things that are always taken for granted.
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Yep they are fired together 1&3 2&4
If needed I could scan and post the Fuel Injection chapter from my 73 FSM just let me know if you need it.
--
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Are you sure it's #1&3 & 2&4? The last article I read said it was #1&4 & 2&3 which makes more sense since they are fired 360 degrees apart.
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Absolutely sure. I'll be glad to post the chapters scans to my site if you need any additional information but to quote the book.
"The injectors operate in two groups, that is, two and two. Injectors 1 and 3 inject simultaneously and 2 and 4 simultaneously"
--
1973 145 Lola & 1972 142 Quinn
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got a breakout box and a scope? watch the trigger points and the injector pulses. i'm thinking the dist shaft is bent and not opening the points enough. HEARD of it happening, never had to look, though. seen it on a 320i with the electronic ignition, 80-81. how's the ignition dwell? good luck, chuck.
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The only breakout box I've got is for Fords. Both sides of the trigger points start to fluctuate & only after having heated up. When cold the duty cycle is normal. Would dwell be applicable since it is only measured in increments of 90 deg. or less? The on -off time should be 50% which would be 180 deg. I think. I tried adjusting the trigger points with shims to vary the dwell, but it seems to have made no difference. If the shaft were bent it should evidence itself when cold too I would think,yet the variation in duty cycle is only+-3 percentage points when cold & all over the map after heating up. Ignition dwell is within normal limits for a points dist. The pertronix mag trigger eliminates most dwell variation I think,so that would eliminate that as a problem to my way of thinking [which may be way off base by the way] Most of my measurements were taken at the computer with thin wire probes at the pins with double checking at the inj. or trigger points to try & eliminate the wires as a source of the problem.
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been a while since i've done djet on volvos, lotsa benzs, though. and i think i'm the only 1 with a djet harness for my bob.
sounds like the trigger points are the problem. getting squirrely after heating up. that's why a scope is nice, you can watch the waveform come apart. pity i can't scan it for you. it's a square wave that runs at 4 volts, 50% duty cycle, each set 180 degrees apart, 2v per division, 10ms per division. 1 and 3, 2 and 4.
where are you? maybe close enough to bring my stuff? i'm in orlando, fl. good luck, chuck.
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Could'nt be much farter away-Chelan Wa.[drat] Unfortunately my scope got sold with my other equipment when I sold my shop back in Mil. Wi. I should maybe think about investing in one again. I wonder if the 4 v. signal from the ecm is going away due to bad wiring? I think I'll sub. that wire in. If that doesn't work, I'll try a used dist & see what happens. The trigger points are new & Bosch replacements so they should be OK. I can maybe find a scope somewhere in the area for a look-see & I'll let you guys know what happens. Thanks again for all the help.
Mike M.
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