Dana—remove the distributor and secure it somehow ( e.g. in a vice) attach a volt/ ohm meter set to ohms to an outside pin and the center pin, turn the distrib shaft and watch the ohmmeter move as you turn the shaft. Doesn’t matter what the reading is, if the meter deflects your know one set of points works well enough. Do same thing on the other outside pin to check the other set of points. You can do the same checks at the ECU connector also to make sure wires show continuity. Or borrow a set of points from Don, our god of D-jet problems…
Non Running Engine Good Compression and Ignition Spark Present Noid Light Test no Signal
- Thread starter neon
- Start date
I meant Neon..
Many thanks we are proceeding with the diagnostics. All the "wires" from ECU to the injectors seem to ohm out appropriately w v low resistance thus presumed intact. All grounds seem good. The distributor trigger contact plug seems to be generating a signal that is low voltage on the VOM and is intermttent on cranking the starter, but not known if correct voltage or waveform to trigger the ECU Again nothing w the noid light testing ( no signal to the injectors) . May try using a dwell meter on the connected ECU to look for a stepped voltage signal, as described on jetronic.org. More later ....
Dana
Hey Bill - nothing like a concrete step by step description. Thanks Thanks He ( I ) can be taught but sometimes the wheels turn slowly ! I have done something similar finding a voltage deflection at the ECU checking pins 4,5, 6, 7 ( if memory serves) on cranking engine which pins receive the trigger point signal. The mystery unfolds and starts to incubate the possibility of a defective ECU - pls not not that !. Funny too the MAP ( which tested OK both vacuum hold and coil continuity - pls note however coil resistances were 90 and 330 Ohm, do not know the spec on these ) does not have a color dot on it, however ECU is red dot. Will contininue to retest and look for grounds I may not have located. Ground from the injector system ( at rear location on valve cover on my car ) is good. Also not 100% sure all key wires are intact but have confirmed continuity on the majority. Strange brew.
My gratitude to all
Dana, CT
Bill - a quick question. You had mentioned that the main relay was on R or L - what is the R/L reference ?- ie when looking from above on the driver side or standing on the passenger side
Tks
Dana
If you haven't swapped the ecu out with another, try that. You'll have to wait for Don to return-he has loaners, or see if someone will lend you there's. It's a quick swap and it really won't matter if the color codes are different.
On my '74, behind the booster, under the MAP, the main relay is left (towards front of coupe), the cold start is right, closer to firewall. I hope the same applies to your coupe.
Jetronic.org makes a fuss over color dots matching with the MAP and ECU, but my colors have worn off long ago, and I have mixed several MAPs with two different ECUs with no problems. Currently using a MAP from a Volvo. Gas mileage/pollution levels may suffer, but my coupe runs anyway.
You have continuity in the MAP coils, that's good. The coil readings are supposed to be 80-120 and 300-400, so you're OK (fyi they vary under engine load, but that's another story...)
Dana, I'm sure you've probably already done this, but look in the ECU harness connection for any mangled connectors. In mine, #16 (power) somehow got "bent"...for the life of me I have no idea how that happened. Not fun trying to straighten it out...
Bill - Excellent thanks , will verify but that was my guess.
Yes have been watching for this, I have a set of mini screwdrivers that I have used to bend them if they seem too wide. Obsessively rechecking grounds and working to figure out if the trigger point system is generating the correct signal. Next update could be a week or so out. Maybe borrow that trigger point set from Sfdon ....
Dana, FIord Blue '73, hoping to take a victory lap soon
Heading home tomorrow.
SFdon, BIll, Ohmess, Coupedegrace - I have verified continuity of wires 21 and 22, as well as 12, to /from the distributor trigger points to ECU. I am wondering what the center pin and wire 12 are. On the ECU pinnout table 12 is described as " supply" but somewhere on jetronic.org it is described as a ground. In my car there is no voltage to wire 12 with the key turned on. Is wire 12 a ground or the power supply to the distributor trigger points ? I am focusing my efforts on the trigger points for now, but may not be able to do much over the next week. I will move on to the test described by Bill (rotating distributor and watching for change from low ohm to open circuit) as long as I can find an easy way to turn engine from the crank nut,( I am afraid to take off the distributor for now) there is no room between the crank pulley and the radiator in which to insert my 3/4 drive ratchet. I am supposed to be getting back my rebuilt 912 engine for my '68 912 this weekend - we will see.
Dana
Dana, you have continuity on the wires in the trigger point circuit, I'd let it go at that, no more testing needed. I would try another ECU...from SF Don if he has one. Do 912s have D-jet? If not, lucky for that...
912Es have D Jet...not 356 based 912s.
Bill, will get to that trigger point circuit resistance varying with rotation test. After that if it shows opening and closing trigger points, I will have to go begging to Sf Don for the ECU, or for some trigger points. Updates probably next week. I am hoping that I do not have to drag Astrid up to Mario in NH. I am in the despair part of the project ...
Ad astra per castra
D
I know your pain..I have had severe hesitation problems recently that have eluded every test I know about, including help from SF Don. I think my rebuilt (maybe not correctly adjusted) MAP is telling the ECU somehow to momentarily stop working, the Volvo MAP (factory) I'm currently using is doing the same. The Throttle switch may also be suspect, but it is correctly adjusted, so I don't know. Short of re-adjusting it (again) I will probably go back to my Webers. There may be some truth to matching MAPs with ECUs and who knows how to do that? Volker at djetronic.org might, maybe I'll check with him.
I tested the trigger points by
Putting the car in gear 3, disconnecting the lead, set multimeter to ohms and tested trigger points resistance.
Spark plugs out.
I pushed the car to rotate the engine whilst watching the resistance change.
These resistance figures were not consistent, so trigger points out, washed in petrol (dry cleaning fluid would be better) refitted them. Small touch of grease onto cam.
She ran again. I concluded oil / dirt had got onto the points.
Worth a try
I did notice than she ran badly for a few miles before being parked, then would not start again.
Putting the car in gear 3, disconnecting the lead, set multimeter to ohms and tested trigger points resistance.
Spark plugs out.
I pushed the car to rotate the engine whilst watching the resistance change.
These resistance figures were not consistent, so trigger points out, washed in petrol (dry cleaning fluid would be better) refitted them. Small touch of grease onto cam.
She ran again. I concluded oil / dirt had got onto the points.
Worth a try
I did notice than she ran badly for a few miles before being parked, then would not start again.
Bill - you do know about Mario at VSR in Bedford NH, I assume ? Probably the best E9 shop in the East.
Can you "back probe" the MAP output and drive while watching the output voltage on the VOM> I do not know however what the expected voltages would be.
And you have swapped out the ECU I am sure. I wonder if these ECU's develop component failure - caps, transistors etc which may be manifest as intermittent operation.
Dana
Can you "back probe" the MAP output and drive while watching the output voltage on the VOM> I do not know however what the expected voltages would be.
And you have swapped out the ECU I am sure. I wonder if these ECU's develop component failure - caps, transistors etc which may be manifest as intermittent operation.
Dana