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You can do one more check to see if the DME computer (ECM) is getting power at terminals 18 and 35. If it is getting power, then ECM is suspect. |
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I will do the test on the power to the ECM tomorrow. But I am just curious. I know I am having problems with the injectors not spraying. Perhaps that is the ECM injector board. But I tested the ECM at prongs 1&19 and got a pulsation to the coil. So, even if I am having problems with the ECM, it appears to be putting out a pulse to the coil. My problem is that the coil is not reading the pulse from the ECM signal and distributing it to the distributor for a spark. Could fault from the ECM come into play under that scenario |
From what I've read, you didn't drop the engine. ? There is a pin on the flywheel the the sensors need. Just a thought, read this thread. Sorta sounds like your problem. http://forums.pelicanparts.com/porsche-911-technical-forum/588695-86-wont-start-after-new-flywheel-no-injector-coil-pulse.html
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As well, there exists some resistance measurements/specs within the Bentley that will give you a static resistive read of both primary and secondary coil condition. Of course, sometimes, when heat is expended, things change: still, a good check. Best! Doyle |
The ground is was referring to at the battery is the neg. battery cable. It is grounded to the right. Of the battery. Pull battery out and you will see it.
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I have questions highlighted in green. Can you answer them pls.?
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Bazaar:
In answering two your two specific questions. 1. No i did not disconnect the ECM (brain on the inside of the car) from the ECM harness when i checked the ground on each left injector prong. 2. When I checked pins 1 & 19 I used a voltage meter. the mechanic who was reading the meter said it was pulsing. I did not see it, and I really do not know if he knew how to actually read the meter. I simply went off of his word. Could you share with me your suspicions that prompted your questions because i am truly stumped |
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2. It is really hard to see the pulsing on a digital meter display. A scope meter will be best. With your test, you really cannot say the ECM is providing the ground pulse to the ignition coil. The ignition coil pulse signal is a series of fast 12V and 0V switching signal. 12V saturates the ignition coil primary coil and zero volt causes a collapse in EMF on the primary coil to induce the high voltage spark on the secondary high voltage coil. The high voltage gives the spark plug the high voltage arcing. Are you going to send out your ECM for testng? You can just wait until you get the ECM back to confirm your ECM is good, then troubleshoot further. |
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I am going to send out the Brain now. I will get it back and then troubleshoot from there. Thanks so much for you and everyone else's patience and guidance. |
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Here are the diagrams for the fuel injectors and spark ignition. This will help. Injectors: http://forums.pelicanparts.com/uploa...1368127706.jpg Ignition: http://forums.pelicanparts.com/uploa...1368127829.jpg Let me know if you need the complete file in pdf. |
Just to give a little information on the coil, the black wire is a 12V source when the key is in the run or start position to the coil +15 terminal. The green wire goes from the coil '-' connection back to the DME, which makes the connection to one of the brown ground wires connected to the intake runner to trigger the spark. There is no signal on the green wire, just a series of intermittant ground connections to trigger the spark. It works like a set of electronic points opening and closing the ground connection.
http://forums.pelicanparts.com/uploa...1368128469.jpg |
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The DME ignition driver circuit provides the grounding to achieve the zero volt pulse. The grounding is internal to the DME circuitry. The DME itself which is located inside the cabin has it's own grounding point and does not need the grounding point in the intake runner. |
Srwilliams, I hope this doesn't confuse you.
I realize this is somewhat off track, but I enjoy learning from others also. I respectfully will agree with you, you are the Engineer and I am the Electrician. I have not had the training in electronics you have and over simplified the ground connection. While not a direct connection, it just seems to me that internal grounds seem to come from the external ground wires on the intake runner. Most of the ground connections seem common from what I can make out of the diagram, aside from the bridge connection for the California emissions ground. http://forums.pelicanparts.com/uploa...1368137151.jpg Also, a note on the coil from the manual for Srwilliams. Testing of the coil should not be with leads on the meter across the coil (+)15 and(-). They also seem concerned with how the terminations are made on the coil. http://forums.pelicanparts.com/uploa...1368137410.jpg |
Sully:
No problem. I am in the background smiling as I pick up little tidbits of scrape information that falls to the side during the exchanges of two heavyweights---Bazar and Sully. In truth, I am learning a lot from the debates and meetings of the minds that the two of you come to. Also, it lets all of the rest of us neophites and DIY people know the level of knowledge we need to reach to be able to effectively work on our cars. I am so impressed by the knowledge that people like Bazar and Sully have, as well as their ability to break matters down on the base level so people on my level can understand. they never once have talked over my head in trying to assist me |
Spoke with a VERY knowing Porsche guy today and he was quite concerned (with all of the disconnects) that the sensor connections didn't get swapped on the reconnect, as this would give you the indications you are experiencing. Hopefully, you've already put that suggestion to bed.
Best! Doyle |
Hey y'all, i take no offense in constructive disagreements. I just wanted to make sure the information on this thread is correct and will be useful to anybody down the road.
This board is all about helping and learning from each other. We all love to work on our pcars. |
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Doyle: Both me and a knowledgeable porsche enthusiast covered the sensor possibility (mis-swap) several times. In fact that is the first troubleshooting we did. But I really want to thank you for the level of your concern of my predicament that you consulted with your own resources. For you to go to that extent to assist me really speaks to your level of concern and consideration. Thanks so much |
My apologies, SRWilliams. I've just now read the entire thread and obviously missed your reference,...so, onward (with the sensors having already been checked).
Best, Doyle |
Injectors not spraying - solved
was this O.P. ever solved? SmileWavy
- a report would be useful, in any case, i am posting this possible solution so that a future comrade who stumbles here via google will have a decent clue about a possible solution i had a similar problem as of 3 days ago; (5 days before that i drove it over 600 miles with no problems) '89 3.2 ... suddenly just began running like on half cyls after a mile (like fuel starvation, then would pick up momentarily, .... then died completely & no start - i went thru testing most of the "usual" suspects starting with the DME Relay; then the Test Plan ( the Relay is good - the pump works per spec ign on & crank, , it has good spark, no NOID indication, swapped DME/ECU, etc); it does start & run on starting fluid; - starting on the circuit tests suggested in this thread, & my enlarged factory wiring diagrams in hand, i discovered no 12V at the injectors, and no continuity from Pin 87 of the DME Relay socket to the injectors - so i apparently had an open in the harness today, i discovered that the injector harness 6-pole plug had simply come undone SmileWavy - it just vibrated loose :( (to paraphrase rusnak "that is weird") - obviously had to be working its way loose for a long while - (spirited driving on rough mountain roads a possible contributor, but the wiring loom was securely bolted to the manifiold per oem just 2" or so from the plug :confused:) p.s. - this thread has lot's of good troubleshooting info i've not seen in many others O.P. QUOTE=Srwilliams;7427450] in fault checking my no-start issue I have traced it down to my injectors not spraying. |
solved - see above edited post
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This is a great and helpful thread and seems to be exactly what I need, for my 86 3.2.
Before I go and check the grounds which seems to be what I need, and from what I understand continuity to the ECM as well, I wanted to ask, should there be power to both sides of the injector connector? I used a lamp tester and I can see power on both sides with the ignition on, is this supposed to be like this and the ECM switches to ground to create the pulse? (I will use a voltmeter now I've learnt how to from here) Its been a long road to start this this 3.2 not started in 7 years or more, a true barn find (parked in a muddy field actually), I did get it started after sorting out no spark/no fuel pump issues and it runs on starter fluid, but no pulse to the injectors. I don't have a noid light but used a very sketchy way to crank with the injectors out and there was no spray, but the rails have good pressure fuel in them. |
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Yes the old injectors were completely rusted through and blocked, I have a set of refurbished ones there now. I will find time to run through the grounds, thanks! |
I've run through all the steps and everything is as it should be;
I have 12v at each injector connector and there's continuity to the ECM terminals 14 and 15 also checked the ground terminal as well, I still don't seem to have any injector pulses, I'm waiting for my noid lights to come in to narrow it down to the injectors, I just bought refurbished injectors. In the meantime I wanted to find out if there's anything else that can disrupt or stop the injectors from pulsing. The ECM is brand new and so is the DME relay |
1. Did you measure the ohms between the ecu ground and the battery neg cable up front ? (Bat disconnected)
2. Idem for intake runner ground ohms to bat neg cable up front ? (Bat disconnected) 3. The CHT sensor on cyl 3 takes its ground from the case - is that coated perhaps ? I think that without a correct CHT reading it will not start. (Ohms value in range when sensor disconnected ?) 4. The ECU is not going to fire the injectors unless it sees 200 rpm or so and a ref signal from the 2 sensors on the flywheel. Measuring the ohms on them is not enough. You can measure the voltage they output (Ac volt mode on multimeter) and it should be >2.4 V (speed sensor), thevref sensor output is a bit more difficult to see on the voltmeter (certainly on the digital ones) as it is one short pulse per rotation. Better yet - I use a cheap oscilloscope (called DSO shell, 35 usd on amazon) to really verify a correct signal from these sensors. Speed sensor (idle at about 900 rpm) https://uploads.tapatalk-cdn.com/202...33f4e62b1f.jpg Ref sensor (freq measurement is wrong here) https://uploads.tapatalk-cdn.com/202...866686a415.jpg And then the coil signal should look like this (primary) https://uploads.tapatalk-cdn.com/202...5bb6bc9e25.jpg And an injector being grounded (see left side of screen) and when fully opened being kept open by a series of short pulses (peak&hold driver). And a large spike at the end when the injector closes. https://uploads.tapatalk-cdn.com/202...0bf28aee6a.jpg Sent from my iPhone using Tapatalk |
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1&2: No I didn't check the ground from the ECU ground or the intake runner ground, I will do that, what readings should we be looking at? 3: The CHT sensor? Would that be the one with the white connector? I just changed the CHT sensor and both the speed and reference sensor, I had no spark till I changed them and gapped to 0.8mm as instructed by the manual. The CHT sensor is this the one that connects in the same bracket as the speed and reference sensor? All of them are new. 4: How and where do I probe the speed sensor to measure? I will have to look into getting and oscilloscope. Thanks again. |
One shorted injector will kill the other 5 from firing. Unplug 3 injectors on drivers side and see if it starts with just the passenger side injectors.
If not flip to the other bank and plug back in drivers and unplug passenger side. And are you 100% you have spark? To prove it's a fuel issue squirt few shots of starter fluid directly into the intake, remove the idle control valve lower hose and squirt 3 or 4 shots of fluid into the intake at that port. Then try starting, the engine will catch and start if you have spark. |
One other sanity check: turn key to RUN but do not start engine. Then go back in engine bay and see if idle control valve is humming and vibrating. If it is it means the DME is booted up and has power. Be sure this is the case.
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Yes we have spark, the car starts and runs on starter fluid. |
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Read post #62 again and get a noid light!. You knew you had spark, which eliminates the pickups.
You knew it's a fuel problem. Others have wasted your time! You can use a test-light in place of a noid light, by having the alligator clip on +12 and the ice-pick touching one of the injector pins. You can also back-probe either pin 14 or 15 on the DME ECM. Disconnecting the temp sensor will allow the test-light to flash brighter. Hopefully, the ECM hasn't been over-voltaged by a bad alternator or jump-charger. This can damage the injector output stage. |
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So what you're saying is clip side of a test-light to battery +ve and probe to any of the terminals of the injector connector or must it be the grounds same ones that run to 14/15 on the harness? Noid lights are about a week away from me... |
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with the back of the connector (black) removed. The connector must be plugged in. |
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