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@DaX that spreadsheet is incredibly informative. Lots of goodies that are not in my Helms manual. I'm still kinda digesting all that info, but it has answered many of my questions already.
Originally Posted by DaX
After the MPFI swap, the following things need +12V supplies:
EACV - This controls your idle, and you'll likely get a CEL if it's not getting the voltage it needs. Resistor box - this distributes the +12V to the four injectors. The resistor box plug should be a 6-pin plug with 5 wires - one +12V in, and four wires that run one to each injector. Reverse lights - my car was originally an auto, so the reverse lights weren't in the engine harness, and instead were at the shifter. When I converted to manual, I had to run my own reverse lights. Not sure where the stock location is for this in the harness. Alternator - this comes from C102 (on my car it is BLK/YEL), which is the big 8-pin connector with the dielectric grease in it and the plastic boot around it that is located on the passenger shock tower. Distributor - this comes from C102 also, and is also BLK/YEL.
These MPFI requirements will be vital if I can figure out exactly what is going on inside the monotech harness. If I know where everything is routed in there, I can then supply power to the correct pins. But to be honest, I'd like to focus on the stock, DPFI side before I try to reverse-engineer Monotech's work. I have confirmed problems with the chassis harness between the main relay and connector C313, and I have 99.9% confidence in the monotech part. If I can get connector C313 back to stock, supplying power in all the spots that a DPFI system needs, I am confident the monotech harness will take over from there, and route stuff correctly. Its only 9 months old and ran my MPFI system perfectly for 8-8.5 months. It's also the nicest looking, shiniest thing under my hood. Also, they say you get what you pay for and that part was $225 while my entire chassis cost $175, lol.
I'm looking at this picture right now:
And comparing your function column to my test results. My tests match your notes at pins 4 and 9, and clearly I'm missing (+12V) at pins 1 and 6. I have (+12v) at pin 7 and you have labeled it (Vout) there. Should I have 12v at all the spots marked (Vout)?
Which pins in C313 should have 12v with key "on" in a stock DPFI system?
And comparing your function column to my test results. My tests match your notes at pins 4 and 9, and clearly I'm missing (+12V) at pins 1 and 6. I have (+12v) at pin 7 and you have labeled it (Vout) there. Should I have 12v at all the spots marked (Vout)?
Which pins in C313 should have 12v with key "on" in a stock DPFI system?
One thing to note, I'm using 'Vout' to indicate that the ECU controls a particular item (typically a solenoid). by sending OUT a voltage signal (actually, by completing the ground portion of the circuit). I'm using 'Vin' to indicate that a particular item (typically a sensor) sends data IN to the ECU via a voltage signal. My car was originally an automatic - was yours also, or was it a manual? On my auto chassis harness in stock DPFI configuration, Pin 7 on C313 is the 'Vout' signal the ECU sends to activate the automatic transmission lockup solenoid - not sure if this is something different on chassis' with manual transmissions, or if this was just left blank. To directly answer your question, no, you should not always have 12V on the pins marked as Vout. With key on, you should definitely have +12V on all the pins marked as +12V...that's pins 1, 4, 6, and 9.
Also, see if these help - DPFI wiring diagrams from Honda. I can't take credit for them, they were posted on H-T sometime in the past. If needed I can also share the same sheets for MPFI. It looks like the wiring for C313 is slightly different for pin 4 on this diagram than how my car was wired. Maybe that's the difference between auto and manual? Or sedan and hatchback? Not sure...but it looks like the GRN/BLK I have at Pin 14 is at Pin 4 on this diagram. This is why I said YMMV....
Nuuu! Not the facepalm, @muellersfan ? What am I doin wrong?
I'm just struggling to understand your focus on a fishing expedition to find an electrical problem that may not exist. Refocus on basic but powerful no-start diagnostics. This unbiased method will reveal the problem without requiring you to guess.
I swapped pins 1&4 at C313 today, got 12v at injectors again, no start. Ran that good #4 pin to #6 spot, got 12v at injectors, no start. Dumped a bunch of carb cleaner in intake, no start. Rechecked spark at plug wires with testlight, got spark there. I keep going back to wiring because I know there are problems there. The only problem I have identified is the lack of power at injectors with everything wired as it was when running, but there is at least one other problem and it seems reasonable to me that it would be near the one known problem?
EDIT: that spark is awful weak n erratic at plug wires. I think I am progressing again.
EDIT2: and spark is gone. I was cranking the engine ALOT this morning trying to get carb cleaner going. Cranked it long time to try and get engine code but never got one. Did very little to the wiring, just swapping pins 1,4,6 around at C313.
Alright ignition coil removed. So, the manual has me check both Primary and Secondary resistance. The primary is measured between the two terminals on top marked (+) and (-) and spec is 0.6 to 0.8 ohms. When I first put the probes in, it reads really high (3 or 4 ohms typically, but sometimes 20+) and starts dropping. It spends a loooong time out of spec at 1.5ohms but eventually falls within spec, never going below 0.6 ohm. Although it may be lower than that, my test probes always read about .3 ohms resistance when in direct contact. For the Secondary resistance, between (+) terminal and winding terminal, I get no reading at all. Same "1" all the way on left of multimeter screen that shows with probes touching nothing (not 1.0 ohms). Spec for that is supposed to be 9.760-14.640 but I get no reading.
EDIT: maybe I'm not testing this properly? I dug out the old dpfi distributer and cracked it open, the ignition coil looks identical, except for a big burn hole near winding terminal.
For the primary reading, determine the internal background resistance of your multimeter:
Touch the two meter probes together. Let reading stabilize. Note reading and subtract it from the primary reading to calculate the REAL primary reading.
However, the secondary reading you reported is screaming "bad coil"!
Do a full ignition tune up before installing the new coil or you may blow the new one.
My guess is that the engine will fire up upon installation of the new coil. If not, recheck for spark and CEL codes. If fine, do the starting fluid test again.
Last edited by muellersfan; 11-05-2018 at 08:16 PM.
@muellersfan full ignition tune up = plugs, wires, ignition coil, cap and rotor?
Then I get to return to my now two-weeks-old friend: "repair open in YEL/BLK wire between injector resistor and main relay"?
Oh, and my plan to get power to injectors by switching pins 1&4 or 6&4 at C313 won't really work. It DOES send power to injectors with key in "on" position, but it introduces a new problem: Instead of priming the pump for 2 seconds, the pump just stays on. The tone changes just a bit after 2 seconds but it never goes quiet. The change in tone leads me to believe it is switched at the main relay, but is also contacting a constant power source? Does this help at all with wiring diagnosis? I believe it originally powered the EACV in my dpfi setup, and it was just sitting there, unused by the mpfi setup so I gave it a shot.
I can put this temporary test fix back in place:
Originally Posted by muellersfan
Temporary test fix:
Cut both Yel/Blk wires at the pierce point and splice to long new wires of the same gauge.
Cut Yel/Blk wires that run to A13 and A15 (~2 inches from ECU connector).
Cut Yel/Blk wire that runs to injector resistors, also leaving ~2 inches of wire.
Run one of the two new main relay wires to the ECU and splice to the cut A13 and A15 wires and the other to injector resistors and splice to cut wire.
Install main relay and ECU connectors.
but it always bothered me that ONLY the injectors will be powered in that scenario, Anything else that is powered by pins 1 and 6 go without. Also with two YEL/BLK wires confirmed open, I feel like one of the signal wires in there are bound to be damaged too. This is why I removed the temp fix a few days after it didn't start the car. Also the cut YEL/BLK wires between relay and ECU tested good for continuity so it seemed the problem might have been right at the pins. Now with a confirmed spark problem I guess it makes sense to put it back. Ugh, I love this car but it sure is killing me right now.
I guess it's a good thing that I'm finding the problems but it makes me wonder how all these systems failed. Like, I definitely had spark the day she was towed home, pretty sure there was erratic spark just this morning. When she 1st went down, the fuel pump had volts at the connector under back seat but wasn't priming. Manual said to replace it so I did and she started priming but then injectors lost power (still have no power at injectors on original wiring, only when I steal power from someplace else and run it directly to resistor box or do that pin swap that powers pump indefinitely). Just a few weeks ago, I had one noticeable problem: the car seemed to stumble a little when battery was under a new load. Like, when cooling fan kicked on, idle would get a little rough for 10-60 seconds and then return normal. Same thing when I kicked on headlights at dusk. Blower fan could effect my idle too. No problems at all with foot on the gas, just temporary idle problems when battery took on a new load. Does this help explain all these failures? Where is the common thread?
@muellersfan full ignition tune up = plugs, wires, ignition coil, cap and rotor?
Yes, minus the coil, which you clearly must also replace.
I can put this temporary test fix back in place:
Yes. Please do this^, along with installing the new coil and the full tune up. Then check whether the engine starts.
but it always bothered me that ONLY the injectors will be powered in that scenario,
I'm less concerned than you because I think the pins lacking voltage were just disabled during the MPFI conversion. Stay focused on no-start diagnostics and your questions will be answered.
@muellersfan Just waiting on my ignition parts, should have them tomorrow. Gonna solder up a possibly-permanent version of your "temp test fix" tonight.
Originally Posted by muellersfan
I'm less concerned than you because I think the pins lacking voltage were just disabled during the MPFI conversion.
This is not the case, I did the mpfi conversion (well, monotech did 99% of the work) and disabled one thing only: a white wire with red stripe was plugged into ECU pin B12, and that wire is still intact. The pin is wrapped up in electrical tape and hangs out next to my ECU to this day. The wiring was incredibly easy; with a working dpfi system and a monotech harness, all you need to do is depin 4-5 wires at ECU, and plug in a few new ones:
So pins 1 and 6 at connector c313 were not disabled in the mpfi conversion, they are definitely needed in the dpfi system and definitely used by the monotech harness in my mpfi system. Both pins have continuity to the injectors and pin 6 on the monotech side has 2 wires coming out of it, I don't know what else is powered by that 2nd wire but it may be critical. I went to the junkyard today and snagged a few pins and I think I have a plan you will approve of:
Basically the same thing I think, it will power the injectors off of main relay pin3, but if that 2nd wire needs juice, it will have it too. Te gusta?
Is this a brand new MPFI conversion that has never run properly? Or did it run properly for an extended time?
After the running a new temporary wire earlier in this thread, you had voltage to both wire branches (to ECU and injectors) coming from main relay pin 3. Isn't this correct?
Is this a brand new MPFI conversion that has never run properly? Or did it run properly for an extended time?
MPFI Conversion was done in February, ran great until late October with one exception: I would get a slightly rough idle when headlights, cooling fan or blower fan were on. Ran great with foot on the gas, but in the drive-thru for example, I would kill the lights and blower fan just to keep things smooth. Nothing I could do about cooling fan though, when that kicked on, it would struggle abit.
Originally Posted by muellersfan
After the running a new temporary wire earlier in this thread, you had voltage to both wire branches (to ECU and injectors) coming from main relay pin 3. Isn't this correct?
MPFI Conversion was done in February, ran great until late October with one exception: I would get a slightly rough idle when headlights, cooling fan or blower fan were on. Ran great with foot on the gas, but in the drive-thru for example, I would kill the lights and blower fan just to keep things smooth. Nothing I could do about cooling fan though, when that kicked on, it would struggle abit.
correct
These answers^ fully support my view that your entire focus should be on basic no-start diagnostics. Specifically, why focus on potential miswiring of the MPFI conversion when the MPFI-converted car ran just fine for 9 months? In addition, a dirty IACV or bad alternator could be a simple explanation for the rough idle under high electrical load.
Redo the temp wiring of the fuel injectors, do a tune up, and install the new coil. Does the engine fire up and run well?
Redo the temp wiring of the fuel injectors, do a tune up, and install the new coil. Does the engine fire up and run well?
No, When I turn key to "on", the fuel pump primes loudly for 2 seconds, then drops a little bit in volume and just keeps going.
Originally Posted by muellersfan
Specifically, why focus on potential miswiring of the MPFI conversion when the MPFI-converted car ran just fine for 9 months?
I have never been focused on a potential miswiring of the MPFI conversion. It is the 100% stock wiring between my main relay and plug C313 that has issues. The stuff that ran both the dual point system and eventually the mpfi system. I don't know everything that SHOULD be happening at that plug, but I know for sure that the injectors were not getting power. The injectors have continuity to several pins on the engine side of that plug, and none of those pins have voltage on the stock, DPFI side.
OK, My monotech harness is almost the same as this diagram, only a couple differences:
1) mine has a solid blue wire in pin 8, the one that went to tandem valve. I believe TND was only for dpfi? I'm not sure where monotech runs this one, I didn't see any solid blue wires at the connectors, but about half of them are shrinkwrapped at or very close to their connectors. I can definitely track this one down with a multimeter, but haven't done so yet.
2) I have a GRN/BLK wire at pin 14. I believe this one runs to my backup sensor.
3) pin4 is not used in the monotech harness
4) It may be worth noting here that I have 2 YEL/BLK wires coming from pin6. pin6 is one of 4 pins tied to my injectors.
At Injector #1, I have continuity to pins 1,2,5, and 6 in plug C122
At Injector #2, I have continuity to pins 1,5 and 6
At Injector #3, I have continuity to pins 1,2,5, and 6
At Injector #4, I have continuity to pins 1,2 and 6
My C313 plug is setup exactly like @DaX 's diagram above. With help from @muellersfan , I was able to confirm that my car has problems between this plug and the main relay. I'm not sure how many pins should be energized with key in "on" position, but I get 12 volts at pins 4, 7, 9 and 10 only. none of the pins that are tied to injectors get power. I also get .12 volts (notice the decimal) at pin 3.
EDIT: that was post #48 I believe, when I quoted myself here, HT dropped all the pictures for some reason.
No, When I turn key to "on", the fuel pump primes loudly for 2 seconds, then drops a little bit in volume and just keeps going.
This^ would NOT prevent the engine from starting and running properly, though there is a malfunction.
With the Key OFF, check for a short to ground in the Grn/Blk wire running between ECU pins A12/A14 and the corresponding main relay pin.
I have never been focused on a potential miswiring of the MPFI conversion. It is the 100% stock wiring between my main relay and plug C313 that has issues. The stuff that ran both the dual point system and eventually the mpfi system. I don't know everything that SHOULD be happening at that plug, but I know for sure that the injectors were not getting power. The injectors have continuity to several pins on the engine side of that plug, and none of those pins have voltage on the stock, DPFI side.
This^ has been your focus, despite the fact that it remains entirely unclear whether these "issues" are causing any problems. Focus on troubleshooting an actual problem (engine won't start). I'm really only trying to help you here.
With the Key OFF, check for a short to ground in the Grn/Blk wire running between ECU pins A12/A14 and the corresponding main relay pin.
There is continuity along that GRN/BLK wire between those ECU pins and the main relay, not sure if there is a short to ground though, how do I test for that? Thinking I need one end isolated, with no path to ground, then supply power to the other side with test light? If light turns on I have a short?
Also, if I came off ungrateful earlier let me correct the record: I am EXTREMELY thankful for all your help @muellersfan ! The problems outside are terribly difficult for me to diagnose, and when I come inside to report my lack of progress I probably come off combative due to all the frustration. I don't mean to be that way, I'm sorry. I very, very, very much appreciate your time and help.
It's extra frustrating that my test results keep changing. I HAD spark before, and then ignition coil tested bad 2 days ago. I had no power at C313 for 2 weeks straight, but today after completing the tune up, the stock harness (as well as temp test fix) supplies 12v all the way to C313, through engine harness, up to resistor box, back into engine harness, and down to injectors. How the hell did that confirmed problem go away? Car still won't start, with brand new ignition system And power at injectors AND starter fluid in intake.
I had a completely new problem today too: I turned the key to "on" and fuel pump primed 2 seconds, changed tone a little, and continued pumping. I have seen that malfunction before and posted about it here lately. But then today when I turned key to "off" and removed the key, the pump was STILL going! Had to run around and disconnect battery negative to get it to stop. Immediately tried the same procedure and it acted the exact same way. Maybe 30 minutes passed, roommate stopped home and I tried to show him the crazy new problem I was seeing, and it was gone. Right now, when I pull the key out, the pump stops, but twice today it kept going with no key in ignition. Does that shed any light on my issues?
Also, if I came off ungrateful earlier let me correct the record: I am EXTREMELY thankful for all your help @muellersfan ! The problems outside are terribly difficult for me to diagnose, and when I come inside to report my lack of progress I probably come off combative due to all the frustration. I don't mean to be that way, I'm sorry. I very, very, very much appreciate your time and help.
No worries, friend. I also do a lot of work on my cars...in Houston TX...so I totally get it.
There is continuity along that GRN/BLK wire between those ECU pins and the main relay, not sure if there is a short to ground though, how do I test for that? Thinking I need one end isolated, with no path to ground, then supply power to the other side with test light? If light turns on I have a short?
No need at this point to isolate the wire. Just turn key OFF, and then test the wire for continuity to body ground at any convenient location on the wire.
It's extra frustrating that my test results keep changing. I HAD spark before, and then ignition coil tested bad 2 days ago. I had no power at C313 for 2 weeks straight, but today after completing the tune up, the stock harness (as well as temp test fix) supplies 12v all the way to C313, through engine harness, up to resistor box, back into engine harness, and down to injectors. How the hell did that confirmed problem go away?
^Sounds like a poor connection at one of the connectors or a bad main relay.
Car still won't start, with brand new ignition system And power at injectors AND starter fluid in intake.
Did you check for strong spark and CEL codes after cranking for 30 seconds?
I had a completely new problem today too: I turned the key to "on" and fuel pump primed 2 seconds, changed tone a little, and continued pumping. I have seen that malfunction before and posted about it here lately. But then today when I turned key to "off" and removed the key, the pump was STILL going! Had to run around and disconnect battery negative to get it to stop. Immediately tried the same procedure and it acted the exact same way. Maybe 30 minutes passed, roommate stopped home and I tried to show him the crazy new problem I was seeing, and it was gone. Right now, when I pull the key out, the pump stops, but twice today it kept going with no key in ignition. Does that shed any light on my issues?
No need at this point to isolate the wire. Just turn key OFF, and then test the wire for continuity to body ground at any convenient location on the wire.
OK GRN/BLK wire has no continuity to ground. YUS!
Originally Posted by muellersfan
^Sounds like a poor connection at one of the connectors or a bad main relay.
Checked over my connections and swapped in a different relay. Things are looking good: I have power at injectors AND pump turns off in 2 seconds. Double YUS!
Originally Posted by muellersfan
Did you check for strong spark and CEL codes after cranking for 30 seconds?
Will check for spark when roomy gets home, probably in an hour or so. I'm guessing spark is there cuz she really sounded like she wanted to start but never quite made it. And now we come to the good part: I finally got a CEL code! Code 15 - Ignition Output Signal.
Checked over my connections and swapped in a different relay. Things are looking good: I have power at injectors AND pump turns off in 2 seconds. Double YUS!
And now we come to the good part: I finally got a CEL code! Code 15 - Ignition Output Signal.
This^ indicates a spark problem. Could be a bad igniter unit or bad wires going to or inside the distributor. Voltage tests are the place to start.
It's not uncommon to find multiple separate problems in older cars.
Started with the voltage tests. I have 12v at 2p connector on top of distributor, and that continues on inside to the two pins it's supposed to on the igniter (BLK/YEL wire and WHT/BLU wire inside dizzy). So passed the voltage tests but failed these 2 "continuity to ground" tests:
As far as grounds are concerned, I'm pretty sure grounds G101 and G151 are the same thing right? The one near the thermostat? It looks good to me, connection is tight and no corrosion. G301 is up near the tank for the windshield sprayers. I have a good solid connection there too. I couldn't find G401 though, it is supposed to be "behind left kick panel" and should branch off the harness next to main relay. I have no ground wires in that area, and no single branches off main harness near the main relay. The wires from my main relay go up and over the fuse box and join the giant mass of wires about to go through the firewall, no ground wires coming out of there that I can see. But I'm getting ahead of myself here, that ground is to be checked in step 6, and I really haven't finished step 5. Need to check for "open in WHT wire between igniter and ECU".
And here is where things get tricky, I was supposed to connect an "ECU test harness" to the main harness and check voltage at B15 and B17 but I don't have that test harness, so I think I need to depin those wires to check them because my probes are too fat to test anything on the B plug. For me, the B plug is the hardest plug to depin on this car (that retainer clip gives me fits, push right side up and left goes down, grr) so I skipped that part and started checking continuity from the other end.
Within the distributor itself from far left pin on igniter I have continuity to one pin in the distributor plug. My distributor has odd colors for those wires, the wire is supposed to be solid white all the way to ECU but mine is black near the igniter, and YEL/GRN coming out the dizzy going to dizzy plug. From there, Monotech uses the stock color (solid white) but I have no continuity in the engine harness from that pin in distributor plug to any of the pins at passenger shock tower. This isn't the first time the engine harness showed continuity problems either. I spoke with Mono last night and I should not have gotten these results earlier:
Originally Posted by EFDXinATX
At Injector #1, I have continuity to pins 1,2,5, and 6 in plug C122
At Injector #2, I have continuity to pins 1,5 and 6
At Injector #3, I have continuity to pins 1,2,5, and 6
At Injector #4, I have continuity to pins 1,2 and 6
pins 2 and 5 should not have shown up in those results. He says the wires are solid all the way through, with no solder points inside, so those results indicate a major meltdown inside the harness even though it looks 100% clean on the outside to me. He wants me to send the whole damn harness to Cali for an internal inspection. I hadn't even found the break in the white wire when I spoke to him. :/
Here is my list of known problems as we sit:
1) break in YEL/BLK wire from main relay to injector box. I have bypassed this with new wires, seems to get 12v where I need it but is probably sending voltage to a few extra places inside engine harness.
2) 2x blown ignition coils. I just replaced this yesterday and it already tests bad for "Secondary Winding Resistance". Tested good before install.
3) no continuity to ground at White wire or Blue wire at igniter. I'm supposed to have ground here before replacing igniter.
4) no continuity along white wire in engine harness.
11-04-2018, 03:26 PM
Re: No Voltage at injectors
