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Thank you for the ECU voltage pics. Yesterday I tried and tried and tried again to get it to a no start spot but it kept firing like normal (frustration sinks in) yes I know I should not be upset that it's working normally but I know the darkside will rise again and I'm sure at the most inconvenient time. so I will check all pins and run more test until I can get it to a no start again.
Maybe Problem is From TOO LOW a resistance not high resistance.
". Sounds like a lot of work, of course, like putting vital signs monitors on a patient
Maybe I should buy 5-6 multi meters from HF and have them all set up ready to go on each wire when I drive around until it wont start again
i'm going to try this with the blue and yellow vs white wire after measuring all the ECU pins.
The variable resistances in the AFM act as variable voltage divider. Total 12V voltage is supplied by B+. The ECU reads voltages @ E2, THA, VS, LC pins produced by those variable resistance.
When the AFM is momentarily disconnected, 12V from B+ is disconnected, resulting in zero or low Voltage at E2, THA, VS, LC, and the truck starts.
Disconnecting the AFM also means resistances between E2, THA, VS, LC pins and AFM is infinity or HIGHER. This seems to make the truck start.
The above suggests that TOO LOW resistance or TOO HIGH a voltage at one of those test points is the cause of no start.
VC is five volt reference, (Vcc).
Since we got here, sort of, my base assumption is the temp readings have discrepancy (Ta, TSW, and coolant temp).
I asked them to unpin TA from the vafm way back when the video of unplugging the vafm first came along..
Is the 5 volt reference key on or off?
THA? You want me to disconnect the THA from the AFM and wire in a switch to see if that could be a possible issue?
Apologies its difficult since so much has been suggested and its been awhile since i've been able to get under the hood.
Last edited by YotaRick27; Feb 13, 2018 at 02:11 PM.
Thank you for the ECU voltage pics. Yesterday I tried and tried and tried again to get it to a no start spot but it kept firing like normal (frustration sinks in) yes I know I should not be upset that it's working normally but I know the darkside will rise again and I'm sure at the most inconvenient time. so I will check all pins and run more test until I can get it to a no start again.
It is good practice, doing the checks when it is functional. It tells you what sort of signals to expect to see, as well develops muscle memory so you can get it done faster before the reading/temp changes
Do the easy bits first. Identify those two wires you had in the thermostat "doohickey" with the continuity checks described in detail earlier.
We need to know exactly what these are to cross them off as possible issues.
Second it would be nice to get the voltage stuff worked out, your low voltage reading at the ECU (assuming that is ecu power pins, I asked you to clarify what the 10.8 voltage readings was and never got an answer). And here is why.. When you are cranking the starter your battery voltage will "sag" (go lower) which means your ECU voltage during cranking is probably below spec and going to effect the sensor readings if not "reboot" the ECU.
Do the easy bits first. Identify those two wires you had in the thermostat "doohickey" with the continuity checks described in detail earlier.
We need to know exactly what these are to cross them off as possible issues.
Second it would be nice to get the voltage stuff worked out, your low voltage reading at the ECU (assuming that is ecu power pins, I asked you to clarify what the 10.8 voltage readings was and never got an answer). And here is why.. When you are cranking the starter your battery voltage will "sag" (go lower) which means your ECU voltage during cranking is probably below spec and going to effect the sensor readings if not "reboot" the ECU.
I don't know what you mean by the 10.8V reference. I posted 3 different photos first was EFI check key on, the two photos that followed were the two pins in the connector on the VSV. I do apologize for not answering this sooner.
Truck acted funny this morning after watching a lot of scannerdanners videos last night I wanted to check the O2 on the header, I put one lead on the O2 wire and the other to ground and it read 1.25V way higher than in spec(running at idle cold) then died once warm and would not start again. Made me think its flooding itself. After pulling AFM and getting it running again I took it for a drive stopped and had a very high idle, check o2 again and now was in spec sitting around 0.75v-0.80v fluctuating of course. but the odd part was it still had a high idle, so high the only way I could calm it down was to tighten the idle screw half a turn away from being completely bottomed out. Then headed to the gym before work 1hr later started up and instantly died had to pull afm to get going again. This I know is frustrating for all you following because I can see yall saying "just check the bloody wires already" I know I know and I plan too this weekend once I get a solid bloody day off of work.
I don't know what you mean by the 10.8V reference. I posted 3 different photos first was EFI check key on, the two photos that followed were the two pins in the connector on the VSV. I do apologize for not answering this sooner.
Truck acted funny this morning after watching a lot of scannerdanners videos last night I wanted to check the O2 on the header, I put one lead on the O2 wire and the other to ground and it read 1.25V way higher than in spec(running at idle cold) then died once warm and would not start again. Made me think its flooding itself. After pulling AFM and getting it running again I took it for a drive stopped and had a very high idle, check o2 again and now was in spec sitting around 0.75v-0.80v fluctuating of course. but the odd part was it still had a high idle, so high the only way I could calm it down was to tighten the idle screw half a turn away from being completely bottomed out. Then headed to the gym before work 1hr later started up and instantly died had to pull afm to get going again. This I know is frustrating for all you following because I can see yall saying "just check the bloody wires already" I know I know and I plan too this weekend once I get a solid bloody day off of work.
You'll get there bud, and when you do you'll have some more solid problem solving skills and a running Toyota to boot.
I thought I was on something (clogged exhaust or cat from 1986) so I pulled the cat last as it died half way up my snowy driveway, had to use the starter in gear to get it in the garage. literally 10PM in my garage pissing off my neighbors by drilling out broken rusted bolts. I got it out and both honeycomb screens looked good and I could see a dim light when I put a flashlight on the back half. Kinda looked like this:
I don't think it was bad because when I started it up it i got the same misfire run like crap till death symptom. gave up for the night and went to bed. This morning before work I went back to the o2 and pulled the wire when running. Did not affect anything. I put a test light in the wire and plugged it back in. When I hook the test light to the o2 then clipped the ground wire it fixed the idle a little. this makes me think the E2 ground might be bad or engine block ground? input?
Last edited by YotaRick27; Feb 15, 2018 at 01:26 PM.
Omg! Stop looking for more problems untill you fix what you have already found, fix your wiring already please.
You have (at least) two unconnected wires in the engine harness.
You have an air conditioning (cut off) temp switch, or coolant temp sender, where you should have the fuel pressure up system temperature switch.
You have low voltage at the engine computer.
You spend all that time taking apart the exhaust when a visual inspection would have told you it wasn't glowing.
You spent time mucking around with the oxygen sensor, neglected the fact it (the sensor) has to be up to temperature before it functions and that the ECU won't read that signal untill the engine meets the requirements of temperature read by the engine coolant sensors.
Omg! Stop looking for more problems untill you fix what you have already found, fix your wiring already please.
You have (at least) two unconnected wires in the engine harness.
You have an air conditioning (cut off) temp switch, or coolant temp sender, where you should have the fuel pressure up system temperature switch.
You have low voltage at the engine computer.
You spend all that time taking apart the exhaust when a visual inspection would have told you it wasn't glowing.
You spent time mucking around with the oxygen sensor, neglected the fact it (the sensor) has to be up to temperature before it functions and that the ECU won't read that signal untill the engine meets the requirements of temperature read by the engine coolant sensors.
I'm going to go pin by pin and wire by wire on the ECU print out this weekend and post the results if i find anything off. Im hoping I can get it to a no start position.
ECU voltage beyond spec, measure battery voltage at the terminal.
Reread first post. Fuel pressure to low, you want 35 and 40psi, you have 31-36.
Low battery voltage, possible bad pump or regulator. Charge the battery, apply jumper-cables or jump box. Retest fuel pressure.
Identify those wires, see below quote. You have some other out of spec things that could be related to bad voltage or typographical error.
Originally Posted by Co_94_PU
why does it happen now? You moved from draught ville California to soggy cold South dakota and you have loose wires flopping around in the harness.
First things first disconnect the wires you attached from each other and the sensor.
You have a multimeter right, do you have aligator clips? You can pick up clips from the local napa, i think a pair is under 2$. You need to trace those wires back to the ECU.
Set the meter to diode/continuity (triangle with lines on either side) if it has one, this mode will sound a tone when you touch the test leads together. If yours doesn't have this mode you want to set it to a low ohm reading range.
Attach either end of the leads to the wire in the engine bay. If you can clip it on to the metal lug great, if you can put the probe/lead between the plastic housing and the metal lug good, you may need a straight pin (t-pin) between the housing and lug then attach the clip to this.
Now inside the kick panel you unplug the computer. You will insert the meter lead into the back side of the connector (side the wire enters) and touch the top/side of the metal wire lug. If you get a tone, or zero ohms (note, not 0L this is open circuit/no connection), make a note of the wire color, its position, and which signal name (three letters).
Leave the computer unplugged for now.
The next process is to verify you have the fpu vacuum switch, that it has the vacuum lines plumbed, and signal wires attached.
Locate the fuel pressure regulator at the firewall end of the fuel rail, follow its vacuum hose to the VSV, there should be a second vacuum hose to the intake. Make sure the hoses are firmly attached (require some effort to twist on the hose barbs), if these are sloppy/loose you need new hose.
Unplug the harness from the vsv. Test the wires at the VSV with the ignition switch in the run position, you should have voltage on one side (meter on 20v DC, one lead on battery negative with the clip, other lead touching the lug), the other wire should connect to the ECU connector (same test as the earlier, continuity, either meter lead at the VSV to) the top left of the large center connector.
Plug the VSV wires back in. Test for voltage at the ECU connector now, you should have battery voltage at that same top left corner (again these are from the wire entry side). Leave the t-pin in this one well use it later, or the ECU unbolted.
Key off, plug the computer back in.
Set the meter to continuity/ohm, one lead on ground and one on that FPU wire. It should read oL/0L. When you put the key to start you will get a tone (zero ohm) if it is activating the fuel pressure up vsv. Make a note of if it does or not.
At this point it will probably start right up. Close the hood and let it heat up, you need it in the no start condition next.
Ok so now it won't start, hopefully it does this in the driveway with out hassles. Does the FPU trigger this time? Use the vafm unplug trick and note if the FPU activates.
Now with the no start condition, remove the VSV from the equation, take the regulator hose directly to the intake. Does it start now, if so the FPU is your problem and we can hack around it untill you can get the right sensor.
Last edited by Co_94_PU; Feb 16, 2018 at 07:11 PM.
My fix is less frustrating, but a requires minor fab work. Pull the CSI wires off and tie wrap them out of the way. Run a wire from +b with fuse block to a PB mounted on a small panel next to your big shifter. Run the wire from the switch to one side of the CSI. The other pin gets grounded somewhere. I used the mounting bolt. I made a gasket for the CSI from thick sheet gasket material and put some goop on it.
Now when you crank the engine you can manually squirt gas into the engine. I find a split second pulse is more than enough, but on a really cold negative degree morning a full one second pulse may be needed, just do not flood it (easy to do). Starts every time for me now.
Test CSI seal with engine running and an un-lit propane torch, if idle improves, it leaks do it twice.
Mine is useable while I figure out what is busted, otherwise it looks like the hack job it is. (lipstick on a rotted pig)
Ok reading some more, it sounds like fuel pressure is too low, should be more like 55psi. do you have a clogged filter under the intake manifold? Did this truck sit for a while till the gas spoiled ? maybe the in tank filter is plugged with alky spoo. Did you fill the tank with unfiltered farm gas?
Ok reading some more, it sounds like fuel pressure is too low, should be more like 55psi. do you have a clogged filter under the intake manifold? Did this truck sit for a while till the gas spoiled ? maybe the in tank filter is plugged with alky spoo. Did you fill the tank with unfiltered farm gas?
My fix is less frustrating, but a requires minor fab work. Pull the CSI wires off and tie wrap them out of the way. Run a wire from +b with fuse block to a PB mounted on a small panel next to your big shifter. Run the wire from the switch to one side of the CSI. The other pin gets grounded somewhere. I used the mounting bolt. I made a gasket for the CSI from thick sheet gasket material and put some goop on it.
Now when you crank the engine you can manually squirt gas into the engine. I find a split second pulse is more than enough, but on a really cold negative degree morning a full one second pulse may be needed, just do not flood it (easy to do). Starts every time for me now.
Test CSI seal with engine running and an un-lit propane torch, if idle improves, it leaks do it twice.
Mine is useable while I figure out what is busted, otherwise it looks like the hack job it is. (lipstick on a rotted pig)
^^ I think the goal of this thread is to PROPERLY fix what ever is going on, rather than hacking things up and still leave the problem in the truck.
I do understand when you need to get the truck running again as soon as possible and using a temporary fix or when you bypass things for testing, though.
However, since we don't know the root cause (or causes) to the starting problems, they could cause future problems down the road, even with your modification, since the unknown problem(s) is/are still in the truck.
I would do three things at this point:
Fix the coolant temp sensor/switch on thermostat housing. EDIT: see TSB posted by Co_94_PU in later posts
Check battery voltage (~12.6 volts); better yet, have the battery load tested
Charge or replace battery as needed
If battery needs charged or replaced, rerun voltage tests at the ECU after charge or replacement
If battery is good, do a voltage drop test from battery positive to BATT terminal on ECU and from battery positive to +B terminal on ECU. Ideally, the voltage drop should be around zero. A significant voltage drop means there is a wiring or connection problem and the ECU is not getting the proper voltage it needs to operate.
Check for cause of low fuel pressure
Fuel pressure regulator not allowing enough pressure?
Not enough voltage at the pump?
Old, weak pump not able to produce needed fuel pressure?
Clogged fuel filter?
Last edited by old87yota; Feb 18, 2018 at 08:51 AM.
Reason: Updated Information
Feb 13, 2018 | 11:37 AM
