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Ignitor, coil, ignition ground. 1of2
This is grounded by chassis ground.
2of2 Chassis/body ground.
Sparatic spark could be a bad ground, as well bad distributor pickup, failing ignition, or just flakey or poor routed wires.
The ignition system is grounded via the frame of the "module" to the inner fender then picked up at the battery.
Spark is grounded via the head strap. (I don't even have that one in place fwiw, mine is via head bolts and/or the alternator harness.. Yeah I know *shrug*)
Injectors ground via the ECU/EFI connection.
I got it to run today but it only runs when the fuel pump diagnostic port is jumped. Also can’t get it go much above idle RPM but that’s because the TPS is all out of whack. So what am I looking at next? Cold start injector?
I got it to run today but it only runs when the fuel pump diagnostic port is jumped. Also can’t get it go much above idle RPM but that’s because the TPS is all out of whack. So what am I looking at next? Cold start injector?
cor is powered by the ignition switch during STArt, vafm takes over when it senses air flow.
So make sure vafm is plugged in all the way. Not a substitute vafm.
Monitor voltage on FP line while moving vafm vane/flap.
Proceed to check signal reaches COR and then replace the COR if needed.
Low fuel pressure/supply could be pump, filter or a crushed line. Also stuck open regulator.
Probably something else but breaks over, back later.
cor is powered by the ignition switch during STArt, vafm takes over when it senses air flow.
So make sure vafm is plugged in all the way. Not a substitute vafm.
Monitor voltage on FP line while moving vafm vane/flap.
Proceed to check signal reaches COR and then replace the COR if needed.
Low fuel pressure/supply could be pump, filter or a crushed line. Also stuck open regulator.
Probably something else but breaks over, back later.
10-4. I wouldn’t be surprised if it’s something with the AFM ... we have these mud wasps and they built a mud den in one of the screw holes on the AFM (looks like it might be the adjustment screw but will have to confirm that when I have the FSM in front of me) I had to blow it out with compressed air so it’s totally possible the little buggers made other nests inside since I had the pipe that runs from there to the throttle body off for about 6 months.
about the fuel filter, if that were it would it even start if the pump was jumped? I did replace a fuel line the one that comes off the metal fuel line on the passenger side frame and goes to the filter but I set it up exactly how the old one was and I replaced the fuel filter as well. The way I have it set up the line that feeds the fuel rail is banjo bolted to the end of the fuel filter that faces the firewall then that comes over the fuel filter and up through the intake to connect to the fuel rail. The fuel line from the tank goes to the side of the filter that faces forward toward the radiator. That’s how it was when I took it appart in the first place so I just set it up how it was. The fuel line was pulled from a 92 pickup and it bolted right on and fit the filter as well.
10-4. I wouldn’t be surprised if it’s something with the AFM ... we have these mud wasps and they built a mud den in one of the screw holes on the AFM (looks like it might be the adjustment screw but will have to confirm that when I have the FSM in front of me) I had to blow it out with compressed air so it’s totally possible the little buggers made other nests inside since I had the pipe that runs from there to the throttle body off for about 6 months.
about the fuel filter, if that were it would it even start if the pump was jumped? I did replace a fuel line the one that comes off the metal fuel line on the passenger side frame and goes to the filter but I set it up exactly how the old one was and I replaced the fuel filter as well. The way I have it set up the line that feeds the fuel rail is banjo bolted to the end of the fuel filter that faces the firewall then that comes over the fuel filter and up through the intake to connect to the fuel rail. The fuel line from the tank goes to the side of the filter that faces forward toward the radiator. That’s how it was when I took it appart in the first place so I just set it up how it was. The fuel line was pulled from a 92 pickup and it bolted right on and fit the filter as well.
Fun fact, those solitary bees and wasps do more pollination than our communal honey bees. (Why do I remember these things ugh)..
My 94 still has some wasp nest in the fill tube breather hose from when it was in Texas. Makes filling take a bit longer, but it's only really annoying once in awhile. Ok back at it..
The vafm is factory calibrated then capped over with a plug. It's not a good sign if yours has been decapped, but we can ignore that. This adjustment screw sets the by-pass air flow oriface. Don't have a lot of details on this. It's the little side chamber you may notice to the right side of the flap on the intake side. I believe it functions mostly at a very low rpm (equates to volume), just based on the physics. For example at startup or idle they are about the same size openings, bring rpm to 1000 and its much different ratios.
This is the bit I would want to make sure was clear of debris, hit it from both sides till your not seeing debris.
Also do a resistance check of the vafm output while moving the vane. It's similar to the TPS in that it's just a resistive track, it differs by way of having a secondary resistance ladder that runs along the arc. This means where a tps can wear thru a single spot and render the range after that point dead (if you go past X it has no throttle signal), the vafm will always be able to read full range (wear out 2000 to 2500 and it will see 2k until you hit 2501). The tps "dead spots" we talk about are actually just dirty tracks.
....
Grungy or gelled up sock on the pump. Debris stired up by the fuel return. Non venting fuel cap. All little things that can cause issues with supply.
Fuel pressure gauge would point at this as an actual issue. Lot more expensive but non intrusive is to look at the current to the pump, preferably with an scope..
So the question was "If you had a filtration issue, would the pump operate?"
Yes. If it has a complete electrical circuit, has all its mechanical bits, something to pump, and most importantly somewhere to pump it, it's going to pump.
When it doesn't have somewhere to pump, line pressure over X, is the concern. It will cavitate or stall, I think both terms.will work here.
This is really more of an issue with the deadhead style pumps. These put out volume solely based on voltage/current and pressure is created by the external regulator.
So taking a step backwards.
Engine speed is governed by air, fuel and spark.
Spark was healthy? Is it still sparatic?
Fuel is there, but how much and at what pressure? You can pull the return line (soft fuel line on regulator) and plumb it into a water bottle for a volumetric test (this is where you find go find that number cause I forgot it again, or one of the others will post), not even going to guess this time. To test pressure there's no reasonable way other than a handful of new crush washers and a fuel pressure gauge.
Air flow could be a concern given you know there are nests. The vafm needs to sweep full range, throttle linkage also, and finally the same blockage problem occurs with air filters as I babbled about above.
I jumped the truck with my matrix and once it had strong voltage it fired up (while jumpered still) and spark was consistent on all wires.
I’ll check voltages on the AFM and I’ll get the TPS set back up tomorrow but regarding the AFM I did open it up this evening and luckily no more visible wasp nests in the air cleaner box or in the trap door for the AFM that I could see. By the way I definitely want to get those 3mm Allen screws to do the conversion because having to pull the thermostat housing to get at the TPS with a short Philips sucks! Do you know the pitch/thread count on them? 4crawler was kind of vague because I think they’d like to sell the screws can I pick them up at ace hardware or something?
So on the same tangent as the AFM troubleshooting... This evening I decided to just get it up to op temp and check for seeps and leaks because no sense in doing all this troubleshooting now if the engine needs to come out again. Got it up to op temp, burped the cooling system checked for leaks and didn’t see anything. I then pulled the jumper and shut her off, she fired right back up without the fuel pump jumper multiple times in a row. I checked my cold start injector before jumping the fuel pump and it was spraying nada and looked pretty gummed up with exhaust residue and oil. I have spare crush washers for that and the ones on it are brand new from the OEM gasket kit I got so I think I’ll pull it and do the test the FSM shows to see if it squirts at all.
About the filtration issue I guess I was wondering more so if the filter being backward could be a cause of choked fuel supply but I suppose you answered that one already. That said I’m pretty sure I’m not backward I had the old filter along side the new one and transferred hoses as they were on the old filter to the new one.
One bit if good news is replacing the temp sender unit on the intake fixed my inaccurate temp gauge readings that I was complaining about in some of my first posts about this truck... 6$ at the junkyard was worth it.
Also the irony here is when I got this tuck it had a hot start problem and now it’s got a cold start problem. Pretty sure the hot start issue was a poorly repaired wire splice to the engine coolant temp sensor on the thermostat housing which I found out about when the connector was sitting on the diff when I pulled the harness out.
Last edited by outdoorjunky; 08-21-2018 at 09:30 PM.
Good to hear some of this seems to be just a low battery..
How many holes are tapped into the thermostat housing? Do you have factory wire ends, or replacements there?
If you have two bungs and non factory ends it's possible they got swapped. My aging memory says these two work in opposition, one opens at temp the other closes at temp. If you have two the extra is an AC cutoff switch.
There is only one bung for the temp sensor that sends to the ECU on my thermostat housing, my truck does have AC but it doesn’t work so that’s something to troubleshoot down the road. It is a factory connector but it looks like it came off another truck because the wire colors don’t match but I could definitely tell they we’re once soldered together and it was the only loose wire in the harness (green wire).
Also the A/C one is not part of the EFI harness, the A/C cowl harness follows along side the EFI harness and goes under the throttle body near the THW sensor wire. The TSW is part of the EFI harness and exits the loom under the plenum near the aft injector wires and gauge temp sender.
Doesn't seem to have quoted everything. Thread link
Again could be wrong wire on wrong switch, should be able to match it from the images from the wiring book.
wait a sec so is that saying it's a Green Blue wire for water temp switch and Green for the AC Temp switch? I don't have the AC temp switch next to the water temp switch on my thermostat housing it's just got the round water temp sensor there BUT I have seen the blue/green wire or maybe it's blue/yellow coming off my AC compressor and connecting to a connector identical to the one in the schematic...the wire comes off the engine wiring harness though. maybe someone combined harnesses at some point? Obviously lots of jerry rigging went on with this thing but NO RUST issues whatsoever so I figured the rest of the stuff can be fixed but rust is like a cancer thats the death to these Toyotas. I am in uncharted territory now with these wiring problems. I have a pretty good grasp of most of the mechanical systems on this truck but when it comes to wiring and diagrams it's still pretty new to me but, I guess thats why I got an old truck in the first place so I could learn or be forced to learn how to fix these things.
wait a sec so is that saying it's a Green Blue wire for water temp switch and Green for the AC Temp switch? I don't have the AC temp switch next to the water temp switch on my thermostat housing it's just got the round water temp sensor there BUT I have seen the blue/green wire or maybe it's blue/yellow coming off my AC compressor and connecting to a connector identical to the one in the schematic...the wire comes off the engine wiring harness though. maybe someone combined harnesses at some point? Obviously lots of jerry rigging went on with this thing but NO RUST issues whatsoever so I figured the rest of the stuff can be fixed but rust is like a cancer thats the death to these Toyotas. I am in uncharted territory now with these wiring problems. I have a pretty good grasp of most of the mechanical systems on this truck but when it comes to wiring and diagrams it's still pretty new to me but, I guess thats why I got an old truck in the first place so I could learn or be forced to learn how to fix these things.
These are taken from the 88, colors may of changed. G-B is green-black (blue is L).
The locations in the harness I don't think changed.
Maybe some typos there. The AC wire comes off the inner fender, FPU wire routes from the middle of the 22re intake.
When in doubt always test continuity from ECU to questioned wire end it's the only definite way to I'd a signal wire..
Wire to the compressor is the clutch.
This AC cut off switch is kind of hard to nail down if you'll have one. Sometimes listed as automatic, tow package, or completely random (think Rad has one and none of the above bits). Wouldn't surprise me to have the switch and never had air conditioning either, once it was there they wouldn't of pulled it if they changed a block of vehicles to base model (why some have sr5 wiring and can use that cluster without running a tach wire).
..
There was/is a detailed thread last winter, early spring maybe, that covers this FPU system and the tech bulletin related to starting issues. If you don't find it we can dig it up. Tomorrow.
Looks like I’ve got some wire tracing and troubleshooting to do this weekend. I didn’t find the tech bulitin FPU thread but I do remeber reading a tech bulletin about the warm start issue I had previous to rebuild. That seems to have gone away probably from fixing the temp sensor wiring. My CTS wire is green black so I’m confident I spliced the right wire to the coolant temp sensor but will still test at ECU connector pins. Looks like I should also be checking the cold start time switch as well. And the circuit opening relay as I believe you already recommended.
Last edited by outdoorjunky; 08-23-2018 at 08:37 AM.
Looks like I’ve got some wire tracing and troubleshooting to do this weekend. I didn’t find the tech bulitin FPU thread but I do remeber reading a tech bulletin about the warm start issue I had previous to rebuild. That seems to have gone away probably from fixing the temp sensor wiring. My CTS wire is green black so I’m confident I spliced the right wire to the coolant temp sensor but will still test at ECU connector pins. Looks like I should also be checking the cold start time switch as well. And the circuit opening relay as I believe you already recommended.
THW, two wire sensor on front of intake. (Tells ECU engine temp)
TSW, single wire on thermostat housing (Signals ECU to open or close FPU vsv, in some I think it's directly wired to the vsv even (early model EFI pre-TCCS, 85 models produced in 84)).
CTS isn't a Toyota term, pretty sure that translates to coolant temp sensor.
https://www.yotatech.com/forums/f116/cold-start-injector-intermittent-help-303272/ <- thread I was referring to.
And I think this is the TSB, might be the previa one..
...
Time for a recap of solved and current issues.
CTS was my shorthand for coolant temp sensor, I’ll try to keep descriptions limit to official Toyota names the best I can.
So about this sensor on the thermostat housing there isn’t any consensus on what the hell it is because people either have 1, 2, or none on their housing and there are so many wrong accounts of what it is. This i think is where some of the confusion lies in my description of the hot soak “fix”. I read that, that sensor on the housing sent temp to ECU but you are saying it’s the green sensor next to
the thermo temp timer switch on the intake manifold above the air valve that sends temp to the ECU right? So to try and nip this in the bud here is a picture of what I have on my thermostat housing. I confirmed the wire I spliced to this connector is GREEN/black which would make it the water temp switch right?
Here are two pics for reference
I gotta really go through this thread and consolidate information because this is getting a little confusing at this point.
but to be clear I'm having a cold start issue, however, I got the truck to start without jumping the fuel pump this evening. it takes a few turns of the key and some cranking to get it to go but then it goes. it will try to start and then die a few times then if I pull the key, reinsert the key, and crank it, it fires right up. I'm pretty well stumped as to why it started firing up without the fuel pump jumped all the sudden and why it has no problem starting back up when it's warm. I was reading here https://www.pirate4x4.com/forum/toyo...ing-relay.html and there is some interesting info on the Circuit Opening Relay which puts things you already said into a better perspective.
Also I still can't seem to get the TPS calibrated. I went through the 4crawler procedure to test it and the readings were mostly in spec but they were sporadic and jumping all around (variable resistance). the only reading that wasn't sporadic was the VCC to E2 (any position) test which read 4.97K ohms which is right around the middle of the road for the spec. with the TPS connected to the harness I can't get RPM's above about 1500 or so before it cuts and then surges repeatedly until I bring down the throttle. If I start the truck without the TPS connected I can rev it without any surging.
About my AFM you were right about that missing set screw cover on the air bypass being a possible indication of someone messing around in there. I can tell someone messed with the AFM because after taking a closer look I can see that the cover is sealed with RTV which is what I saw someone doing in a youtube video to seal it up after they opened it up and messed with the settings.
Any thoughts on why the truck now wants to start without the fuel pump jumpered? Intermittent Circuit Opening Relay?
Last edited by outdoorjunky; 08-23-2018 at 08:17 PM.
Switch on the housing, single wire, TSW at ecu (either ground or not, closed or open).
Sender on front with timer switch, two wires, THW at ECU (varys resistance with temp, swings from A to B as temp changes)
not sure if you saw all the info I wrote in my last comment I was editing while you were replying I think. Regarding the AC cutoff switch I read it was an option on some trucks with tow package or auto trans ... I don’t have that switch on my thermo housing or anywhere on the engine.
not sure if you saw all the info I wrote in my last comment I was editing while you were replying I think. Regarding the AC cutoff switch I read it was an option on some trucks with tow package or auto trans ... I don’t have that switch on my thermo housing or anywhere on the engine.
I was fighting my phone but yeah I caught the AC part. Was just being thorough, I'm 100%/certain of my description of those devices and now you should be too. That AC signal doesn't go to the ECU and isn't part of the engine harness.. You've probably certainly got the TSW switch hooked to the correct engine harness wire.
Still looking for a recap of current issues you are having. Last I can recall was a hot start issue, and I wasn't certain but they might you said that went away?
im almost out of time here, but I'd say it's worth checking the COR. Wires intact, clean firm.terminals, no rattles or odd things.
With a voltmeter or testlamp on the FP diagnostics port you should see battery voltage every time you open the vane in the VAFM, as well if the key is in STArt position.
If this isn't what you get proceed to checking signal reaches the COR. I don't know the pin number for the activation circuit offhand, will have to dig that up. This will verify the vafm and ignition switch and all the wiring upto the COR.
Probably missing some questions, I'll check back later, sorry.
08-21-2018, 11:51 AM
can I pick them up at ace hardware or something?
