1995 4runner 3.0 wont start after replacing knock sensor
05-06-2016, 05:59 PM
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1995 4runner 3.0 wont start after replacing knock sensor
Need some guys.
So my 1995 4runner 3.0 A/T 2wd, was throwing the knock sensor code and acting up when it did. So ok, I will fix it. Well...........now everything is back together and I cant get it to start, been at it for two weeks now. Here is what I have done so far...
1. Replaced Knock sensor and pigtail, got knock sensor from dealership.
2. Put everything back together, it would crank but no start. So I bleed fuel line at fuel rail. still no start.
3. Checked and replaced(swaped with starter relay) EFI relay.
4. Jumped diagnostic box so fuel pump would come on, could here it come on and fuel running through the lines. Still no start.
5. Check for codes, no codes.
6. Checked for spark by pulling plug and holding to block, I have spark and plug looks dry, thinking injectors not spraying.
7. Bought Used ECM from ebay, still no start, same issues.
8. Checked voltage and fuel injector plug while cranking over engine, got 10 volts.
9. Tried spraying starting fluid, still no start.
10. Replaced battery, thinking I just had overall low voltage. Still no start.
Im at a lost, don't know what to do next, except buy a new ECM. Please help....
So my 1995 4runner 3.0 A/T 2wd, was throwing the knock sensor code and acting up when it did. So ok, I will fix it. Well...........now everything is back together and I cant get it to start, been at it for two weeks now. Here is what I have done so far...
1. Replaced Knock sensor and pigtail, got knock sensor from dealership.
2. Put everything back together, it would crank but no start. So I bleed fuel line at fuel rail. still no start.
3. Checked and replaced(swaped with starter relay) EFI relay.
4. Jumped diagnostic box so fuel pump would come on, could here it come on and fuel running through the lines. Still no start.
5. Check for codes, no codes.
6. Checked for spark by pulling plug and holding to block, I have spark and plug looks dry, thinking injectors not spraying.
7. Bought Used ECM from ebay, still no start, same issues.
8. Checked voltage and fuel injector plug while cranking over engine, got 10 volts.
9. Tried spraying starting fluid, still no start.
10. Replaced battery, thinking I just had overall low voltage. Still no start.
Im at a lost, don't know what to do next, except buy a new ECM. Please help....
05-07-2016, 08:28 AM
#2
Simple logic would tell you that if it ran before, then you did something that's preventing it from running now. I don't know what all you did. But something didn't likely just totally fail all the sudden. Like the ECU, EFI main relay, or battery. So I don't know why you messed with those. They would be pretty close to last on my list. Well maybe not the EFI main relay. But...
In short, you most likely either broke something or didn't assemble something correctly. You didn't mention checking for blown fuses, or inspecting the COR. So you might want to check those next.
In short, you most likely either broke something or didn't assemble something correctly. You didn't mention checking for blown fuses, or inspecting the COR. So you might want to check those next.
Last edited by MudHippy; 05-07-2016 at 08:31 AM.
05-07-2016, 07:56 PM
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Check to see if you have power actually getting to your ECM. You should be able to unplug one of the connectors and check it at the harness. I don't have any real good ideas right now but it sounds like an electrical problem for sure. I'm trying to retrace what all you had to take off to get to the knock sensor. I know my 89 model 3VZE has a ground wire connected to the back of the plenum that I had to remove to get mine off. I'm told that this is a very important ground point for the engine control but I myself, don't know what it's for. The only other thing I can think of on your way to the Knock sensor would be the injector harness but I know from experience that it will run on three cylinders so it would be unlikely that you damaged the power supply to all 6. One more thing you can rule out quickly would be whether or not your are getting spark to your cylinders. If you do, then you can rule out several things. Also check that you got everything back together right on your throttle body. You said you checked fuses. Just to be sure, did you check the 15A EFI fuse? In my 89 it's in the driver side kick panel. It's just a regular old generic fuse but your truck will not run without it. I'm sure you have checked it already but there are some folks that check the relays but are unaware of the little fuse.
05-09-2016, 05:56 AM
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I have checked the little fuses. Think Im just going to pull the upper intake back off and start over, checking all connections, and hoses. Im just dumbfounded on this. I know its gonna be something simple, always is.
05-09-2016, 05:59 AM
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I may go ahead and replace the injectors while im in there as the truck has 270+ miles on it. And replace the injector connectors as well, as they were brittle and breaking(the plastic).
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05-09-2016, 09:21 AM
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I got my injectors on Ebay for about $150 shipped. I went with some 4 hole "upgrade" injectors that had a different connector than the original. I chose these because they came with adapter pigtails which I grafted into my harness to replace the severely brittle and cracked connector wires. They have been in there for a year and seem to be a pretty good product, especially for the price.
05-10-2016, 12:29 AM
#9
With all the parts replacing did you ever look at the ground for the ECU ??
They sometimes can be real finicky .
One day just snugging mine up was enough to cause all sorts of problems like you are having .
Took a few hours to walk through every thing I did.
They sometimes can be real finicky .
One day just snugging mine up was enough to cause all sorts of problems like you are having .
Took a few hours to walk through every thing I did.
07-13-2016, 09:31 AM
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ok, i jumped back on this project after no luck and had to just walk away from it. So I pulled the upper intake back off and went ahead and replaced the injectors and pigtails for them. Put it all back together, and still will not start up. will crank over, but no starting up. I am dumbfounded! I also reinstalled the old ECM back.
07-13-2016, 10:16 AM
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If you have spark, but the engine will not fire even with starting fluid, then I would suspect that the distributor is way off. (So that the plug is firing at some place other than 10° BTDC.)
Use your timing light while cranking to check. You don't need it dead on, just close. If that doesn't solve the problem, put your timing light on each plug lead and check for a flash; that's the easy way to confirm the plugs are firing.
Try starting it with the jumper between B+ and FP. That takes both the COR and the VAF out of the equation (the pump is forced to run with key-on, and you know the pump DOES run with the jumper.)
For the engine to fire it just takes Fuel (even starter fluid), air, and spark (but at close to the right time). Until you get it firing, don't waste effort on the grounds, the COR, injectors, fuses, ECM, .... They don't matter (just yet).
The injectors have 12v on one lead with key-on, and the ECU grounds the other lead to open the injector. So checking the voltage on the injector doesn't tell you that the ECU is commanding it to open (but it's better than nothing, and detecting the short ground pulse is not going to be easy with the gear you have). The only time that the ECU will NOT command the injectors to open is when the IGF signal from the igniter is missing for a few cycles. That's not easy to test for directly, but at least be sure your igniter connector is not messed up. And that should throw a code. (Okay, the ECU will also not open the injectors when you're coasting downhill, but that's not your case.)
By the way, remember that you MUST replace the crush washers any time you open part of the pressurized fuel rail. Even if all you did was "bleed" the fuel line. They are a dealer-only item, but they are cheaper than dirt.
Use your timing light while cranking to check. You don't need it dead on, just close. If that doesn't solve the problem, put your timing light on each plug lead and check for a flash; that's the easy way to confirm the plugs are firing.
Try starting it with the jumper between B+ and FP. That takes both the COR and the VAF out of the equation (the pump is forced to run with key-on, and you know the pump DOES run with the jumper.)
For the engine to fire it just takes Fuel (even starter fluid), air, and spark (but at close to the right time). Until you get it firing, don't waste effort on the grounds, the COR, injectors, fuses, ECM, .... They don't matter (just yet).
The injectors have 12v on one lead with key-on, and the ECU grounds the other lead to open the injector. So checking the voltage on the injector doesn't tell you that the ECU is commanding it to open (but it's better than nothing, and detecting the short ground pulse is not going to be easy with the gear you have). The only time that the ECU will NOT command the injectors to open is when the IGF signal from the igniter is missing for a few cycles. That's not easy to test for directly, but at least be sure your igniter connector is not messed up. And that should throw a code. (Okay, the ECU will also not open the injectors when you're coasting downhill, but that's not your case.)
By the way, remember that you MUST replace the crush washers any time you open part of the pressurized fuel rail. Even if all you did was "bleed" the fuel line. They are a dealer-only item, but they are cheaper than dirt.
Last edited by scope103; 07-13-2016 at 10:21 AM.
07-13-2016, 10:49 AM
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If you have spark, but the engine will not fire even with starting fluid, then I would suspect that the distributor is way off. (So that the plug is firing at some place other than 10° BTDC.)
Use your timing light while cranking to check. You don't need it dead on, just close. If that doesn't solve the problem, put your timing light on each plug lead and check for a flash; that's the easy way to confirm the plugs are firing.
Try starting it with the jumper between B+ and FP. That takes both the COR and the VAF out of the equation (the pump is forced to run with key-on, and you know the pump DOES run with the jumper.)
For the engine to fire it just takes Fuel (even starter fluid), air, and spark (but at close to the right time). Until you get it firing, don't waste effort on the grounds, the COR, injectors, fuses, ECM, .... They don't matter (just yet).
The injectors have 12v on one lead with key-on, and the ECU grounds the other lead to open the injector. So checking the voltage on the injector doesn't tell you that the ECU is commanding it to open (but it's better than nothing, and detecting the short ground pulse is not going to be easy with the gear you have). The only time that the ECU will NOT command the injectors to open is when the IGF signal from the igniter is missing for a few cycles. That's not easy to test for directly, but at least be sure your igniter connector is not messed up. And that should throw a code. (Okay, the ECU will also not open the injectors when you're coasting downhill, but that's not your case.)
By the way, remember that you MUST replace the crush washers any time you open part of the pressurized fuel rail. Even if all you did was "bleed" the fuel line. They are a dealer-only item, but they are cheaper than dirt.
Use your timing light while cranking to check. You don't need it dead on, just close. If that doesn't solve the problem, put your timing light on each plug lead and check for a flash; that's the easy way to confirm the plugs are firing.
Try starting it with the jumper between B+ and FP. That takes both the COR and the VAF out of the equation (the pump is forced to run with key-on, and you know the pump DOES run with the jumper.)
For the engine to fire it just takes Fuel (even starter fluid), air, and spark (but at close to the right time). Until you get it firing, don't waste effort on the grounds, the COR, injectors, fuses, ECM, .... They don't matter (just yet).
The injectors have 12v on one lead with key-on, and the ECU grounds the other lead to open the injector. So checking the voltage on the injector doesn't tell you that the ECU is commanding it to open (but it's better than nothing, and detecting the short ground pulse is not going to be easy with the gear you have). The only time that the ECU will NOT command the injectors to open is when the IGF signal from the igniter is missing for a few cycles. That's not easy to test for directly, but at least be sure your igniter connector is not messed up. And that should throw a code. (Okay, the ECU will also not open the injectors when you're coasting downhill, but that's not your case.)
By the way, remember that you MUST replace the crush washers any time you open part of the pressurized fuel rail. Even if all you did was "bleed" the fuel line. They are a dealer-only item, but they are cheaper than dirt.
07-13-2016, 10:52 AM
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oh and what does the "B" stand for in BTDC? I get TOP DEAD CENTER., never mind, it just hit me, BEFORE TOP DEAD CENTER.
Last edited by nuknuk; 07-13-2016 at 10:54 AM.
07-15-2016, 07:47 PM
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Ok, well the timing is on and have spark on all wires. Did however notice that while I was trying to crank it that if I pressed the has pedal, I woul get a knocking noise out of the mass air flow housing. Like the flapper gate in there is is tapping. Only happens if you press the gas pedal while trying to crank it.
07-20-2016, 06:10 AM
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went ahead and replaced the distributor cap and rotor, and spark plug wires, still nothing!! Thinking the mass air flow is bad? what else could it be? Air in fuel lines?
