So, you have spark, but no injector pulse?
I don't see why you wouldn't have gotten some combustion when you sprayed starter fluid, then.
I don't see why you wouldn't have gotten some combustion when you sprayed starter fluid, then.
7MGTE 1989 Won't Start
- Thread starter jkendall86
- Start date
jkendall86;2034860 said:
The injector has power on one side, and the other side is grounded by the ECU to turn on the injector. That means when you check the voltage of the disconnected injector plug you should see 12V on one side and the other side will be 0V (actually its really an open circuit).
However, things will get complicated if the paired injector(1 & 4, 2 & 6, 3 & 5) is still connected. Then the constant 12V from the supply will go through the other injector's windings and show up on the "ground" side of the connector as well. No current is flowing. For that reason, do the test with all injectors disconnected.
What you described sounded exactly like that, so I would conclude your wiring is fine.
If the noid is not blinking, then most likely issue is the CPS. Have you pulled the CPS out and spun it by hand with ignition on to see if you can hear the injectors click? Its a much better approach than using the starter.
I'm still confused about the spark. It was described as checked and fine for all 6, then there was some doubt, and now I don't know what the status is. If you've got spark, your CPS is fine, and you should also have injection.
Here is the relevant wiring diagram:
http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=46
As for the low compression, the first thing I would do is check with a different gauge. Could just be measurement error.
I think you should go through these checks:
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=122
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=123
You will need a good DMM and either a terminal extractor or eyeglass screwdriver or similar tool to release the terminal locks on the ECU connectors. You need to remove the connectors from the ECU, then release the terminal locks on the connectors. The locks are basically little plastic inserts within the connectors that keep the terminals from pulling out of the backside of the connector. You need to disengage these locks to give yourself access to the terminal so you can touch the DMM to the terminals.
This is a good way to check many of the system circuits all in one place and may help show you some related circuits that are having trouble. It helped me find a bad crimp when I redid my entire harness from scratch.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=122
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=123
You will need a good DMM and either a terminal extractor or eyeglass screwdriver or similar tool to release the terminal locks on the ECU connectors. You need to remove the connectors from the ECU, then release the terminal locks on the connectors. The locks are basically little plastic inserts within the connectors that keep the terminals from pulling out of the backside of the connector. You need to disengage these locks to give yourself access to the terminal so you can touch the DMM to the terminals.
This is a good way to check many of the system circuits all in one place and may help show you some related circuits that are having trouble. It helped me find a bad crimp when I redid my entire harness from scratch.
After reading posts from PI and suprarx7nut, i looked over the wiring diagrams and concluded I should connect all the electrical up to do my injector diagnostics. I had been checking the injector pulse with the coils unplugged. Once I plugged them in, my noid light began to flash while cranking. And while I did at one point see spark on a tester, now I do not while cranking. I even tried a third cps to spin to see if I could see spark, I did not. I do have a DMM and in the process of doing a continuity check of all wiring associated with the CPS, IGNITOR, Grounds and Injectors back to the ECU....There must be a break somewhere.
As for the compression, i have used 3 different gauges with two sets of hoses....mostly the same numbers....but that will wait until I can get the wiring sorted out.
As for the compression, i have used 3 different gauges with two sets of hoses....mostly the same numbers....but that will wait until I can get the wiring sorted out.
jkendall86;2034961 said:
I'm not sure you can see spark while turning a CPS by hand. At least I don't think that's a real useful diagnostic tool. Get everything reassembled and back to "complete". Diagnostics can be quickly rendered useless if even one key connector isn't plugged in so try to keep the engine as complete as possible when troubleshooting.
Anxious to hear back. Keep the updates coming.
jkendall86;2034961 said:
I will drive to Oregon and take care of it for $2500 in travel money, plus $250/hr straight time. You will have your answer in less than 2 hours.
Suprarx7nut....thanks for the reply....I didnt think spinning the cps would work either, but thought I would give it a shot.
Supranewbie....I put a shot of oil in each cylinder....didn't really change anything....
Nick M...I appreciate the offer, but I think I should use those funds to just purchase another built engine with a new wiring harness....I've owned several of these cars, but this was the 2nd one I purchased. I have had very few problems with this one, and may problems with the others. This is very frustrating....my first inkling was the cam sensor wiring cause it was so messed up....but that proved not to be the case, I think. I have had CPS problems in the past, usually pretty easy to fix, if the wiring is done right, but this has been maddening....and informative as well. Each time I work on one, I learn something new...this time I have learned many new things....I just hope I can come to some conclusion on this.
Supranewbie....I put a shot of oil in each cylinder....didn't really change anything....
Nick M...I appreciate the offer, but I think I should use those funds to just purchase another built engine with a new wiring harness....I've owned several of these cars, but this was the 2nd one I purchased. I have had very few problems with this one, and may problems with the others. This is very frustrating....my first inkling was the cam sensor wiring cause it was so messed up....but that proved not to be the case, I think. I have had CPS problems in the past, usually pretty easy to fix, if the wiring is done right, but this has been maddening....and informative as well. Each time I work on one, I learn something new...this time I have learned many new things....I just hope I can come to some conclusion on this.
Whats the chance the cold start injector is stuck open and flooding the engine? Low compression, spark, won't kick off with starting fluid....??
Continually reading threads about non starting 7mgte's....one common thing is a CPS wiring....I wired it by this:
CPS....................Harness
Green.................Red
Red....................Blue
White.................Black
Yellow................Yellow
Is there any other way it should be? this is a late 89....
CPS....................Harness
Green.................Red
Red....................Blue
White.................Black
Yellow................Yellow
Is there any other way it should be? this is a late 89....
suprarx7nut;2034999 said:
Of course you can, after all the cam just turns the CPS. Its an excellent diagnostic tool for this kind of problem since it eliminate all the noise and commotion of the starter and you can actually hear the injectors click and the spark snap. If you have a spare known good CPS you can leave the original in the car untouched.
For the wiring, I would forget about the colors, as they fade and are not reliable. Trace the wiring instead if there is any doubt. The two G1/G2 and NE pickups are shown below. They should connect to the similarly named ECU pins. The G- ground is tied to all three pickups.
^ This. Not only is it common sense from a technical standpoint but I can't remember how many times I've done it myself. Also mentioned it many times in the past here. Why would I do that if it doesn't work?
Sigh. You try to help and what do ya get....
Sigh. You try to help and what do ya get....
PI...I can clearly see the colors on both sides of the clip, I was more concerned about whether to match colors (as I have read some do) or to them as listed in my last post. I think the listed matching is correct. I am putting all electrical parts back together to see if it now has spark and fuel...
jetjock....when its all together, I will use another cps to spin to look and listen for spark and fuel...\
I have moved enough wiring around and replaced enough things that it should fire....if not, then I will take the DMM to the harness and look for breaks.
jetjock....when its all together, I will use another cps to spin to look and listen for spark and fuel...\
I have moved enough wiring around and replaced enough things that it should fire....if not, then I will take the DMM to the harness and look for breaks.
Yeah, do that. Best to unplug the fuel pump relay when doing it though.
I owned the car 25 years. I'm not just pulling stuff I post outta my butt.
And even if the CPS had to be spun harder to up signal amplitude what's wrong with using something like a drill motor? Rocket science this ain't. Then again these days there's ignition pulse simulators available. I never bothered whipping one up but it wouldn't be difficult. Might be a little project for when 3p is bored. It'd be a cake walk for him.
I owned the car 25 years. I'm not just pulling stuff I post outta my butt.
And even if the CPS had to be spun harder to up signal amplitude what's wrong with using something like a drill motor? Rocket science this ain't. Then again these days there's ignition pulse simulators available. I never bothered whipping one up but it wouldn't be difficult. Might be a little project for when 3p is bored. It'd be a cake walk for him.
I would definitely trace the wired in the cas and at the ecu, all the wiring diagrams I have seen have the wrong color to pickup (from what my and 2 others cas is)
^Agree. I would not base anything on wire colors. Trace the signals from ECU pin to pickup coil. Its easy enough to do with a dmm and back probing. Not only does blue fade to green, but there is no guarantee the internal CPS wire colors match any sort of standard over the years.
jetjock;2035070 said:
That's a neat trick with the CPS manual manipulation. I figured the signal from the coils would need more speed from the [insert technical name of spinning CPS part here] than you could muster up with a simple hand turn to get a clear signal, but that's cool it doesn't require that much speed.
The more you know...
I've always used a drill, I figured it would need to spin fast enough to get "sync" before the ecu would send signals to the injectors and coils
It syncs on the first Gx pulse which is always less than half a turn. It will work if spun as slow as 75 rpm.
Wow! That's totally doable by hand awesome, while we are in the topic, is there ever a instance where somebody would need to adjust the gap on the vr sensors for a stock car?