Won't crank, engine spins?

larril · 08-18-2011, 07:08 PM

Sooo, if the ecu knows the cps, is off... it won't send a signals to the injectors? Or... it's just off and not firing at the right time?

Sounds like a dumb, question... had a similar problem with a Chrysler LHS, famous for dropping a timing belt when the water pump croaks... If the cams and crank aren’t in sequence… the computer wouldn’t let the sparks fly… no fire to plugs…

One time…, same scenario… shuts down, no fire… I went ahead and bought the water pump, and new timing belt…. Took all the covers off…. Belt and timing were all good. Turned out the crank sensor (pickup) had gone bad… replaced it… back in business.

Back to ’88 7mge, tried typing a short how did I get here twice, apparently my log in timed out, and when I tried to post or submit… lost it all.

Third and last try…

My nephew, slung a rod out the side… I ended up with it. Red 88 targa top, automatic, original everything… Swapped out the motor with one off ebay… worked fine. Put a lot of little new stuff, water pump, radiator, plugs, plug wires, intake, exhaust gaskets… new radiator hoses, and all but one heater hoses… (see below) window switches, fog lamps with original equipment, wiper and turn indicator column assembly… Almost like new… only 22 years old.

Daughter took it off to college. A yoyo, tried to make a right turn from the left hand turn lane across the two straight lanes… she ripped the right side off a Chevy aveo… Only had to replace the left fender, running lights, straighten the bumper under the facia/ apron… straighten the left headlight to clear for up/down… Back on the road…, till a little leak in a heater hose… short piece I din't change teh first time..., and waiting too long to get off the road, had me taking the head off the first engine…, straighten, machine… rebuilt, installed on the ebay engine.

Life was good, few months… then started having problems, starting… mind of it’s own. I went and drove it 3 hours home…, ran like it was starving for gas. When I accelerated, it smooth right out… then back to rough…

Went to a shop in town to make a schedule…, got ready to leave… wouldn’t crank. He put a light probe in the back of the fuel injectors… said they weren’t getting a signal.. Came back later same day, cranked and took it home… its sat there for 12-14 months… Sent my daughter back to school with a 2003 passat.

I need it for daily driver for next daughter… but I got to have better success this time. I appreciate what it is… powerful, great handling, little 20+ year old car…

Back to current subject… could the ecu know its out of time… or just far off enough to get no fire…?
If that’s it…, I’ll be glad, nobody here knows anymore about me than this… I’ll slink away, and keep my mouth shut, and not show my red face anymore.

Factory LSD... ???

Old Man Supra · 08-18-2011, 10:46 PM

Hi, Well from my run in with the ECU it knows everything! Its the brain of the car and if its not telling the rest of "THE BODY" what to do and how to do it your SOL. I had a friend hook up my battery wrong and it fried the ECU[but amazingly nothing else] but I did not know that right away and I went through alot of the same things you checked out. Once I replaced the ECU with a new used one from another same model year Supra it roared back to life and I have not had any other issues since, the car now runs perfect.............like it did before. When I first got the car [1986 Supra non turbo] I had many issues with the alarm system.................I'd drive the car park it for awhile then it would refuse to start as the alarm was cutting out the juice to the starter.............it was maddening, some times it would start right away after locking and unlocking the doors to reset the alarm sometimes not. I fixed that by clipping the wire under the hood to fool the alarm system now it starts every time. The forum is a great place to find out what it is and how to fix it,I have learned a lot from the forum members here. I'm also lucky to have a friend that is a former Toyota mechanic. : ) I wish you the best of luck getting it sorted out.When the Supra is running the way it should its a incredible car. Best, Gary

El Supracabras · 08-19-2011, 03:38 AM

I hope ya didn't spray the ether in the AFM.
It sounds like the timing is off which could be caused by damaged wiring to the CPS (cps is in the distributor on n/a). It uses this input for both fuel and spark timing.
Try the ecu, (since you're getting one) hopefully it's that easy. Also check your grounds, they tend to get a little crappy over the years. If it's not those, take a look at the wiring to the CPS. Good luck.

larril · 08-19-2011, 02:25 PM

Not the ECU. New one in..., no change.

Probed the cps plug. four terminals..., each of the three tested with the fourth... showed what the spec called for.

Check grounds...? (little more detail)

So as for wiring..., and I read other threads last night... I take it that the wiring harnes coming to the cps... could be suspect, takes a lot of heat, often the culprit...?

Also think I saw where you commented, on difernet thread, swapping/ replacing the plug,... is this all the same subject?

Looking at a repair manual..., it was calling to measure the gap three places down in the cps... can do, but is this a logical problem...

'88 7MGE, a/t, n/a

El Supracabras · 08-19-2011, 06:13 PM

The two grounds on the bottom of the intake manifold near the firewall are the ecu grounds. ALSO check coil ground. If they are corroded or broken the ecu will not function right and will give the same symptoms you describe..
The cps wires tend to break right where the wire is terminated inside the connector. They can be re pinned but the connector is usually flaking apart by now (hence the connector swap). The wiring can be damaged anywhere around there. If you are in doubt of the connector and just want to get the car running, you can just cut the connector off completely and crimp or solder the wires together.
You said it "fires on a few cylinders" this would indicate (to me) that the computer has no idea what position the crank is in. It would have a 1 in 6 chance of getting it right without the cps signal.
I know this may sound silly but have you checked the ecu fuse? Have you checked to see if there are any stored codes?
This is the connector I like to use for lotsa stuff.
http://www.jegs.com/i/JEGS-Performan...ductId=1354645

larril · 08-20-2011, 12:27 PM

After reading... went and checked the connector, wiggled here wiggled there... nothing suspicious. Found the ground wires, they were on the bolt, but it wasn't pulled up tight. Swapped the bolt for a shorter one, pulled up tight... Little ecouragement but she fired up...
Pretty sure it was the ground wires...
Timing needs improvement... when I had teh head machined and rebuilt, I didn't see the special instructions, for installing a "new" timing belt. Used the same dowel locations in the front of the cams. as when removed. Goning to break it back down to that part and come back up..., reading all the instructions.

Thanks for the help, looks like you nailed it.

08-18-2011, 07:08 PM	#1
larril Stock Join Date: Aug 2011 Location: Brewton, AL Posts: 5	Sooo, if the ecu knows the cps, is off... it won't send a signals to the injectors? Or... it's just off and not firing at the right time? Sounds like a dumb, question... had a similar problem with a Chrysler LHS, famous for dropping a timing belt when the water pump croaks... If the cams and crank aren’t in sequence… the computer wouldn’t let the sparks fly… no fire to plugs… One time…, same scenario… shuts down, no fire… I went ahead and bought the water pump, and new timing belt…. Took all the covers off…. Belt and timing were all good. Turned out the crank sensor (pickup) had gone bad… replaced it… back in business. Back to ’88 7mge, tried typing a short how did I get here twice, apparently my log in timed out, and when I tried to post or submit… lost it all. Third and last try… My nephew, slung a rod out the side… I ended up with it. Red 88 targa top, automatic, original everything… Swapped out the motor with one off ebay… worked fine. Put a lot of little new stuff, water pump, radiator, plugs, plug wires, intake, exhaust gaskets… new radiator hoses, and all but one heater hoses… (see below) window switches, fog lamps with original equipment, wiper and turn indicator column assembly… Almost like new… only 22 years old. Daughter took it off to college. A yoyo, tried to make a right turn from the left hand turn lane across the two straight lanes… she ripped the right side off a Chevy aveo… Only had to replace the left fender, running lights, straighten the bumper under the facia/ apron… straighten the left headlight to clear for up/down… Back on the road…, till a little leak in a heater hose… short piece I din't change teh first time..., and waiting too long to get off the road, had me taking the head off the first engine…, straighten, machine… rebuilt, installed on the ebay engine. Life was good, few months… then started having problems, starting… mind of it’s own. I went and drove it 3 hours home…, ran like it was starving for gas. When I accelerated, it smooth right out… then back to rough… Went to a shop in town to make a schedule…, got ready to leave… wouldn’t crank. He put a light probe in the back of the fuel injectors… said they weren’t getting a signal.. Came back later same day, cranked and took it home… its sat there for 12-14 months… Sent my daughter back to school with a 2003 passat. I need it for daily driver for next daughter… but I got to have better success this time. I appreciate what it is… powerful, great handling, little 20+ year old car… Back to current subject… could the ecu know its out of time… or just far off enough to get no fire…? If that’s it…, I’ll be glad, nobody here knows anymore about me than this… I’ll slink away, and keep my mouth shut, and not show my red face anymore. Factory LSD... ??? Last edited by larril; 08-18-2011 at 07:10 PM.

08-18-2011, 10:46 PM	#2
Old Man Supra Stock Join Date: May 2010 Location: Minnesota Posts: 13	Supra ! Hi, Well from my run in with the ECU it knows everything! Its the brain of the car and if its not telling the rest of "THE BODY" what to do and how to do it your SOL. I had a friend hook up my battery wrong and it fried the ECU[but amazingly nothing else] but I did not know that right away and I went through alot of the same things you checked out. Once I replaced the ECU with a new used one from another same model year Supra it roared back to life and I have not had any other issues since, the car now runs perfect.............like it did before. When I first got the car [1986 Supra non turbo] I had many issues with the alarm system.................I'd drive the car park it for awhile then it would refuse to start as the alarm was cutting out the juice to the starter.............it was maddening, some times it would start right away after locking and unlocking the doors to reset the alarm sometimes not. I fixed that by clipping the wire under the hood to fool the alarm system now it starts every time. The forum is a great place to find out what it is and how to fix it,I have learned a lot from the forum members here. I'm also lucky to have a friend that is a former Toyota mechanic. : ) I wish you the best of luck getting it sorted out.When the Supra is running the way it should its a incredible car. Best, Gary

08-19-2011, 02:25 PM	#4
larril Stock Join Date: Aug 2011 Location: Brewton, AL Posts: 5	Not the ECU. New one in..., no change. Probed the cps plug. four terminals..., each of the three tested with the fourth... showed what the spec called for. Check grounds...? (little more detail) So as for wiring..., and I read other threads last night... I take it that the wiring harnes coming to the cps... could be suspect, takes a lot of heat, often the culprit...? Also think I saw where you commented, on difernet thread, swapping/ replacing the plug,... is this all the same subject? Looking at a repair manual..., it was calling to measure the gap three places down in the cps... can do, but is this a logical problem... '88 7MGE, a/t, n/a Last edited by larril; 08-19-2011 at 02:28 PM.

08-19-2011, 06:13 PM	#5
El Supracabras 3" Exhaust Join Date: Feb 2010 Location: Chicago Posts: 240	The two grounds on the bottom of the intake manifold near the firewall are the ecu grounds. ALSO check coil ground. If they are corroded or broken the ecu will not function right and will give the same symptoms you describe.. The cps wires tend to break right where the wire is terminated inside the connector. They can be re pinned but the connector is usually flaking apart by now (hence the connector swap). The wiring can be damaged anywhere around there. If you are in doubt of the connector and just want to get the car running, you can just cut the connector off completely and crimp or solder the wires together. You said it "fires on a few cylinders" this would indicate (to me) that the computer has no idea what position the crank is in. It would have a 1 in 6 chance of getting it right without the cps signal. I know this may sound silly but have you checked the ecu fuse? Have you checked to see if there are any stored codes? This is the connector I like to use for lotsa stuff. http://www.jegs.com/i/JEGS-Performan...ductId=1354645 Last edited by El Supracabras; 08-19-2011 at 06:48 PM.

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08-19-2011, 03:38 AM	#3
El Supracabras 3" Exhaust Join Date: Feb 2010 Location: Chicago Posts: 240	I hope ya didn't spray the ether in the AFM. It sounds like the timing is off which could be caused by damaged wiring to the CPS (cps is in the distributor on n/a). It uses this input for both fuel and spark timing. Try the ecu, (since you're getting one) hopefully it's that easy. Also check your grounds, they tend to get a little crappy over the years. If it's not those, take a look at the wiring to the CPS. Good luck.

08-20-2011, 12:27 PM	#6
larril Stock Join Date: Aug 2011 Location: Brewton, AL Posts: 5	After reading... went and checked the connector, wiggled here wiggled there... nothing suspicious. Found the ground wires, they were on the bolt, but it wasn't pulled up tight. Swapped the bolt for a shorter one, pulled up tight... Little ecouragement but she fired up... Pretty sure it was the ground wires... Timing needs improvement... when I had teh head machined and rebuilt, I didn't see the special instructions, for installing a "new" timing belt. Used the same dowel locations in the front of the cams. as when removed. Goning to break it back down to that part and come back up..., reading all the instructions. Thanks for the help, looks like you nailed it.