Help - Engine cranks, but won't start (no spark), options exhausted
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Help - Engine cranks, but won't start (no spark), options exhausted
I've got a '93 T/A that threw a SES 36 and 41 before dying. Car stalled two or three times a week apart and then just wouldn't start anymore. Preliminary diagnostic were pointing to the original opti (117k) or Ignition Control module. I ended up replacing both parts along with the coil, plugs, fuel filter, water pump (just to be safe), and opti-pigtail harness. The spark plugs I had put in six months prior along with new wires were black... I tried using a spark tester from autozone--a little tool that I just clipped to the coil pack output, set a gap of about 1/3 of an inch and then attached a wire from the other end to a ground point on the car. No spark was produced (assuming I did it right).
I've run voltage tests on the connectors under the dash (red, pink, yellow, brown, and orange wires) and the voltages all appear correct when I turn the key to the various positions. I checked the connector that has been known to melt under the dash and it's perfect and the dash lights up and the security light goes out after 3 seconds.
I've got voltage on the A & D (outer) pins on the Ignition Control Module harness and on the C pin on the opti-harness connector. The only voltage I wasn't able to verify was a pulsating test light when cranking, but again, all of the ignition components are brand new and behaving just like the old ones
I've tried checking my grounds--the negative battery patch ground up top on the passenger front, the ground to the block just under the coil, and the flat braid wire ground to the side wall under the antilock system. I do have two connectors that I still want to replace, the MAP connector and the 4 prong connector going into the throttle body which is pretty hashed. I don't know if either of those are the problem, but I wouldn't think so.
Back before it all happened I was worried that I got some water in the gas from the winter with a near empty tank for a couple of weeks, but I got it running later and put some HEET in the tank to deal with the water, not to mention running another tank of gas through it, so I think it's good.
I'm really at a loss now other than either an open circuit I can't track down, or possibly the PCM, which I don't know that I can test without taking it to a dealer, which is exactly what I'm going to have to do unless someone reading this has other suggestions I can attempt tomorrow. If I could just get some dang spark I'm sure it would run. If you've made it this far and have any suggestions to help put a little spark or bang into my 4th of July tomorrow I'd appreciate it
Thanks.
I've run voltage tests on the connectors under the dash (red, pink, yellow, brown, and orange wires) and the voltages all appear correct when I turn the key to the various positions. I checked the connector that has been known to melt under the dash and it's perfect and the dash lights up and the security light goes out after 3 seconds.
I've got voltage on the A & D (outer) pins on the Ignition Control Module harness and on the C pin on the opti-harness connector. The only voltage I wasn't able to verify was a pulsating test light when cranking, but again, all of the ignition components are brand new and behaving just like the old ones
I've tried checking my grounds--the negative battery patch ground up top on the passenger front, the ground to the block just under the coil, and the flat braid wire ground to the side wall under the antilock system. I do have two connectors that I still want to replace, the MAP connector and the 4 prong connector going into the throttle body which is pretty hashed. I don't know if either of those are the problem, but I wouldn't think so.
Back before it all happened I was worried that I got some water in the gas from the winter with a near empty tank for a couple of weeks, but I got it running later and put some HEET in the tank to deal with the water, not to mention running another tank of gas through it, so I think it's good.
I'm really at a loss now other than either an open circuit I can't track down, or possibly the PCM, which I don't know that I can test without taking it to a dealer, which is exactly what I'm going to have to do unless someone reading this has other suggestions I can attempt tomorrow. If I could just get some dang spark I'm sure it would run. If you've made it this far and have any suggestions to help put a little spark or bang into my 4th of July tomorrow I'd appreciate it
Thanks.
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Joined: Sep 2004
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We have to make a few assumptions to continue. The first is that a 93 uses DTC36 and 41. That's the first I've heard of it. Of the 2 codes, start with the 41 since it involves a possible open circuit on the white trigger wire from the PCM to the ICM. And the fact that a 36 should not shut er down.
If you don't see 1 to 4 VAC on that wire while cranking, remove at least one end (example at the ICM) and ohm it from that connector to the PCM.
We don't know which pin at the PCM has that wire, however, there will only 1 or 2 that could have a white wire so visually check for it. I suggest you remove both ends and ohm from the contacts instead of back probing.
If you don't see 1 to 4 VAC on that wire while cranking, remove at least one end (example at the ICM) and ohm it from that connector to the PCM.
We don't know which pin at the PCM has that wire, however, there will only 1 or 2 that could have a white wire so visually check for it. I suggest you remove both ends and ohm from the contacts instead of back probing.
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Joined: Nov 2005
Posts: 9
We have to make a few assumptions to continue. The first is that a 93 uses DTC36 and 41. That's the first I've heard of it. Of the 2 codes, start with the 41 since it involves a possible open circuit on the white trigger wire from the PCM to the ICM. And the fact that a 36 should not shut er down.
If you don't see 1 to 4 VAC on that wire while cranking, remove at least one end (example at the ICM) and ohm it from that connector to the PCM.
We don't know which pin at the PCM has that wire, however, there will only 1 or 2 that could have a white wire so visually check for it. I suggest you remove both ends and ohm from the contacts instead of back probing.
If you don't see 1 to 4 VAC on that wire while cranking, remove at least one end (example at the ICM) and ohm it from that connector to the PCM.
We don't know which pin at the PCM has that wire, however, there will only 1 or 2 that could have a white wire so visually check for it. I suggest you remove both ends and ohm from the contacts instead of back probing.
All of the fuses appear to be good as well under the hood and on the door panel location. Any other suggestions?
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Joined: Oct 2004
Posts: 690
From: St. Charles, IL
FYI-Since your car is a DC system (direct current) utilizing a storage cell (12 volt DC battery) you need to have your multimeter set to the DC scale.
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Yeah, I only set it to AC for that specific test because the Hayne's manual I had said explicitly to do so when cranking the motor. Well, It looks like I'll be towing the bird to the dealer in about 8 hours...
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Joined: Nov 2005
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Well, I took the '93 T/A in for a diagnosis at the dealer after replacing the ignition coil, ignition control module, optispark, spark plugs, fuel filter, and water pump and still having a no spark condition. The dealer thinks it's one of the following:
1) Bad optispark (It's a brand new AC Delco off of ebay last week)
2) Incorrectly installed optispark (I don't see how this is possible on the '93... 3 bolts, 1 keyed pin that only goes on one way)
3) Problem with the timing chain.
Given that the problem existed before any of the above parts were replaced, I doubt it's either 1 or 2, so perhaps it is the timing chain... I didn't pull the cover when I replaced the opti. Dealer wants $600 labor and diagnostics already done thus far, plus parts if necessary. Any thoughts anyone? I guess I should have pulled the cover...
1) Bad optispark (It's a brand new AC Delco off of ebay last week)
2) Incorrectly installed optispark (I don't see how this is possible on the '93... 3 bolts, 1 keyed pin that only goes on one way)
3) Problem with the timing chain.
Given that the problem existed before any of the above parts were replaced, I doubt it's either 1 or 2, so perhaps it is the timing chain... I didn't pull the cover when I replaced the opti. Dealer wants $600 labor and diagnostics already done thus far, plus parts if necessary. Any thoughts anyone? I guess I should have pulled the cover...
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You don't need to go into the cover to diagnose a chain problem. There are 3 possible scenarios with regard to the chain.
1 The chain is broken. In that case the cam will not rotate. You will have no compression on several cylinders and obviously the rockers will not move. Very easy to spot with the valve cover off.
2 The chain jumped a tooth or more and you can see this by again viewing the relationship of the rockers moving with regard to the movement of the piston toward TDC. Again done with the valve cover off and plug out using a wooden dowel or pencil in the cylinder to view the piston movement.
3 The chain has a lot of slack. This can also be viewed by rotating the crank back and forth with the valve cover off. movement back and forth of the crank and no valve (rocker) movement indicates slack. Understand.
Also with regard to the chain. A chain problem other than a broke chain, will not eliminate spark. It could only occur at the wrong time. So if you have a no spark condition and the rockers are moving, it can't be from the chain.
These guys you are dealing with don't sound too bright. They should have done this already and have narrowed down the possibilties BEFORE they spoke to you.
One other thing that occurs ALL the time. The mechanic takes his/her best guess at the problem. The better the mechanic obviously the better the diagnosis. They do the work and replace the parts and find out the problem is not fixed. So now they move on to the next thing. Until they finally fix the problem. BUT they don't undoe the previous repair (too costly) and they usually convince the owner that the problem was both (or more) of the repairs they did. In other words, they charge the customer for both repairs even though the first repair was not the problem.
You see this alot with fuel AND ignition repairs to the same vehicle.
BEWARE of this shoddy billing. If I were to have work done, I would only agree to pay for diagnosis upfront and write it on the work order in your hand writting and initial it. You must give approval for repairs BEFORE they are done.
Let them know up front you will only pay for repairs that you receive the original parts back. With exception of gasket, filters, hoses and the like.
I always try to take every angle I can to narrow down the possibilities before estimating a job. They could do more to diagnose your problem and they should.
BTW you didn't do a very good job of tracing down the seemingly apparent problem with the white IC wire going to the ICM. If this wire is either completely open or intermittent, it will give the appearance of an opti problem since it is used to trigger the coil.
After you checked for AC voltage (you were on the wrong scale for some reason). You should have traced the white wire and ohmed it from end to end.
Did you mention it to the shop? Did they do anything to eliminate it as the cause of the problem?
1 The chain is broken. In that case the cam will not rotate. You will have no compression on several cylinders and obviously the rockers will not move. Very easy to spot with the valve cover off.
2 The chain jumped a tooth or more and you can see this by again viewing the relationship of the rockers moving with regard to the movement of the piston toward TDC. Again done with the valve cover off and plug out using a wooden dowel or pencil in the cylinder to view the piston movement.
3 The chain has a lot of slack. This can also be viewed by rotating the crank back and forth with the valve cover off. movement back and forth of the crank and no valve (rocker) movement indicates slack. Understand.
Also with regard to the chain. A chain problem other than a broke chain, will not eliminate spark. It could only occur at the wrong time. So if you have a no spark condition and the rockers are moving, it can't be from the chain.
These guys you are dealing with don't sound too bright. They should have done this already and have narrowed down the possibilties BEFORE they spoke to you.
One other thing that occurs ALL the time. The mechanic takes his/her best guess at the problem. The better the mechanic obviously the better the diagnosis. They do the work and replace the parts and find out the problem is not fixed. So now they move on to the next thing. Until they finally fix the problem. BUT they don't undoe the previous repair (too costly) and they usually convince the owner that the problem was both (or more) of the repairs they did. In other words, they charge the customer for both repairs even though the first repair was not the problem.
You see this alot with fuel AND ignition repairs to the same vehicle.
BEWARE of this shoddy billing. If I were to have work done, I would only agree to pay for diagnosis upfront and write it on the work order in your hand writting and initial it. You must give approval for repairs BEFORE they are done.
Let them know up front you will only pay for repairs that you receive the original parts back. With exception of gasket, filters, hoses and the like.
I always try to take every angle I can to narrow down the possibilities before estimating a job. They could do more to diagnose your problem and they should.
BTW you didn't do a very good job of tracing down the seemingly apparent problem with the white IC wire going to the ICM. If this wire is either completely open or intermittent, it will give the appearance of an opti problem since it is used to trigger the coil.
After you checked for AC voltage (you were on the wrong scale for some reason). You should have traced the white wire and ohmed it from end to end.
Did you mention it to the shop? Did they do anything to eliminate it as the cause of the problem?
Last edited by Guest47904; Jul 9, 2007 at 09:03 PM.
Thread Starter
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Joined: Nov 2005
Posts: 9
Problem finally resolved!
You don't need to go into the cover to diagnose a chain problem. There are 3 possible scenarios with regard to the chain...
I always try to take every angle I can to narrow down the possibilities before estimating a job. They could do more to diagnose your problem and they should.
BTW you didn't do a very good job of tracing down the seemingly apparent problem with the white IC wire going to the ICM. If this wire is either completely open or intermittent, it will give the appearance of an opti problem since it is used to trigger the coil.
After you checked for AC voltage (you were on the wrong scale for some reason). You should have traced the white wire and ohmed it from end to end.
Did you mention it to the shop? Did they do anything to eliminate it as the cause of the problem?
Yeah, so it wasn't the chain and there was no need for the tech to go there and he never ended up trying as it didn't make sense...
I always try to take every angle I can to narrow down the possibilities before estimating a job. They could do more to diagnose your problem and they should.
BTW you didn't do a very good job of tracing down the seemingly apparent problem with the white IC wire going to the ICM. If this wire is either completely open or intermittent, it will give the appearance of an opti problem since it is used to trigger the coil.
Actually, I think I did a pretty good job tracking things down--the white wire was fine--no problems with grounds or shorts...
After you checked for AC voltage (you were on the wrong scale for some reason). You should have traced the white wire and ohmed it from end to end.
Actually, the Hayne's manual I have explicitly states switching to AC voltage for just that one test--it must be a misprint...
Did you mention it to the shop? Did they do anything to eliminate it as the cause of the problem?
So while I would unplug the pigtail at the connector on to the side of the intake and check voltages and be good, the harness was swapping the signals into the opti and thus no spark or output from the optispark. I never suspected that such a simple, brand new wiring harness would be wired wrong. That junk harness has cost me the original $38.95 for the part, plus $60 to tow it to the shop, plus 3.5 hours of labor and diagnostic ($353.44) put my total bill at $452.39!
I've emailed the seller and am awaiting a response...
That said, the car starts right up and passed safety and emissions with flying colors...
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Exact diagnosis on invoice
"117049 Run Diag. And Isolation Tests, Charge Battery No System Voltage, Run Isolation Tests, Test Pcm Output And Inputs, All Outputs From Pcm To Dist. Tests Okay, No Output Detected From Dist To Pcm No Low Or High Reference Voltage Signal Present, Test Circuit Continuity From Dist To Pcm, All Circuit Tests Okay, Access Dist. To Test For Cause Of No Signal, Customer Has Replaced Dist. Upon Inspection Detected Connector Harness From Dist To Computer Jumper Harness Ignition Circuit Are All Misswired (backwards) Pull All Pin Connections And Rewire Correctly. Reassemble Vehicle And Verify Proper Operation, Ok. Fill And Bleed Cooling System. Ok. 3.5 74"
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