92-95 Honda Civic No Start - Crank Sensor signal

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1 week 5 days ago #201818 by zcarfix
Troubleshooting a 92-95 Honda Civic no start. Have had a history of no start issues with both no start/no crank and no start/crank. One of those past no starts was a starter motor. After that was replaced, typically charging the battery or a jump-start would solve the problem. This time, the car stalled during the rain. And did re-start but then stalled again right after driving. There was water in the passenger side floor. The car did start on jump starting and was able to be driven home. The difficulty is that it seemed to be an intermittent issue. Sometimes it would start, sometimes it would not. Currently, the car is a no start/ crank. Since the issue seemed like a main relay problem, that was checked. That was not the issue. The coil does pass resistance tests. A new ICM was tried, the car did start. But the car stalled repeatedly on a short test drive, but not initially. Then the car did not start. Again a no start/crank. Then there was no spark and no signal to the fuel injectors. Testing of the distributor parts showed that the coil and igniter ICM were okay since the coil sparks when the signal to the distributor is manually sent by disconnecting the connector and using a test light on the signal wire. This seems to at least isolate the current no spark problem to the signal to the distributor. The Crank Sensor may not be sending a signal to the ECU, or the ECU may not be sending the signal to the distributor. Or the wiring may be faulty. The problem is that I have not had the Honda Test Wire Harness for the ECU connectors to test those individual signals. And also have not had a probe that I can use to back probe the ECU connectors since the DVM probe that I have has the standard thick probes. Are there other alternatives to bypass this signal sent to the distributor to see if the car will start? It looks like I would again need a very thin probe to try to connect to the distributor connector. And what should I do to bypass this signal to try to start the car?

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1 week 5 days ago - 1 week 4 days ago #201820 by relative4
Replied by relative4 on topic 92-95 Honda Civic No Start - Crank Sensor signal
I get a strong impression of corroded grounds or poorly insulated or cracked wiring somewhere. I would carefully inspect all the engine bay grounds and all relevant wiring harnesses.
You can get a set of probes at Harbor Freight or eBay for very cheap.
Last edit: 1 week 4 days ago by relative4.

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1 week 5 days ago #201822 by zcarfix
As part of the troubleshooting, I did go through and visually inspect wires that were easily accessible. And did not notice any being damaged. That does not mean that there isn't a problem with the wiring, which is one possibility. Also, I did disconnect the (-) negative battery lead and then the (+) battery lead and then disconnect the OBD-1 harnesses to the ECU. And then checked the power and grounds to the harness with the ECU disconnected. And I also removed the 10mm bolt to the thermostat housing and cleaned up the ground to it by sanding the wire connector with sandpaper and using some contact cleaner on the bolt. And for good measure, I added an additional ground wire using a 10 gauge stranded wire that I connected to the same bolt and to chassis ground, where the battery terminal grounds to. I did also do a voltage drop test with the ECU disconnected but didn't find anything. Next is to keep the ECU in the loop. Note I did open the ECU and did a visual inspection and it did seem okay. And heard that sometimes the capacitors burn out or wear out and replacing them solves ECU issues, which I have not ruled out.

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1 week 5 days ago #201832 by zcarfix
Did check on Harbor Freight's website. They did have some "stainless steel" probes that look like dental picks, item #61872. Though it only has one straight probe and I'd prefer two. You'd still need alligator clips to connect or an extra hand to hold both. They have 18" Test Leads (alligator clips) #66717 $3.59, which are not high quality and for low voltage which is okay for attaching to a probe but not for checking sparks. And 36" Test Leads #66712 $2.99. This wasn't really what I was looking for. I also checked Ebay and after searching for awhile I did find some items that I might be able to use. Note that it would be more helpful to actually give an item number or exact title of the item in Ebay than to simply say check Harbor Freight or Ebay! Since price and delivery time is important, I am still looking for what I have around the house to use.

Update: Did do a quick "short test" with a test light, and at first thought that there wasn't a short. Then connected the LED test light and it lit. So I went one by one removing fuses and came up with nothing to remove the LED going on. It was not full on, and the icandescent test light barely lit then went dim. So proceeded to do a voltage drop test on each fuse. And I did find one fuse that had a small voltage drop. Removed it for fun and tried to start it. Nope. Crank no start.

Started to go through a troubleshooting flowchart, and took a few measurements of voltage drop on the ECU pins A23 and A24 separately. And noted some more tests that I can do the next day. No conclusion yet.

A distributor base arrived in the mail, and I thought to just plug-n-play it in to see the car starts, pointing to the Crank Sensor in the distributor housing or other sensor in the housing. The distributor didn't fit, as it appears to be the wrong part. So no conclusion there either. While I prefer not to throw parts at this problem, this was $35 including shipping so I purchased it a week ago. Now to have to send it back and possibly get a replacement. I'd prefer to have a way to test the Crank Sensor that is in the Distributor housing so that I can verify that it is the problem. And it would be nice to know what the cause was so that it doesn't happen again. I want the car to run without leaving me stranded. or stalling or having another no start, no crank, or crank-no start.

Aside from that, I want a brand new 2019 car...

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1 week 4 days ago #201833 by relative4
Replied by relative4 on topic 92-95 Honda Civic No Start - Crank Sensor signal

zcarfix wrote: Note that it would be more helpful to actually give an item number or exact title of the item in Ebay than to simply say check Harbor Freight or Ebay!


www.amazon.com/Tool-Aid-23500-Back-Probe/dp/B00G9C3RSU

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1 week 4 days ago #201841 by zcarfix
Thanks for the Amazon link to the back probes. Note that I did also find some other ones on Amazon. In the meanwhile I have been using what I have around the house.

Update: Honda flowcharts are quite funny. They want you to put a known good ECU in to test, then if the symptoms "go away", replace the ECU! That is not really helpful. What would be more helpful is an ECU tester such as an Honda OBD-1 Engine Simulator. Note that I did see this online but it isn't sold anymore, and the item that I had seen online may not necessarily fully test the ECU to show that it is good to drive let alone start your car. And this doesn't solve the problem of finding out what made the ECU go bad in the first place, which it looks like the Honda flowcharts don't fully test. Though testing intermittent problems may not be fully possible.

Still inconclusive after today's flowchart tests. Note that I did already go to the junkyard to search for a replacement ECU but did not find it. Nor did I find the right Honda Main relay (for a spare or for swap-in testing). Junkyards don't have so many of the older Honda cars! They do sell these used online. Which costs more and has a shipping waiting time. Still have some more tests that I can do. If those are still inconclusive then it may be time to toss some parts at it. Or tow it to a Honda mechanic.

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1 week 4 days ago #201842 by relative4
Replied by relative4 on topic 92-95 Honda Civic No Start - Crank Sensor signal
I guess it's not desperate parts swapping if it's the manufacturer's procedure.

Regarding junkyards, you can save a lot of time with car-part.com.

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1 week 2 hours ago #201891 by zcarfix
Update: Did some more tests after taking a couple days off being frustrated with the car. and wondering where my new 2019 car is! There is no fuel pump priming with the Main Relay connected. An after marker Main Relay previously purchased is the same. Both relays buzz out correctly. Had already done the flowchart for testing the main relay and wiring. Jumper the main relay harness and fuel pump primes. Checked the fuel pressure at the service bolt after fuel goes through the fuel filter, getting about 40 psi which is within specification. Although at the lowest end. Did already change the fuel filter to an after market part during this troubleshooting and as more maintenance. Fuel pressure is fine. Did wonder about the fuel pressure regulator, so went to that flowchart test. But it is missing steps, and apparently only works when the car is running. See below, I've quoted the three steps. Decided to test the distributor sensors, to eliminate the crank sensor. Found the flowchart and did some quick resistance measurements. All fine. So, at least for now I conclude that the distributor is okay, the igniter and coil are okay since I had previously got spark by sending the signal manually to the distributor. May still want to get an after market distributor to carry in the trunk. Since I really hated getting stranded. Though at this point, I am leaning heavily towards the ECU being bad. There are still some tests that I can do, namely backprobing the ECU to check for the crank sensor signal being sent or received. And also checking for the signal to turn on the fuel pump during priming.

The Honda Service Manual test for the fuel pressure regulator:
"1. Attach a pressure gauge to the service port of the fuel filter. (40-47 psi) (with the regulator vacuum hose disconnected and clamped)
2. Reconnect the vacuum hose to the pressure regulator.
3. Check that the fuel pressure rises when the vacuum hose from the regulator is disconnected again. If the fuel pressure did not rise, replace the pressure regulator. "
Obviously, it is missing steps. Such as start engine or at least turn ignition key to On-2. And then turn key off. Then start again. So with a no-start car it looks like I'd need a different procedure. But it wouldn't cause the no-start since there was enough fuel pressure to start the car.

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