symptoms:
1. Turn ignition switch to on - Fuel pump runs (since I replaced it) and lights come on as normal
2. Push Clutch in - buzzing sound from Starter Signal Relay (Denso Part # 056700-8570 - next to the Main Relay)
3. Turn key to position III - typically engine cranks but won’t start
4. If the steps above are completed without hesitation the car will often start right away
5. Once the car is running if the clutch is depressed (activating the clutch switch and the Starter Signal Relay presumably), the car will stall out and die
6. If the car is running and the Starter Signal Relay is removed you can drive it as normal with no issue
I’ve replaced the Main Relay, the Fuel Pump and the Starter Signal Relay and still am experiencing the same problem. The CEL comes on and remains illuminated until the car starts - I’ve jumped the diagnostic connector and it still remains illuminated (until car starts).
The car was driven through some water during flooding here in May which could be a contributing factor. It was running for a month after that so I’m not convinced that contributed.
This one really has me stumped…if anyone has an idea where I might begin checking I’d be grateful!
I assume the purpose of the starter signal relay is to act like a safety switch and supply power to the starter solenoid when the key is set to the START position. If that is so then it seems to me that something else is bridged to the circuit and causing the engine to die when the relay switch is closed and I assume provides power to something that shouldn’t be tied to the circuit. Do you have any wiring diagrams for this?
I do have some wiring diagrams but they relate to the 94 Accord Coupe so I’m not sure they’re 100% correct. I may have to do some more digging on that. I’m not sure what the starter signal relay provides power to…could be the starter solenoid and it also seems like I read that it signals the ECM to allow power to the starter. Since the car will stall when I step on the clutch, I’m guessing it’s somehow shutting off the fuel supply or spark.
The wiring print should be pretty close to the same I would think. What does it show the relay providing power to?
Edit:
I just had another thought. Does the starter turn on if you engage the clutch when you turn the key from the OFF to the RUN position? If so, there is a problem with the ignition switch.
It looks like the clutch interlock switch activates what they call the Starter Cut Relay (which I think is what I’m looking at) which in turn provides power to the starter solenoid. I’m attaching the diagram I’m referencing…this is a M/T…can’t remember if I mentioned that explicitly before.
And, no the starter engages only when the key is turned to the Start position.
Thanks for the diagram. That helps me a lot. Fuse 9 that supplies power to the relay shows that it is supposed to be hot only in the START position. If that is the case I can’t see how the relay could cause a problem.
Edit:
Do you have a meter to test with and know how to use it well? We may need to test the wiring.
So an analysis of that would lead to the conclusion that something is allowing that circuit to be hot when the key is not in the start position, correct? But if that were true, I would expect the car to start with the key in the run position and the clutch pedal depressed, no? Just trying to talk through the possibilities…
Maybe the ignition switch is part of my problem…
Edit:
I can borrow a meter…I’m planning to buy one as well. I can use it but I wouldn’t say I’m an expert…
Your thought process is correct. The starter should run if fuse 9 was hot in the RUN mode. Something is causing trouble in that circuit though and I have another thought. Perhaps there is a ground problem and when the clutch switch is closed it is allowing a voltage to backfeed through the starter cut relay coil. To see if that is so lets try a test. Start the engine and then remove fuse 9. Then with all the other things in place press on the clutch and see if the engine tries to die then. If there is no problem now then clean the grounding connections between the chassis and the battery.
That sounds like a great approach…I’ll see if I can give that a shot tonight and I’ll report back then. Thanks so much for the help!
You’re welcome for the help. I have a hunch that the test will prove out as I can’t see how anything else can be happening with this trouble. I will watch for your response of the test.
I tried to start the car tonight and just couldn’t get it to turn over…in the midst of all that I had the thought that maybe when I replaced the main relay a couple months ago, I got a faulty one and that was causing the buzzing and short in the circuit. So, I swapped it out with the one I had in there before and sure enough, no buzzing. I also held the main relay while the ignition switch was turned on and could feel it click although I still didn’t hear the fuel pump prime.
Finally got the car to start by having my wife pop the clutch while I pushed the car with my truck and we let it run for a while, I took it for a spin around our neighborhood and it did fine shifting through the gears so apparently that main relay I put in was a piece of crap.
Got back to my house and shut the car off. Turned the key to the On position, the relays clicked and I heard the fuel pump prime for 2 seconds, turned the key to start and she fired right up. That’s the first time in a while the fuel pump seemed to prime correctly. I’ll try it in the morning to see but it could be the fuel pump was the issue all along and the other swapping I did caused the other symptoms. Could also be low voltage or something wasn’t kicking the fuel pump to prime very well…I’ll reserve judgment on that until the morning.
I’ll post then what I find…hopefully it’ll start up without any issues.
Glad to hear things are looking up. The main relay might provide voltage to the ECU and some sensors possibly, I’m not that familiar about your model. You might try another relay. Check the voltage after the relay to make sure you are getting the full voltage after the relay contacts.
No start from it this morning…no prime from the fuel pump. I’ll check voltage to it when I have a chance…it’s strange how it seems to prime just fine after the car has been running but when it sits I don’t get any prime. I swapped out the battery with the one in my truck to be sure it wasn’t a lack of voltage there and also cleaned the battery contacts…still no go. I’m wondering if it’s the ECU but it seems like I would have some other issue while the car as running…thoughts?
If the engine is cranking ok then the battery has to be in good shape. I suspect the fuel pump circuit has either a bad wire connection to power or the main relay may be faulty since you seemed to have some success yesterday with it. It would help if you posted the schematic of the fuel pump circuit so I could look it over.
This should show it pretty well…I picked up a multimeter and I’m going to test the Main Relay for continuity to see if I can confirm or rule it out as the problem. I’ll also test voltage to the fuel pump with a jumper wire in place in the main relay wire and if those both pan out I’ll run through a flowchart of testing some things on the ECM from my shop manual.
I suspect that the fuel pump will work ok if you try powering it directly. The drawing you provided shows a blk/grn wire going ‘to starter system’ and tieing to the ECM main relay coil and pin B9 of the ECM. It looks like that is what provides power to the relay coil for the fuel pump. There is also an interesting connection to power through a resistor in the ECM relay that ties to the fuel pump relay. My first check for power would be pin B9 of the ECU to make sure that power was ok in the start mode. Also check the connection point on the relay.
You’re correct about the fuel pump working with direct power…I used a jumper wire in the main relay and tested that and it ran fine. I also took the main relay out and tested for continuity and ran through the flowcharts for testing it and the ECU. The only step in the testing process that seemed to point toward wiring was testing continuity from the A7 pin on the ECU to the GreenBlack wire in the main relay harness - I couldn’t get continuity between those 2 although I did get continuity between the A8 pin and the GreenBlack wire on the main relay and from what I’ve read A8 is shorted to A7 so I would suspect there is a good connection there or I wouldn’t have gotten continuity at all.
I also walked through the steps to analyze why the CEL stays illuminated with the key in the Run position instead of shutting off after 2 seconds and all signs there pointed to a faulty ECU. I may do another round of testing before finding a used ECU from the salvage yard but right now that seems to be the most likely solution.
I’m attaching the flowcharts I used. Let me know if you see anything they may have omitted.
Here are the flowcharts I used for testing the ECU…couldn’t fit them all in one post 
You stated you didn’t have continuity between pin A7 of the ECU and somewhere on the wire harness. If you didn’t check it at the ECU relay you need to do that. Since that wire provides the ground for the relay coil to turn on the fuel pump that connection is critical for the relay to operate. There should be close to zero volts on pin A7 when the pump is supposed to be on.
The CEL light may be on due to a valid fault code. I woundn’t worry about that right now. At least until the engine is running.
I checked continuity between the No. 1 pin on the Main Relay connector and the A7 pin on the ECU. While I didn’t detect any continuity there I did find continuity between the A8 pin on the ECU and the No. 1 pin on the Main Relay. Since there is no wire running into the A8 pin on the ECU I found some other pinout info that said the A8 is shorted to the A7, which would explain getting continuity there. I may do some more checking at the A7 pin to see why the circuit isn’t showing continuity since it’s just a single wire from end to end.
I don’t have the test harness so that makes some of the ecu tests a little bit of guess work. Everything I tested from the main relay side checked out just like it should so it seems to be an issue with the ground from the ECU, the wiring between the ECU and the Main Relay or the ECU itself. I still haven’t opened up the ECU to see if it’s burned up or not. All the ground tests I did came back like they should.
I’m trying to think of how I could use a jumper wire in the ECU connectors to mimic the voltage used to prime the fuel pump. It seems like I could accomplish that by jumping the connection from A25(+), B1(+) and A7(+) to A23(-). I arrived at that because those pins are the ones that go to the main relay and the testing diagrams instruct using A23 as the ground for all of them. I’m attaching another diagram I’m referencing for the main relay. Please let me know if my logic is screwy with this…I’m an electrical testing noob
Edit: I just thought about this some more and if the continuity appears to be between A8 and the pin on the main relay then I should test that for voltage as well as the voltage between A7 and there. Either way I that seems to be the circuit I’m most interested in right now.