DSMAddicted

Gentlemen,
Trying to troubleshoot a '95 DX Hatch.

Car won't start when it's been raining. When this happens, we are unable to hear the fuel pump prime when turning the key.

We put a good quality new distributor a few months ago (Richporter Technology) and we reflowed all solder points on the main relay, so I am ruling those out.

Doing the paperclip trick doesn't seem to yield any CEL code.

Any help will be immensely appreciated.

TIA!

HondaPartsHero

Does the check engine light come on for two seconds then turn off? If it stays on then repair or replace your main relay.

MisereNoire

Also check your negative battery cable to frame grounding point for water infiltration, this happened to me once before. as soon as i dried out the connection and retightened the cable bolt down, it started no problem. Ended up replacing my cables and grounding points with stuff I built...havent had a single problem with it since.

delsolintegra

Probably the ECU. Moisture and humidity effect the capacitors in the fuel pump priming circuit causing the fuel pump not to come on for 2 seconds when you turn the key to second position.

On a dry day the ECU may work, for a while. Eventually the capacitors totally fail.

Borrow a known good ECU to test.

You can visually check the circuit board and look for bubbled or burnt capacitors but it's not always obvious to the eye.

Capacitor C14 is the big one but some of the others could also be the problem.

DSMAddicted

Quality contributions guys, thank you for your time.

Replies inline:

Hard to tell, since we've had the paperclip in the connector (CEL code blinking method) for months, trying to catch a code. I removed it yesterday, will look for this if the issue returns (see below). Weird thing is, car has started perfectly fine on the hottest days this past summer (one of the things that bad relay solder joints dislike) - provided it hadn't been raining.

Excellent advice, I can't believe I had not thought about it before, seeing how I dealt with "dirty ground"-related issues on past cars. I know for a fact all grounds are in place, but it's a great time to clean the surfaces.

Bingo. You know... I had not mentioned the ECU because I didn't want to clutter the initial post, but I actually wound up replacing all the caps last night minutes after posting this thread. I inspected the ECU several months ago and none of the caps appeared to be swollen, but upon very close inspection some seemed to have leaked a tiny bit, very difficult to tell. So we ordered a capacitor kit from YellowUp on eBay back in June and sat on it until now. Had some trouble reflowing the old caps for removal (I suspect a mixture of temperature and non-optimal soldering tip) so I am not at all proud of the cleanliness of my work, but I got all of them replaced:



Car started right up, but all that means is that I didn't mess up anything major; we'll have to check when we get solid rain again.
I think we'll clean the negative contacts tomorrow and keep our fingers crossed.

Thanks for the advice, will report back.

NotARaCist

iTrader: (1)

For what it's worth, the solder reflow quality probably doesn't have anything to do with your abilities or hardware. That solder is 20 years old. It's seen better days. What should be done with work like that is de-soldering the connections, and flowing fresh solder.

Former User

Why not resolder the main relay while you're at it?

DSMAddicted

True, but I couldn't find my roll of wick and I know I could have used it, along with a smaller soldering tip.
But so far so good man, keeping my fingers crossed.

I did, several months ago. Main relay seems to be performing solidly.

tony_2018

When working with electronic circuit boards I always have a magnifying glass.

DSMAddicted

Agreed. Wish I had one last week.

UPDATE: Car is still displaying the issue.

Just to recap, this is what's been done already:

• Reflowed main relay solder points
• Replaced ECU caps
• Cleaned battery contacts and ground from battery to chassis
• New Richporter Technology distributor
• Freshly rebuilt starter (forgot to mention this earlier)

Car is still having trouble starting with high humidity/rain. Fuel pump won't prime, car turns but doesn't start.

After a few minutes of waiting in the car and switching the ignition key back and forth to the ON position, eventually the fuel pump will prime and car starts right up.
^^^ none of this happens when humidity is not high or weather is dry (hasn't rained) ^^^


Once car is started, she drives perfectly well.

Any insight will be immensely appreciated. TIA!

eghatch9295

iTrader: (1)

time to test your ignition switch and your thermostat ground for corroded wires. ive stripped the insulation back on them to find 6 inches of green powder, never good.

tony_2018

Time to start checking for any holes where humidity can travel through.

delsolintegra

I went with a replacement ECU from a junkyard for about $125.

I don't trust my soldering skills and I would probably cause more damage than I cure.

Also when the caps go bad they may damage some other part of the circuit board. I think what you tried to do with replacing the caps was well worth the shot.

ECU experts like phearable could probably figure it out or probably already know the solution. There was another member from Puerto Rico who said he even had the schematics for the ECU but the circuit board is over 20 years old and was probably never meant to last this long.

I'd just get a replacement ECU and play with the old one if you want. If you fix it you'll have a spare.

MisereNoire

2 things come to mind, one of them covered by eghatch9295...the other would be looking for moisture on/under/by the carpet where your ecu is bracketed in. if water is infiltrating on the passenger side of the firewall/dash/pillar, the buildup of moisture could cause condensation to build up in the ecu harness (and water reaching the pins in the connectors could cause problems).

That being said, i would tend to agree with eghatch9295 that you need to carefully inspect your ignition switch.

tony_2018

its cool, but fyi circuit boards are repairable. You just have to be able to trace, and fix the path. Time consuming but my skills repairing circuits did get better. Unfortunately the tv repair shop i had worked for back then got flooded out, and my boss finally decided to retire ( well deserved one too ). I really wish he had handed it down to me, but oh well. The equipment were all damaged and so were all the service manuals.

1993Civichatch

Hello everyone - first post.
i have this EXACT issue.
Was this issue ever resolved ?
I see a good conversation going, but then it just stops with the post I attached above.
is there another page or two that is hidden ?
- thanks
1993 Civic Dx hatch bone stock.
was stolen and had the steering column cut up.
Steering wheel and ignition switch wiring replaced from another EG hatch.
HOWEVER, the problem was there before the car was stolen ( so that seems to rule out the ignition switch, unless the donor car had the same issue. )

spAdam

iTrader: (1)

Yes, this is most likely a capacitor issue in the ecu.

1993Civichatch

Thank you, but the ECU was replaced with the same issue.
😕
I might have to buy another ECU, since this one was "refurbished".
This is getting expensive.

PapaBen

Not a ECU capacitor issue in my case.

PapaBen

I have same issue as a few others on this thread. I only have fuel pump priming issues on cool / rainy days. Today, I narrowed it down to Pin 8 on the Main Relay, which should go low to activate the fuel pump relay. What I observed is Pin 8 is staying high but after waiting with the ignition switch on it will go low and run the pump normal. It appears to be related to the ECU, but I am not convinced it is the capacitors. I replaced all the capacitors in the ECU and although the symptoms seemed to improve, I am back at square one with determining what is the issue. I don't know what the whole startup sequence/logic is for the ECU, but I suspect there is an input to the ECU not reaching a logic state needed prior to priming fuel.
I am confident that these ARE NOT the causes with my particular startup issue and this is supported by others on the thread which have swapped ECUs, reflowed solder joints, replaced Main Relay, etc.:
Main Relay
ECU capacitors
Ignition Switch

I also don't expect that the issue is moisture intrusion to the ECU since eventually the prime will occur and then immediately I can repeat the whole scenario.
I am looking for a specific reason why Pin 8 on the Main Relay (from the ECU) is staying high. All other grounds/voltages, etc. appear to be as expected. For troubleshooting, I don't want to force a ground on Pin 8 as I am concerned this could damage the ECU.

1993Civichatch

I seem to have fixed the issue after the replacing the ECU.( crosses fingers ! ) This is the third one in 5 years.
However, in my long journey of trying to pinpoint the problem, I wanted to share two things that helped me the most.
The first being a test of the main relay.
If you turn the key to the first click where you see the dash lights ( but not have the car crank ) you should be able to hear a click from the main relay. If you hold the main relay while this happens, you will be able to FEEL the click. ( I just gently squeeze it with two fingers. No need to fully remive it even ) Be careful not to touch the metal parts !
This is a sign that it is working correctly.
The second thing I found most helpful was this excellent test here : https://troubleshootmyvehicle.com/ho...e-main-relay-3
Good luck, and let us know if this helps !

PapaBen

UPDATE:
Traced wire back to ECU pin A7 (internally connected to A8?). Pin A7 behavior is the same as Pin 8 on the Main Relay, so I am also ruling out that Pin 8 wiring to the ECU. Still looking for what triggers ECU pin A7 (Main Relay Pin 8) to go low. Guess this could point to a grounding issue somewhere?

Can only troubleshoot this during failures. Currently, all is back to normal. I guess we'll wait for another rainy day!

PapaBen

Thanks for the reply, but I've ruled out the Main Relay and I forgot to mention it is not the fuel pump either. It is definitely centered around the ECU pin A7 not going low during the startup sequence. I watched it for several cycles and most of the time if I am patient, A7 will go low and all is well...prime occurs and car will start. All else appears to be normal and expected. Waiting for the next failure to further investigate. I quickly checked the link you sent and it covers most of the more common issues that I have already ruled out, but I'll give it another go when the failure occurs again. I still think there is a logic input/signal to the ECU that is not reaching a required state or an intermittent ground.

1993Civichatch

I hated waiting on a humid day to see if the car would start or not.
This sounds silly, but perhaps you could force the test by leaving a damp towel on your dash ( If the sun is out and it gets hot in the car, you would get lots of humidity as it evaporates. )
If you get back in the car and see lots of condensation from the towel on the glass, but the car still cranks, that might point to a ground issue in the engine bay.
The main ground I found that people have issues with is the one that ( if I remember right ) is connected near the distributor )
I would just pull that ground anyway and clean it an retighten just to be sure.

PapaBen

Actually, not silly at all. I was considering hosing down the car tomorrow and giving it another go. Thanks for the tip on the ground near the distributor. I saw mentioned several times about thermostat connections and grounds. Not sure how they are related but I'm assuming the ECU is going through a "pre-launch checkup" before giving the "go" to prime.