1991 Honda Civic DX won't start after floor was flooded with rain water.


Asked by Sep 24, 2013 at 12:22 PM about the 1991 Honda Civic DX

Question type: Maintenance & Repair

My daughter's boyfriend left a window open on his 1991 Honda Civic DX. It rained, and the floor flooded.  He had it to Sears, and they said the battery, starter, etc. were OK.  Car cranks but won't turn over.  My brother suggested replacing the ECU, as long as we can get a the correct part number from the casing, and it is pre-programmed from the factory.  Is this worth a try?  It doesn't sound too hard to install.  Help!  He's a poor student.

25 Answers

okay...a corroded MAIN ground connection 1/0 cable to chassis has been compromised...enough current is NOT gettin' thru....wirebrush clean...the lug and the spot where it bolts...one of those wirebrush twirly goodies that goes onto your electric drill works ideal to get it down to a shiny conductive surface...this ground serves the ECU, the Fuel pump, the ignition and all the accessories such as windshield wipers and headlights....YES it is THAT important as point 1-0 on the schematic~

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I would hazard to guess that the battery is older than five (the point at which the thing makes the alternator start cookin' to tryNcharge it back up again) ....so the tin/antimony alloy battery (no LEAD) will degrade ten percent per year~ keep that in mind when you look at the "knock-off" labels on the top of the battery~ ....in short----clean up the MAIN connection....GET an NEW battery...assure the connection to the engine block is solid~

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If this is the model that has the ECM under the passenger floor board them I would say yes to replacing the ECM, just make sure that the floor and carpet are completely dry, moisture is death on electronics, make sure all of the connectors are clean also. Might try a salvage yard for cheap parts, most of them will have a warranty on the part.

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Best Answer

Tennis shoes: We cut away the soaked (and smelly!) carpet on the passenger's side floor, and found a metal plate. Presumably if we take off the nuts, we'll find the ECM. I think we will try replacing the ECM. My brother suggested buying the part form E-bay, but a junkyard might be a better bet first (thanks for the idea). From what I've read, besides the ECM, there's also a TCU for the transmission. I'm wondering if both are compromised??? I guess I'll start with the ECM and see what happens. Judge Roy: We used sand paper on the battery terminals! They seemed clean though. I will ask the car owner the age of the battery. BTW, the headlights did work. Thank you both.

kudos to my DAD who pioneered this NON-LEAD technology~

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have never in my days seen a BAD ECU....not good power or ground...YES, but isn't the fault of the ECU~they are built tough to take varying voltages and available amperages and still keep your car's engine doin what it should...I often reflect on radial Airplane engines what have NO semiconductors, yet a Magneto that creates the spark on time....have we stepped backwards...collectively with over-engineering things....the judge begins to wonder~


I just had a ECU go bad on 2002 Jeep, the built in voltage regulator went full charge in the ECM , so they do just fail. I agree about Magneto ignition system, they were very reliable but can't be computer controlled for todays requirements, but you still see then a the drag races usually one for each cylinder head.


Wow, you guys are going way over my head. Isn't Magneto one of the X-Men? All kidding aside, I took the ECU out, and I'm ordering one from someone on Ebay. The type is 37820-PM5-A80. Someone from a Honda dealer told me that it wouldn't need to be programmed. Under the ECU, I found a piece of rubber-covered foam. The foam was soaked through, so I had to cut the whole thing out. I put it outside to dry. Would it be OK to re-use it if it dries out? I'm not sure what the rubber and foam are for, but I don't want to assume they're for nothing. Thanks again for your help.

1 out of 1 people think this is helpful.

the foam and rubber are there so that any high-voltage what may touch the chassis will not affect the delicate electronics....keep the insulation there...we don't want any "sparks" to be seen by the connections to the ECU~

actually a Magneto is THE method for issuing a spark on an airplane motor, because it DOES NOT have any semi-conductors in it but is just wires passing before a magnet issuing the spark...what ignition system could be easier?~ they got it right with airplane propeller motors, but not any more?


Hey operator 13, thanks for both your responses. I will try to get the rubber/foam piece dried out for reuse. I didn't quite understand what you said about the magneto; curiosity sent me to Wikipedia. Very interesting! What did you mean by "not anymore"? Magnetos are still used in aircraft...I know this is off-topic!

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glad you are interested...at the airplane museum in Wisconsin there was an interactive magneto display where a person could turn the prop and watch the sparks...NO 'lectronics~ that's what operator_13 (my alter ego) was tryin' to tell you~


Judge, I got it! Thanks! If I'm ever in Wisconsin.... BTW, the battery for the Civic was purchased this year. We received the ECU in the mail today; will try it tomorrow.

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it's in Oshkosh...you remember oshkosh-bgosh?~


Op 13: I can remember Oshkosh! Thanks! Well, we connected the new ECU today, and it made no difference. The engine cranked and cranked (we were jumping the battery), and would not turn over. Just as it had been before. I don't know what else to do.

2 out of 2 people think this is helpful.

lets get down to basics...air, fuel, spark....timing....when you put it to the "on" position do you hear the fuel pump turning? the fuel rail energizing? Is there any spark what you can tell? is it sparkin? if you had a little kid put the wire on his tongue would he survive or get a jolt and hit his head? sounds like you've got NO SPARK...am I correct?

the ground connection to the "brain box"....the ECU may not have been installed properly....on a gut intuition am going to have to say this COULD BE the case~....only reason is because you were just learning of the delicate nature of these isolated electronics...and a ground wire may have been overlooked...(or connector)~


Do the diagnostic lights on the ECM turn on when you turn the key to on? If not the you have missed a connection or ground somewhere as 13 stated. If they do then go back to the basics as 13 said, you may have just blown a fuse.

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from a flood condition tennisshoes? gotta be something devious and full of corrosion~


I will try reconnecting the ECU, check if the accessories work, and check the fuses. Thanks! I probably won't get a chance to do it till next weekend. The car was towed from Sears (they couldn't find the problem) to an electrical specialty place. The owner wanted $375 to diagnosis the problem, which seemed ridiculous to me. The car is sitting in his parking lot now. With work and school schedules, it will probably be next weekend when we can have a go at it again. Thanks for all your suggestions.


After crying to my brother about this issue, he took pity on me and made the 3-hour drive to my house Saturday night to look at the car. The next day was Sunday and rainy We drove to the the electrical specialty shop where the car had been towed. As soon as my brother heard the engine crank (while the battery was being jumped), he said the crank didn't sound strong enough for the engine to turn over. We decided to get the one-year-old knock-off battery tested. Funny thing about the terminal connections to the battery -- the positive connection was very loose. It couldn't be tightened enough to secure it to the post. Anyway, the nice fellow at AutoZone said that the battery was beyond hope, so I bought a new one. We put the new battery in, and while we could crank without a jump, the engine still wouldn't turn over. While my brother was removing the distributor cap, the owner of the electrical specialty shop where the car had been towed, saw my brother and me working in the parking lot. He told us that we weren't allowed to work on the car on his property, citing insurance reasons, and, we'd better either turn over the title to him on Monday (he had promised my daughter's boyfriend $200 for the car) or get it off his property. Otherwise, he would have it impounded and towed...blah, blah, blah. He'd heard plenty of sob stories, he said, and he wasn't interested in ours. Gone are the days, he said, when you could get Uncle Charlie to fix your car. (I pointed out that this was Uncle Peter, but I don't think he was listening.) Peter got the cap off, and scraped the carbon off something or other with my nail file. I promised the owner I would relay his message about the title to my daughter's boyfriend. He left, us, probably reluctantly, to finish up. (I understood his position. Didn't like it, but understood it.) Peter put the distributor cap back on, Crank, crank, crank...and the closest sound we had gotten to a turnover, but still no luck. We decided to go back to AutoZone and get a spark plug tester. Half way there, I reconsidered. It was late, rainy and a Sunday night. There seemed no point in pursuing this any further. Much as I hate to give up, it seemed there was not much choice. Back to the car we went. Well, I thought, why not give it one more try. Crank, crank, crank, crank, VROOOM, the engine roared to life!! Wow, we couldn't believe it. My brother drove the car back to my house, and guess what? He said the brakes are really bad! Geez, I sure won't let my daughter drive in his car until the brakes are fixed. Now he's thinking he should buy another thousand dollar car, but hey, it doesn't hurt to get an estimate on a brake repair. Peter says the pedal practically goes down to the floor, and the car is very slow to stop. Sigh...but, hey, it runs! Thanks to everyone for their help. Between the new battery and the ECU, your advice really helped me out, plus I definitely learned a lot.

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Yay...these things help sometimes~!

Did you know that a simple can of WD-40 will dry out the ignition system with a spray over the top of things high-voltage electrical (like the coil and distributor)~ did you look for carbon traces on the inside of the distributor cap?

1 out of 1 people think this is helpful.

Yes, my brother scraped carbon off the inside of the distributor cap. Thanks for the WD-40 tip, and all your help. I sincerely appreciate it! Now to find out what's going on with the brakes...! Hopefully they just need to be bled.

Nellebear---those distributor caps are like a couple of bucks only...the only places to "scrape" would be the contact points and the little springy button in the middle....like he shouldn't be scraping anything else it could be damaged...the little springy button in the middle gets lost, but the thing will still work...sorta, so throw that bazooba away and get a new cap~....as far as the brakes go....Air got into the brake system? causing a squishy pedal? either the seals on the master cylinder are okay (in which case there is no need to ADD any brake fluid) or there is a brake fluid leak in one of the hoses or calipers...did you check to see how much "meat" is left on the brake pads? 1/8? 10mm or none left....the extension of the caliper cylinders takes some of the brake fluid (displacement) but should not leak any~

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