Intermittent Starting Problem

I have a 1990 Honda Civic. I have been having this odd intermittent starting problem for a year now. It ONLY has difficulty starting when the weather is hot. In the morning, everning/night, and during the fall/winter it starts like a champ, on the first crank every time. But during the hottest parts of the day it just won't. It sounds like it wants to but just doesn't. Now if I wait 30 minutes or so and try again it starts normally.
I have gotten a tune up, changed the fuel filter, air filter, flushed the radiator, and checked the battery but the problem persists in this very predictible way. I read from someone else's post that for many Hondas the main relay is the culprit so last weekend I bought a new main relay from the auto parts store. Much to my dismay, the starting problem persists.

What am I not thinking of?? What else could pose such a specific problem--starting problems during the hottest part of the day only, reliably starts 30 minutes after first attempt, never a problem at night or during winter?

Sounds like the famous Main Relay Problem. Search the forum for more info. Just type in a Main Relay and click search. Oh and welcome to AutomotiveForums. This is the place where you can find almost anything on our civic's :thumbsup:

Actually he states that he already replaced the main relay.
As to why its not starting though, I'm not sure how heat could affect it though.

Yep, as I said I replaced the Main Relay last weekend but I continue to have this problem. Now what I've also noticed is that my power door locks do not work during the day as well but work perfectly fine at night after sunset. I had hitherto ignored it because I assumed they were apples and oranges. The starting problem behaves for all the world like a Main Relay problem but after having replaced it I've had to do some extra thinking....I wonder if it's possible for there to be a POST-relay problem, i.e. there is a circuit or harness which is shared by the power lock and Main Relay. If this can occur it may explain why the problem seems so much like a Main Relay problem. Although possible, I doubt the stars were so misaligned that I bought a defective Main Relay too. LOL. I sure would love to hear what you guys have to contribute about this problem. (Btw, I have already checked all the fuses).

did u check out ur spark plugs? maybe its time for new spark plugs and a new wire set, i had the same starting problem with my old mazda.....only on hot days and i got new spark plugs and a new wire set and everything was all gravy. if that's not the problem maybe ur distributor cap is soiled or something and isnt getting the right contact that it should.....just take it off and clean out the contacts

Already changed the plugs (not the wires), checked the distributor and cleaned the rotor and contacts; also checked the distrubtor cap for cracks/fissures.

Well I'm hitting myself right now. Just discovered that I DID NOT replace the main relay a week ago. I replaced the 'fuel pump relay'. I placed myself at the mercy of the auto store...since I didn't know what the main relay looked like I asked them for one and then found the identical part in my car and swapped them out. If it wasn't for a bit of fortune I may have gone on thinking I replaced the right part. Well ok, I'll keep an eye on the car now and let you guys know if all is well.

call me a wanker but aren't the fuel pump relay and main relay the same thing

thats what I was thinking but I wasnt going to say anything.

Yep, that's what I thought. If you go to autozone.com, under parts click on 'electrical' --> 'relays' --> 'main', it lists two GP-Sorensen relays as the 'Main Relay'. But this is NOT the main relay. This is a Fuel Cut-Off relay--beats me what the exact difference is but it has 4-pins. The Main Relay has 7-pins. It's confusing because they are both beneath the dash to the left of the steering column. The weird thing is they don't even list the real Main Relay anywhere on there!! Obviously the part is miscategorized on autozone's computer system and hense, it led them to give me the wrong part. Man almighty! I'll never walk into my auto parts store with the same blind naivete again! Thank goodness for Google Images which showed me a pic of what the Main Relay looks like and caused the light bulb to go on in my brain....I mean if i didn't bother to persue this further after the fact, would I have ever found out? I could have gone down a very expensive and laborious road, replacing the fuel pump, ignition coil, etc. The moral of the story is that even autoparts stores makes category/inventory errors so keep plugging at it when your suspicion is high.

This is definitely a story for the books!

A picture tells allhttp://honda.hybrids.jp/tech/parts/images/main_relay/main_relay_3.jpg

Exactly!!!

Relay location from Helms http://www.binghamtonlife.com/manual/2gsm/images/91-23-6.jpg

My intermitting starting problem could be that but I'm finding that my "starter relay" gets a tad loose... next page in Helms http://www.binghamtonlife.com/manual/2gsm/images/91-23-7.jpg

The main relay is a honda dealership item, cant get it at parts stores.

I had the same problem and replacing the main relay fixed it. AutoZone and O'Reilly don't have it in their data bases but I walked into a NAPA store with my old relay and the guy didn't even have to look it up - said he sells lots of them.

Actually he states that he already replaced the main relay.

Oops. Slipped by me when I was reading.

I took the other relay back to autozone today...whatever it was. I told them about their error in the computer database and stood by as the guy looked it up, then apologized. Still caused me too much frustration and aggravation but perhaps they'll fix it (though secretly I doubt it cause updating the database seems to be a corporate or higher up decision and I doubt one of those local store guys will make the necessary call).


I left the main relay hanging down below the dash; hopefully, that will keep it cooler.

hey the thing u replaced was is acctually on the fuse box? Because I replaced that a while ago and it seemed to stop doin it and then start up again. They wouldnt take back the relay bc i didnt have a reciept even though i used to work there. Im gonna get the real main relay someday in the future, bc its a pain in the ass and its embarrassing.

Yea, the thing I initially replaced was on the fuse box (it has 4 pins). I have since learned via a posted reply that neither autozone nor o'reilly sells the Main Relay, but NAPA does. I don't have a NAPA close by so I just went to the dealership's parts department and bought one. The problem is with the manufacturing of the main relay itself so even with a new relay the defective construction persists within and it's a matter of time before I'm back in the same position (but hopefully that will be another 100K miles down the road).

NAPA usually carrys stuff like that because most shops (in this area anyway) buy from NAPA, believe its that way nationwide.

Well, in the aftermath of Ivan and Jeanne and who knows what other storms the temperature has been lower since installing the new main relay. I have not had any starting problems since but it's difficult to say I will not since it never has problems during fall/winter/spring. I fear I may have to wait til next summer for the true test to find out if I finally got the culprit.