Hi, want to help my daughter with her 94 Accord. I think I am well versed in mechanics an electronics, but I cannot make any sense of this " doesn't start in hot weather issue" There are videos and tons of blogs all over the net, but none of them make much sense or explain the problem, because I like to understand the what and the why.

Car runs great year round. summer is a nightmare when daytime temps get up there 90+. This is not a battery issue, it appears to be something electrical. runs well in hot weather, goes where she wants performs well. Go out in the cool evening, drive to a movie, come back, starts fine. Hot just does it. She drives to work an at the end of the day of sitting, even in a shady spot beneath the trees , tries to start it. The key on turns on the pump, its easy to hear it for a few seconds. It cranks over but will not fire. Does no spit, or give any indication that it is going to fire she has spark, and I do not know a simple way to tell if she has fuel. Wait about half and hour to and hour and it fires right up and runs like a honda. no more problems, until the next day, when work is done and its time to go home.

All over th web, I read its the' main relay' and it fails from the heat. Well, a relay won't fail from warm weather, and I wish someone would make up their mind and explain why the main relay is called the fuel pump relay. :-) I will buy her the parts she needs, but there is no indication of which part is failing. In fact, the part is called two different names. I am confused.

Me? I am disabled and cannot climb under to replace this magical relay, so all I can do is talk her through it. relays go into sockets, so why does everyone talk about unwriting it and needing soldering?

I can't fix the problem if I don't know what it is, so would someone in the know explain the two different relays. Part stores list them as different numbers. Weird. I figure Honda experts have dealt with this before, so I am hoping someone can clarify the problem and expand on the real solution.

The gas cap is removed to relieve pressure, and it does no help. At the moment, she even drives without the cap on. my apologies to the environment, but its only until we solve this :-) As all who work on cars know, the toughest thing is intermittent. issues , hard to replicate.Tough to know when its solved till it bites back next week.


Folks say "open the doors and 'cool' the interior'" In a way, this is part of what she does, getting in and out, trying, failing, walking way, waiting, getting back in, trying, lather, rinse, repeat..

So Today I will be getting her a 12v fan to just blow around beneath the dash and move the hot air out after work, and if that helps. a can of freeze mist from my electronics work bench to spray on the relay, is up next but everyone who explains where the relay is located, does it poorly and never mentions which relay it is. Its not easily found or hit by the spray.

Near as I can tell, from searches, this is HUGE problem with accords and I would really like to know what the word is among those who work with them. Heat? no usually killer of relays. replace the relay? Which one? Plenty of 94Honda Accords on the road, so I am assuming someone knows the secret and I have just not found that person or that source

I just want my daughter to not have to fear over getting home at the end of the day and I sure don't want to pay a dealer to fix it :-)

Help? Please?

John, on behalf of Melanie ;-)

 

Operation: The main relay, actually contains two individual relays.
One relay is energized whenever the ignition is on, and it supplies the battery voltage to the ECM power to the injectors, and power to the second relay.
The second relay is energized for 2 seconds when the ignition is switched on before starting, and when the engine is running, to supply power to the fuel pump.

 

Thank you for clarifying that Jeff.. Since its audibly apparent that the pump is turning on for several seconds. I guess its a safe bet that the fuel pump relay is functioning? That leaves, as you explained it, the 'main' relay to look at as not powering up the ECM an the injectors? I do not wish to impose with lots of inane questions, but so much contradictory information shows up on a search, is this relay just a pull it out and plug in the new one device??? some imply it requires soldering and cutting wires, which my experience tells me is incorrect. I will spring for a main relay if she can just get under and put it in. mostly, I am stuck on heat making a relay fail to function, but others are wiser than I am ;-)

If the fuel pump turns on, audibly, I guess its the main relay so perhaps I need to verify that the ECU is getting power and the injectors are indeed being pulsed? I can check this how?

So grateful for any advice and thankful for your time and efforts.

John

 

here is an OE part number for ya. 39400SV4003

gotta jam now, try to get back to you later today.

 

The common failure of those main relays is cracked solder joints on the printed circuit board inside the relay case. So many people fix them instead of buying a new relay.

Once the relay is out you can pop open it's case & re-melt the joints on the board. Or... lots of people are not comfortable with that kind of repair so they buy new relays.

Does the pump run for 2 seconds even on the occasions when it doesn't start?? Often, the relay fails when the interior of the car is hot, then you open the doors & windows, call for help, hang out for awhile, THEN the interior has cooled down and the engine starts right up...

So if it's not the main relay, then you're back to figuring out lack-of-fuel vs. lack-of-spark.

 

A can of freeze spray from your electronics bench might not be the fix. That might over-cool and open up the cracked solder again.