90 civic will not start when hot

my son has a 90 civic that will not start when it is hot outside or when the engine is hot. once it starts it runs fine. some people say fuel pump, but i think that it wouldn't run right after it started if that was the
problem. I saw another post about a main relay being a problem but i'm not familiar with that, either what it does, where it is located, or what to do about it. is this a coomon problem with that breed of civics and can anyone tell me where to start looking to fix this problem
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I forgot to mention that it cranks just fine, it just won't turn over. Almost like it is out of gas, but that is not the problem. sometimes starting fluid gets it running. sometimes it does not. any ideas?
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jerry250d wrote:

It's most likely the main relay. It controls current flow to the fuel pump and the fuel injectors. It can be found under the dash on the far left side just above and to the left of the coin tray. It's a common problem. You can read more about on Tegger's FAQ, http://www.tegger.com/hondafaq/startproblems.html#mainrelay . In addition to the problems with the cracked solder joints that Tegger describes, the relays inside the unit tend to get pitted like an old set of points. If you're good with electronics, you can try resoldering it (but that won't help if you have the pitting problem). Or, you can just get a new one from the Honda dealer. I think they run around $40 or so.
Eric
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I just had the main relay replaced on my 93 Accord. Are the new relays subject to the same failure as the one they are replacing or has Mitsuba fixed their manufacturing process? Thanks, Rich Eric wrote:

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I'd bet the vulnerability is still there. The basic problem is they mount heavy items (the relays themselves) on circuit boards using the solder for the mechanical support, then mount the whole thing to the car chassis so the road and engine vibration can fatigue the solder. A lot of mfrs do it because the problem rarely shows up within the warranty period.
Mike
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Michael Pardee wrote:

Hmmm, wouldn't a potential solution be to soft mount it to the chassis with some rubber bushings?
Eric
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I'd sure think so. Even if it only softened the vibrations it could make a big difference.
Mike
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Michael Pardee wrote:

Or do what I did, leave it dangling under the dash...it works fine, and it's readily accessible if it ever fails again. ;-)
Jonathan
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Leave it dangling to short out something,or to flex or abrade the wires for another type of failure. Or a under-dash fire.
Bolt it back down after resoldering,and it will be fine.Probably last longer than the rest of the car.
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Jim Yanik
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It souinds plausible, but too simple. With all the development Honda and other makers do every minute of every working day, why wouldn't they have already done this themselves? It would just be a rubber grommet.
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TeGGeR

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Just a guess, but the relays probably last long enough to suit them. I have to remind myself the MY 2005 is almost over, and when we see a '95 with a bad main relay it is a ten year old car. Jim has a point - resolder and remount it, and probably get another decade or more life out of it. I remember when it was cockeyed optimism to expect 15 years out of an engine, so maybe I shouldn't complain.
Mike
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Michael Pardee wrote:

i don't think it's the g's from the road that are the deal - there's more shock from the contacts opening & closing. much more likely thermal fatigue from the relay heating up & cooling down. those things run much too hot imo. but ventilating them leaves them open to crud accumulation, so you can't win. best design would be something with mechanical [screw] mountings for the relay chassis, not the soldered ones like present, a thermal conduction path from the relay chassis to the external mounting, and restrict solder only to the electricals. but that would likely cost double the current arrangement, so given that this car is 15 years old, and a new relay will likely last another 15, it's not /that/ big a deal to buy a new one & forget about it.
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And/or mechanical stress from the relay action.(relay frame and contacts flexing under operation,along with thermal stress)

Exactly.
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Good points, all of them. I hadn't considered the heat aspect.
Mike
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Extremely common http://www.tegger.com/hondafaq/startproblems.html#mainrelay
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Took the words right out of my mouth!
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jerry250d wrote:

Let me guess: The starter turns the engine properly, but it seems like it's not getting any fuel. And if you keep the key turned long enough, the Check Engine light will come on. Am I right? If so, the problem is definitely the main relay, which these other guys have been pointing you to. (I added this because I own a 1990 Civic myself and am very familiar with this problem) If you own and are handy with a soldering iron, you can fix this problem yourself for free. See Tegger's FAQ. Also, read through the thread I posted, subject is "90 Civic Main Relay and More"
Good Luck!
Jonathan
P.S. You can bet on having to replace/fix the main relay every 2 years or so if you don't buy a brand-new one. I've had my Civic since 2001 and I've just now fixed the main relay problem for the 3rd time. However, I admit the first two times I just bought another used one cheap from a junkyard. ;-)
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I resoldered my 94 Integra MR only once in 4 years.Not a single problem since. And I live in Florida,a sunny,hot climate.
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Jim Yanik wrote:

Oh, heh, I meant this is the first time I've resoldered it, too. The last 2 times I just bought used ones and they only lasted two years. Good to know that the resoldering job will last longer. Saves $money$!
;-)
Jonathan
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