90 Civic Main Relay and More

Car: 1990 Honda Civic LX, 5-speed, 1.5L SOHC DPFI.

Question: Can anyone explain, or point me to a site that explains, the
exact functions the main relay is responsible for?

Here is the reason why I ask. My main relay is screwed up, because it
will not start when it's hot. I have to reach down and squeeze the crap
out of it while pressing the clutch and turning the key for my engine to
fire. (Yes, I have unbolted the relay from its original position and
have it dangling beneath my dash. Otherwise, I couldn't drive my car
anywhere) Once I do get the car to start, while it does run, it
sputters when idling. (The "rhythm" of the sputter is quite irregular)
The power curve is very erratic. Between 1k-2k RPMs, acceleration is
very sluggish, (even in 1st gear) almost like I have a fouled plug.
(That's not the issue, the plugs and wires are all brand-new) Once I
pass 2k, there is a surge of power, then at 5k, another surge of power.
Kind of a nifty effect, but I know it's not supposed to do that. I
recently replaced my distributor, and the timing is set right in the
middle. (I have no timing light to set it exactly) Regardless of how I
set the timing, the sputtering is still present, so I've pretty much
ruled it out as the cause. I'm using Bosch Platinum "+4" spark plugs,
and Autolite Ignition #86472 plug wires. All engine components and
other parts are stock, with the exception of an air-intake (metal pipe
with cone filter) and a DynoMax muffler with 2¼" exhaust pipe.

Thanks in advance for any info!

Jonathan

 

I can't tell you how many times i've seen the bosch 4 plugs make a
honda run bad.. Use the factory plugs and see what happens.
Chip

 

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Unbolting it was actually a mistake. The vibration from the engine is
what keeps it running when the car gets hot inside. That's why smacking
the dash will often allow the car to start when it otherwise wouldn't
Just unplug the relay, and get a computer geek or handy guy to resolder
it. It runs the fuel pump, and kills it if the engine doesn't run for
x-seconds . . fire safety, mostly, I think.

'Curly'

 

You hadda ask...
http://www.tegger.com/hondafaq/startproblems.html#mainrelay

 

sometimes it amazes me the troubles people will go to rather than just
replace a failing part, $40 and 20 minutes and your worries with the unit
would be over.

 

In addition to the other valuable responses, I urge you to get ahold of a
timing light and reset the timing correctly. The engine will be noticably
funky, and could even suffer detonation damage, if the timing is even 2
degrees off.

Mike

 

If the main relay is same as I had looked at in a newer Civic, the
main relay is how a tiny transistor inside electronic controller turns
on and off power to major engine functions. I noted this newer Civic
would not trip its relay when the car was used in hot weather and after
running for a while. If the transistor is not quite large enough, then
it will not output enough current to trip the relay. Once the relay is
tripped, less current will hold the relay closed. The main relay
would fail to trip often after the car was only shut off for a few
minutes or less - when the transistor was warmest and therefore may
have been outputting less current.

This transistor that drives the main relay is inside the controller -
would be same (marginal) by design.

Unfortunately the car did not remain long enough for me to prove this
analysis by putting an 'amplifier' between that transistor (inside
controller); thereby eliminating the problem. I do know for a fact
that the main relay would not trip during warmer temperatures AND when
the car was running only seconds perviously. After sufficient time for
electronics to cool (anywhere from 5 seconds to less than a minute),
then the main relay would trip - and car would start.

 

i'd be amazed if the relay has been wholly replaced with a semiconductor
device - semicons have a voltage drop across them - acceptible for some
applications, not others. can you cite a reference to the device in
question?

 

Why doncha RESOLDER all the Main Relay cracked solder joints,and ELIMINATE
the main relay as a trouble source?
Then you can check other things if the trouble still persists.

 

When you don't have $40 at your disposal, sometimes you have to make-do.

Jonathan

(Planning to resolder my main relay)

 

Planning on doing just that. I was just wondering if the sputtering
could be caused by timing AND/OR the main relay?

Jonathan

 

The Main Relay is not associated with "sputtering". But then I've never
encountered anyone who has driven around with it unbolted, either.

What you may want to do is to bolt it back in place once the motor is
running, and see if the sputtering is gone.

 

One thing that occurred to me, that I didn't mention, from time to time
I have gotten those "code 16" errors on my ECU while driving on the
interstate although my car still seems to run just fine. I was
wondering if that could have anything to do with the sputtering...
(i.e. Incorrect injector pulse) Anywho, I just finished resoldering my
main relay, so I'll report back tomorrow and let y'all know the results.
Thanx a million for everyone's help!

Jonathan

 

It's possible. See here:
http://www.tegger.com/hondafaq/mainrelayoperation/badmainrelay.html
(the second and the last graphics)

Followups are always nice.

 

"sputtering" could be bad plug wires,bad distributor cap/rotor,maybe
ignition coil breaking down,a bad igniter module.Maybe even a clogged or
sticking fuel injector,which might explain that trouble code you mentioned
in another post.

But you have to eliminate known problems first(MR),and test one thing at a
time.

 

Distributor cap, plugs, and wires are brand-new, less than 3 months old.
I have an almost-new coil and igniter that I suppose I could
replace. (My distributor has been replaced, and my old distributor that
"died" has the almost-new coil and igniter in it. I left the coil and
igniter that came in the used, but working, distributor that's in my car
now)

UPDATE: Resoldering the main relay did indeed fix the starting problem,
but the sputtering is still present. I will admit it seems not to be
quite as bad. I suppose I need to get a timing light...

Thanx again to everyone for all your help!

Jonathan

P.S. There were 4 cracked dry joints that I had to resolder.