View Single Post
  #2  
Old October 8th 17, 12:42 AM posted to rec.autos.tech
Scott Dorsey
external usenet poster
 
Posts: 3,914
Default Why is my 1985 s 10 2.8 engine so hard to start ?

> wrote:
>Ok,i have been searching for an answer to why my truck is so hard to start.=
> I have done everything i know to fix this but no luck yet . I have put a r=
>e-manufactured carburetor on it.I have checked all the vacuum lines,replace=
>d the fuel pump. manual pump. I have a clear fuel filter that look good. I =
>have done a tune up,plugs,wires,cap,pickup module,exc... I have even done a=
> compression test that passes easily. The engine runs good, its just hard t=
>o start. Im stumped !


Fuel, air, spark, timing, and exhaust.

Is the mixture good? Is the choke closing down for starting and then opening
up once the engine warms up a bit? Look at the butterfly and mark where it
sits with a sharpie. If you block it partially with your hand or with masking
tape, will the engine start properly? The fuel mixture needs to be extra rich
for starting. The automatic choke sets it that way, if it's working, which
it often doesn't.

If you put the timing light on it while it's running properly, do the marks
line up? And then when you put the light on when you're trying to start it,
is the timing retarded or do the marks still line up? The timing should
shift severely back for starting and then the vacuum advance move the timing
up once the engine catches. Make sure it's moving the timing, don't spend
your time dicking with the vacuum system unless you verify that it isn't.

Is there a good hot spark when you pull a plug out and watch it? An awful
lot of "carb problems" turn out to be ignition problems.

If you disconnect the exhaust system, will it start right up? A partial
exhaust blockage may produce high back pressure at starting, but then the
blockage may be forced out of the way once the engine starts running.

Don't just replace things, check them out one at a time. Think about what
is different between starting and running... and three big things are the
choke position, the timing advance position, and the exhaust pressure...
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Ads