Why is my 1985 s 10 2.8 engine so hard to start ?

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 !
Reply to
ralphenglehart29
wrote:
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
Reply to
Scott Dorsey
Thanks Scott, i have done all you have suggested. I am somewhat mechanically inclined,i fix all my own issues, but this has me stumped !
Reply to
ralphenglehart29
Thanks Scott, i have done all you have suggested. I am somewhat mechanically inclined,i fix all my own issues, but this has me stumped !
Reply to
ralphenglehart29
I've had a starter cause hard starting. Running too slow to get good starting compression. My celebrity 2.8 was injected and a bad fuel pump caused long cranking. But on my Lumina 3.1 it was the starter causing it. It failed after a few weeks of hard starting/slow cranking.
Reply to
Vic Smith
Everything that Scott said was spot-on accurate. With the engine cold, did you look down the carb with the choke open and work the throttle several times to see if you get a solid stream of gas yet? Let us know... Ben
Reply to
ben91932
Nobody seems to have asked the pertinent question;
Is it hard to start *hot and/or cold*???
It makes a big difference as to where you start and direct your diagnosis
Reply to
Xeno
You mentioned 'rebuilt carb'.
I don't know and I don't know your vehicle but rebuilt carburetors nowadays can have the wrong aperture(s) in the venturi cluster. Rebuilders seem not so diligent about matching these for each application (many port sizes in the same part blank get mixed after cleaning and before assembly). Tracking down the actual spec and wire-gauge measurement are tedious but if you've eliminated all else, compare that to your original. Drove me nuts until I checked it and swapped in the original.
Reply to
AMuzi
On Thu, 5 Oct 2017 22:28:26 -0700 (PDT), snipped-for-privacy@gmail.com wrote:
Is it always hard to start, or just after it's been sitting, like overnight?
Reply to
Bill Vanek
rt. I have done everything i know to fix this but no luck yet . I have put a re-manufactured carburetor on it.I have checked all the vacuum lines,repl aced 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 don e a compression test that passes easily. The engine runs good, its just har d to start. Im stumped !
Reply to
RalphD66
rt. I have done everything i know to fix this but no luck yet . I have put a re-manufactured carburetor on it.I have checked all the vacuum lines,repl aced 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 don e a compression test that passes easily. The engine runs good, its just har d to start. Im stumped !
It hardest to start after sitting overnight, but its still a little hard to start after its been running.
Reply to
RalphD66
I think others have already mentioned the obvious, so try a couple of other things. In the morning, make sure there is still fuel in the float bowl. If not, there might be an internal leak (well plugs). Also, check for fuel continuing to drip into the intake - it might have a bad needle and seat.
Finally, this is the tough one. There is an issue called "coking" on some vehicles. Carbon builds up in the intake near the ports, and/or on the intake valves. That carbon - the coking - absorbs fuel vapor when you are trying to start the engine, and the result is that the engine is too lean to start easily. The main characteristic is that it is much, much worse when cold. The fix is obvious if it is a buildup on the valves, but if it's in the intake, that's another issue. Good luck with that. And I don't know of a proper diagnosis for this. It's more like a process of elimination, and that's all that's left.
I also found this discussion on Google, coking is one of the mentions:
formatting link
Reply to
Bill Vanek
On Fri, 13 Oct 2017 21:25:03 -0700, Bill Vanek wrote:
I forgot to mentions that another obvious symptom of this is a severe hesitation until it warms up. That could also be the accelerator pump, but I'm sure others have mentioned that.
Reply to
Bill Vanek
start. I have done everything i know to fix this but no luck yet . I have put a re-manufactured carburetor on it.I have checked all the vacuum lines, replaced the fuel pump. manual pump. I have a clear fuel filter that look g ood. 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 to start. Im stumped !
d to start after its been running.
There is no hesitation at all. the engine runs great after it starts.
Reply to
RalphD66
Then it's not coking. If you have a float gauge, check the level while it's running. Leave the air cleaner off, and let it sit overnight, and check the float level in the morning before you try to start it. If the float is bottomed out in the bowl, you have a leak in the float bowl, and that's your problem.
And to be honest, that doesn't seem all that likely. So let's get one thing straight, what do you mean by "hard starting"? Does it crank properly, or is it cranking slowly? Does the car start right up and then stall repeatedly? Or does it simply crank at proper speed without starting from the very beginning, and then finally start after extended cranking? And when it does start, is there black smoke, and rough running?
Reply to
Bill Vanek
to start. I have done everything i know to fix this but no luck yet . I hav e put a re-manufactured carburetor on it.I have checked all the vacuum line s,replaced 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 ev en done a compression test that passes easily. The engine runs good, its ju st hard to start. Im stumped !
ard to start after its been running.
It's your electric choke on the carburetor. Look for the thermostat housing on the side of the carb and adjust it.
Reply to
dsi1
Is coking really an issue with modern engines and fuels?
I remember my father talked about taking the car to the mechanic every spring to pull the heads and scrape everything down with a chisel, back when HE was a kid.
Shouldn't be TOO hard to clean the intake.... but the original poster has had the carb off and should have seen if it was gunked up in there. --scott
Reply to
Scott Dorsey

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