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New Q-jet Hard To Start -- Update From SMI

nvrenuf

nvrenuf

Holy crap, it's running!
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I have a freshly reman'd q-jet built by SMI. I have driven it and it runs good but I've noticed that when it sits for a long time (couple of weeks or more) it is extremely difficult to start. The motor will spin over but never actually start, like it's out of gas. If I pour a small amount of gas into the carb it will fire and run for 3-4 seconds then shut off.

I have an electric fuel pump (with return) and my pressure gauge shows ~6 psi with key on and/or running.

The battery is fully charged with 12.6x volts.

It's an electric choke carb, what's the proper starting procedure? Pat the pedal before starting or no? Maybe I'm doing it wrong.

Suggestions? :ears:
 
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Sitting a couple of weeks the fuel is evaporating. You need to get the fuel bowl filled first then give the pedal a few taps. It sounds like you are trying to start it like it is fuel injected. This old iron likes little fuel before firing.
 
I usually turn the key on and wait 15-20 seconds for the system to build pressure and prime. I've always run a carb but this is my first with a choke so I was wondering if my starting procedure was correct or if I was "confusing" the choke by stroking the pedal a couple of time.

Between waiting for the electric pump to build pressure and the electric choke I just don't understand why it's hard to start. :dunno:
 
It should fire up within a few seconds,provided you stepped on the gas a few times so the choke can close and set the fast idle speed--especially with the electric fuel pump...mechanical one might have allowed some fuel to bleed back into the lines and require a slightly longer cranking period before starting..
Letting it spin over some before firing helps oil pressure to build up before it runs too,which isn't a bad thing,really..

Your sure the choke closes fully when stone cold,and the pull off is opening it slightly after it starts?..

If the carb seems to need "priming" by adding gas after sitting,it could be the well plugs are leaking,or maybe the bowl has an internal "leak"...but ethanol gas does dissapear pretty fast if left out to the air,it could be its simply evaporating due to the heat where you are..

I've yet to see a carbed engine that "likes" ethanol,whether it be on a small engine or a V8...they simply dont run as well with it compared to the leaded fuel they were designed for..some guys I know with antiques are adding Marvel Mystery Oil or 2 stroke oil to their gas in order to add some upper cylinder lube to the engine,it can also slow down the rate the gas evaporates and eventually breaks down into shellac or varnish..
 
diesel4me said:
Your sure the choke closes fully when stone cold,and the pull off is opening it slightly after it starts?..
Click to expand...

I'm not sure about this so I'll double check. Like I said, this is my first carb with a choke.

I know the well plugs are epoxied, I saw them when it came back from the builder.

I never did get it to run yesterday, I messed with it for about 10 minutes and finally gave up. I only got it to start a few seconds by pouring fuel in. I an on replacing the plugs next weekend in case I fouled them.
 
Did they send any kind of instructions for setting it up?
I had similar issues with my JET quad before I went to FAST system.
I don't know exactly what the issue was with it emptying the float bowl/acc pump well, but it did happen everytime it sat for a week or more. I don't have the issue with my old 76 CC 454 w/ factory quad...it will fire up within seconds even after sitting a couple weeks.

Proper procedure for a quad is to push the gas pedal to the floor, let up, push it again 1/2 then let off...this should close the choke plate (the smaller plate in front of the carb that covers the primary throttle bores) and give the engine a couple shots of fuel from the accelerator pump. That choke plate should just be closed by the bimetal spring under the black plastic or cast aluminum choke housing on the pass side of the carb. That spring contracts when the engine is cold (less than ~60* degrees and it should close the choke plate fully) and expands (opening the choke plate) as the engine warms up. It needs to be supplied by 12v ignition switch on/run to open the choke coil up, and that should take about 4-5 minutes to open fully. If the choke plate isn't closing at cold temps you can adjust that housing to move the choke plate...when making that housing adjustment, the throttle should be opened 1/2 way or more to allow the high idle linkage to operate the choke plate, and to set the cold idle speed cam for a higher idle, that is controlled by a screw (on the pass side of carb down towards the baseplate...usually a torx head screw facing the front of the carb) shoot for 1500 rpm when on cold idle. As you crank the engine there is a small vacuum canister (choke pulloff) that is on the front pass side of the carb that should open that choke plate about 3/16" to allow some air into the engine while cranking/cold running conditions..make sure that has a good vacuum line and the canister actually works...its not uncommon for them to leak as well, and not allow that choke plate to open.

The fuel draining from the bowl is the bigger issue here, I don't believe it would evap in a weeks time, but rather its leaking into the engine...so watch your oil and give it a sniff test if you've had a lot of fuel drain into the engine it could dilute your oil and be explosive. If this has only happened a couple times I wouldn't be too worried about it.
check the fuel pressure while cranking to make sure fuel is getting to the bowl, if sufficient, then check the acc pump squirter to see if its shooting gas into the carb when the linkage is cycled...if not then you need to figure out why its not getting into the bowl...like a sunken float that won't allow the needle off its seat and allow fuel flow.
then proceed to figure out why the fuel is draining out of the bowl as well.
Good luck John!
 
That's a ton of good info. Thanks Dave!
 
I guess it really depends on how long you have to crank it. It should take longer after sitting but not be difficult to start. Mine fires right up when I drive it daily, but when it sits for a while it requires more cranking. I am running a mechanical pump though.
 
Yes, would think with an electric pump running constantly, you'd have no issue with empty float bowls. As mentioned, choke setup is critical.
 
By pouring fuel directly into the primaries (or secondaries, wouldn't matter) you are changing the AFR, just like choke would do.

After turning key to "run" (not start), if you have the air cleaner off, what happens when you manipulate the throttle? Can you see the squirts of fuel from the accelerator pump shot? With fuel in the float bowl then this should happen. If it does, it's not likely a fuel delivery problem.
 
dyeager535 said:
By pouring fuel directly into the primaries (or secondaries, wouldn't matter) you are changing the AFR, just like choke would do.

After turning key to "run" (not start), if you have the air cleaner off, what happens when you manipulate the throttle? Can you see the squirts of fuel from the accelerator pump shot? With fuel in the float bowl then this should happen. If it does, it's not likely a fuel delivery problem.
Click to expand...

I'll check this later this evening.
 
fwiw, Q-jets are noted for having issues if the float level is off.
 
With an electric fuel pump, couple of seconds is all that is needed to fill the bowl even after an extended layover time. Crank and a couple of pumps of the pedal and it should start. at worst 5 seconds or so.

Assuming everything is set up correctly of course and ign is in tune. If not your not getting fuel in the bowl or the accelerator pump is not working.

On a cold quadrajet that's been sitting is asking too much with out a couple of pumps of the pedal and a little cranking.

The bowl will go dry after a while and can actually boil away on a hot engine leaving only a small amount of fuel left to evaporate.

You can turn on the elect pump, take a straw and put it down the vent and push the float down GENTLY and the carb should flood if your getting fuel in the bowl. And as was stated before first try to move the throttle by hand and look down the primaries and see if you have a stream of fuel shooting down to verify you have fuel and the accell pump is working.

Fresh rebuilt carb shouldn't be having problems but Don't know anything about SMI.
 
Subscribed, as I am happy with my carb from SMI. I do think that I cracked the epoxy on the well plugs of mine due to not having enough heat protection for the carb. My electric fuel pump primes the carb quick enough, but... Mine does need the choke to be set with a pump of my foot when temps get below 55 or so.

Call Sean at SMI, he seemed willing to help, and take care of his customers.
 
I played with it a little this afternoon...

-Battery = 12.52v
-Key on fuel pressure = 5psi (AC Delco brand, OE style in tank pump)
-Untouched choke flap 90* closed, 2 strokes of linkage by hand left the flap open
-Outside temp = 88*

I left the key on for 30 sec with pressure reading steady @ 5 psi. When I stroke the linkage I do not see any fuel spray in the primaries. Same when I manually push the accelerator pump.

I tried to crank it and noticed the fuel pressure drop to almost zero and despite the 12.52v charge the motor spun fast but quickly slowed to what sounded like a half dead battery.

Still baffled by the dry carb.

Do you think 2 problems? Possible bad battery + something with carb?
 
I can't do it now but I think I'm going to disco the fuel line from the carb and see what kind of volume I'm getting there.

Also going to have the battery checked.
 
Odd question but how are all the rubber fuel lines in your rig?

Every rubber line from the carb to the gas tank, I've heard, if they're old they crack over time and where they can be cracked or brittle, they allow the fuel to seep back to the tank or just get air in them causing that pause when attempting to fire up.

My '85 K30 has this problem and after sitting for two days its harder to start than after one day. I haven't taken the time to change all the rubber lines out yet but I have crawled under there and found dry rot cracks on them.
 
All of the rubber is new, I only reused the factory hard lines.
 
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