Carb/Fuel problem [Archive] - Team Camaro Tech

: Carb/Fuel problem


400bird
Jun 19th, 07, 02:50 PM
Ive got a 67 firebird and recently I have had some hard start issues.

Its only after its been sitting for a while, like overnight.
It turns over just fine, had plenty of spark, the problem is fuel...

When I first hit the key it just barely fires but doesn't 'catch' and keep running, i then have to continue cranking for like 45 seconds to get it to start. For that 45 seconds or so it sounds like its just freely cranking over without any fuel.

So this morning I pulled the top of the carb off and the fuel bowls were empty, and the line to the carb was dry.
The float adjustment was fine, the filter screens were very clean and the needles and seats looked good

It has an edelbrock 1406 carb (600 cfm, electric choke) and a mechanical pump

So, i guess my question is what should keep the fuel from draining out of the carb, is there a check valve in the fuel pump?

Thanks
Jon

400bird
Jun 19th, 07, 05:42 PM
I just installed the fuel pressure gauge i bought months ago

I have about 4.5 and bouncing at idle, 4 steady at anything off idle
but when I stop the engine it take 15 seconds for the pressure to drop down to nothing

wiskeesour
Jun 19th, 07, 06:06 PM
check valve in the pump is inop.

400bird
Jun 19th, 07, 06:09 PM
thank you, i was not sure if there was a check valve in the pump

thanks again

Everett#2390
Jun 19th, 07, 06:10 PM
Mech fuel pump won't hold pressure very long. Hard starting when cold? Depress gas pedal a couple of times to set choke and dump a couple squirts of fuel into intake.

No fuel overnight in bowls? Heat soak of carb, evaporating fuel from bowl. Might install a heat isolator plate between carb and intake. A plastic/composition one, or wood.

wiskeesour
Jun 19th, 07, 06:17 PM
check valve in the pump is inop.


Wait uh minute....is it the stock pump or OEM factory pump?

77wolf10.85
Jun 19th, 07, 06:23 PM
Well, no check is necessary because the fuel inlet level is higher than the bowl level. But the fuel pump itself should have checks.

Your gas is either vaporizing out the top or possibly leaking thru the carb into the intake. Sounds like you've had the carb awhile and would have had vaporization problems before now. I can't right off top of my head think of a possible external leak on an Edelbrock where you would lose evry drop.

The only problems I've ever had on Edelbrocks have been caused by dirt. I would kit it and try again.


http://www.edelbrock.com/automotive_new/mc/carbs_acc/carbs_access_main.shtml


somebody will come along that has maybe had this problem on an eddy

Your 4# fuel pressure is a little low. Heck you may be losing the pump. Do you have a vented gas cap? I can't hardly imagine the tank sucking back hard enough to vaporize all the fuel in the bowl and return it to the tank, but stranger things have happened.

Hey why don't you try unscrewing the gas cap tonight and see how it does in the morning. Yeah, that beats hell out of buying one of Edelbrocks high $ kits.

400bird
Jun 19th, 07, 07:17 PM
Wait uh minute....is it the stock pump or OEM factory pump?

no, its looks something like a holly mechanical pump, and may be but I dont know
it has been there for a long while

wiskeesour
Jun 19th, 07, 07:19 PM
Eddy's are pretty simple...Ive worked a couple and I remember them only being 2 pieces. I cant think of a spot where they would allow vaporization of the fuel....I would check checks in the pump and make sure tank is venting proper...

400bird
Jun 19th, 07, 07:25 PM
Mech fuel pump won't hold pressure very long. Hard starting when cold? Depress gas pedal a couple of times to set choke and dump a couple squirts of fuel into intake.

No fuel overnight in bowls? Heat soak of carb, evaporating fuel from bowl. Might install a heat isolator plate between carb and intake. A plastic/composition one, or wood.

Setting the choke and pumping the empty accelerator pump doesnt really help

the problem is not only when cold, just after sitting for a few hours, the motor could still be 100*
it seems like the problem is just time, not really the temp

And i just went out and ran it for a few minutes (only got to about 150*), checked to make sure there is fuel sitting in it and I will check tomorrow and see if its still there

400bird
Jun 19th, 07, 07:29 PM
Well, no check is necessary because the fuel inlet level is higher than the bowl level. But the fuel pump itself should have checks.

Your gas is either vaporizing out the top or possibly leaking thru the carb into the intake. Sounds like you've had the carb awhile and would have had vaporization problems before now. I can't right off top of my head think of a possible external leak on an Edelbrock where you would lose evry drop.

The only problems I've ever had on Edelbrocks have been caused by dirt. I would kit it and try again.


http://www.edelbrock.com/automotive_new/mc/carbs_acc/carbs_access_main.shtml


somebody will come along that has maybe had this problem on an eddy

Your 4# fuel pressure is a little low. Heck you may be losing the pump. Do you have a vented gas cap? I can't hardly imagine the tank sucking back hard enough to vaporize all the fuel in the bowl and return it to the tank, but stranger things have happened.

Hey why don't you try unscrewing the gas cap tonight and see how it does in the morning. Yeah, that beats hell out of buying one of Edelbrocks high $ kits.

I am not lossing every drop. there were still about 7 or 8 in there this morning LOL

Yes, i do have a pretty new locking vented cap, and a full tank right now

But I when I was out there a few minutes ago, the pressure was down to 3.5* so I guess i need to find a new pump or a rebuild kit for this one

77wolf10.85
Jun 19th, 07, 07:49 PM
The fuel pressure will bleed off.

Badbird
Jun 19th, 07, 07:50 PM
Are you sure the float level and the float drop are adjusted properly?.....I have a #1407 and both float adjustments were way off!....On mine, the float level is 7/16" and the float drop is 1".....If everything is OK then I think it's time for a fuel pump with a maximum pressure of 5-6 psi

Everett#2390
Jun 20th, 07, 04:28 AM
But even if he gets a new fuel pump, it still is not going to remedy the "no-fuel" in the carb issue. I suspect evaporating fuel from heat since he mentioned no fuel squirting from accelerating pump.

The reason the engine is cranking so long is the fuel pump is sucking fuel from the supply and filling the bowl. Takes time/strokes. Since you have only 4 psi, maybe a new pump is warrantied. Definitely would help shorten the cranking time.

I'd find or make a heat isolator for the carb. Lay an A/C thermometer about the base of the carb or shoot it with a temp gun to see the temp.

You might try another brand of fuel, different recipe. Maybe the station you trade at got a snoot full of winter recipe, it will evap fast in summer.

400bird
Jun 20th, 07, 12:23 PM
Are you sure the float level and the float drop are adjusted properly?.....I have a #1407 and both float adjustments were way off!....On mine, the float level is 7/16" and the float drop is 1".....If everything is OK then I think it's time for a fuel pump with a maximum pressure of 5-6 psi

I have not measured the drop, but it looks like its about 1". The level is 7/16"

77wolf10.85
Jun 20th, 07, 01:06 PM
Did it lose all it's gas again today?

400bird
Jun 24th, 07, 11:12 PM
Sorry that took so long, I checked the carb this morning
It lost most of the fuel but there was more left that usual, and it started quicker

But do you guys think a leak in the line from the tank to the pump could cause the problem?
Well, I found one. Hopefully i got the fitting tightened up enough and it doesnt leak again, I guess I will find out tomorrow...