esmartuek

So I bought a 1403 prior to moving here (Lubbock, TX) from Fort Bragg, NC
Installed great, got the adapter for the EGR, hooked it all up, and it ran funny... found out the fuel line was being pinched, so I fixed that and it ran beautifully, my wife drove it down here averaging 25mpg (up from 12 with the stock carb)

As soon as she hit the city limits, it started running funny.
When I arrived, I checked it out:
The engine would idle starting at about 1500 and steadily rise. I had to end up taking off the air cleaner and manually choke the car to get it to stop running (it would diesel like mad just turning off the ignition)

I found a vacuum plug that had deteriorated, and I replaced that, now instead of the rise in idle, the carbeurator shoots up gas from all sorts of spots on top. a friend said it's probably a mixup in vacuum hoses, but I can't seem to find a diagram to fit a LG4 engine let alone with a non CC carb.

does anyone have any advice on this?

I'd provide pictures, but my camera got stole by the movers =(

Edit:
I'm sorry for the lack of specifics, I haven't worked on my camaro for about 7 months so I'm at a loss on everything.

Edit2:
I found an image of the carb, this is the best I can do to explain the problems that I've seen:

five7kid

iTrader: (14)

Some vacuum diagrams: https://www.thirdgen.org/techbb2/sho...hreadid=257699

Your picture didn't show up, at least for me.

I'm not that familiar with Edelbrock carbs, but it doesn't sound much like a vacuum leak to me. More like a stuck open throttle plate and an improperly operating float.

esmartuek

So I completely took apart my vacuum system and compared serial numbers and images and got a damned good idea of what's what... found which image is closest to my own system and compared it all with my Parts and Illustration Catalog CD. I think I really got some things screwed up when I installed the new carb.

the question is: Why did it run so well from NC to TX?
and: Might running the vacuum system wrong and driving 2000 miles permanently ruin my new carb? I'd hate to have to get a new one cause I voided the warantee by installing it improperly.

so my assumption at this point is:
I screwed up installing it so I broke it cause I didn't give myself enough time to get it all right before moving.

Apeiron

There's not really anything in there that can break.

esmartuek

well, I completely redid the vacuum hoses and left the entire bowl vent valve, the purge valve and other emissions items disconnected, I capped all the plugs that went to those, and I hooked up all the hoses only to where they were designed to go, started it up and it was still having backpressure >.<

If I could get it to actually Idle, I'd check the timing.. I'm sure now that I have the vacuum advance hooked up to the right place that the timing is totally off... but I've never had it idle like that before even when totally retarded or advanced.

It smells rich, it runs flooded... but the vacuum didn't solve it (at least I got them hooked up and I finally know what hose goes where)


back to the drawing board.

MattW

iTrader: (1)

from what i have read it seems like the edelbrock floats are adjusted to a certain spec and then should be left alone....i believe it is done using feeler gauges and then just bending a tab......you may wanna check out edelbrocks website on setting the float level....beacuse hopefully that is all your problem is...... it says right on the box that if you are using a pump greater than 5.5 or 6 psi (can't remember the exact number)...it can cause damage to the float assembly.....but then again that doesnt explain why it is just now messing up....unless something is up with the fuel pump return or something.....

im not for certain im just throwing out ideas.....

hope something i suggested helps you out...

esmartuek

Is it possible for the stock fuel pump to even generate enough pressure for that to happen? I'm not sure, but I don't remember seeing a fuel regulator in the diagrams I've seen of the 87 LG4s...

five7kid

iTrader: (14)

I'll have to admit that I haven't seen a fuel diagram for an '87. From what I have heard, they used an in-tank electric pusher pump and an engine mounted return-style mechanical pump.

If you've replaced the mechanical pump with a non-return style, then the electric could be pushing too hard and overwhelming the needle/seats. It could get worse with time, assuming the needle/seat is slowly contaminated by gunk going through the fuel system.

What do you have for fuel filter(s)?

esmartuek

Fuel filter is the one that edelbrock sells and recommends for all of thier carburetors. It's inline and I hooked it up using the hosing that came with it about 5" from the carb.



is exactly my vacuum diagram.... I recognised every bit of it immediately.

I'll fix the first picture link...

Stekman

You are correct on terms with the in-tank pusher to alleviate vapor lock, however 2 things of question:

1.) I think it's a fairly low PSI pump, not certain, though.
2.) I would be under the impression that the mechanical pump would end up "deadheading" the pressure and volume then down to whatever it's (the mechanicals) output is.

Have you messed with the 2 idle mixture screws on the front of the carb at all? I have seen a few reports on other web forums where people have had their idle mixture screws vibrate out of calibration. No personal experience on that, though.

contact

esmartuek,

how are you regulating fuel pressure?

if gasoline is shooting out of the top of the carb,
there is something wrong with the floats,
or there is too much fuel pressure.

five7kid

iTrader: (14)

The in-tank is fairly low PSI, like TBI pumps, but if you dead-head it, it will be more than 6 psi.

You can blow through a mechanical pump. In normal operation, a mechanical pump regulates pressure via the return spring - outlet pressure is as much as the diaphragm will push based on the spring force. There is an outlet check valve to provide the suction on the inlet when the pushrod pushes the arm down, and an inlet check valve to provide the pressure on the outlet when the arm springs back. If the inlet pressure is higher than the pump outlet check valve's cracking pressure, it'll let fuel by - the pump basically sits there doing nothing.

A return style mechanical pump has a higher outlet pressure capabiliy, and regulates outlet pressure via a relief valve to the return port. If a pusher pump provides more inlet pressure than the pump would normally provide for outlet pressure, the excess goes to the return, and the outlet pressure stays at 6 psi.