I purchased an 87 LG4 with the CCC Qjet and someone had stolen the carb, so I found one off of an '82, GM# 17082204 E4ME like I believed it should have. I installed the carburetor and basically what happens is the car wil fire right up and rev or even idle fine for about 30 seconds, then, fuel starts pouring out of the front vent of the carburetor like a waterfall and the engine sputters and dies. I can fire the engine back up by putting the pedal to the floor to clear a flood but it just does the same thing again. I even rebuilt the carb, it looked great inside, still did the same thing. I even replaced the fuel pump which had already been replaced maybe thinking I got a bum one and still the same waterfall. One of you Q-Jet gurus please help! Maybe the fact that I have an '82 carb on it? I thought all the carbs from ~82-87 CCC were the same, this one was even off of a 305 LG4 '82 Camaro... Thanks in advance

'82-'87 CC carbs aren't identical, but they are close and pretty much functionally equivalent. My '82 Berlinetta #2 actually had an '87 carb on it.

87's had both an engine-mounted mechanical and an in-tank electric fuel pump. If you used an engine-mounted pump without a return line, the in-tank electric will overwhelm the carb's inlet needle & seat. Result: Flooding.

So, what kind of fuel pump did you put on?

I installed another block mounted mechanical fuel pump.

It had 3 lines on it so it was a return style, two lines from the passenger side framerail and one going to the carb.

THANK YOU I just pulled the 20Amp fuse that was in the Fuel Pump Inj spot and the car runs great!

Why in the hell would they have both?

Vapor lock. When fuel in the supply line gets hot and the engine-mounted pump tries to suck it out of the tank, the fuel, now at a lower pressure and higher temperature, changes to vapor. Mechanical pumps can't pump vapor, and carburetors don't operate off of vapor, so the engine starves.

Having a pusher pump in the tank keeps the line pressure higher so the fuel remains liquid. Having the return keeps the fuel moving so it doesn't pick up as much heat.

Sounds like you've got a problem with your return line. Check to see if it's plugged or crushed somewhere. You're better off with the in-tank pump operating, as the mechanical pump won't be able to keep up as well trying to suck through a non-operating electric, and you'll be even more susceptible to vapor lock.

This makes sense because the car was running good for a minute and now it will not idle and runs bad...

Well it seems that if I leave the fuel pump fuse installed, the car will run for a minute until it floods like a waterfall and dies.

Then when I pull the fuse and clear the flood the car runs great for a few minutes, then it refuses to idle and has a few hard starts to death or just plain won't start.

Any other ideas? The car does run well when it does, it is so weird.

Timing was double checked and set at 6*, new plugs and wires, cap / rotor / dist look great, I just bought a new fuel pressure tester and will post the results tomorrow.

I hate to hijack this but theres a fuse for the fuel pump? Where's that at????

The fuel pressure data will be helpful.

Did you verify the return line isn't restricted?

Right in the under dash fuse panel, mine is labeled "F/P INJ2" 20A fuse

five7, the fuel pressure data is sad.

I fired it up cold and it was running rough and refusing to idle again, fuel pressure spiked to maybe 12# for a second then it was pretty much rock bottom at 0#

So then what I did was remove the in-carb fuel filter and now the car idles and runs but shows no fuel pressure on the gauge, maybe it blipped to 3# mark a few times.

I feel it is making progress as the car runs and seems like it wants to stay running now, but no pressure is obviously bad.

Should I consider swapping the block mounted fuel pump for a high output one like Holley / Edelsnot etc.?

Maybe the in-tank pump is dead now? It is weird how I can leave the fuel pump fuse in now and the carb does not flood which makes sense if the gauge reads 0#... Is there a way to test the in-tank pump on these?

I jacked up the car to try and find an in-line fuel filter but do not see that or any obvious kinks or damage.

Thanks again!

I kinda know what you mean, the po of my car did a carb swap and just hooked the fuel lines from the fuel pump into the mechanical pump, when I'd turn the key on the glass fuel filter would fill up but it wouldn't ever seem like it was pushing too much pressure it seemed just fine.

So yours was not making proper fuel pressure too 781?

What I am pondering is swapping in a '82-86 fuel tank pickup / sending unit and a high output block mounted like a Holley or Edelbrock unit.

Were these block mounted '87 pumps designed to just regulate pressure? I mean they do have a return line... But can they pump the 6# of fuel pressure by themselves? It sure seems not...

I am thinking now maybe the in-tank is dead or a restriction or both. Also, maybe the block mounted pump just plain can't do it alone???

No mine made enough pressure, it should have been too much but it ran just fine with it hooked up it seemed like. I don't know if our mechanical pumps act as pressure regulators when the return line is hooked up or what, I really wouldn't think it would be. I think TBI pumps should run what? 14lbs of pressure? And TPI is in the 40's somewhere...I wanna get rid of my block fuel pump and just put in a pressure regulator though. You can take your gas line off your fuel pump and turn the key on and see if any gas comes out to check your pump if you want to, thats what I did.

The in-tank pump will not be able to feed your carb by itself.

You also shouldn't need a high output replacement for the mechanical.

Your initial problems sure sound like a blocked return line. Try a few things:

Disconnect the rubber supply line to the mech pump and you should be able to jump out the fuel pump relay and verify that it is working. It should flow a good bit but you won't get much pressure.

Disconnect the return line from the mech pump and run it into a fairly large container or all the way back into the tank. If this solves your issues you know to look for a crimped or blocked return line.

Thank you for some stuff to try naf!

I still have the problem though, when I jumper the fuel pump relay (org to tan/wht) I can hear the in-tank pump kick on and it suddenly shoots up to say 10-20# and I pull the jumper because I don't want to fry the pump.

If I run the car with the return line disconnected at the pump, it shows 3-6# of psi for a few seconds and then proceeds to go to 0 and die like always.

How are you disconnecting it and where are you letting the fuel go that should be recycling through this line while the engine is running?

I disconnected the return line at the fuel pump and ran it down into a small 1gal gas can...

This is the wrong way to do it I take?

Should I have it in a bigger can with more gas? The only other one I have hanging around is a 5gal

The return line (the smaller one) should be flowing fuel (intended to go back to the tank) when the engine is running with either, or both pumps. If no fuel is flowing out of that outlet on the mechanical pump, then I'd suspect a bad mech pump.

It was flowing fuel out of the return line of the mech pump and still dropping to 0

One thing I just noticed was that auto parts sites like RockAuto list a "1st design" pump and a "2nd design"

From what I read the second design pump is the one with the in tank fuel pump like my '87 and I have installed on my car the "1st design" pump, Airtex # 41216

Do I need the other pump listed as a different part number (42691)?

First off, the fuel pressure you're reading will vary as the needle opens and fuel flows into the carburetor. When it's not flowing the fuel pressure will be fairly steady, as it opens fuel pressure will drop.

If it's dropping to zero as the carb overflows that would be expected. Problem is, your fuel pressures below 7 psi shouldn't be holding the needle up (and sinking the float).

If you were measuring 10-20 psi from the in-tank at the carb, those higher pressures would likely cause the overflowing. If these readings were obtained with the return line open into a container, your mechanical fuel pump is likely not bypassing correctly. In fact, the return line should flow a good bit of fuel with the motor idling. Maybe fill up a 1 gallon container in a few minutes, either way you should have a fairly good stream continuously coming out of the return line.

Has this problem remained consistent between different fuel pumps AND different carburetors?

I'm seeing part number 42691 as designated for the Canadian model, which may or may not have come with the in-tank (?).

I'm also seeing 41216 as the proper pump for the LG4 for '87 (with in-tank) AND '85 (without in-tank). So I think you have the right pump.

It occurs to me that the proper in-tank pump shouldn't be capable of 10-20 psi. I measured mine once and could barely get a reading (this was with return line flowing). Is there any evidence that someone prior to you has swapped in a different in-tank pump? Has the car ever run properly for you?

I purchased the car because the carburetor was stolen on it, everything else was there, so I put on an '82 carb (rebuilt it like 3 times now ) and started this thread...

It looks like the P.O. replaced the mechanical fuel pump before with the exact same one I put on, I do not have another carb to try on it at the time...

The in tank pump might have been swapped incorrectly as I have not done it. Should I check for evidence of a fuel pump swap / drop the gas tank ? As I am thinking I was going to have to to check for obstructions anyways.

The car has never really ran properly for me and never stayed running for very long, but it seems to run good when it gets fuel psi on my gauge teed in next to the carb inlet. If only it could keep doing that

Try this: Drop the mechanical pump inlet hose into a fuel container and let it draw fuel from an alternate source. This would take out the in-tank pump which is either a restriction when it isn't running or a possible problem when it is.

If the problem persists with the pump drawing from an alternate source we need to look at the carb. First verify the filter is good and fitted properly. Trash in the lines can continually block the needle and seat.

Next: You can take off the airhorn, and with just the in-tank pump running, verify that the float is properly closing the needle and seat. You'll have to hold down the little j-hook float hinge and jumper the fuel pump relay but you should be able to see the fuel well fill and verify that the float is rising and shutting off fuel.

I had assumed somewhere earlier that a diff carb had been installed with the same problem.

Firstoff, naf, thank you again for all of your help!

I dropped both the supply and return hose into my 1gal container and sure enough, the car ran good, fired up well and after running at 0# for a minute, finally showed a steady 3-5# of fuel pressure on the gauge. Not all over the place like beofre.

Then after a few good restarts it dropped to 0# again but I think the supply hose got dry / some air and I should have put it in my 5gal container...

IMHO I would rather drop the tank than take the airhorn off the carb again haha

Saturday I am going to the junkyard and I will pull an 82-85 carb sending unit without a pump and call it done I'm thinkin'!

Glad you got it figured out!

Personally, I'd keep the in-tank pump. A pusher to the engine-mounted mechanical is a very good system to have.

You might try one more test: Put the supply line in the bucket with the return line hooked back up and watch the pressure.

Yeah, try it with the return line hooked back up.

Check the 8th digit in the VIN, it should be an "H" for the LG4, an "F" or "8" would be for the TPI. Perhaps your car's been converted to carb?

The supply hose was the only hose hooked up when I tested the lines at the back by the fuel tank. It read a steady 6# and ran great again.

I just dropped the tank the other day and it is obvious that the pump / sending unit is an original for TBI or TPI, the fuel pump is not the smaller looking one I see in the parts pictures for the carb cars.

Yes the car is original VIN H for carb, some dummy just put the wrong pump in there, the tank was obviously dropped b4

I would keep the other in tank pump but that depends on whether or not I find an '87 carb car in the junkyard. I realize the reality of that is rather slim and will more than likely find an 82-86 carb sending unit without the pump so I have no problem unplugging the fuse or cutting the electric pump plug etc. if that means the car will run and stay that way.

Another one for the 'crazy-weird' file.