Trouble in Paradise (carburetor)

[GWJeeper]

So I've owned the 91 GW about 7-8 weeks and have been driving it frequently to learn all of it's little quirks before making any serious changes. Sadly my wife took it on some errands a couple of days ago and it chose that trip to lay down and die.
It wouldn't idle at all just shut itself off, so I played feather the throttle and managed to limp back home. I've checked the anti-diesel solenoid and it appears to be working as it should. It cold starts just fine but as the choke begins to open and the idle slows down it begins to surge up and down. Checking with a tach it's surging between 450 and 850 rpm constantly just like it was breathing. I've tried to make some adjustments to the throttle plate screw and anti-diesel solenoid trying to hit a point where it stops surging. Finally around 1000 rpm it stabilizes and holds that rpm but sounds like it has a performance cam in it which I'm pretty sure it does not.
Engine appears to be dead stock, 2150 carb and all of the mindlessly complicated emissions controls and vacuum hoses are intact. I've never worked on any car from this time period with all of the smog controls so it's pretty confusing. Any thoughts or advice would be greatly appreciated.

[SOLSAKS]

dang
I absolutely hate the fact it died on your wife while on errands
( of all times right )
just when you had driven it and thought all was good to go,......

the most simple and cost effective solution:

some guys who are mechanically inclined say rebuilding the factory 2 barrel
is simple,.....

so if you are skilled,.... it prob needs a rebuild. and will prob. do fine after.

I opted to install a 350 dollar edelbrock carb with edelbrock intake
( that eliminates a lot of issues.....but not cold starts and warm up time )

prob the best option, but more expensive is the fuel injection upgrade
that many have done......once you get it tuned and all issue resolved with fuel injection I am sure it is great.
several diff fuel injection brands with diff price ranges.

hope you get it smoothed out so the wife can enjoy it with no issues.

good luck.

dave in NC

[letank]

Try to do a little more debugging... as you already found out that increasing the idle is helping...


if you have an EGR valve, unplug the vacuum hose to see if it improves the idle


loose spark plug leads at spark plug and cap as well as coil top


as always recheck all vacuum lines


does the exhaust smells like unburn fuel... as in Power Valve (PV) not connected to a manifold vacuum port or fubar PV

[rws31]

Sounds like a flooding carb to me.

Hold the throttle at that 1000 rpms where you said it sounded like a race cam.

Go look at the exhaust and see if it is blowing out black smoke.

If it is, pull air breather off and look down carb throat while it is running and see if you see gas running in the throat. Run it just enough rpms to keep it running.

Another indication of a flooding carb is excessive cranking time to get it to start and it blows out more black smoke. If it does take a long time cranking to start, hold throttle wide open when cranking to see if it starts faster.

And you can look down the carb after you shut it off to see if gas is dripping in carb. Don't open the throttle plates to see, you will see it dripping above them.

And be careful crawling up onto a running motor. And that does stink that it died on your wife.


It is odd that it runs fine while the choke is on and surges when it opens.

If it is not dripping gas into carb and blowing black smoke, when it warms up and the choke is open, slowly close the choke to see if it runs better. If it does, it is running lean. Trash in carb.

A lean carb usually doesn't give you that race cam sound.

[GWJeeper]

res31, I tried holding the linkage at a level that stopped the surging. I then began to close the choke, about 1/2 choke it began to smooth out a bit and when the choke was completely closed the idle was much better, not perfect but the surging was gone.

While you guys were responding I trotted down to the parts store and bought a carb kit, I'm leaving Wednesday morning to go to Back to the 50s in St. Paul. I'll rebuild the carb when I get back and see if that improves the situation.

SolSaks, I've given serious thought to going to TBI but I just can't bring myself to do it. At the moment I have one friend having an Edelbrock system installed on one of his cars and a Holley unit on another. The Edelbrock engine was run in on a dyno and the system appears to be working, the Holley system has been a nightmare for him and his mechanic. Another friend is getting ready to remove an FITech unit from a brand new engine and go back to a carburetor as they can't get it to run worth a damn.

Yeah leaving the wife stranded is way down the list of things you want involved in. I've messed with hot rods, sports cars etc since high school and only been stranded twice, both times I was by myself thank heaven. The first time was out on the interstate with a new purchase that kept dying from trash in the gas tank, the other time was a broken crankshaft in a 356 Porsche at 11:30 at night, 15 degrees outside at the top of Windy Point on hwy 285 southwest of Denver.....good times

[rws31]

Sounds like you narrowed it down a bit. If closing the choke makes it run better, it is not flooding.

Look for vacuum leaks before you tear into the carb. It would be a bummer to do a rebuild and still have the problem. Good luck with it.

[joe]

On a near 30 year old 91 odds are fair to good the carb could use a rebuild. First suspect would be an air/vacuum leak causing a lean condition. Check "all" your vac hoses. If any even look suspect, cracked, weathered, aged replace them. Stuff's only like 50 cents/ft. and just normal preventative maint every 10-20 years. Also check the carb base gasket for air leaks. If your carb kit didn't come with a new power valve...get one.
A tip on cleaning the carb: Unless you've got loose mobile crud in the system, spray carb cleaner is a joke. Carb cleaner of any type isn't magic instant hit-it-poof-crud-is dissolved juice. Needs time to work. Go with old school carb cleaner in gal cans with the soak basket included. "Gunk" brand used to be very good but think the greenies outlawed it. Most common now is Berryman's and it works well. Let it soak overnight to 24hrs. Key word is "soak" not spritz. Then rinse/flush thoroughly with water and blow out all the passages with dry compressed air. Wear safety glasses/goggles.
Unfortunately even that doesn't always work if you've got hard sugar like E10 deposits.
2150's are easy to rebuild but cleanliness counts.

[nograin]

The fact that it needs choke after warmed up is the big clue.

There's two possibilities
- huge air leak
- lack of fuel

The first is less likely but one place it can come from is the PCV Valve connecting hose. '91 prob still used the unique molded hose that has been unavailable new for the past couple years. That's an easy visual check.

Lack of fuel could be from a number of places but here's where I'd start:
1. Supply hose to fuel pump. This rubber hose seems to be vulnerable to deterioration. Something about the location.
2. Dirt in key passages of the carburetor. If you find black bits in the bottom of the bowl, it probably charcoal. I found they are particularly a problem in the idle passages - big clue is turning the fine mix screws does nothing.

Ristow had a nice photo essay on disassembling and cleaning a 2150.
I have a thread on repairing the charcoal cannister if that's what you find in the carb.
I've never had a problem using spray carb cleaner on normal clean and gasket replacement. Tried Berryman's once and was not impressed but I know lots of guys who love it - so see what works for you.

To see threads in the archives (like Ristow's rebuild thread) go to the archives subforum and change the view threads option to "from the begining". Or use the search function and select tech archives instead of the default.

The emmissions stuff isn't quite so bad when its broken up into each system. The sticker in the engine compartment is the best guide for hose connections but will leave you just wondering what the H*ll is this mess for.

[nograin]

Some possible helpful threads.
Ristows 2150 rebuild thread

http://www.ifsja.org/forums/vb/showthread.php?t=101921

A lot of photos identifying vacuum lines and devices on a '90

http://www.ifsja.org/forums/vb/showthread.php?t=185148

Some more carb pics http://www.ifsja.org/forums/vb/showthread.php?t=186961

Schematic of fuel and air flow at idle and light throttle cruising (under 50 mph or so).

http://www.ifsja.org/forums/vb/showpost.php?p=1690550&postcount=4

[GWJeeper]

Guys thanks for the thoughts and advice. We've been at the Back to the 50s car show in St. Paul for the last three days but driving back to Oklahoma City tomorrow and will get serious about fixing the GW. You've given me several possible problems to investigate and as I begin doing so I will post progress (or lack thereof)

[GWJeeper]

Back in the saddle working on the GW, first step was to remove the carb for a rebuild. It's currently soaking in carb cleaner to get the majority of crud off. So far I've found what appears to be a rubber plug about the size of a pea rolling around in the float bowl along with several pieces of black gravel that I assume are bits of charcoal. I'm guessing that the piece of rubber originated in the charcoal canister and worked it's way into the float bowl through the vent but who knows.

In addition to the crud in the float bowl virtually every bolt and screw were barely finger tight, I think I could have removed the four bolts that secure the carb to the manifold without a wrench. The screws that secure the power valve cover were barely snug. I would think that with all of the fasteners being so lose the possibility of vacuum and fuel leaks would be high.

I'm amazed at the lengths that engineers went to trying to meet federal emission standards, it seems like so many of the measures taken were simply stop-gap solutions while they were trying to perfect radical changes to the engines. Fuel injection cured so many problems but the add on units that guys are installing seem to create a whole new set of problems.

[SOLSAKS]

glad you are getting closer to fixing it.

you are right, miles of vacuum lines, etc, etc on late 80s early 90's carb engines

and you are right , in my opinion, on the add -on F.I. units creating even more issues,....

when a carb is right, there is nothing wrong with them,....

I have had 40year old vehicles as daily drivers for a long time

like a 78 K5Blazer, starts everytime, choke works as intended, and I love to hear it MOAN when I bring the back barrels in,....WOOP WOOP !!!!

nothing sounds as good as a Roaring 4bbl carb !!! at 8MPG's

dave in NC

[nograin]

I agree Dave - even though the wagon has a 2 bbl - its super responsive when all is well.

So far I've found what appears to be a rubber plug about the size of a pea rolling around in the float bowl along with several pieces of black gravel that I assume are bits of charcoal. I'm guessing that the piece of rubber originated in the charcoal canister and worked it's way into the float bowl through the vent but who knows.

Yes, maybe, no.
LOL.
If the gravel bits compress in your fingers then probably charcoal.
Unlikely the rubber plug could not fit through the inlet.
Could be:
tip of the accelerator pump check valve
viton tip of a inlet valve (although can't recall seeing one of those on these carbs)
Tip of the vapor solenoid valve. Save it! It would come through big vent line on the forward edge of the carb top. I'll need to look at one of those valves again to see if that's even possible.

Post a photo (using flckr or whatever). Or e-mail it and I'll post it for you.

In addition to the crud in the float bowl virtually every bolt and screw were barely finger tight, I think I could have removed the four bolts that secure the carb to the manifold without a wrench. The screws that secure the power valve cover were barely snug. I would think that with all of the fasteners being so lose the possibility of vacuum and fuel leaks would be high.

They don't need much torque. Agree very likely if gaskets got dried out or damaged from newer fuel forumulations then fasterners would lose tensions.

I'm amazed at the lengths that engineers went to trying to meet federal emission standards, it seems like so many of the measures taken were simply stop-gap solutions while they were trying to perfect radical changes to the engines. Fuel injection cured so many problems but the add on units that guys are installing seem to create a whole new set of problems.

Don't know they ever intended to put EFI on these engines. The 3-way cats helped a lot. Remember when the baby Cherokees came out (XJ) the talk was the SJs were no longer going to be offered. True or not IDK - there was no internet then. LOL. Certainly the SJ Cherokee was done. That much was true.

Carbs are good at providing what the engine asks for. EFI is really good for forcing the fuel and timing combinations for emissions purposes without compromising efficiency and response too much. But yes the fuel and electric systems needs major reworking - its not a bolt on magic bullet.

[GWJeeper]

So I finished up rebuilding the carb today. While I had it off the car I took the opportunity to replace about 75% of the various vacuum hoses as well as the fuel lines in the engine compartment.

Took a few moments of cranking to refill the float bowl etc and then it fired right up. Idle was up around 2000rpm with the high idle and then when kicked down dropped to about 800. I adjusted it down to about 625 for now and with my trusty halon fire extinguisher in hand went for a short test drive.

It's like a different car, idle is quieter and smoother, no more bog and sometimes die when cracking open the throttle rounding a corner. Much better acceleration from a stoplight ( although hardly breath-taking).

No gas leaks and apparently no or at least much fewer vacuum leaks. I'll have to wait to properly adjust the electric choke and fast idle kick down, the temperature here in central Oklahoma was high 90s today so the lack of cold starting adjustment wasn't an issue.

Stopped while I was out to get gas, the GW fired up immediately on turning the key. Very pleased with the improved driveability, now to run it around for a few days, recheck all of the various fasteners for possible loosening and let it try to reestablish some level of trust with my wife.

I think some of the success was from leaving an Edelbrock catalog on the fender overnight, hopefully the 2150 got the message that it might become a boat anchor if it didn't fly right. Thanks for all of the thoughts and suggestions.

[GWJeeper]

Carbs are good at providing what the engine asks for. EFI is really good for forcing the fuel and timing combinations for emissions purposes without compromising efficiency and response too much. But yes the fuel and electric systems needs major reworking - its not a bolt on magic bullet.

Instead of calling them "Plug & Play" they should be called Plug & Pray