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quadrajet carb
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First Month Member
Supporting Member of Barthmobile.com 11/13
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quote:
Originally posted by Brady and Hilary:


The problem, to be more specific, seems to be after the motor gets hot it "bogs down". I think that's the best way to put it. especially under load going uphill. I push the accelerator and it sounds like it's flooding out or something and I've got barely enough to get up the hill.


Could you describe the "flooding out or something" in a little more detail? Generally, flooding out means way too rich. This usually has some soft missing and black smoke out the exhaust. Sometimes exhaust popping, too, but not always.

Does the choke fully open when warm? If the choke does not open fully, it could keep the secondary closed. I broke in my new 502 with the secondaries closed, and it was a little down on power up steep hills. Smiler

quote:
I will check the plugs, wires and cap. I'll probably just replace them.


Never hurts. Be sure to put a sleeve on #8. I use a Taylor "Space Age" Thermo Tech is good enough for the others.

quote:
The heat riser? I think this has been disabled. The return lines from the exhaust manifold were literally rotting off. My mechanic thought it was a lost cause and took them off and welded bolts into the holes on the manifold. Wouldn't that only effect cold start ups though?


Some of your description makes me think the AIR (smog pump) system has been disabled.

The heat riser is a butterfly valve on the outlet of the right (usually) exhaust manifold. I think your year is vacuum controlled, but they jumped around a lot to manipulate emissions. If the heat riser is stuck fully open, it will indeed only affect cold start ups. However, if it is stuck closed, or partially, it could pose too much restriction for good power.

Another possibly is a restricted exhaust. Some tailpipes or exhaust pipes are double-walled, and can form a restriction. Or a muffler could develop a restriction. This is uncommon on a non-catalytic converter vehicle, but they can drive a good mechanic crazy if he doesn't check.

Scientific method: Read back pressure with a gauge.

Barnyard method: Cut the exhaust pipes at a straight section aiming straight back. Poke a stick up to the manifolds to check for restriction. Test drive. Reassemble with slip-together couplers or band clamps.


.

84 30T PeeThirty-Something, 502 powered
 
Posts: 7397 | Location: AZ Central Highlands | Member Since: 01-09-2001Reply With QuoteReport This Post
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Oh, and I'll check the vacuum lines too. I know some of them are dry rotted going to the heater controls, so others are probably in bad shape too.


1986 Regal 25ft.
454 Chevy
 
Posts: 33 | Location: The Great American West | Member Since: 04-25-2009Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 8/11
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Years ago, I had a Tiffin coach with the same problem even after someone had replaced the fuel pump, fuel filter, etc. I fabricated a fuel pressure gauge using the same size fittings as the carburetor and fuel line out of fuel hose and a "tee" to screw the gauge on. Went down the road and watched the fuel pressure drop to zero under load. It turns out that there was another in-line filter very near to the fuel tank that had been covered over with foam insulation. It took twelve years to plug, but it sure did. That filter was heavy when I finally got it out! Good Luck !
Billy T


Billy & Helen Thibodeaux
Owners of Billy Thibodeaux's Premiere RV, Inc. Scott, LA 70583 I-10 Exit 97
The Farm is near Duson, LA I-10 Exit 92 then N 1 mile on right
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Data Tag: 9404-3908-36XI-2C
1994 Sovereign 36' Widebody on Spartan IC (Mountain Master Lite) Chassis.
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Toad: 2018 Chevy Colorado ZR2 Diesel with M&G Car Brake
 
Posts: 343 | Location: 1mile north of I-10 Exit 92, Duson, LA USA in The Heart of CAJUN COUNRTY ! ! ! | Member Since: 05-14-2005Reply With QuoteReport This Post
First Month Member
Supporting Member of Barthmobile.com 11/13
posted Hide Post
quote:
Originally posted by billyt53:
Years ago, I had a Tiffin coach with the same problem even after someone had replaced the fuel pump, fuel filter, etc. I fabricated a fuel pressure gauge using the same size fittings as the carburetor and fuel line out of fuel hose and a "tee" to screw the gauge on.


That's a good point, Billy. I considered mentioning a fuel pressure gage, but installing one is fraught with fire danger if it is not as carefully as you did.

In order to read the fuel pressure AFTER the filter element, I used a longer filter snout from an Oldsmobile Q jet and drilled and tapped it at the right spot for a 1/8 NPT fitting and a hard line going to an isolator and then to the cockpit gauge via a hard line with a section of braided SS brake line located to allow for engine movement.

I have done some temporary lashups that were not quite as safe. Frowner


.

84 30T PeeThirty-Something, 502 powered
 
Posts: 7397 | Location: AZ Central Highlands | Member Since: 01-09-2001Reply With QuoteReport This Post
First Month Member
Supporting Member of Barthmobile.com 11/13
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We have talked about filters in the carb and underneath. There is also a filter inside the tank. Sadly, it is accessed by dropping the tank and taking out the inlet plate.

I once suspected the in-tank filter, but was loathe to replace it until I had to. I did a temporary jury rig by cutting the fuel line at a convenient location near the tank, and connected a hose to the engine side and ran the other end down the filler neck. Sure enough, the problem went away, telling me to replace the in-tank filter.

One more thing.......Dump in enough Red Line SI-1 Complete Fuel System Cleaner to match the amount of fuel in your tank. The stuff is really good. I have even had it do the job where the much-vaunted SeaFoam did not. It also made my genset love me again.


.

84 30T PeeThirty-Something, 502 powered
 
Posts: 7397 | Location: AZ Central Highlands | Member Since: 01-09-2001Reply With QuoteReport This Post
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quote:
Originally posted by Brady and Hilary:
We're planning on heading to Albuquerque next week...
Any luck finding your gremlins? I was thinking more about your situation. On my rig, I had a mechanic replace all the steel lines for fuel and brakes. In the past, I'd had a GM station wagan and a C60 truck, and they'd behave strangely when the fuel lines started to rot through. They'd run good around town, but on the highway, they'd sputter and buck. What was happening was that the increased fuel demand of highway speeds would cause the fuel pump to suck air through the rust structure of the pipe. Only rarely would there be a fuel stain under the vehicle when parked. On the wagon, I tested the theory by running a a fuel hose from the tank to the fuel pump and it ran fine. On the C60, well, I needed a tow truck when the problem occured. It broke by the side of the road, and I was able to tell I was getting fuel to the carb, but not enough to keep the thing idling.

Other things to be paranoid about: the fuel filler hose, and the hose at the top of the tank between the tank fittings and the steel lines.

Bring spares of anything that is small and relatively cheap like hoses, ignition parts, fuel pump, things that could easily be installed, but which might not be readily at hand in the middle of Kansas.

happy motoring!
Matt


1987 Barth 27' P32 Chassis
Former State Police Command Post
Chevrolet 454
Gibson Exhaust
 
Posts: 321 | Location: Massachusetts | Member Since: 07-28-2006Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 6/12
Formally known as "Humbojb"
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On our return from DC GTG we had what sounds like the same problem you had. We trouble shot the same as you all did, called Bill NY & he talked to the mechanic who did everything bill told him to do. I ran our rear tank down almost to empty which was a "mistake" because it had had some trash in it running it down to empty stirred things up & we believe that debris clogged up the carb. The mechanic that came to rescue us took the carb apart while I held the flashlight & there was some trash in it. To get us home he turned the distributor to the right a hair to give us high rpms & said that should get us home. 6 hrs later we were home. Sent the carb out to be rebuilt & are waiting for our rear tank to be returned from the refurbisher. Having the sending unit re furbed too.
Tere


Jim and TereJim and Tere

1985 Regal
29' Chevy 454 P32
8411 3172 29FP3B
Gear Vendor 6 Speed Tranny
 
Posts: 3363 | Location: madisonville tn usa | Member Since: 02-19-2005Reply With QuoteReport This Post
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There might be a real good deal on a Regal if you're in the neighborhood of Cave City, Kentucky.

Here's the story. We left Harrisville, PA on April fifth. We didn't make it thirty miles down the road when she started acting up again. Same problem as before. When it gets warmed up (anywhere past a quarter of the way on the temp. gauge) it poops itself on hills. I was pressing so hard on the gas that the throttle cable broke. It took four hours to rig something up so we could continue to Carrollton, Ohio. It was a total hellride the rest of the way. Every time we got to a hill I would grit my teeth until the top. It would hesitate and then surge, hesitate and surge the whole way up. It was like riding a bucking bronco. And if I would give it gas until the secondaries opened up, it would just gurgle and I would have nothing.

Roger and Diane at A1 Twin Valley were kind enough to check us in at nine at night so we got some sleep and then started calling mechanics in the morning. It was either get it fixed right then or turn around and try to make it back home where we would ditch the motorhome and press on in the car.

We found a guy in Minerva that would look at it. He checked the plugs, wires, cap, rotor, timing, heat riser, and fuel pressure. He said the fuel pump was leaking out of the weep holes and it was only pushing 4 PSI when it should have been between 7 and 9 PSI. He replaced it and my rigged up throttle cable. Also, he said that the ends on my battery cables we pretty iffy so he replaced them too. Then he sent me on my way.

We drove from Carrollton to Shelbyville, KY the next day with only one instance of the hesitation, and that was on the interstate when I was going about 65mph up a pretty long grade. I thought maybe I was just asking too much and it was very slight. I thougth we'd been saved!

Then today it started again. It was much warmer today than when we left Carrollton on friday. We got maybe sixty miles down the road and I felt it again. Subtle at first, but then getting worse as we went and the engine got hotter. I stopped to refuel and put premium in it thinking that it might just be tempermental, but that seemed to make it worse! After that it actually stalled out once and later it backfired twice going uphill.

I'm at a loss here. My wife is fed up and ready to go home or sell it. I'm not too far behind.

A couple of questions.

How fast should I expect to be able to drive this? Are modern highway speeds too much for this drivetrain?

What octane fuel should I be running?

Does anyone know a good mechanic in or around Cave City?


1986 Regal 25ft.
454 Chevy
 
Posts: 33 | Location: The Great American West | Member Since: 04-25-2009Reply With QuoteReport This Post
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Oh, and he checked the vacuum lines too.


1986 Regal 25ft.
454 Chevy
 
Posts: 33 | Location: The Great American West | Member Since: 04-25-2009Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 03/10
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Brady, some of the other folks have more knowledge than I have on this subject. This really sounds like vapor lock. Check and see if the fuel lines are next to any hot surface, etc. sky


1990 Barth Regency
32RDGB1 Wide Body
3208 Cat 250 HP
Gillig Chassis
Center aisle
 
Posts: 508 | Location: Murphy, NC | Member Since: 03-01-2006Reply With QuoteReport This Post
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Someone else had talked about vapor lock in a different post. This could be the case. How close is close? The fuel line switches to outside of the frame rail when it gets close to the exhaust manifold, but that's still only four and a half to five inches away. I can't remember what post it was, but it was something to the effect that half inch fuel line was installed to avoid vapor lock. Or something like that. My Regal has half inch line running from the tank to the pump. ???


1986 Regal 25ft.
454 Chevy
 
Posts: 33 | Location: The Great American West | Member Since: 04-25-2009Reply With QuoteReport This Post
Picture of Brady and Hilary
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Does this thing have an accelerator pump?


1986 Regal 25ft.
454 Chevy
 
Posts: 33 | Location: The Great American West | Member Since: 04-25-2009Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 7/17
Picture of Doorman
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Don't know if this will help u at all. qjets do have a accel. pump.remove air cleaner with engine off. You should see a steady spray/squirt when u open the butterflies.Top of carb has to come off to replace pump. Our 86 Regal has 60 gal.tank with electric pump in tank-high presure hose to fuel regulator mounted on side of frame next to tank-rubber and steel line to inline filter- to engine fuel pump. About 4psi from reg to pump, 7psi pump to carb. check for vaccume leaks.make sure vaccume advance diaphram isn't leaking. Wish you best of luck.


1986 31' Regal -1976 Class C
454/T400 P30 -350/T400 G30
twin cntr beds - 21' rear bath
 
Posts: 844 | Location: Dayton, Ohio | Member Since: 09-27-2009Reply With QuoteReport This Post
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Just to add to things to check for that are a long shot,but make sure advance weights are not stuck, I had a problem of loss of power on a prev. M.H. Turned out to be a bad gas cap that wasn't venting. Ran fine for 20 min or so then would start surging.


1986 31' Regal -1976 Class C
454/T400 P30 -350/T400 G30
twin cntr beds - 21' rear bath
 
Posts: 844 | Location: Dayton, Ohio | Member Since: 09-27-2009Reply With QuoteReport This Post
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Supporting Member of Barthmobile.com 8/16
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This post reminds me of how many times I've gotten something for dirt because the previous mechanics were clueless and the owner just got frustrated to the point of doing something rash.

Hell, I almost was paid to take the Barth off of the previous owners hands. I wanted to leave making everyone happy so I offered to pay them instead.

I'm sorry that you're having problems but in all honesty it's probably something relatively easy to figure out.

I'll be the first to admit that my knowledge of a Q-Jet is limited, but most of the times it isn't a carburetor problem.

Have you checked the weights in the distributor yet? These things seize up and a previous mechanic might not have checked it.

Have you used a vacuum pump or a vacuum source to see if the vacuum advance on the distributor is acting up?

Have you checked the voltage to the coil when it's hot and while it's plugged in?

Have you checked your fuel lines for a collapsing condition?

Maybe you're not getting air into the tank as fast as the fuel is leaving... What you might have is a plugged vent in the tank or the cap or even the wrong fuel cap.

Seeing that it acted up right after you fueled it... Because of more fuel, you would have less air in the tank so it would tend to happen sooner. Try driving with the fuel cap off to see if that helps. Yes, people have junked good vehicles for this very simple condition.

Have you replaced both fuel filters? There is one in the carb and one inline between the tank and the fuel pump.

I'm pretty sure that I could go on for awhile asking you to check this that and the other thing. I wish I could just tell you what it is but unless I'm diagnosing it myself I can only guess at a few different things.

I had one car that acted up only when hot. The previous owner had installed a tach lead into his distributor. Every time it heated up the wire would rub onto the intake manifold and cause it to miss.


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