Back about a year ago, "Brady and Hilary" had some problems with fuel delivery. Finally they got running again after many repair ideas didn't work, and after finally a mechanic installed an additional electric fuel pump. They sold their rig, an 86, with a 454. I have an '87 with a 454.

Today, coming back from NH, I had a problem. I started the trip with a full tank, 75 gallons. After 240 miles of excellent running, there were some backfires that sounded like they were through the carburetor, like a lean condition was happening, and I was running out of gasoline. That was my hunch, so I quickly asked my Garmin where the next gas station was. It was a half mile ahead, so I added $75 dollars there, about 21 gallons. I started it up, and there were some continued backfires in the carb, and also out the exhaust. I thought it must have been an HEI or distributor failure to cause that, and I hoped for a vacant lot to pull off in. Going up a hill it continued to sputter. I fluttered the throttle so that the accelerator pump would throw some more fuel in and allow me to ascend the hill; cars were backing up behind me on this state road. By the time I reached the top of the hill, all was well! I was able to floor it and accerate with no problems and made it home the remaining 60 miles.

I think I have a fuel pick up tube problem. Here's a link to the B&H story, and pictures of the top of my tank from work I did a couple years ago. (I should have checked the darn thing then!)
http://barthmobile.com/eve/for...=455101172#455101172

Can you think of an alternate explanation? Dealing with a nearly full 75 gallon tank is some heavy lifting. My P30 was assembled 25 years ago, and this pickup tube is probably the only tube or hose I haven't replaced or had replaced yet.

On a bright note, I am happy with my Moroso plug wires and how well the engine cools itself with the recent fan clutch.

Go RVing!
Matt

It sure sounds like you have a lean condition. But, what could it be? Vapor lock, equalizing air not getting into the tank to replace the fuel that is being used, a collapsed suction hose, plugging up inline fuel filter, filter in the carb collapsing under psi, the sock in the fuel tank plugging up, the carb is failing, your fuel pump is getting weak and is ready to fail, EFI issues, etc...

I always go with my first instinct when I have a problem like this.

I too had the same scenario happen to me on my EFI Barth and I wound up replacing my fuel filter first. Then, after that didn't help, I replaced my intank electric fuel pump and that fixed the problem.

Of course, we have 2 different setups. You have a carburetor on a GM Powered 454 and I have electronic fuel injection on a Ford powered 460 but your description mirrors my issues too.

quote:

Originally posted by Bill N.Y.:
While driving, it stumbled and then ran with a severe loss of power... It appeared to me like it was low fuel psi or a bad fuel filter. I removed and replaced the filter with no increase in power. I drove it home and then halfway home I got full power again.

If this was me, driving your coach, I would pull off the carb filter and check to see if it is collapsing... Yes? done! No: I would replace the fuel filter inline and then I would also replace my fuel pump.

For you however, I believe the cross country trip you took in your Barth makes you an expert on your coach. You handled every scenario with little effort so I believe you should go with your gut on this.

You're fuel filler cap may be a "vented" type that was used on '80's GM chassis. If you want to try it out the next time you get a sputter,loosen the cap 1/2 turn. If that fixes it then you need a new gas cap. Since vented caps are no longer sold you will have to drill a small hole in it. Perhaps the cap was replaced some time ago with a modern one and the tank is being negatively pressurized. By filling up, you equalized the tank for the last leg of your trip.

Oh the joy of diagnosis! In terms of heavy lifting, I sure would rather replace the gas cap!

This is something that would feed in to the "venting" theory. This is the first big trip I took since replacing the 6' of Dayco 80304 fuel filler hose, which was leaking when I filled up, with two Gates fuel filler elbows and steel pipe. Maybe the fissures in the Dayco hose, which allowed gasoline to leak out when I filled it, also allowed the pressure to equalize.

But now, since I have a full tank, wouldn't the symptoms of a non-venting gas cap show up worse?

My gut is telling me it is the gasoline filler tube, and that it would prefer that it would be the gas cap, and that dealing with 70 gallons of gasoline is going to make removing the tank a big problem.

Had I not already redone the floor, I would immediately consider cutting an access hole through the floor to get to to the top of the tank.

I don't mind stopping every 100 miles to top it off, but I am worried that if I have a fuel pickup tube issue down low, it might migrate up the tube. But it does make lots of sense to inspect the fuel filters. It sure is an easy step to take. My gut also tells me to rule out the easy things and the inexpensive remedies first!

Oh yeah!
Matt

Matt, There's a small filter in the carb itself if you have a old quad. jet carb. It's under the big fitting where the line enters the carb, lossen and pull back the line and then lossen and screw out that big fitting, take note there's a spring that holds the filter seated and note the way the direction the filter goes in. Also be carful screwing the fitting back in, it has a very fine thread and you dont't want to bug up the threads.

Maybe you already knew, but many don't and change there in line one only and wind up changing pumps and lines, pickups, even carbs that finaly fix it.

Myself, I pull them out and throw them over my shoulder and use two inline type one before pump and one after!

Good luck

quote:

Originally posted by BarthBluesmobile:


I think I have a fuel pick up tube problem.

Dealing with a nearly full 75 gallon tank is some heavy lifting.

I dropped mine last year. soaked the nuts ahead of time and sucked out the tank, then removed the drain plug to catch the rest. New hoses and a repair to the FQ sender.

I have always had an electric pusher pump next to the tank on all my tow and RV vehicles. Never had vapor lock, even in extreme conditions. I don't even use a mechanical pump;

A fuel pressure gauge can tell you a lot. On the Qjet, I like to take the pressure right off the inlet fitting. I substitute a longer Olds fitting to provide more area to drill and tap for the nipple.

First thing to try, though, would be the filler cap, as Bill NY mentioned.

I got a load of bad gas once on another vehicle, and the load of crap in my tank floated around and drove me crazy for a while until I put in a fuel pressure gauge. Ended up dropping and cleaning the tank.

quote:

My P30 was assembled 25 years ago, and this pickup tube is probably the only tube or hose I haven't replaced or had replaced yet.

Sounds like it would be a good idea to replace it, just as PM.

Thinking back on this year, I recall one day earlier this year when I was getting going in the Barth Bluesmobile and went up an on-ramp. I had the backfire in the carb a couple times during that event. I thought it was odd that I never had an "air bubble" in the fuel lines before". The highway was level and there were no problems. I filled up soon after though, and was down about 20 to 25 gallons.

I am really thinking it is the fuel sender. "Brady and Hilary" said their problem was when going up a hill. My problem was when going up hills. Most of my trips the the past couple years have been on level ground so I might have had this problem and not known it.

Thanks to the glory of Google, I found the Spectra FG12X. It is intended for use on the 1994-1997 P30 chassis when equipped with an 80 gallon tank. That is an FI engine so that is why two of the tubes have flared connections.
http://ecat.spectrapremium.com...catalog&splash=false

http://www.rockauto.com/dbphp/...nk_Sending_Unit.html

I have an email out to the customer service people at Spectra (they are in Canada) about the depth of the fuel pickup, and the diameter of the mounting interface. I might just be picking up one of them soon.

Of course, I am going to look at the issues with the filters and gas cap. But I sure like the input from Bill H about PM. Every other element in the fuel delivery system except for the pressure regulator and this sender unit has already been replaced, and has less than 12K miles on it.

I am guessing that RVs might have a more notable "hill effect" on the fuel delivery given that the tanks are mounted along the frame, as compared to most cars and SUVs. Some pickups might have the side saddle tanks, but I don't think there are many of them running after 25 years in the states with rust.

Happy Motoring Again!
Matt

My 71 Nova, from when I was a kid, suffered from a slight backfire when I was really hammering it going up a hill. My autoshop teacher told me to check the element inside the fuel filter inlet (carb filter). It was slightly crushed. He said to me... Bill,that 70c filter has driven many of mechanics mad. It crushes under higher psi and starves the fuel filter housing.

Of course, he was right again... For less than 2 bucks I was all fixed up again.

I am assuming that your pickup doesn't have a fuel pump inside of the tank - right?

quote:

Originally posted by Bill N.Y.:
My 71 Nova, from when I was a kid, suffered from a slight backfire when I was really hammering it going up a hill. My autoshop teacher told me to check the element inside the fuel filter inlet (carb filter). It was slightly crushed. He said to me... Bill,that 70c filter has driven many of mechanics mad. It crushes under higher psi and starves the fuel filter housing.

Of course, he was right again... For less than 2 bucks I was all fixed up again.

Didn't I read something about a regulator on the coach?

quote:

Originally posted by Wharf Rat

Maybe you already knew, but many don't and change there in line one only and wind up changing pumps and lines, pickups, even carbs that finaly fix it.

Myself, I pull them out and throw them over my shoulder and use two inline type one before pump and one after!

Good luck

That's the blankity blank filter, Bill and they were a little, this will get them in for a tune up device GM built in. Later they stoped putting drain plugs in the automatic traneys! Bad bad bad

My experience has been that when the carb filter gets clogged, it pushes against the spring, and unfiltered fuel is allowed to enter the carb.

On a P30, this can cause the needle to leak with flooding as a result. This flooding will chase fuel up into the charcoal canister, and little charcoal granules will be washed into the float bowl and really make a mess of things. Looks like black kitty litter.

DAMHIK.

All P30 owners should run out and install a small inline filter in the line going to the charcoal canister to avoid this massively inconvenient possibility.

quote:

Originally posted by bill h:
My experience has been that when the filter gets clogged, it pushes against the spring, and unfiltered fuel is allowed to enter the carb.

Makes sense to me...

It's not like the fuel wasn't filtered - Wouldn't the inline filter also filter out the impurities too? I remember my 71 had one filter inline at the unibody frame mount area on the drivers side.

It has been many years since autoshop class and I no longer work on gassers anyway, but I do remember it not backfiring anymore after replacing the crushed filter inside of the bowl... Maybe from swelling it choked it out and made it lean?

I don't know anymore and at 16 my whole thought process was to get in and drive. I also think I remember it was a bear to start because the fuel leaked back after sitting for an extended time.

Heck, I could even be confusing the 2 incidents.



To be 16 or 17 and work at the old ATI gas station as a fuel jockey back in the early 80's.

quote:

Originally posted by Bill N.Y.:

quote:

Originally posted by bill h:
My experience has been that when the filter gets clogged, it pushes against the spring, and unfiltered fuel is allowed to enter the carb.

Makes sense to me...

It's not like the fuel wasn't filtered - Wouldn't the inline filter also filter out the impurities too?

Yeah, I can see how you would think that. The inline filter filters anything that comes in from behind it, but the carb inlet filter filters anything from the inline filter forward. In my instance, I had recently put in some RedLine Fuel System Cleaner. I have always loved the stuff. It made my Koholer genset run right for the first time in my ownership.

My theory on the clogged carb inlet filter and the "unfiltered" fuel entering the carb is that there was a 20 year layer of varnish lining the fuel line between the inline filter and the carb inlet filter. The Redline loosened this up and it clogged the filter, causing it to open and allow crud to make the needle and seat leak, causing flooding. My carb guys nodded their heads when I told them about it. When they saw the black kitty litter in the float bowl, they knew exactly what had happened. It was their recommendation to install the filter in the line to the carbon canister to prevent a repeat performance.

So, folks, learn from my experience, and change filters soon after using a strong fuel system cleaner on a vehicle of unknown history.

If you use a cleaner regularly or semi-regularly, you will probably be spared the drama. I use Seafoam for vehicles that do not have serious problems. Seems to keep things cleaner and keeps the gas from aging.

quote:

I do remember it not backfiring anymore after replacing the crushed filter inside of the bowl... Maybe from swelling it choked it out and made it lean?

Yeah, once something gets swelled up, a restriction could result.

It is also possible that the filter or spring was incorrectly installed. The wrong spring (too strong) could prevent the bypass function from operating, and could put too much pressure on the paper element and crush it. Fram filters are notorious for doing that. I don't know if they were that bad back then, though.

Can you imagine a Corvair with six of those inlet filters to contend with?

Hi,
Time to follow up. I'd noted this year, when coming back from the track at Thompson (where my older boy races the quarter midgets), that a certain on ramp with a rapid rise always caused problems with the backfiring through the carb when the gas tank was about half full, and never when the gas tank was full. I generally have kept the gas tank filled due to my worries of the fuel problems.

Today was 40F and clear in Massachusetts so I finally pulled the fuel tank out. I was shocked to see that the fuel sender has an interface to an electric fuel pump attached to the sender, and the connection is made with only a compression type hose clamp (made from plastic), and the electric pump had come loose. So, I was getting fuel to the quadrajet only because the engine mounted pump was drawing fuel from a stub of a steel tube about half way up the depth of the tank. I was speculating about rust holes!!!!

I got pictures and I will post soon. My camera battery died.

I did note that on the FG12X, the new one, that there are additional mounting holes which appear to provide a screw connection to hold the fuel pump in place also. My existing fuel sender unit does not have this feature, and relies on a single hose clamp.

Talk about your SINGLE POINT OF FAILURE! Hardly in an easily maintainable location!!!!

I bet you this isn't the first P30 Chassis rig of the era to have this problem.

Happy New Year!
Matt

quote:

Originally posted by BarthBluesmobile:

I bet you this isn't the first P30 Chassis rig of the era to have this problem.


Matt

Our 30 footer has a long run from the front engine to the rear-mounted tank, and that 502 is thirsty.

The 502 does not have a pad for mounting a mech pump, so I mounted an electric pump on the frame rail as close to the tank as possible. It is readily accessible for maintenance and there is nothing inside the tank to act up. If it fails, the holes are already there to use the genset pump in its place.

We climb some pretty hot, steep mts, and so far so good. (at least for the last 11 years).