Fuel Tank Switch Question...

[Colorado Coach]

Hey everyone, I just purchased an '88 Okanagan (Thanks for the CL find @Oldbagpipe!) and drove her home from Washington to Colorado a couple weeks ago. I got to replace the alternator in an Autozone parking lot outside Billings, MT, but that wasn't the only mechanical issue I had getting her home. At one point the engine started missing like crazy and I pulled over to call the seller. His first question was, "Well, you didn't run either of the tanks below 1/4 full, did you?" Ummmm, well, yeah, of course I did. This is a vehicle MADE for travel, and that might have a been a useful piece of info to have before leaving on a 1400 mile trip home.

Anyway, he felt terrible he'd forgotten to tell me about that, and explained that there was probably air in the fuel line. I had to remove the doghouse, locate a small Schrader valve (exactly like the kind on a tire tube) on the front fuel rail and "bleed" out the air that had gotten in there. It worked and I was back on the road shortly.

Anyone have any suggestions about how to fix this before I take her to a mechanic? The seller said he would only put about 80 miles on the front tank, then switch to the rear tank and start looking for a gas station. I could do this, I suppose, but with two 20 gallon tanks (that's what this baby has, correct?) at a conservative 10mpg, I'd prefer to go 350 miles between fillups on a road trip, not 100.

Side note- both gas gauges are WAY off. They usually read 1/4-1/2 ABOVE "F" when I first fill up, and they hit "E" when the tank is only around 1/2 empty. (Or should try to remain optimistic and say "half full"?) Can gas gauges be re-calibrated? If so, is that something a I could do myself you think? I mean, I did swap out an alternator with borrowed tools in a parking lot.

[skater]

For the gauges, it sounds like the pumps have been replaced and the senders are the wrong ones. 10 mpg might be a little optimistic, by the way.

Actually I wonder if that's the problem with the pumps, too - like you, I would have expected I could run the tank dry without a problem. So I wonder if they installed the wrong fuel pumps, too, so they aren't picking from the bottom of the tank. That's kind of an odd explanation, but it might fit with how the gauges are wrong, too.

[Colorado Coach]

Good call. Thanks Skater! Man, you’ve been busy answering ALL my questions on here. I really appreciate the help.

So I found a video on YouTube (https://youtu.be/l-1q9vIsuKw) of a guy replacing the fuel pump in a B190, and it doesn’t look all that complicated. I’m thinking of picking up two new fuel pumps and just attempting the swap myself. I’ve replaced brakes before; how bad could this be?

Anyone have any advice? Normally I’d pull my car into my garage for this type of job like I do for oil changes, but Okie certainly ain’t gonna’ fit in there. Is there any reason I’d need a level surface to drop the tanks and replace the fuel pumps? She’s parked on the street in front of my house right now, which is mostly level. Any reason I can’t just do the fuel pump job there?

I’m assuming on a chassis this common, pretty much any auto parts store would be able to look up which exact fuel pump I need and have two in stock for me to purchase. Any suggestions on where I should buy them? I’d prefer to get them at a brick and mortar store if possible, just to make a return easier & quicker should I need to.

Lastly, the seller (although a very mechanical guy) owned this thing for a couple years doing the whole “80 miles on the front tank, <50 miles on the rear” method and was convinced it had two 15 gallon tanks. He was somewhat shocked when I told him I’d run one of the tanks nearly empty and put 19 gallons in it at the next gas stop. Just out of curiosity, what size tanks should I have on here? Did it come standard with two 15 or 20 gal. tanks? Or something completely different? If my tanks have been switched at some point, any chance that’s why it might have the wrong size fuel pumps in there? I discovered the engine is a ‘95 (at least that’s what year alternator it took) while replacing it on the drive home. I knew when I bought it it had a rebuilt engine with only 7k miles, I just didn’t know it wasn’t an ‘88 like the old one it replaced.

Any help or advice from ANYONE is appreciated here. Thanks guys. I’m looking forward to driving Okie with a few friends up to Laramie in a couple weeks for the CSU/Wyoming game. Gotta’ have her running her best for that drive.

[Abie Sea]

I have long dealt with fuel problems. My 89 Airstream B by Okanagan is very close to your 88, though I have noticed many of the Okanagans of an earlier vintage were on an E250 chassis rather than the E350. My front tank is 15 gallons and the back is 20 gallons. neither gauge worked, and I had problems associated with the front tank. The engine would stall when it was to the point of perhaps being over heated. I replaced the pump and gauge in the front tank. Although the gauge worked, the problems continued to this day. The back tank with out a gauge reading seems to work in all conditions. I keep close track of what I have put in each tank and miles on each tank. I normally figure a conservative 8 MPG and run the front tank until I run into problems and then switched to the back tank. Anticipating gas prices and distance between stations with an idea on price. I usually erred on keeping more gas in the tanks than absolutely necessary.

My efforts have been chronicled in the index. I have heard concerns that there are problems with drawing the tanks to empty that impacts the pumps. I understand there is a wealth of problems with the two tank system in the Fords of our vintage. I have not found a good explanation for temperature affecting fuel from the front tank and not the back tank, but I have adjusted to the situation. Good Luck on finding a solution to your problem.

[skater]

Okay, so this 1993 engine is interesting. Was the 1988 model fuel injected? I'm not sure exactly when they switched over, but I thought it was 1989.

The carburated engines had two low pressure fuel pumps, one in each tank, along with the aforementioned selector valve. The fuel injected engines (like my '91) have those plus a third high pressure fuel pump mounted on the frame rail near the fuel filter, after the selector valve. If you have a '93 engine, you'll have all three pumps. (I assume the low pressure pumps make it up in volume.) This is good for you to know, even if it isn't useful at the moment. The pessimist might say that it's more parts to fail.

I'll also note that by '93, they had switched to a single larger tank, but I guess, thinking about it, the engine doesn't care if there is 1 tank, 2 tanks, or 8 fuel tanks. It just wants to drink as much as it can.

Dropping the tanks isn't that hard - I did it to both of mine. I did also have to remove the propane tank, which in mine is located just behind the driver's door, underneath. This was necessary to access the bolts for the front tank. I drained both tanks as much as possible first - front tank got pumped out via the generator connection, which you may not have, rear tank via one of the many holes in the fuel filler hose (or the breather hose next to it).

If those hoses are old, and you have replacements in hand, I'd just cut the old ones to slither in a siphon hose. Don't bother trying to siphon out through the fill; there's a ball valve in there that is meant to stop leaks in case of rollover that makes it essentially impossible to get a hose through. So many TV shows lied to us!

Someone on the FB group was going to just cut through the floor from inside, which works and is easier if you have to do it again, but to me it's just not really the right way to do it. Of course, you'd have to do some measuring to figure out where to cut.

Tip, do not cut the T-bolts on the rear straps - I did, then I discovered they weren't available anywhere, so I had to rig something. Do whatever it takes to be able to reuse those.

I got new fuel pumps via Rockauto, but any parts store should be able to get them. Of course, they might have to order them, too.

Watch the rear tank sizes, I accidentally ordered the wrong one the first time and spent $40 to ship it back. Mine is 15 in the front and about 22 in the rear. Don't order the one for the cutaway bus, it's way too large.

Good luck! My restoration thread has some pictures, but it's all kind of jumbled together.

Before the fuel pump replacement, I also used a "dead reckoning" method - 100 miles on the front tank, 150 on the rear. At 8 mpg, that meant I'd use 12.5 gallons of the 15 in the front (I'd subtract for running the generator) and 18.75 on the rear (of 22), leaving a bit of safety.

[Colorado Coach]

Thanks Skater. All good info here for this project and the next one, I’m sure.

At this point, I might just turn her over to a mechanic with print outs of everything I’ve learned from you guys on this thread. Until then, I’ll just be using your dead reckoning method.

Side note- just had our first kid camp out in the driveway last night. I can’t remember the last time they had so much fun or slept in that late. Looking forward to some real camping trips soon!


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