Many of you know the old Gray Ghost Custom Cruiser wagon was originally a Diesel car and got converted to gas early in its life. When the crank failed. the owner didn't want the car any more so the Charlotte Zone service manager bought it and stuffed a gas 1975 350 in it. That's a story in its own right but for another day.

The car has had its diesel fuel tank and sender all these years and ran with no problems till a couple years ago when it became difficult to start after sitting and would vapor lock in hot weather. Switching it to non-ethanol fuel solved that issue for a while. Then early this year, it ran out of gas three times with the gage showing 1/4 tank. Put a gallon of gas in, it started right up and driving straight to the gas pump could never put more than 17 gallons in it- and it has a 22 gallon tank, so I figured gage was accurate.

After the 3d time I was getting antsy. I took it to a fellow who had correctly diagnosed what was wrong with my 93 F150 (suffice to say two mechanics had said the trans was failing, and this guy found the catalytic converter about 90% plugged), thinking maybe a baffle in the tank had come loose and wedged against the pickup tube.

After a couple weeks he called me to come look. The tank was still in great shape, but the filter sock was completely crudded up. A new gas sending unit solved the problem but why, with a plugged sock, would it run until it reached 1/4 tank?

The shop book told the story. The engineers designed the Diesel tank sock to do exactly what it was doing. Apparently, the recommendation was to run Diesel 1 in winter to avoid gelling and paraffin buildup on the sock. But in case a Diesel owner didn't pay attention (imagine that!) and ran Diesel 2 in winter, if the sock plugged, there was a check valve engineered into the sock. Fuel pump suction would open the check valve and keep the engine running UNTIL... the fuel level reached 1/4 tank, at which point the check valve would uncover, the fuel pump lost suction, and you were then out of fuel.

So, after 35 years I don't think the sock owed me anything, and I learned something in the process.

 

That's interesting. Failure methods are always fun to learn how they were thought up.

 

Post a picture of the sock, in a frame, hanging in your shop.

 

Another nugget of information that may help someone else some time, and an interesting story in its own right.
Thanks for sharing.

Roger.

 

I have swapped a lot of diesels to gas but unaware of that info, The most important thing I remember was to remove the fuel gauge cover and cover the words DIESEL FUEL ONLY, One of the first cars i changed over a customer let someone use his car and it got filled with DIESEL, from that point on the words were covered.

Johnny

 

I did the gas conversion on my 81 Custom Cruiser and fortunately never had an issue and that was basically one of my winter drivers... Unfortunately the vehicle developed a lot of floor rust issues and I removed the drive train and salvaged all the parts I thought would be usable (such as fiberglass tailgate etc.) in the future for other projects...

 

I think you have a good mechanic. I wonder how many would have figured this out.

 

So, what's the story? Inquiring minds need to know.

Glad you figured out the fuel starvation problem.

 

I have a buddy that runs a small repair shop in a small town. I hang out there a few hours every week with my eyes and ears open for the exact purpose of learning their troubleshooting revelations like the one posted by the OP. Great stuff !!!

 

This guy is good at troubleshooting and will tackle things other shops don't want to fool with. He's a transmission guy first and foremost (that's why I took the truck to him) but haven't found anything yet he can't figure out and fix. He has rebuilt a couple of Slim Jims so I'm not worried if one of mine quits. The water separator on the Diesel sender threw him though- no one in the shop had ever seen one and kept asking if it had a low fuel light.

The wagon's gas engine transplant was a warranty job. The same dealership that the wagon came from sold a 75 Delta 88 that had a casting flaw in the block-a hairline crack at the fuel pump mount that seeped just enough oil to drive its new owner nuts. He raised enough racket that Olds replaced the engine under warranty with about 2k miles on it. The Zone took it back and after a year or so the ZSM got it, brazed the crack, stopped the leak and it eventually went in the Gray Ghost.

It developed a dead cylinder and rather than get into a top end rebuild (coulda been a lifter, coulda been a bridge, coulda been a flat cam lobe, coulda coulda...) I yanked it and put a 1974 350 out of a Vista Cruiser in it. The VC had 108k showing and had a great drivetrain and a perfect interior, but it was rotted halfway up the body. Put a timing set in it and cleaned the valley and oil pan and it currently has about 230k and runs great.