[wfbarto]

I recently dropped the gas tank on my 66 Bonne vert project and pulled out the gas tank sending unit. It was acting erratic the last time the car was in use, so I hooked a multimeter up to measure the resistance through the sending unit as you raise and lower the float unit. On the side of the unit is stamped "90 Ohms". Well...sure enough....the spread was about 90 ohms from a low of 20 up to 110 ohms at tank full. The problem seemed to be that as I raised and lowered the unit, the resistance read out was not linear but seemed to jump around significantly until you held the unit very still in one position and then it would stabilize. My question....is this normal or indicative of a bad unit that needs replacing? The read out would jump around if I put the slightest side pressure on the float so that it pressed against the pivot point of where the float connecting into the sending unit. Second question, if it is bad, does anyone know where you can buy replacement units? Thanks!

P.S. I posted this over in the Electrical Issues tech section also.

[Deadhead]

I have seen non-AC units being reproduced & sold on E-Bay. I am not positive, but I think it is 1-A Auto that is selling them. Whoever it was, I asked about AC equipped cars & they were not doing those. Don't know if you could swap out the electronics or not if you have an AC car. Price was reasonable.

I have done the same as you with a meter, & I think the answer is that the coil gets worn down to where the contact is insufficient to give an accurate reading.

[stevep]

If you can't find one, a guy in CA will rebuild yours for about $80 bucks. His name is Jack Marcheski and he advertises in Hemmings under "sevices offered".He will get it and rebuild it in the same day and it is in priority mail the next day. He has done a few for me so far.

If 1-A Auto has them, do not hesitate to buy from them. They are a good company.

[mike nixon]

you can also try gently bending the contact of the swingarm side so it rides tighter on the coil portion. don't move it much, just enough to tighten it up.

mike

[64catdroptop]

The problem you're seeing is a cracked resistor. As the contact moves over the resistor where there are cracks, you get a momentary "open" reading, giving you the eractic needle movement on you multi meter. Are you using an analog or digital meter?

Matt can probably give a better idea on the sending unit function.

-r-

[wfbarto]

Originally Posted by 64catdroptop

The problem you're seeing is a cracked resistor. As the contact moves over the resistor where there are cracks, you get a momentary "open" reading, giving you the eractic needle movement on you multi meter. Are you using an analog or digital meter?

Matt can probably give a better idea on the sending unit function.

-r-

Yes....that is how it is acting (I was using a digital meter). Is this something that the novice can fix? I was looking at the metal enclosure that the resistor is in and it looks like it has tabs so that one can open it up. Or is this better left to a "pro" and should I find a guy like the one Steve described in CA and send it to him to repair for $80?

I checked on 1A-Auto and they do not have one shown on their website or in their e-bay store. I sent them a question asking if they have one or can get one. There is, however, one listed on e-bay currently by Northcoast Musclecar

The unit shown at the link above is stated as being a replacement for 65-66 Pontiac Bonneville, Catalina and Star Chief but the picture does not match the unit that was taken out of my car. Could be just a stock photo that they are using so I sent them a question about it. No reply yet....are these guys okay...anybody used them?

Deadhead...are you serious or pulling my leg.....there are different sending units for AC vs. Non-AC cars? Why would that be? This one was pulled off of a Non-AC car which when re-built will remain Non-AC.

Thanks for all the help!

[mike nixon]

a/c cars had a return line on a lot of models.

mike

[Deadhead]

Originally Posted by wfbarto

Yes....that is how it is acting (I was using a digital meter). Is this something that the novice can fix? I was looking at the metal enclosure that the resistor is in and it looks like it has tabs so that one can open it up. Or is this better left to a "pro" and should I find a guy like the one Steve described in CA and send it to him to repair for $80?

I checked on 1A-Auto and they do not have one shown on their website or in their e-bay store. I sent them a question asking if they have one or can get one. There is, however, one listed on e-bay currently by Northcoast Musclecar

The unit shown at the link above is stated as being a replacement for 65-66 Pontiac Bonneville, Catalina and Star Chief but the picture does not match the unit that was taken out of my car. Could be just a stock photo that they are using so I sent them a question about it. No reply yet....are these guys okay...anybody used them?

Deadhead...are you serious or pulling my leg.....there are different sending units for AC vs. Non-AC cars? Why would that be? This one was pulled off of a Non-AC car which when re-built will remain Non-AC.

Thanks for all the help!

What Mike said. The big cars had a second tube on there for the return. It really does work. Sometimes I can hear gas flowing back into the tank from the return. I am surprised that they did not just do this universally since AC cars have greater cooling capacity, & I have not often been running the AC when I hear the return functioning. Seems like the non-AC would run typically hotter w. 4 blade fan, no shroud etc.

For $80 I think it would be better to have an old one rebuilt. Especially with that kind of fast turn-around and for something immersed in gasoline. Repro parts are just generally sketchy, and at least half the time I have had to bag them for wrong application or quality that is bad enough to make them unusable. You often have to modify them to make them work. Major time wasting for the $. I should not complain so much, but when you have a perfectly good example of what you are trying to fabricate in front of you it is inexcusable.

[64catdroptop]

"I should not complain so much, but when you have a perfectly good example of what you are trying to fabricate in front of you it is inexcusable."

Deadhead, tell that to the people in Taiwan.

You should see some of the sheet metal I have to work......... I feel your pain every day!
-r-

[mike nixon]

[QUOTE=64catdroptopDeadhead, tell that to the people in Taiwan.

You should see some of the sheet metal I have to work......... I feel your pain every day!
-r-[/QUOTE]

i hear you on the sheetmetal, there've been day where i'd have been better off starting of with flat steel.

quality doesn't matter in china/ taiwan, the 2:00 a day does. really pisses me off when i buy something and it doesn't fit.

mike

[wfbarto]

Originally Posted by Deadhead

What Mike said. The big cars had a second tube on there for the return. It really does work. Sometimes I can hear gas flowing back into the tank from the return. I am surprised that they did not just do this universally since AC cars have greater cooling capacity, & I have not often been running the AC when I hear the return functioning. Seems like the non-AC would run typically hotter w. 4 blade fan, no shroud etc.

For $80 I think it would be better to have an old one rebuilt. Especially with that kind of fast turn-around and for something immersed in gasoline. Repro parts are just generally sketchy, and at least half the time I have had to bag them for wrong application or quality that is bad enough to make them unusable. You often have to modify them to make them work. Major time wasting for the $. I should not complain so much, but when you have a perfectly good example of what you are trying to fabricate in front of you it is inexcusable.

The tank on my vert (non AC car) has no return line. I will have to crawl under my 4 dr hdtp to see if it has one since it is an AC car....have not been under there yet as I have only had it a few months. I do not think I remember seeing a return line from under the hood though so I will have to take a look specifically for that.

I will probably just send this off to the guy in CA for repair. FHummel in the Elec Issues section was describing how he has opened them up before and cleaned them to work better but it sounds like a touchy job to me. I will put his reply in quotes below so you all can see it.

I also had another person recommend to me ...John Wolf Enterprises, of Ohio, who does this kind of work. The contact number for them is 440-942-0083. Anybody heard of them or the quality of their work? This recommendation was sent to me by Quanta Products at www.gastanks.com One other option is at Rockauto.com where they list gas tank sending units for sale. Here is the info they have:

1966 PONTIAC BONNEVILLE 6.4L 389cid V8 : Fuel/Air : Fuel Tank Sending Unit ItemPriceCoreTotalSPECTRA PREMIUM Part # FG88A
Sending Unit; Exc. Station Wagon; 5/16" Outlethttp://www.rockauto.com/catalog/geti...unit/fg88a.jpg
$40.89$0.00$40.89
SPECTRA PREMIUM Part # FG88B
Sending Unit; Exc. Station Wagon; 3/8" Outlethttp://www.rockauto.com/catalog/geti...unit/fg88b.jpg
$48.79$0.00$48.79

The price is sure nice.....however, the pictures provided do not look exactly like my unit!

Here is the message that FHummel posted in the Elec. Issues section. What is a crocus cloth that he references?

Yes, I have opened a unit or two. The resisitor (a rheostat configuration) is wire-wound and the moving arm is a lightly spring-loaded brass contact. It may be possible to open the unit and clean up the brass contact to give a steadier reading, but you cannot get rid of the worn spots on the wire portion - it is closely wrapped and quite small in diameter and should be treated very carefully or it will break and it can't be fixed, only replaced. The wire (normally round when new) will be worn flat in certain areas (as mentioned by someone else - where the gas level has been kept most of the time). As the car is driven, the gas 'sloshes' around and the float jumps up and down, or 'oscillates', thereby wearing the contact and the wire. The more miles the car has, the more wear there will be. Corrosion plays a part as well, since the contact and wire will oxidize due to moisture in the tank. Therefore my original suggestion that you may be able to clean up the unit and get more stabile readings. Just go lightly using a fine abrasive such as crocus cloth or very fine wet/dry sand paper used for paint finishing, 600 grit or finer. Flush any residue off afterwards. DO NOT USE EMERY CLOTH!!
Good luck, Frank Hummel, Jr.

[mike nixon]

crocus cloth is a polishing cloth used in cleaning electronic parts. napa or carquest will carry it.

mike

[Deadhead]

Rockauto is where I saw that one. That is the price etc. Tempted to order one just to see if it would fit the tank. Since I don't need it it would probably work.

You don't have to crawl under the car if it still has the filter on it. You can see the return line on the filter or going up to it. Might save you a slither.

I took a sending unit I have apart & saw the same as posted above. You can see where it is worn flat. I figured it would have to be rewrapped to work right, & the wire is finer than thread. Not something to mess with IMO.

[Fat Cat]

Not to try and hijack this thread, but I'm curious to know what people have done to modify these sending units to accept 3/8" or 1/2" sending and return lines, if anything at all. I will be needing to do this on my car soon and would like some input.

-Steve

[mike nixon]

Originally Posted by Fat Cat

Not to try and hijack this thread, but I'm curious to know what people have done to modify these sending units to accept 3/8" or 1/2" sending and return lines, if anything at all. I will be needing to do this on my car soon and would like some input.

-Steve

i've drilled out the suction line,ran the larger line thru the hole and soldered it in. depending on how the oem sender is fastened i've either clamped,soldered or tack welded the sender to the new tube. if the sender's welded to the original feed line i usually leave a section of the line attached with enough on either end to use as a fastening point to the new line. i prefer soldering as it doesn't have as much heat involved, there's less chance of damage to the electronics, and it permanently attaches to old to the new. just be sure your mounting height is the same position as the original.

mike

[Fat Cat]

Thanks Mike. That doesn't sound like it'll be too hard. Soldering everything back together sounds like the way to go then, and it holds up ok? I've done plenty of soldering on electronics, but never on any piping or other metals. What do you recommend doing about the sock filter on the end of the pickup? Can new ones be had anywhere?

About fuel line size... what is your recommendation? I've got a 560hp 474 running an 850dp and a blue Holley electric pump. Holley says 3/8" is all that's needed yet I've done plenty of searching on the boards and everyone seems to think 3/8 is a waste and 1/2 is the way to go. I honestly don't have any plans in the near future of any big motor upgrades so it's safe to say this is what I'll be running for quite some time.

Thanks.

Steve

[mike nixon]

socks are available at any good parts store in various sizes / configurations.

if you can fit 1/2 in it do it and then neck it down to 3/8, this way you can upgrade later without much hassle.

soldering hasn't failed me when it's done properly [good prep work].

mike

[Fat Cat]

Sounds good. I'll let you know what happens.

[DARKITEC]

Posted a response in thread http://forums.maxperformanceinc.com/...d.php?t=590691 Mine was irratic as well but it was the float sticking inside the canister, there was a calcified rust build up on the exterior of the float and on the interior of the canister. Once I had removed that gunk, it seems to be working well. Top of the tank had some rusted pin holes, that was allowing moisture into the tank.

As for the return line, mine originates at the fuel pump wouldn't it be easy to verify if the car has one at the fuel pump without crawling under the car?