Fuel Sending Unit

[Henry Cloutier]

Hi everyone,

I'm hoping you all can point me in the right direction regarding the fuel sending unit in the 69Z. I jumped in to warm the engine today and the console fuel quantity gage pegged past full. I did fill the tank just before putting her in the garage last week so I thought the float may have just stuck so I rocked the rear of the car to no avail. Removed the gage cluster cover and tapped on the gage as well as manually moving the needle which moved freely back to empty. Turn the power on and the gage sweeps back to past full. I located the connector by the trunk lock cleaned the connector blades and reconnected which didn't help. I provided another ground to the harness side at which time the gage moved back to past empty. So now I'm researching new sender units and I see there are multiple models to choose from; different supply sizes of tubing some with return lines etc. Which one is correct for a 1969 Z28? I can't drop the tank here but I do have a garage I trust to do the work and they let me supply my own parts. I would like to have all parts in hand before scheduling them to perform the work.

Thank you!

Henry

[169INDY]

Sweeping PAST full scale is a sign of a Open i.e. greater than 90 ohms. (90 should read Full).

Disconnect at the trunk and perform these two checks first;

1) Temporary for a very short duration disconnect & Ground the lead that goes to the body harness forward, confirm Gage sweeps (Left-CCW)  fast towards and past empty. i.e. 0 ohms

2) Take an Ohm meter and read thru the brown wire pumper that goes towards the "PIN" on top of the fuel sender, I would anticipate it reads around 90ohms since you state you recently "filled" the tank. Ohm meter set up as, Lead (either) to chassis ground; Lead (Other) to brown connector that leads in-between body and top of tank to the Pin terminal on the top of the sender.

Report findings.

[z28z11]

Henry,

Here's an OEM NOS 6428845 on eBay currently; if you don't want to pay this much for one, there are a number of reproductions out there that will fit, but buyer beware - I've heard a lot of horror stories about cheap reproduction units not functioning well. Single 3/8" fuel line, no return line to answer your original questions about diameters and number of lines.

https://www.ebay.com/itm/NOS-68-69-Camaro-Big-Block-Fuel-Sending-Unit-3-8-Original-OEM-6428845-New-in-Box/303808456123?hash=item46bc6525bb:g:f24AAOSwLYBf1Tls

Assuming your unit doesn't survive out from the suggested check, years of corrosion/crud in gasoline take their toll. There are also companies that will rebuild your original sending units -

Regards,
Steve

[Henry Cloutier]

Hi you all,

So the first check findings are: Grounding the chassis lead at the trunk connector results in the gage sweeping CCW to below empty, also triggers the low fuel light.
Second check: checking ohms from the sender connector in the trunk to ground is open. Meter reads infinite.
 I searched as best I could for the ground wire connection on the tank but could not locate it. Course I'm a little older now and a little rounder so getting under the Z is impossible. I probably could back up on the floor ramps and get there. My understanding is the ground connection is near or on the passenger side tank strap?...

Indeed they are proud of the sender on ebay. I have concerns as well with aftermarket stuff especially given where most of it is made these days. I don't think I have the luxury of sending the original out if that's what turns out to be the culprit since this will most likely take place in a 3rd party shop bay.

Thanks for all your help with this!

Hank   

[z28z11]

If I can make a suggestion, send it to or contact Instrument Services, clockandguages.com, I consider them one of the best, if not the best gauge and instrument repair guys in the business. More than several mentions on this site, they won't be cheap but they'll do a OE quality job. They'll get my '68 tach to repair directly -

Regards,
Steve

[Henry Cloutier]

Thanks Steve,

I just found their website. I'll call them and see what they can do for me. Perhaps they can do some sort of exchange.

Best regards,


Hank

[169INDY]

Hi you all,

So the first check findings are: Grounding the chassis lead at the trunk connector results in the gage sweeping CCW to below empty, also triggers the low fuel light.
Second check: checking ohms from the sender connector in the trunk to ground is open. Meter reads infinite.
 I searched as best I could for the ground wire connection on the tank but could not locate it. Course I'm a little older now and a little rounder so getting under the Z is impossible. I probably could back up on the floor ramps and get there. My understanding is the ground connection is near or on the passenger side tank strap?...

Thanks for all your help with this!

Hank   

OK The First Check Validated the Performance of the Dash Gage & wiring back to connector. The second Check could indicate a OPEN in One of the following: a) Lead from Trunk body harness to the Pin on top of sender, b) Sender resistor is open, c) Ground lead open from Sender brazed ring to terminal grounded to body.

The next step would be to empty the tank, unstrap, disconnect rubber line/s and drop the tank and inspect the Pin terminal and then direct test of the sender.

Here is a photo of the positioning of the sender on a 69 tank for reference. 

[Kelley W King]

I think crappy gas and sitting up makes fuel senders a maintanance item these days. Both my 69,s units have been replaced. It used to be a boat thing.

[Henry Cloutier]

Thanks everyone for all the awesome information regarding the fuel issue! I've never been great at electrical problems, even the simple ones and you all have gotten me thru the troubleshooting and I know now where I need to get to affect repairs. The photo pretty much eliminated any thought of reaching up without dropping the tank especially since this car has a traverse muffler system. Of course I just tanked it last week so it's almost full other than the 20 miles I put on her the other day hoping to shake the float loose if it was hung. I agree on the gas issue, there is one station I found on this side of town that has no lead no ethanol 91 octane. For sure a long way from what the engine and fuel system was designed to be using.
I do believe the tank has been replaced as it is stainless so the sender may not be factory either. Maybe once the tank is down I can shim it somehow to get the filler a little lower in the access hole. This probably explains why I can barely get the fuel hose nozzle into the filler neck.

Thanks everyone!!

Hank 

[z28z11]

Henry,

The sender in Jim's pic is a Rochester unit, hence the vent return line. Scared me for split second - I thought it was yours.

Hopefully the issues are on the wiring side - even GM NOS OE units can be a problem, depends on when they were made when they obsoleted the part. I replaced one in my '97 Silverado twice to no avail - discovered the GM example was now made in China. Go figure -

Regards,
Steve

[169INDY]

IF I may Add some Fuel Sender Testing TIPS and Photos that might of some help in the Future: Typical AC DELCO current offering (*Made in China)
Photos: Box Label, Fuel Sender, Sender top / Pin terminal, Sender in tank resistor.

[Henry Cloutier]

Thanks guys,

I didn't notice the extra fuel line until you mentioned it Steve, shows what I currently know about these things. Last time I had a tank dropped was on my 73 Vega to replace the electric fuel pump! I matched Jim's second photo post and compared to the photos of the unit now heading my direction. I ordered from a company called 1aAuto. The sending unit inbound is built by TRQ. Most likely from China as most things are these days. Turns out this 1aAuto is located in Olathe KS about 3 hrs up the road from me. Reviews seem acceptable, part cost 54.95/free shipping and comes with the o ring and retaining ring. Since I'm going to have to have an outside service drop the tank I want to be armed with a replacement sender if it turns out it's not the ground or wire.

Best regards,

Hank

[Kelley W King]

Seems everytime I have a fuel tank problem it is full. Good thing about a 69 camaro it is easy to siphon out. Years ago our area had a ice storm that knocked out power for days with only a couple gas stations open. Both my 69,s were full. The old siphon hose saved the day.

[Henry Cloutier]

Interesting,

There must be a mechanical reason the senders fail once the tank is full. I had just tanked mine and drove home (about 4 miles) everything was working as I've come to know normal. Gas gauge never read all the way full, always showing about a needle width from full since I've owned the car. Showed just that as I parked her and sat for a few days before I started her up and the gauge pegged. I remember syphoning tanks, usually cause someone had run out of gas or the lawnmower needed it. We weren't sophisticated enough to own a real pump so very once in awhile one of us got a mouthful of gas. Yuck!

Hank   

[169INDY]

One Last area of concern is verifying the Sender Pin terminal connection on top of the sender & tank.
These can remotely or possibly be cause of the open circuit; due to, Vibration caused looseness, Failure of the female ring terminal to clinch the pin, or least possible a pinched broken conductor.

Photos