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'79 Eldorado Biarritz Fuel Pump/Sending Unit

Started by Caddy_Guy, May 26, 2020, 05:19:38 PM

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Caddy_Guy

Hello folks!

I'm the 3rd owner on my '79 Eldorado with the 350 EFI and I've run into a bit of an issue.

For the life of me, I cannot find a fuel sending unit for this year. I can find the fuel pumps quite easily.

My current situation is that my external fuel pump is seeping fuel, my internal one is non-functional, and the sending unit is reading full 100% of the time.

I had read somewhere that Bruce R. has some sort of external pump deletion that uses just an in-tank pump. I'm very interested in this situation and would love to get some assistance on it.

I work on all my own stuff, but working on a 40 year old car can be quite challenging sometimes!

Thanks for the help in advance!
-Dusty Brossart
*1979 Eldorado Biarritz
*1993 Sixty Special
*2010 DTS

79 Eldorado

Hi Dusty,
Welcome to the forum. I'm sure Bruce will answer if he sees your post. Considering your question it may have been better to post in the technical section. Unfortunately the technical section includes all years so occasionally a topic can be buried before "everyone".

The sending units are resistance based so if you have the tank down did you check the resistance of the sending unit at various float positions? I'm thinking that maybe you can isolate where the issue is because the issue might be after the sender. I know there have been several threads mentioning the rubber line deteriorating from the in-tank pump as well. Maybe you've already had it down and tested everything.

Nice car!

Scott

TMoore - NTCLC

Bringing this back up to the top -

I went out to start one of the 1979 Sevilles that I have not driven in a while, and had a no start situation.  Luckily, the first step at trouble-shooting was checking fuel pressure, and I discovered I was not getting fuel, despite hearing the chassis pump run.  Went under the car for further troubleshooting, and could hear both pumps engaging.  Removed supply line from the chassis pump, and blew air - going into the tank, but not bubbling in the gas.  This points directly at failure of the short rubber line on the fuel pump (third time I have had to replace it on this car).

If I am going to drop the tank, I also wanted to find out if there has been any luck with finding a high-pressure in-tank pump to get rid of the chassis pump (and, while I am at it, would like figure out what others are doing to get rid of that cumbersome fuel filter).

Let us know what the latest developments are -

Thanks

TJ Hopland

3 lines in how many years?  If its since 79 that isn't so bad. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

79 Eldorado

Quote from: TMoore - NTCLC on May 28, 2020, 06:59:59 PM
...This points directly at failure of the short rubber line on the fuel pump (third time I have had to replace it on this car).
Maybe it's obvious but it was not to me when I first looked for submersible fuel hose... there is a specific type needed for a submerged application. I initially thought I had the best normal hose Gates sells so I must be ok but that's not the case. They sell a specific version for in tank use. I wanted to just make certain others knew this.

Quote from: TMoore - NTCLC on May 28, 2020, 06:59:59 PM
If I am going to drop the tank, I also wanted to find out if there has been any luck with finding a high-pressure in-tank pump to get rid of the chassis pump (and, while I am at it, would like figure out what others are doing to get rid of that cumbersome fuel filter).....
I actually like the filter they used. I even considered using one like it for another car based on my experience with the Eldorado. I could still find something nearly identical sold by GM as new about 5 years ago. I didn't end-up using it because I realized they are very likely not rated for the pressure output of a normal modern in tank fuel pump. That's especially true if the regulator is located after the filter. The reason I like those is the element is easy to change (cup drops down without messing with the lines). I do know there are filter made by a company called system one which are similar shape to a frame mounted cylindrical pump so maybe using something like that where the external pump is would work with the higher pressure in-tank.

From having looked for a pump which would work in a short depth tank they aren't so easy to find once you start adding the space needed for mounting/connecting to the sender. I wasn't working on the Eldorado when I was looking but the tank I was working on was shorter depth than any aftermarket replacement was made to fit (I think they wanted a minimum of about 7 inches). I guess the Eldorado tank will also ideally need something very short. At the time I was looking I also came across the Holley hydromat. I didn't have any baffles in that tank so I needed something to avoid starving the pick-up. If you haven't seen any of the videos of it working they are pretty incredible.

Hopefully Bruce will pick-up on the thread and let us know exactly what he used. He may have found a high enough pressure pump but not so high that he had to replace the filter. He likely mentioned it in another thread. There's also a high probability that he documented it in his photobucket page so if you are searching and find a link to photobucket try there.

Scott

bcroe

Good information in the above posts.  My first thought is the dual
problems could be caused by a poor ground to the tank unit, check
it out.  Things are a little messy down there, the auto leveler
sense unit is also on the circuit. 

In my case I ended up rewiring that whole area with 2 grounds to
the front and rear.  My tank unit had sending unit issues I managed
to cure, and used the special submersible Gates hose to connect the
pump.  I put a high pressure pump in the tank and got rid of all the
stuff in the frame except an in line filter.  I am not giving DIY
instructions on that since any error can be dangerous.  The pump
is a Walbro 190, that 255 I think is oversized for a mild mannered
small block.  A little bailing wire makes sure the top of the pump
stays in position.  good luck, Bruce Roe