Fuel/Gas Gauge Problems & Questions

I just replaced my fuel pump in the 95 Riviera I picked up a few weeks ago. It was a snap, The only trouble I had was getting the old locking ring knocked loose, but it came off afer some patience and persuasion with a rubber mallet.

BTW, the ENTIRE pump and sender assembly is very affordable now. There is no reason to spend $400-500 on an entire unit from the dealer. . If you are already "in there" and pulling a 15+ year old pump just to fiddle with the sender, I'd do the preventative maintenance to replace the whole thing. I wouldn't be surprised if the pump itself is on borrowed time at this point.

At Rockauto the entire pump assembly for the 95 is only $200 for the Delphi or ACDelco unit. I believe it is the same part for later years.


Here is the FAQ for the fuel pump:

https://rivperformance.editboard.com/t8943-faq-fuel-pump-general-questions-compatibility-troubleshooting

If one has to replace the fuel pump, are there any aftermarket pumps besides the OEM stock pump that can be used? Ive heard Racetronics mentioned a few times?

Is that a drop in fit?

When I was researching the replacement of the pump for my 95, I read somewhere that the OEM pump was already more than sufficient for the pressure and flow we would need for this engine's reasonably conceivable HP output (within reason).

The ACDelco and Delphi (OEM supplier) units are reliable and relatively inexpensive, and a drop in direct fit (other than on older models having to update the electrical connector).

So I went with the Delphi which seemed to actually have slightly better feedback on other 3800 forums.

I played with outboard high-perf fuel pumps for a while on motorcycles, and in the end found the OEM solution to really be best unless your fuel pressure/flow needs outstripped what the OEM pump could provide. And usually the OEM pump was sufficient for quite a bit more HP than stock. Fiddling with extra home-made fittings, etc in the end just seemed like high risk when dealng with fuel versus a drop-in fit with OEM. I don't like modifying fuel delivery systems any more than I have to, especially if a daily driver. A weekend racer, yeah, daily driver... not so much


But YMMV of course. For reliability and fit, I went with OEM.

Al

al_roethlisberger wrote:

The ACDelco and Delphi (OEM supplier) units are reliable and relatively inexpensive, and a drop in direct fit (other than on older models having to update the electrical connector)

Good note. Anything older than like 2007 gets updated. GM changed their Fuel Pump connectors across the board to a 4-wire flat. All Delco kits come with a new pigtail and 4 shrink style butt connectors. I had to re-wire mine in the winter when my pump took a poo.

Ive driven 107 miles highway today, and my gauge hasnt moved much. From tge full position. Is this common? Is it broken lol

Mine stays on F for the first 50-75 miles on the highway.

( ----- > Moving thread from Showroom)

Right. Fill it up, and it stays on Full for awhile. Once it gets to 1/2 tank, it seems plummet towards E lol. I think that's just a GM thing. It seems like every one I've owned does the same thing.

Lol good point. Right now its a hundred and fifty four miles and I'm not even on three quarters of a tank yet and its all highway driving I'm heading to New Jersey

mines like that or was till my maf went blah. gotta fix that asap!

highwaywarrior wrote:

Ive driven 107 miles highway today, and my gauge hasnt moved much. From tge full position. Is this common? Is it broken lol

I think it's a quirk of the low-bidder GM fuel level sender. Only fix I know is to rip it off the pump and install a different unit. You can check with a meter to see if it is linear and you can check the float arm n the pump assembly to see that the float can move the whole range.

Hi guys, my gas meter acts weird, if I put in 6 gallons on an empty tank it goes up to the half way mark, anyone else had this deal? I know our tanks have like 19 gallons so this isn't right, it's not a big concern I'm just wondering.

I noticed its like that with every car I have ever owned. half tank actually means quarter tank. Thats why it drops like a rock after half tank.

Ok that's good I guess lol, I'm glad it's not an issue. Thanks Todd!

I can typically drive about 140miles before my needle move at all. Same is typical of our century, lesabre, and the 91 reatta. Strangely, the 88 is dead accurate

Interesting, I guess buick just wants us to be happy thinking we got a lot of gas in our cars lol

This is all theoretical, but I've seen the sender and the tank, and I think the reason for the non-linear gauge reading is likely the shape of the tank itself. The tank is tapered, wider at the top than at the bottom, but the float that commands the fuel gauge is a linear sender from what I can tell.

Actually, because of the shape of the float arm and the float itself, the first 1/4 of float drop (from "F" to 3/4) requires the smallest change in fuel level. This might seem like it's to compensate for the tank being wider at the top, but we know the gauge does not move for the first 50-100 miles when full. This indicates the float is submerged and does not report. So considering these things, it would seem the float is still close to being a linear sender, at least mechanically speaking.

Considering the shape of the tank, for a given amount of float movement when the tank is near full, the car must consume more fuel then for the same float movement when the tank is near empty. For example, say the sending unit has 8" of total float travel from "F" to "E". Being linear, each 2" float movement represents 1/4 tank on the gauge. The first 2" from full is a larger volume of fuel (maybe 6 gals). The last 2" is the smallest volume of fuel (maybe 3 gals). These are just guesses, but if you look at the shape of the fuel tank you can see that there is considerably less fuel capacity in the bottom half vs. the top half.

GM used the exact same tank for AURORA, BONNEVILLE, DEVILLE, LESABRE, PARK AVENUE, and SEVILLE, so if they used the same sender and gauge markings, the metering should be similar with all these cars. Why did they shape the tank this way? Maybe to attenuate fuel sloshing and cut-outs at very low fuel levels. I've run my Riviera's tank dry before, and once I remember taking turns extra hard on an empty tank in order to conserve fuel. Never did the engine cut out. At the first signs of running out of gas in a Riv, you are out of gas. There is no grace period!

Mine float is in need of replacement. half a tank is close to empty now. the light used to come on at 1/8 and now sometimes comes on at 1/4 and on occasion at 1/2. after filling to full i can still add 5-8 gallons.