Fuel tanks and pumps (questions for the '82 guys)

[MaineShark]

Will an '82 fuel tank fit properly in a '79? I know there were some changes to the rear end after '79, so I'm not sure if that changes the tank mounting, or if the body changes have any effect on the filler neck...

Also, what is the flow rate of the stock electric fuel pump? Are there any Delco or aftermarket replacement pumps that will drop in place, and offer higher flow? (I'd like to stick with in-tank, for noise reasons)

Thanks,
Joe

 

[82X-FireVette]

From '78 to '82, the cars are pretty much the same, so I would assume the fuel cells will fit. The tanks were lined with a rubber bladder at first and then changed to a polyurethane liner later. The rubber bladder starts to collapse with age. The fuel pump in the '82 is marginal with about 9-10 psi. The '84 fuel pump is much better and can be fitted to the '82 bracket with simple modifications.

 

[Ken73]

Actually the '82 pump is the same as the '84 pump. The '85 pump will offer more flow.

PSI is dependant on the regulator, not the pump itself.

The tank itself should fit fine though.

 

[MaineShark]

Thanks for the input, guys. Any ideas of available flow rates?

Joe

 

[vettenick]

Don't worry about flow rates unless your engine is highly modified. Don't use the '85 pump on a cross fire set up. TBI systems operate at 9-12 psi. The '85 is tuned port which operates at 35 psi. You will probably overpower the regulator,causing an over rich condition. In other words the regulator may not be able to dump the excess fuel fast enough, and that will result in more fuel into the motor. The computer is programmed based on the lower pressure. Thus the actual time the injector is on is set up based on that pressure. If you change the pressure (almost triple!) the computer will be confused. It will base its strategy on the input from its sensors. It will think everything is OK, but when the oxygen sensor says it's running rich because of the extra fuel, now the computer will try to lean it out. This will cause a driveability problem for you.
Your stock TBI pump can supply more than enough fuel.

 

[vettenick]

By the way...I'm assuming that you are running a Crossfire set up.
If you're running a carb, then neither pump will work. Carb systems operate at 5-7 psi.

 

[Ken73]

Don't worry about flow rates unless your engine is highly modified. Don't use the '85 pump on a cross fire set up. TBI systems operate at 9-12 psi. The '85 is tuned port which operates at 35 psi. You will probably overpower the regulator,causing an over rich condition. In other words the regulator may not be able to dump the excess fuel fast enough, and that will result in more fuel into the motor. The computer is programmed based on the lower pressure. Thus the actual time the injector is on is set up based on that pressure. If you change the pressure (almost triple!) the computer will be confused. It will base its strategy on the input from its sensors. It will think everything is OK, but when the oxygen sensor says it's running rich because of the extra fuel, now the computer will try to lean it out. This will cause a driveability problem for you.
Your stock TBI pump can supply more than enough fuel.

Bzzt. Wrong.

Flow does not translate into pressure. I've got an '85 pump in my '82 and it still runs at 10PSI. It doesn't make it run rich - the excess fuel just goes through the regulator.

The '82-'84 pump doesn't flow worth a crap.

 

[MaineShark]

I don't actually plan on connecting any injectors to the pump, at all. I want to use the low-pressure pump to keep a surge tank full, so a high-pressure pump can draw off that to feed conventional injectors.

As far as flow rate, my future plans probably go up over 500 hp, so...

Joe

 

[vettenick]

For the record the TBI pump flows at 34 gph. The TPI pump flows 42 gph. The TPI has a dead head pressure of 70 psi as opposed to 25psi for the TBI pump.
Ken, I'll bet if you hooked up a scan tool to your car, you'll see that the block learn and Integrator functions are off their normal readings.
Have you checked? What are the readings?

 

[vettenick]

Again, Mainshark, the stock pump is more than enough. If your motor is using more than 30 gallons/hour, you better be close to a gas station...only kidding!
Fuel systems and computers must be matched. If you chage one and not the other, you will have a problem.
Good luck!

 

[vettenick]

Ken, if you take a pump and place it in a system that flows 25% less, that puts a load on the pump...which translates into a shortened pump life. If flow and pressure didn't matter, why do you think GM has so many different pumps?

 

[Ken73]

For the record the TBI pump flows at 34 gph. The TPI pump flows 42 gph. The TPI has a dead head pressure of 70 psi as opposed to 25psi for the TBI pump.
Ken, I'll bet if you hooked up a scan tool to your car, you'll see that the block learn and Integrator functions are off their normal readings.
Have you checked? What are the readings?

I most certainly have. Check www.winaldl.webhop.net - I developed this tool for exactly this reason. I got pretty close to 128 before and after the install.

Biggest problem with the '82-'84 pump is it doesn't flow enough at higher RPM/loads, hence the upgrade to the '85 pump. Any upgrades on an '82 or '84 really necessitate an '85 pump.

 

[vettenick]

Ken, if your block learn waas at 128 before the change, doesn't that indicate that the ECM was able to handle the fuel load?
If the # was 135 or higher, I would agree that your fuel supply was not sufficient . Just curious.

 

[Twin_Turbo]

nick, pressure is created by forcing flow through a restriction. Max pressure is measured when forcing volume into a dead restriction.

The 85 pump will flow more but the regulator controls pressure, if the regulator opens more, more fuel will return to the tank. The only way the larger capacity pump can increase pressure in the system above what the regulator is set at is when there's a restrivtion in the system, being a too small return line, a regulator that does not flow enough.... and so on.

As for it ebing hard on pump life, that's BS! The only way it can be hard on the pump is when the pump hsa to operate at max. capacity pressurizing a system to about the full potential. Nothing easier on a pump that being capable of easily flowing fuel through the system at a low pressure setting. the pump won't get hot from running hard and the large flow od duel actually cools it.

How does the TBI system flow 25% less? The systems both consume about equal amoutns of fuel, engine size the same, af ratio same, power output about the same. Where's the 25% in this story?

 

[vettenick]

Twin Turbo, my response was: "The tbi pump flows 25% less, not the system". Which brings me back to my original statement: "Why add a pump that has the capability to flow 25% more when the engine won't use it?" In the application that was mentioned, adding the PFI pump won't make any difference.

 

[Twin_Turbo]

The answer is very simple. The TBI pump is designed to be able to pressurize the system to about 15 psi max at WOT (max fuel consumption). It is just enough for a stock system.
However, with time as the pump wears that will drop and most pumps are now worn to the point that they will never be able to deliver that at WOT, resulting in WOT performance problems and also when mashing the throttle off idle or low rpm. You can replace it with a TBI pump and it will run fine. However, when you modify your system and go with larger injectors, a higher fuel pressure (for more fuel) or a VAFPR the pump will not be able to deliver. The later model pump is an easy and quick solution. The pump will be able to supply more than enough fuel for the system.

It has been tested and tried, numerous people made the swap and almost all noticed a great improvement in drivability and throttle response. some did not notice any or just a little improvement, those probably had pretty good stock pumps or the pump had been replaced recently. '

I think I was one of the first to install that pump (I did it over 5 years ago when I still ran the CFI system) and have tested it thoroughly and the pump was one of the best improvments I ever made. The ability to run a higher fuel pressure and custom tune the ECU for fuel delivery (pulsewidth) or running a VAFPR can seriously decrease CFI related problems like fuel puddling and stumble.

 

[Ken73]

Ken, if your block learn waas at 128 before the change, doesn't that indicate that the ECM was able to handle the fuel load?
If the # was 135 or higher, I would agree that your fuel supply was not sufficient . Just curious.

No, if it was 128 before and after, it means that it didn't have to compensate at all (i.e. the pump did not cause a rich condition, which would result in a BLM of 127 or less.)

A BLM of 135 would mean it was running lean, which a better fuel pump would most likely help (although if the engine has been modified and the fuel tables were no longer accurate, raising fuel pressure or reprogramming the ECM would be necessary.)

 

[vettenick]

I agree, but getting back to the original problem... the engine in question is stock. So...would a different pump make a difference?
No. So why spend the money?
This was a good subject! lot of different opinions!

 

[Twin_Turbo]

It's very simple, replace it because the pump wears and won't be able to supply enough fuel AT OWt (and therefore won't be able to deliver theglow to achieve necessary pressure)

Worn fuel pumps are the most common cause for WOT and responsiveness problems. The stock pump is designed to jsut be able to deliver the 13PSI at wot. ANy wear or a demand for more fuel (mods) will make the pump a limiting factor.

 

[Ken73]

Why spend the money on a stock pump that costs about the same, and will wear to a point where it becomes ineffective sooner than a later model pump? It doesn't make any sense to me NOT to upgrade. It's not like it's a complex install anyway.