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Gas Tanks, Fuel Pumps and Fuel Starvation ?s
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TOPIC: Gas Tanks, Fuel Pumps and Fuel Starvation ?s

Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45497

Last year, I rented Jim Pantas' SE30 Pink Panther at Sebring. I do not recall what year the car was. I would fill the tank to the top, and about halfway through a 30 minute session, the car would sputter for just a second after I made a hard turn. I think it was right-hand turns that it didn't like. As the time got later in the session, the sputter got worse and longer. I believe Pantas said the problem was it had some kind of dual fuel pump system from the factory that didn't work well, or maybe it needed the dual pump system and it only had the single pump system, I don't really recall. What I do recall is that he said the car needed a tank change.

Am I going to have issues with the tank and pump system in my 87 325is? Can you run a 1987 325is hard for an hour without fuel starvation issues?

Thanks in advance.

-Scott
2010 NASA National Champion
2009 NASA National Champion
2008 NASA National Champion

Re:Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45499

  • Ranger
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You're just going to have to give it a go and see what happens. Some cars have the problem, others not. Seems to be a number of causes for similar symptoms, so those that fixed it often did it in different ways. Each track has a different hiccup point for my '87. Roebling is the worst for me where I start hiccuping at ~1/2 tank, which is a bit shy of an hour. The PO replaced everything but the tank and vent lines.
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Re:Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45501

I can run my '87 down to almost empty now. I replaced the tank, both pumps, the filter, damper, and crossover. No starvation issues at Watkins Glen, which I was getting before coming out of the esses.

Re:Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45509

  • Patton
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Got 3 '87 cars. One runs good, the other two cut out at half tank.

Set the car up, weight wise, to where you fill up to the brim to race. The fuel weight is where you want to have weight, right?

Problem solved.

RP

Re:Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45511

  • Steve D
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Patton wrote:
The fuel weight is where you want to have weight, right?

It is the ideal location, but it sloshes around more than I like my ballast to...
Steve DeVinney
Spec E30 #410 (sold)
Atlanta, Georgia
NASA Southeast Spec E30 Champion - 2011
NASA Southeast Spec Miata Champion - 2012
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Re:Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45515

  • jlevie
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A weak link in the early 55L tank is the cross over tube between the tank saddles. If there is rust in the tank (highly likely for an original tank) it can settle out in the cross over tube and restrict flow. I've seen them so plugged up that you can't clear the tube with a blow gun until you rod out the tube with a spring wire. Fuel will seep through the clog and eventually equalize the fuel levels, but you need fast response on the track.

The other problem that rust causes as the tank runs down, which affects the early and late tanks, is that sediment on the bottom of the tank gets stirred up and clogs the pump inlet screen. The sediment will fall off once the pump isn't running and everything is fine until the situation reoccurs. The less fuel there is in the tank the more sloshing and stirring occurs. Rust is also highly abrasive and will wear the pump(s) and reduce their effectiveness.

A weak or failed transfer pump in an early tank will also cause problems as the tank gets to half full or less.

The weak link in a late model 63L tank is the internal siphon that lifts fuel over the saddle. It works fine as long as there is plenty of fuel returning from the engine bay. But if the pump isn't delivering full volume, the filter is restricting flow, or the return line is obstructed the engine can suffer starvation in right hand turns with a low tank.

The fix for any/all of this is to make sure that you don't have a rusty tank, that the pump(s) are operating within spec (see the Bentley for the test suite), that the fuel filter is clean, and that the return on a late take isn't obstructed.
Jim Levie, #38
MidSouth Spec E30 Series Director

Re:Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45868

  • swooper
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jlevie wrote:
A weak link in the early 55L tank is the cross over tube between the tank saddles. If there is rust in the tank (highly likely for an original tank) it can settle out in the cross over tube and restrict flow. I've seen them so plugged up that you can't clear the tube with a blow gun until you rod out the tube with a spring wire. Fuel will seep through the clog and eventually equalize the fuel levels, but you need fast response on the track.

The other problem that rust causes as the tank runs down, which affects the early and late tanks, is that sediment on the bottom of the tank gets stirred up and clogs the pump inlet screen. The sediment will fall off once the pump isn't running and everything is fine until the situation reoccurs. The less fuel there is in the tank the more sloshing and stirring occurs. Rust is also highly abrasive and will wear the pump(s) and reduce their effectiveness.

A weak or failed transfer pump in an early tank will also cause problems as the tank gets to half full or less.

The weak link in a late model 63L tank is the internal siphon that lifts fuel over the saddle. It works fine as long as there is plenty of fuel returning from the engine bay. But if the pump isn't delivering full volume, the filter is restricting flow, or the return line is obstructed the engine can suffer starvation in right hand turns with a low tank.

The fix for any/all of this is to make sure that you don't have a rusty tank, that the pump(s) are operating within spec (see the Bentley for the test suite), that the fuel filter is clean, and that the return on a late take isn't obstructed.


Just encountered fuel starvation issues for the first time today at Summit Point on the Shenandoah Circuit. Can anyone tell me which cars had the early 55L tank and which ones have the late 63L tank? Also, how do you check to see if the the return is obstructed? Thanks.

Re:Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45870

  • Ranger
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I think the only ambiguity is the '88. Otherwise it's early model and late model. RealOEM can probably get it down more specific.

To see if return or crossover is obstructed, remove them and blow air thru.
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Re:Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45881

  • jlevie
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Cars built from 9/87 on have the 63L tank.
Jim Levie, #38
MidSouth Spec E30 Series Director

Re:Gas Tanks, Fuel Pumps and Fuel Starvation ?s 4 years, 5 months ago #45927

  • ilateapex
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jlevie wrote:
Cars built from 9/87 on have the 63L tank.


My 8/87 has the big tank (I think). No crossover at the bottom and one in tank fuel pump.

Michael
Michael Osborne #36
Great Lakes Region Spec E30 Series Director
Ashland, KY
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