Fuel Starvation

#1

In my '86 with a transplanted i motor, I’ve got fuel starvation when exiting a hard right hander. I believe this was discussed in an earlier thread, but any ideas?

#2

I had the same issue with my '87. What I heard was that if you just converted this car from the street, you need to replace the internal pump. our version of the car has two pumps. I experienced the starvation prob at my first outing. Before the last event, I replaced both pumps, the regulator, the damper and fuel filter. No starving at all. Also, got the bonus discovery of finding out that someone jacked on the tank and broke my in-tank pump. When I drove it on the street a couple times after I bought it, I didn’t experience it, only at the track.

#3

There are a couple of things that can result in fuel starvation only apparent on the track. Obviously, at the top of the list would be a failed or marginal in-tank transfer pump. But that only applies to early production cars. Someone else will know the when the design changed to a single in-tank pump, but I want to say that it happened in late 88 or early 89.

Another cause of fuel starvation on the track is a rusted tank. In extreme cases the transfer tube between the two saddle halves may be plugged. That can cause starvation in right hand turns since the fuel will slosh to the left of the tank and can’t get back. And a heavily rusted tank with lots of sediment in the bottom can experience starvation at high rpm only after the car has been thrown around the track a bit. The sediment gets stirred up, collects on the inlet screen and …

The fix for a rusted tank is either a new tank, or to acid clean and seal the tank you have. A salavage yard tank is a crap shoot and what you find there may be worse than what you have.

#4

It happens all of the time…Car runs okay until pushed hard at the track on fast sweeping right hand turns.

Solution: For '87 cars, purchase a new external fuel pump. For later model cars, get a new in-tank pump.

Ask me how I know.

Regards, Robert Patton

#5

How much fuel is in the tank when you get the starvation? I have an 89 and wanted to test how low I could go and not have any problems. Once I had a problem I came off track and it took 11 gallons. I figure as long as I keep enough gas in there I shouldn’t have a problem.

#6

Trent - I have an '87 and started to have fuel starvation in the last 2 laps of the 55 min enduro at Rockingham last month. When I came in I had about 3 gallons (13 liters on the digital display)in the tank. So, for future events, this is target minimum for me. This is the first time we have had fuel starvation problems with this car.
Ed

#7

Patton wrote:

[quote]It happens all of the time…Car runs okay until pushed hard at the track on fast sweeping right hand turns.

Solution: For '87 cars, purchase a new external fuel pump. For later model cars, get a new in-tank pump.

Ask me how I know.

Regards, Robert Patton[/quote]

Bobby is correct again. The 89 is the first year of the single pump car. I had fuel starvation on my 89 with the long sweeping right at Roebling Road. A new pump fixed the problem. As I recall Carter had the same issues. The fuel pump on an 89 seems to get weak over time.

There is an old thread somewhere around here on the subject of coverting single pump cars to a dual pump setup. If BMW didn’t make your model year that way than coverting it to a dual pump isn’t legal at this point in time.

#8

My dual pump car with an apparently dead in-tank pump would starve with about a half tank left at VIR in right hand turns.

#9

Somewhere between 1/2 and 3/4 would do it.

#10

I was having problems with mine at about half tank @ watkins glen, I’d come of a hard right hander, particularly into the uphill sections (like the toe of the boot and the top of the esses). With the back seat out I can hear the fuel pump whining away (a lovely electric whirring noise) when I start it so I don’t think my in tank pump is dead, though I could probably use a new fuel filter (go know when that was changed last). Anyone out there try one of these:

http://store.nexternal.com/shared/StoreFront/product_detail.asp?CS=carronline&RowID=307&All=True

for $55 bucks I was going to give it a shot, I figured the wost it could do is nothing and when I finally take the car off the street I’d put a fuel cell in it.

#11

Gasman wrote:

[quote]Patton wrote:

[quote]It happens all of the time…Car runs okay until pushed hard at the track on fast sweeping right hand turns.

Solution: For '87 cars, purchase a new external fuel pump. For later model cars, get a new in-tank pump.

Ask me how I know.

Regards, Robert Patton[/quote]

Bobby is correct again. The 89 is the first year of the single pump car. I had fuel starvation on my 89 with the long sweeping right at Roebling Road. A new pump fixed the problem. As I recall Carter had the same issues. The fuel pump on an 89 seems to get weak over time.

There is an old thread somewhere around here on the subject of coverting single pump cars to a dual pump setup. If BMW didn’t make your model year that way than coverting it to a dual pump isn’t legal at this point in time.[/quote]

9.3.1.3. Fuel System

9.3.1.3.2. Any fuel pump may (3.1) be fitted.

Steve is generally correct in thinking that it must be left as it came from the factory, unless it is specifically mentioned in the Rules. However, 9.3.1.3.2 allows any fuel pump. And if a driver is substituting the stock pump, make sure you read all the rules regarding fuel pumps.

Carter

#12

Carter, I understand that any pump can be used but can we assume that "any pump" means plural? I think the quetion of single verses dual pump legality was raised in the last thread. Can a single pump car be coverted to a dual pump car?

#13

Reviving an old thread…

Did the question ever get answered by the PTB? Does “any pump” include multiple pumps?

Thanks,

Steve D.

#14

I wish I read this thread earlier. I had issues this weekend with anything less than 3/4 of a tank at Watkins Glen. Any hard cornering or uphill stretches caused the engine to drop. I have an '87 and the in tank pump is doing anything at all from what I can tell. No vibration or noise when the engine is on. The fuel filter was also clogged with some delicious rust colored water. Took me a day and a half to finally figure out what was wrong. Reading here would have taken 2 minutes to figure out.

What is the consensus on the pump setup? Single? Dual? Aftermarket?

I’ll find out soon if I need a new tank as well.

#15

I also have an 87, after developing problems with starvation following long right handers with around 1/4 tank or less. I replaced both pumps and the filter in an afternoon with stock and the problem never recurred. Good luck with yours.

Ed, I’m curious about your digital display. Is that in the stock tank, and is it pretty responsive? Can you share info and/or part number? I know a few guys that would like to have a more accurate read on fuel. Personally, I have had the light come on and when I park it to find out I still had 1/4 tank. Thanks!

#16

I replaced both pumps, both regulators and the filter and have had no problem since. (87’ car)

Once the light comes on I can usually go around 4-5 laps before I get steady starvation at multiple corners. If I come in when the light comes on there is usually 1/4 of a tank left.

JP

#17

AJ - It is actually the factory on-board computer display. I’m not sure it is any more accurate than the gauge if the sending unit is bad. But it does give a read-out in liters of fuel remaining, which if the sending unit is OK, gives a more precice reading than the guage. You can get the value by holding down the 1 and the 1000 button simultaneously.
ED

#18

Ah, thanks Ed!