dual pump starvation fix

[lateracer]

My track car has fuel starvation issues about when the tank gets below the halfway point.

I've got a two pump set up and I'm not really sure if one/both pumps are going bad. I'm inclined to replace the in-tank with a walboro 255, but I'm not sure it's the right replacement for a high volume low pressure pump.

Another solution I'm considering is replacing the external pump and using an accumulator as well.

I don't want to buy a new in tank AND external if possible. Suggestions?

[Imagine_M]

only time i have experienced starvation is when my intake pump is starving so id work on that one...

[jlevie]

What you describe sounds like a weak or failed transfer pump (the one in the tank). The transfer pump's operation can be hampered by rust in the tank. As the tank runs down fuel sloshes and stirs up rust, which collects on the inlet screen of the pump and chokes off flow.

The first thing I'd do would be to pull the in-tank pump and sensor and use a stick to stir the bottom of the tank. If there's a layer of rust you'll feel it and can see it with a flashlight. The fix for a rusty tank is to replace the tank or acid clean and seal the tank you have. Cleaning and sealing the tank is not difficult and is far cheaper than a new tank. Unless you get real lucky a used tank may have the same rust problem. If there is rust in the tank the crossover tube may be partially plugged, which will inhibit transfer of fuel between the sides of the tank.

Once rust in the tank isn't an issue, a new in-tank transfer pump should allow you to run the tank down to 4-5 gallons before experiencing starvation in corners.

[lateracer]

Thanks guys.

Jim, I've been reading your (repeated) posts on these solutions. My exhaust and drive shaft are coming out pretty soon for some other work, so I'm going to pull the tank, clean out the transfer tube and do an acid wash/seal on the tank. Looks like you've done this job before. What kit did you use? Found POR's kit.

[E30Gus]

I think this is a common problem with the earier E30's.
I have the same problem at the track with two new fuel pumps. A good fix is the in-tank accumulator. Otherwise keep the tank full which is what i have to do until i get the accumulator in my tank. Not discounting Jlevies comments as it can be part of the problem but my bet is that you would have the same problem with a new tank and pumps.

[lateracer]

I think this is a common problem with the earier E30's.
I have the same problem at the track with two new fuel pumps. A good fix is the in-tank accumulator.

Any recommendations on accumulators? I've heard the IE accumulator is OK, but I've never seen any pics or illustrations. The concept seems simple enough, just not quite sure where the best place to mount it is.

[E30Gus]

The IE one goes in the tank under/around the fuel pump. Basically the return line keeps it filled up so that during right hand corners you have enough fuel to prevent starvation for a bit.

[jlevie]

The clue is to what is needed is when the starvation occurs. If it only happens when that tank is down to less than 5 gallons in right hand turns, a surge tank of 1qt or more will allow the car to burn off all but about a gallon of fuel. If the starvation happens before that, like on a half empty tank, other problems in the fuel system are present and need to be dealt with. I dealt with this and other problems on my previous Spec E30 and the tank saga is below. On that car once all of the tank/pump issues were addressed we could run the car for 5-7 laps after the low fuel light came on in enduros. That was a good 1 & 1/2 hours of racing and a fuel stop would result in 10 gallons of gas being put in a tank that held 14.5gal.

Fitting a surge tank requires a fair bit of modification to the fuel system and it presumes that the rest of the fuel system is working correctly. You do this to allow the car to run down to less than 2 gallons of fuel, not to fix other problems.

I rigged the new Spec E30 (an 88 with the 63L tank) with a transfer pump on the left side that assists the siphon in moving fuel to the pump pickup. I haven't yet run it in a long enduro, but it should let me burn off all but a couple of gallons of fuel. If it doesn't, the configuration will be changed to a pair of transfer pumps feeding a 1qt surge tank that feeds an external high pressure pump.

The tank saga:

A twenty year old car with a steel gas tank can have a surprising amount of
rust in the tank. That rust can and will clog the pump inlet screens and
filter and cause the high pressure pump to have a short life. While a
new tank will certainly fix that, you can clean and seal the tank for a lot
less money.

My 87 325is suffered from this. The car ran fine on the street but the first
time I took it to the track for a test & tune it was as if the car had a soft
rev limiter that decreased by 500-700rpm per lap. Some particulate matter did
come out of the tank when I drained the gas, but with the in-tank pump out I
could see a layer of crud in the bottom of the tank that was about an 1/8"
deep. On the track that stuff got stirred up, clogged the inlet screens &
filter, and starved the engine. It also ate up the internals of the high
pressure pump. Rust is a fairly abrasive material.

The first attempt at a fix was to have the tank acid dipped and install new
pumps & filter. Either they didn't leave the tank in long enough or the acid
was a bit depleted, but the result was less than satifactory as the next time
I had the car on the track the high pressure pump started buzzing and I ran
into the same starvation issue.

After taking the tank out again and sloshing about a gallon of fuel around I
got loads of rust out of the tank. The new filter was heavily loaded and the
inlet screen of the high pressure pump was also loaded up. And the cross-over
pipe was completely plugged. This time I was determined to get all of the rust
out and follow that up with sealant to lock down anything that was left and
prevent further rusting. I used a gas tank sealer kit from Eastwood, but went
a bit further than they suggest.

The tank, having been recently acid dipped had no varnish in it. So a simple
wash with a strong TSP solution removed the remaining organics. I made up a
simple plug for the hole where the in-tank pump mounts that could easily be
removed. Think of a round disk of plywood with a bar on the bottom and a couple
of screws to snug the bar up. Drop that into the opening, rotate slighty to
engage the lock ears on the tank and tighten the screws. The remaining
openings were closed up with pieces of a freezer bag held in place with rubber
bands.

About a gallon of diluted acid in the tank was about right. That was enough to
slosh around well but not so much as too make the tank to heavy. I used an acid
mix sold for cleaning masonry that's composed of Hydrochloric and Phosphoric
acids at about double the normal dilution. Over the course of a couple of
hours I'd slosh and flip tank every fifteen minutes to wet all parts of the
tank with the solution. At the end of a couple of hours I drained the tank and
disposed of the pretty well spent acid by reacting it with limestone gravel.

To flush the tank I made up a right-angle spray nozzle with plumbing fittings
and a 1/4" hose barb. That allowed the nozzle to be inserted into the tank and
a high velocity stream sprayed into all corners. This was done with the tank
at about a 30deg angle (drain plug hole down) and the fluid collected into a
bucket. When the water ran clean and no more loose junk came out I repeated
the acid treatment and flush. It took all of one Saturday and part of Sunday
to get the tank to the point that no more rust could be seen and nothing was
being flushed out of the tank.

The last steps were to use the acid etch from the Eastwood kit, flush with
acetone, and apply the sealer. Before putting the sealer in the tank I removed
the cross-over pipe and sealed those openings. And after the sealer had been
applied and before it had a chance to harden I blew out those openings and the
tubing that runs across the top of the tank with compressed air. After drying
for a couple of days the tank was reassembled and reinstalled in the car.

Once sealed the inside of the tank had a fairly uniform white coating. I did
see a few specks of matter that I wasn't able to flush from the tank, but
those were well locked in place by the sealer.

Cleaning and sealing the tank is pretty labor intensive. But at a total cost
of less than $80 it is a lot cheaper than a new tank (~$300 for this car).

[kenika65]

Great write up wow! Extremely visual

[E30Gus]

^ Again The Man!
Hey would an intermediate step be to take the crossover pipe out and clean that out and get out as much rust as possible? Possibly to make tha tank last a while longer without re-coating the inside. I remember lookin in my tank as much as I could but didn't see a whole lot of rust loose in the tank. I guess what I am saying as a daily driver I cannot afford to do the tank coating thing but I don't the fuel starvation going on while on the track.
G

[jlevie]

You could drain the fuel, remove the cross tube, and make sure that it is not obstructed. But if you get starvation at around a half tank, the transfer pump and/or rust is the prime suspect.

Oh yeah, if you have all the materials on hand you can clean and seal the tank over a weekend if you pull the tank Friday evening.