E30 external fuel pump connections

[jlevie]

On a race car you always want to use off the shelf un-modified parts for all critical subsystems, like the fuel system. If a part breaks just before or during an event you need to be able to replace that part quickly with a readily available substitute. So I highly advise against modifying a transfer pump to replace the high pressure pump.

To avoid having to modify the tank, use the high pressure pump from a late production 318is. It has both a feed and return fitting. Use the return fitting for the fuel from the left side transfer pump. Be aware that there is hardly any clearance between the top of the tank and the car body. You'll have to run a metal line (like I did) and in a similar location to avoid interference. Even with that I found it necessary to space the tank down 3/8" to avoid interference. That meant making some special spacers to go above the rubber isolators. I found it pretty much impossible to use loose spacers, so I made some that have a sleeve that goes into the rubber parts.

[scrowner]

I get the easily available/fixable solution. But I need cheap. TRE pump has the fuel rail pressure I need. I have ONE high pressure in-tank pump and its mechanicals but if I decide to use it I need to make the hole in a fuel tank which I am not confident in doing. It is a fuel tank I am playing with and I am still fairly new to the car modification scene. So I became concerned about drilling and fitting and sealing the tank using your techniques.

So in my world, I thought if I use and old in tank pump mechanicals, I have the fittings - outside and available. The connection seemed simpler and more manageable to me. I just needed a high pressure in-tank pump to replace the low pressure one and this site provides steps to do so with about 1/3 the cost of getting the mechanicals and in tank pump for the 318is.

Thanks for stating the clearance issues. I really have no way to "make" a collar for the tank interface to the body of the car and may end up with something I can get at the local hardware store to give me enough clearance to allow the above tank connections. I will understand better tomorrow but I am confused why I can not use flex fuel line between the pumps. I do have some steel fuel lines from another E30 and was simply going to go from pumps to flex to steel between the two in tank pumps. I do see that all the connecting lines on the top of the tank are small steel lines - hence showing the clearance issues. But the old tank will have some of these - I hope - to use.

[jlevie]

The problem with flex line is it's diameter. I used 3/8" copper and still had to make spacers to lower the tank.

The only time cheap and race car can be used in the same sentence is something like, "There is nothing that is cheap to do on a race car!".

[scrowner]

Yeah, yeah.... but the word "race" is being used lightly here. After all, the team is racing chumpcar and lemon. We should be getting the tank in next week. All the mods are done. The newer tank we got fits right up to all the mount holes of our 325e. We are getting closer to having a car that is less likely to have a fuel starvation problem.

[scrowner]

I just wanted to post some testing results of my 1991 63L tank install into a 1986 325e.

Issues when installing:

1. We syphoned out gas from the old tank by breaking free the rubber filler pipe at the rear of the tank, passenger side. We did this because the drain plug in the tank was mashed higher due to some previous person jacking the car on the fuel tank. This rear rubber filler pipe is tough to remove, the hose clamp is in a tight area and we ended up cutting it off - still hard to get tools in there to do this.

2. The expansion tank which is never visible but in the passenger wheel well, has three air connections. One is large and goes to its own fitting on the 86 and 91 tanks - same size pipe. Then there are two small black plastic air connection that have a short rubber piece of hose. They are different sizes. Small one goes to the driver side tank and the larger one goes to the charcoal canister up by the engine. On the 86 the Charcoal canister run is a steel pipe that runs up to the top of the tank where the fuel pump is. This steel line must be cut out. I cut is down by where the 86 main fuel lines are located and removed this steel line. The steel line will prevent the bigger 91 tank from getting installed. The 91 tank has a plastic line that runs on top for the canister connection.

3. We hammered the rear seat section that is on the front of where the tank fits in. Just a bit of minor hammering to push this seat section in. This is two vertical metal pieces that in a 4 door 325e is found behind your your legs.

4. I was told a bunch of fitting issues for the tank. But the newer 63L tank just slide right up in place and I used the same bolts and one nut. The 86 tank has a single nut on the passenger corner of the tank with a bolt stud attached to the car. All the 91 holes lined up just fine. I did not use any spacers on the tank, as the 3 lines on the top of the 91 tank sat in a recessed area. The fitting reguires to lift up the rear of the tank first, make sure the tank is as far to the driver side of the car as there is a piece of angled metal on the passenger side near the front of the tank position that has to be wiggled past.

5. I know the tread talked about putting in a transfer pump from the driver side to move fuel to the passenger side. We did NOT do this. We did however modify the mechanicals of the old 91 as shown on this forum to put in a TRE-Performance fuel pump. This went smooth and the instructions are great for doing this.

6. On the 86, there is an external pump. This was removed as well as all the silly BMW, accumulator and dampener parts. I pulled the electrical for this no longer used fuel pump back up through the hole in the cabin. Then there are three short hoses up on top by the fuel pump and three short hose connections down the driver side of the fuel tank. All using 5/16 or 8mm fuel injector fuel hose.

7. The fuel pump worked just fine. However, in our car we only get 10.5V at the pump with an 8 Amp draw. This is a bit different than the original fuel pump draw of our 86. This is also causing us to get a better battery to allow fuel pump operation and engine cranking at the same time. We attempted to connect up the bigger wires of the 86 going to the original external fuel pump. But we saw no improvement of voltage drop. We were told to re-wire at the relay but we decided the pump is over kill for the 40 PSI requirement of our injectors and we are running it as is.

8. I know we were told to clean and seal the '91 tank. However upon reading the sealing/cleaning kit instructions, temperature plays a big part in getting the stuff to setup. We are in a garage that is not heated. So, we did not clean nor seal this 91 tank. We did carefully inspect the tank and it was like new on its inside and inside top. This is a lemons car and we saved a few bucks not doing this. I would suggest doing this if you are converting in a warm climate.

We went the Summit Point Raceway WV this past Friday and rented the whole Main Circuit track for 2 hours. We ran the first hour with what was in the tank and we had NO fuel starvation. When we topped off after the first hour the tank took 13.3 gallons of the 16.6 max! We ran another hour, HARD, and had no fuel starvation.

We were successful. The project was scary for us new to car hacks. But in the end it was straight forward and easy to do.

[scrowner]

We ran this modification to the fuel system this past weekend at CMP lemons. Ah, it work spectacularly but we have a bad comparison point with the previous old 1986 two pump system. We had no fuel starvation. However, we used WAY more fuel than we did in the previous races. Previously, we were using around 4 gallons per hour. With his new fuel tank and TRE pump, the car was using 6-7 gallons per hour. Yes, as you would expect, the engine performed with a bit more horsepower - very noticeable. So, if you go about doing this double pump to a bigger single pump for a junk car racing machine - be prepared for using a bunch more fuel. Good luck!

[scrowner]

Another update to this E30 fuel system modification. We ran the car at Rockingham and Charlotte with Chump car. Rockingham was a 2 day enduro, both days 7 hours of continuous racing. First day ran great with no fuel starvation issue. Second day the car would stall in the last 1.5 hour of racing. The stall would follow with not being able to start the car for about 3 minutes. Once it started the car would run for 10-20 minutes and then do the same thing. The stall followed either right or left hand turns. The first time it happened it was down to about 7 gallons in the tank. 2nd, 3rd, 4th time it happened was later in the last stint of the day but my guess was the tank was still 9+ gallons.

We read here about bad fuel pump relays on E30s and ours was original and we had a high current draw with the new TRE fuel pump. So, we replaced the 3 main relays of the car and wrapped the plastic housing of the 3 relays with cool tape.

Charlotte was a continuous 14 hour race. No fuel issues with pit stop running about 1.5 to 2 hours, for the first 8 hours of the race. Then at about 8+ hours into the race the car would again simply stall and the driver would have to wait for about 3 minutes before it would start. Not waiting would cause the car to just crank but not fire. This stalling only seemed to happen late in the stint - lower fuel - and upon exiting a turn. The team pitted and fueled earlier prior to 1.5 hours of driving and ran the rest of the race with out seeing the issue.

So what is causing this silly issue? Seems to be heat related, seems to be lower level of fuel related, not the fuel relay heating issue as the relay was cool to the touch upon pitting after the issue. I think it is going to be said to put in a transfer pump - but why is the occurring only later in time in the races?

[djdropit]

Pump Relays?

[scrowner]

Pump Relays?

As stated - the fuel relay was replaced to new prior to the Charlotte race. So, nope. I am going to contact Treperformance to see if they have some thermal cutoff in the pump.

[scrowner]

Just to be complete about this fuel system conversion on a '86 325E:

With new system as stated above, running some courses, the "fuel starvation" would still be present. It would rear its head about 1 hour into a race and get worse as fuel was used. Other courses (Summit) ran smooth and would allow us to almost run dry - at least at or around 2 hours of running. The system - briefly - 86 E30 325e, '91 fuel tank, all external fuel pieces removed except for charcoal and fuel filter(converted to a single pump system), TrePerformance pump installed into '91 hanger in the tank, second sender (driver side) in the tank but not wired up, added relay right next to fuel pump with minimal wire running from battery to second relay - old relay simply used to turn on second relay which improve voltage at the pump to be over 11V with pump operational.

After conversations with TrePerformance, their 5000 hour test is done ONLY fully submereged. As we know - fuel is used and the pump slowly exposes to air. They indicated they do not have a thermal cut off. This whole thing just bothered me.

We went to VIR race back in June - and first driver at a little over an hour had fuel starvation. I had purchased a standard BMW pump (AIRTEX) and hanger for a '90 325is system prior to the race. When the driver pitted, I swapped the the TrePerformance pump and hanger with the new AIRTEX pump and hanger. No more problems. Ran the whole race without fuel starvation and could do 2 hours+.

So it is possible to convert a dual pump BMW fuel system over to a single. I am not positive I need to add the relay when using the new AIRTEX pump but the relay remains in place. The '91 tank is bigger but fits with just a bit of persuasion into the pre-88 325 cars. My personal opinion is to not use TrePerformance pumps for endurance racing environment. The TrePerformance guys did offer to replace my pump, thinking it was "defective" but I passed on this.

[rwh11385]

Jim, this thread is gold - thanks for your advice in it.

The dual pump system isn't a problem in a track car provided that both pumps are good, the cross over tube isn't plugged, and that the tank doesn't have loose rust in it. I have a whole season of racing 3 hour enduros in an 87 where we ran the tank do to almost nothing twice in each race as proof of that.

When I first got the car I experienced exactly what you describe, even though I'd replaced both pumps with new OE units. I cured the problem by dropping the tank, acid cleaning it, and sealing it.

We were considering swapping our early tank to late, but I think the best course right now could just be cleaning the rust out and sealing it, making sure both pumps are functioning correctly.

The tank was easy to pull due to a transmission swap and will follow your directions from spece30 to recondition it.

There was so much crud in our tank, the first race we ran (with no real driving time between saving it from some kid's front lawn and throwing it into lemons) we kept losing cylinders thanks to clogged injectors and were scrambling to clean or replace them throughout the first day. The second day, we ran clean throughout thanks to dropping magnets into the fuel tank that kept enough fine rust from entering the fuel pump/lines to let us drive without issue.