Dual Fuel Pump set up: DIY 1996 e36 (alternative setup)

[bimerok]

Thanks John for posting this up. This is the reason.

As I learned in the middle of this project, the regular fuel injected hose is not made to be submersible in fuel and will degrade fairly quickly.

I'm also not sure on the pressure rating, but this line is made for a fuel cell and to be submerged in gasoline or ethanol.

By the way, tomorrow is my first track day at NJMP so I'm looking forward to see how this set up will perform.

[mrf]

Can't speak for Bimerok but here's one reason why:


From: http://www.racetronix.biz/itemdesc.a...FT-150&eq=&Tp=

Ah, that definitely sold me on it. Thanks!

bimerok, eagerly awaiting your post track day thoughts on this!

[bimerok]

So had a chance to test my dual pump set up and I was disappointed to see fuel starvation starting at about 1/4 of tank. Right now I'm not sure as to why I'm still having this issue. I did run sticker tires compared to prior the pump mod...

At another thread I saw a comment saying that person experienced starvation when using used/older pumps and fixed the issue by putting a new pump. I'm trying to confirm if that was the case with main or transfer pump...

Not sure what to look for yet...

[flink]

So had a chance to test my dual pump set up and I was disappointed to see fuel starvation starting at about 1/4 of tank.

The (nasty ebay) pumps which I buy come with the pump sitting about 1/2" too high in that white collar. I have to push the pump further down (takes a LOT of force) to get the sock sitting at the bottom of the tank. Grab your 12" ruler and verify that the pickup is sitting as low as it can.

1/4 tank is rather a lot though.

[bimerok]

The (nasty ebay) pumps which I buy come with the pump sitting about 1/2" too high in that white collar. I have to push the pump further down (takes a LOT of force) to get the sock sitting at the bottom of the tank. Grab your 12" ruler and verify that the pickup is sitting as low as it can.

1/4 tank is rather a lot though.

Both of my pumps are OEM. The one that is used as transfer is my original pump that was replaced due to the level sensor issue, which I fixed before reusing it again. I'm pretty sure it sits all the way down.

Right now the transfer pump is clocked so that the slant points towards the outside of the car. I'm not sure if rotating it more closer to the outside rear corner of the tank would be any help and if the float will allow it...

[NeilM]

Right now the transfer pump is clocked so that the slant points towards the outside of the car. I'm not sure if rotating it more closer to the outside rear corner of the tank would be any help and if the float will allow it...

I don't know that this is the only possible DS pump orientation that works, but the one that worked for me was:
1) Float mech modified per Andrew Kalman instructions.
2) Pump clocked normally.
(Note that for me this means that the DS pump's external fuel transfer port is pointing in exactly the wrong direction, so I had to loop the hose 180 degrees and resolve the resulting kinking issue with an internal spring. Since you're using an internal transfer hose that shouldn't be a problem. That corrugated plastic hose looks perfect for the application.)

I can run well down into the reserve light with no problem.

Neil

[mrf]

So had a chance to test my dual pump set up and I was disappointed to see fuel starvation starting at about 1/4 of tank. Right now I'm not sure as to why I'm still having this issue. I did run sticker tires compared to prior the pump mod...

At another thread I saw a comment saying that person experienced starvation when using used/older pumps and fixed the issue by putting a new pump. I'm trying to confirm if that was the case with main or transfer pump...

Not sure what to look for yet...

Stupid question, but you verified the transfer pump was coming on when needed etc.?

[bimerok]

Stupid question, but you verified the transfer pump was coming on when needed etc.?

Yes, I did that . And plus, I would not be able to go past quarter from the full without it.

[Mr. 5]

I don't know if this is a stupid question or not, but how would this setup work with daily driving and only using just the main pump for daily driving?
I would think that since the standard siphoning system is gone then it wouldn't do its job by transfering the fuel over.
Of course, you can turn on the second pump, but I'm just talking about daily driving.
So, will it transfer over still without the second pump turned on?

[Maynor]

You'd cut your gas supply in half if you didn't run the 2nd pump daily driving. It's a return fuel system so the 2nd pump is always getting feed by the unused engine fuel. You want the 2nd pump running full time for that reason.

There is no draw back to keeping it on.

John

[bimerok]

^ this.

The only reason I put the switch for the second pump is because initially I had few other ideas about feeding the main pump. Ideas went away, but the switch stayed.

[Mr. 5]

OK, got it.
Thanks!

[jakermac]

I have the dual pump setup in my car (93 325is) and it doesn't work nearly as well as I'd hoped. When I 1st got the car, it was still on the original pump (130,000 miles). It failed at about 135,000. I replaced it with a new OEM VDO pump (original style with return fitting). Before replacing the pump, I used to be able to run down well into the reserve light at autocross without starvation.

Since replacing the pump, suddenly I'd get starvation with 2-3 gallons in the tank (reserve light just starting to come on). I then installed the 2nd pump, oriented to the outside driver's side of the car. That doesn't seem to have made any difference to where I was with the single new pump. I've looked at the old OEM original siphon left side setup, and it reaches much much further down to the left side of the tank than the 2nd scavenge pump does. I'm considering extending the tube that comes off the bottom of the siphon pump to allow the filter sock/pickup to reach just as far as the original setup did. Any thoughts on this?

Also, I suspect that the original 135,000 mile pump that was in the tank (and failed) might have reached further/lower in the tank than the new pump that replaced it. Anyone have any feedback on that possibility as well? I may build a fixture to do some comparisons of reach between the 2 pumps.

[bimerok]

So far I have mixed experience on dual pump setup. After installing dual pump it did not work well on the track where I rearly had starvation issues (NJMP Thunderbolt). But last weekend I went to NJMP Lightning, where I first discovered the starvation issue at little over 1/4 of tank and now the set up worked fine until I was into reserve light.

I'm still not sure what's up with it or if it is worth while as exact the same set up on my cousin's 97 M3 with stock motor did not improve anything at all. He is still getting starvation at the same levels he was before dual setup.

[GrifM3]

So far I have mixed experience on dual pump setup. After installing dual pump it did not work well on the track where I rearly had starvation issues (NJMP Thunderbolt). But last weekend I went to NJMP Lightning, where I first discovered the starvation issue at little over 1/4 of tank and now the set up worked fine until I was into reserve light.

I'm still not sure what's up with it or if it is worth while as exact the same set up on my cousin's 97 M3 with stock motor did not improve anything at all. He is still getting starvation at the same levels he was before dual setup.

Which kit is your cousin using?

[bimerok]

Same one - home brewed.

[peapodf50]

Sorry for digging up an old tread, but I am having starvation also and would like to do something similar to this setup.m I am wondering if there are any updates to this.

I am running a walbro 255 pump, so I do have an extra stock pump off of a 99.

Please update

[bimerok]

So far I haven't changed anything in my setup and it still has starvation issue. Same thing on my cousin's e36 M3. For now I just make sure that I keep it at least above 1/4 of the tank.

Very annoying.

[peapodf50]

1/4 tank is better than having to keep it at a 1/2 tank like I do now. I will have to look into it more now that I have some down time

[Cobra1956]

Will be installing an additional pump in a few weeks. Thank you for saving me a couple of hundred $$$.

[jakermac]

I have the dual pump setup in my car (93 325is) and it doesn't work nearly as well as I'd hoped. When I 1st got the car, it was still on the original pump (130,000 miles). It failed at about 135,000. I replaced it with a new OEM VDO pump (original style with return fitting). Before replacing the pump, I used to be able to run down well into the reserve light at autocross without starvation.

Since replacing the pump, suddenly I'd get starvation with 2-3 gallons in the tank (reserve light just starting to come on). I then installed the 2nd pump, oriented to the outside driver's side of the car. That doesn't seem to have made any difference to where I was with the single new pump. I've looked at the old OEM original siphon left side setup, and it reaches much much further down to the left side of the tank than the 2nd scavenge pump does. I'm considering extending the tube that comes off the bottom of the siphon pump to allow the filter sock/pickup to reach just as far as the original setup did. Any thoughts on this?

Also, I suspect that the original 135,000 mile pump that was in the tank (and failed) might have reached further/lower in the tank than the new pump that replaced it. Anyone have any feedback on that possibility as well? I may build a fixture to do some comparisons of reach between the 2 pumps.

As a follow up to this post, last spring I looked into this further. I took the old failed pump which I still had and measured the depth that the sock reached into the sump of the tank. I then compared it to the new VDO pump that I'd put into the tank to replace the failed pump. The old pump reached about 1/4" deeper into the sump than the new VDO. I cut the OEM plastic that surrounded the pump to let me slide the pump a bit further (1/4" - duh) down into the sump. Then I screwed a gear clamp around the assy to hold the pump in place. Oh, and I took the extra pump out of the driver's side of the tank and put the original syphon system back in.

I am now back to what I had before the original pump failed, and run the tank very very far into the warning lamp at autocross without any starvation. I have had it so the needle is at or slightly below the empty or bottom line on the gauge and it still does not starve. In fact I've put 3 gallons in after having it at this level and the needle sits at the 1/4 mark.

I know my car is a 93, but I suspect it wouldn't be that hard to convert a 96-up car to the older style tank.

[MatthewH]

I was having starvation issues at half tank on my 1994 325i and just replaced the pump. I ran it nearly completely empty at the last event without starvation.

[Cobra1956]

Interesting info. I have S54 power in my e36. Maybe the issue is fuel pressure and not fuel pickup since Bimerok still had some issues. I do plan on looking into how low the sock/pickup is. Got the pump pretty cheap so not worried there but I fuel anytime I am under 3/4 just to make sure I don't have any issues. Won't get at this for at least three weeks but grateful for this thread.

Jaker, if you have Bimeroks set up, or did, and your primary pump was bad or going bad, your issue might not have been starvation in the first place. Having more fuel on the passenger side would be of no benefit if the pump can't send it to the engine. My issue is on sweeping right handers.

[jakermac]

Jaker, if you have Bimeroks set up, or did, and your primary pump was bad or going bad, your issue might not have been starvation in the first place. Having more fuel on the passenger side would be of no benefit if the pump can't send it to the engine. My issue is on sweeping right handers.

Not the case. When my pump died, at the time there was only 1 in the tank. It was after changing that pump, and suffering newfound starvation issues that I went the dual pump route.

[MatthewH]

My problem also occurred on right hand sweepers. I did find one of the rubber bushings had split (these feel really hard now) and the sock thing had torn as shown below:



Above is the original Bosch pump and I replaced it with a used VDO unit from a 323i shown below.



I did make sure the sock was orientated towards the left edge of the swirl pot in the tank.