Fuel return "Tee" for FI with a carb fuel tank?

DurocShark · Post by **DurocShark** » Fri Dec 01, 2006 6:00 am

Those of you who put fuel injection on a carb'd bus with the single output fuel tank...

What did you use for the "Tee" to connect the return line from the pressure regulator to the feed line from the tank?

Post by **Amskeptic** » Fri Dec 01, 2006 7:54 am

DurocShark wrote:Those of you who put fuel injection on a carb'd bus with the single output fuel tank...

What did you use for the "Tee" to connect the return line from the pressure regulator to the feed line from the tank?

Not recommended. VW used two separate lines to the tank for a reason. The fuel in the tank acts as a large heat-sink. It is criticial for injector cleanliness and startability to have cool fuel. Hot fuel is more prone to boiling (poor starting) and evaporation during heat-soak which leaves a gummy residue of coke in the injector passages.
The tee you speak of is like bypassing the oil cooler. . . . it can be done but with consequences.
Colin

DurocShark · Post by **DurocShark** » Fri Dec 01, 2006 8:42 am

I agree.

This is for a test and I want to make sure the tee I use is able to handle the pressure. Let me 'splain.

I've eliminated the AFM and distributor as problems in the guac. So while pondering I read the post here somewhere that blasting compressed air in the feed line cleared whatever was blocking it.

Hmmm...

It makes more sense that I have something in the tank that's too big to fit in the fuel lines, but is plugging it on the tank side. And without taking the tank out there's no real way to confirm it.

But I was thinking that if I blocked the return nipple on the tank and tee'd the return to the feed line the pressure from the return would keep it clear.

I wanted to try it while it's around freezing here so I don't overheat the fuel pump. If I get my 3 weeks of daily driving without a problem then I can be confident that's where the problem is and can plan a drop to get that tank out.

Creative troubleshooting.

Also, I REALLY want to resolve this before BBB.

Post by **Amskeptic** » Fri Dec 01, 2006 8:59 am

DurocShark wrote:
Creative troubleshooting.

Due to the interest in retro-fitting FI, I thought you were speaking of installation engineering, but yer not, you're troubleshooting and have my blessing to do whatever is necessary.

So are you actually dealing with a temporary fuel starvation that you blame on fuel delivery? No little wear through on the AFM track acting like you are running out of gas every time the wiper passes over it?
Colin

DurocShark · Post by **DurocShark** » Fri Dec 01, 2006 9:04 am

Amskeptic wrote:
DurocShark wrote:
Creative troubleshooting.
Due to the interest in retro-fitting FI, I thought you were speaking of installation engineering, but yer not, you're troubleshooting and have my blessing to do whatever is necessary.

So are you actually dealing with a temporary fuel starvation that you blame on fuel delivery? No little wear through on the AFM track acting like you are running out of gas every time the wiper passes over it?
Colin

Not that I could see with a flashlight.

I'm going to look again in daylight (or pull it and bring it inside) before I start this. But I'm fairly confident there was nothing wrong.

vwlover77 · Post by **vwlover77** » Fri Dec 01, 2006 10:22 am

Another thought.....

Confirm the blockage by doing the fuel pump volume test. That is how I verified that I had blockage in the tank. Fuel was dribbling out and the volume was nowhere near what it should have been. Cleared the clog with compressed air, and the volume went way up - exceeding spec by a wide margin.

As another test, with the ignition on and engine not running, move the wiper in the AFM so the fuel pump runs. If there's blockage, it will whine and cry about it. If not, it will run smoothly and quietly.

Of course, if your blockage is intermittent, these tests may be inconclusive, but once mine clogged up, it tended to stay clogged for a while. What actually allowed it to unclog the first couple times it happened I don't know - bleed off of the suction maybe?

DurocShark · Post by **DurocShark** » Fri Dec 01, 2006 10:29 am

Hmm... I wonder how expensive a true fuel pressure gauge that mounts in the dash would be...

Post by **Amskeptic** » Fri Dec 01, 2006 7:39 pm

DurocShark wrote:Hmm... I wonder how expensive a true fuel pressure gauge that mounts in the dash would be...

Those of us with no gauges believe that all you have to do is set the engine up correctly and then go drive it.
Colin

DurocShark · Post by **DurocShark** » Sat Dec 02, 2006 2:58 pm

Amskeptic wrote:
DurocShark wrote:Hmm... I wonder how expensive a true fuel pressure gauge that mounts in the dash would be...
Those of us with no gauges believe that all you have to do is set the engine up correctly and then go drive it.
Colin

Yeah, but it would be nice to see exactly when the pressure drops from the drivers seat. I can't have someone in the back seat all the time watching a temporary gauge...

I posted pics of the AFM in a separate thread. The tracks don't cut all the way through anywhere.

vdubyah73 · Post by **vdubyah73** » Sat Dec 02, 2006 3:03 pm

Tank venting properly? Next time it craps out run around and open the gas cap, If air whooooshes in there's yer problem

Bill

DurocShark · Post by **DurocShark** » Sat Dec 02, 2006 3:03 pm

Oh, an additional symptom:

The fuel pump starts getting noisy a little bit before I get the engine shutdown. Because there was time between the noise and the cut out, I was just assuming it was the filter getting plugged.

I saved one of the other filters I pulled out and poured water through it backwards into a coffee filter. Nada came out. If it was plugged, SOMETHING should have come out.

The pump noise happened with both pumps before my original pump crapped out.

DurocShark · Post by **DurocShark** » Sat Dec 02, 2006 3:07 pm

vdubyah73 wrote:Tank venting properly? Next time it craps out run around and open the gas cap, If air whooooshes in there's yer problem

Bill

I tried that a while ago. No dice.

But... If that was the case: It probalby wouldn't happen immediately after pulling out of my parking space in the morning. Not impossible, but unlikely that I could create enough vacuum to lock it up that soon. Plus my fuel cap doesn't seal for crap. Always getting gas dripping out of that filler neck when driving "spiritedly". Stupid smog place lost my good cap when I had the Guac smogged.

Randy in Maine · Post by **Randy in Maine** » Sun Dec 10, 2006 8:14 pm

Remove the tank and cut to the chase.

You could have had it done by now.

DurocShark · Post by **DurocShark** » Sun Dec 10, 2006 8:24 pm

Randy in Maine wrote:Remove the tank and cut to the chase.

You could have had it done by now.

Not really, no.

vwlover77 · Post by **vwlover77** » Sat Jan 20, 2007 9:15 pm

DurocShark wrote:It probalby wouldn't happen immediately after pulling out of my parking space in the morning. Not impossible, but unlikely that I could create enough vacuum to lock it up that soon. Plus my fuel cap doesn't seal for crap. Always getting gas dripping out of that filler neck when driving "spiritedly".

Your problem sounds EXACTLY like mine. There is debris in the fuel tank, too big to fit down the fuel line to the filter, that occasionally clogs the outlet to the fuel line. I'm planning on pulling out my fuel tank after lowering (but not removing) the engine to get the junk out of it.

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Fuel return "Tee" for FI with a carb fuel tank?

Fuel return "Tee" for FI with a carb fuel tank?

Re: Fuel return "Tee" for FI with a carb fuel tank