Debris in fuel tank. Where's it coming from????

[DMC3165]

I'm in the process of cleaning my tank prepping for my new DMC fuel pump/sender combo. But I'm finding alot of debris in the tank and on the pickup screen. Where is it coming from? Any ideas what to check next. Tank was cleaned 4 years ago. And wiped down last year. Any ideas would be helpful.270742707527076

[Bitsyncmaster]

Try pushing a rag through that pickup hose and see if the hose is disintegrating. Just because the color of the debris seems to match the color of the hose.

[NightFlyer]

I'm in the process of cleaning my tank prepping for my new DMC fuel pump/sender combo. But I'm finding alot of debris in the tank and on the pickup screen. Where is it coming from? Any ideas what to check next. Tank was cleaned 4 years ago. And wiped down last year. Any ideas would be helpful.

If you have/had any teflon lined hoses in the system (especially on the return), the teflon lining is known for deteriorating and flaking into the fuel. The rubber diaphragm in the accumulator will also slowly deteriorate and mix in with the fuel, however, usually the filter catches most of this particulate - except for the particulate that comes out with the fuel in the back of the accumulator and flows directly into the return line (thereby bypassing the filter), although this usually only ever occurs when the accumulator has suffered a failure. Other than that, any rubber in the tank itself, including the sealing boot, will deteriorate and contaminate the tank directly. Running ethanol blended fuel greatly exacerbates the deterioration of the rubber components.

You can replace all the rubber components in the system (which does NOT include the nylon cored lines - they're fine) with lines that are specifically designed to tolerate ethanol blended fuels to prevent a majority of this, although there isn't much you can do about the rubber diaphragm in the accumulator, except to install a small inline filter on the rear relief hose.

Best of luck - you're going to love the new pump/sender combo unit!

[DMC3165]

Now I'm curious if anyone has ever installed a small inline filter on the return line. Seems like an interesting idea. Not sure if it would create too much back pressure in the fuel return. But nevertheless it's an interesting idea. Was thinking of picking up one from a generic auto parts store. Like an old carburetor filter an putting it in. Seems like a great way to protect the tank and fuel pump.

[NightFlyer]

Now I'm curious if anyone has ever installed a small inline filter on the return line. Seems like an interesting idea. Not sure if it would create too much back pressure in the fuel return. But nevertheless it's an interesting idea. Was thinking of picking up one from a generic auto parts store. Like an old carburetor filter an putting it in. Seems like a great way to protect the tank and fuel pump.

It wouldn't need to be installed on the main return line, but rather only on the short rubber hose that connects the accumulator relief to the main return line, #3 in the image below - that way, you'd be keeping any deteriorating rubber in the accumulator out of the main return line and tank.

http://jason.kitcarmagazine.com/delorean/wpe3C.jpg

[DMC3165]

I gotcha. It's a good idea. My accumulator is also about 4 years old. Not really sure if that's the culprit in this case. But I was having constant problems with torn and leaking boots. So I'm thinking it's possible my crud was getting in from outside the tank. Or it could've been something I missed when cleaning the tank the first time. My sending unit however was original and when removing it earlier I noticed the top where the wires are looked slightly collapsed. Also the low fuel light wasn't working anymore as a result of the sending unit contacts being damaged. So maybe I had additional debris coming in from there too? I really don't know. I just got back from the local hardware store with some tack clothes and plan on giving the inside of the tank a thorough once over before installing the new pump.

Just out of curiosity there's nothing in the fuel distributor that would send that kind of debris back into the tank is there?

[Jonathan]

Now I'm curious if anyone has ever installed a small inline filter on the return line. Seems like an interesting idea. Not sure if it would create too much back pressure in the fuel return. But nevertheless it's an interesting idea. Was thinking of picking up one from a generic auto parts store. Like an old carburetor filter an putting it in. Seems like a great way to protect the tank and fuel pump.

Your curiosity might help explain to me why my car's PO did put one of these in. I hadn't come up with anything that made sense until I saw this thread. I only really discovered it was in there recently, and only because I replaced the orange fuel hoses. I don't think the filter was causing any grief (to my knowledge) and I have not noticed any differences since it was removed. I realized my orange hoses weren't in that bad of shape after I had cut them out and got to see inside them . The Teflon did not appear to be shedding off into the tank yet anyway. They are gone now and that's fine with me anyway.

Dave and I were speculating as to whether this little filter would have been putting enough back pressure on the system to have me need a fuel mixture adjustment once I got back up and running. That hasn't been necessary as of yet and it is running as well as it had ever been.

You're right about it being a low pressure line. More or less atmospheric because of it's proximity to the tank. A couple of psi perhaps? It was on with hose clamps, which had it been on a different part of the system might have been an issue for leaks or worse.

Here are a couple of the pictures I took. Hope this helps with your questions as this thread helped me figure out a bit of my own car's history/logic :)

2707727078

[DMCMW Dave]

Do not put a filter in the return line. Any restriction in the line at all really plays hell with the fuel distributor pressures.

[David T]

Do not put a filter in the return line. Any restriction in the line at all really plays hell with the fuel distributor pressures.

There is the strong possibility that the junk you found was in the fuel when you filled up at the gas station. Junk collects in the tank or, if it is fine enough to get past the prefilter and pump, it gets caught in the fuel filter. I agree the return line is the wrong place to put a filter for a lot of reasons.

[NightFlyer]

Do not put a filter in the return line. Any restriction in the line at all really plays hell with the fuel distributor pressures.

Exactly - I'd never recommend placing a filter on the main return line, as even though in Jonathan's case it didn't really seem to make all that much (if any) difference, the potential to cause undo strain/wear on other components in the system (PPR o-rings, etc) is present.

The only place I'm recommending an in-line filter is on the hose that connects the accumulator to the main return line. A lot of K-jet accumulators don't even have a relief line behind the internal diaphragm - not even sure why our does? Its sole purpose appears to be to give the fuel/pressure someplace to go if there's a failure of the diaphragm. Could explain why we seem to be more subjected to hot start problems than other k-jet users - especially those who don't have relief lines on their accumulators. I'm not even sure if the relief line is check valved into the main return or if it's just an open tee?

Anyway, installing an inline fuel filter on the accumulator relief line shouldn't cause any adverse effects - and a clear one could actually assist you in identifying accumulator failures.

As to whether or not there's anything in the FD that could cause contamination - the o-rings could deteriorate, but other than that, not really. The biggest potential for contamination from something in the FD would be old stale fuel.

[Rich]

The only place I'm recommending an in-line filter is on the hose that connects the accumulator to the main return line. A lot of K-jet accumulators don't even have a relief line behind the internal diaphragm - not even sure why our does? Its sole purpose appears to be to give the fuel/pressure someplace to go if there's a failure of the diaphragm. Could explain why we seem to be more subjected to hot start problems than other k-jet users - especially those who don't have relief lines on their accumulators. I'm not even sure if the relief line is check valved into the main return or if it's just an open tee?

The accumulator line in question is much more than a relief line. A better term for it is a safety return line. It normally does not need to be there, correctly enough, because there's normally no fuel in that side of the accumulator. Its main function is to route any fuel that ever bypasses and fills up the dry side of the accumulator diaphragm safely to the fuel tank. Without it in place there is the risk of 75psi fuel being pumped out in/under the middle of the car's frame in case the accumulator diaphragm, a wear item, ruptures/tears/leaks.

Anybody who finds a D that's missing the return line should replace it. I can't explain the existence of "a lot of K-Jet accumulators" without this line.

There is one downside of this safety return line - it masks one of the symptoms of a busted accumulator, namely, fuel visibly leaking out the dry side. But leave it there.

[NightFlyer]

Anybody who finds a D that's missing the return line should replace it. I can't explain the existence of "a lot of K-Jet accumulators" without this line.

Here's a fuel accumulator on a Volkswagen with K-jet - note that there's no relief line on the accumulator's dry side connecting it to the main (or any other) return line.

http://www.vw-one.co.uk/Fuel%20AccumHMJ.jpg

http://www.mjmautohaus.com/catalog/images/0438170027.jpg

[DMC3165]

I will probably skip the filter for now. I am surprised at the amount bod debris I found in the tank considering it was cleaned a few years back. In looking closer at the crud in the tank some of it seemed like a fibrous material? Maybe like old cork gasket? No idea where that could've come from. It may be external junk getting in there too. My pump/boot area has been a source of constant problem s for the past few years. It's one of the reasons I've finally decided to convert it to the new style setup. I just want to be sure there's nothing further back in the fuel system somewhere that's degrading abd will only cause future problems with my new pump.

[DMCMW Dave]

Here's a fuel accumulator on a Volkswagen with K-jet - note that there's no relief line on the accumulator's dry side connecting it to the main (or any other) return line.

http://www.vw-one.co.uk/Fuel%20AccumHMJ.jpg



Interesting design. I wonder where the displaced volume from movement of the diaphragm goes as the system "charges".

[Bitsyncmaster]

Interesting design. I wonder where the displaced volume from movement of the diaphragm goes as the system "charges".

Maybe there is no spring and it just compresses air. Like a well water tank works.

[DMCMW Dave]

I was thinking of that (I have such a tank I'm my basement). It would be a lot less forgiving of a slightly leaky diaphragm. On a well tank there is at least a way to adjust the air charge.

[Dangermouse]

The accumulators we use on our hydraulic systems (in my industry) use nitrogen

[NightFlyer]

I was thinking that it functioned like a pressure tank as well.

You'll note that the little silver thing on the back has a head that would appear to accommodate a flat head screw driver. I'm wondering if this isn't a spring loaded pressure relief valve of some sorts that simply vents/discharges to atmosphere.

All I know is that I know a few people with Volkswagens running K-Jet that have such an accumulator setup.

[Rich]

Here's a fuel accumulator on a Volkswagen with K-jet - note that there's no relief line on the accumulator's dry side connecting it to the main (or any other) return line.

http://www.vw-one.co.uk/Fuel%20AccumHMJ.jpg

Thanks for the photo. I thought you were saying you had seen a lot of DeLoreans where the tank-return line was missing, as in the hose was gone and the accumulator fitting was bare. This tells me that on the carst you refer to there is no accumulator fitting at all for the hose/line to connect to.

Are you sure this VW wasn't running a later iteration, like KE-Jetronic?

In any case the back end of a DeLorean - and maybe lots of other models - K-Jetronic accumulator has a fitting on it for the safety return line.

The chamber on the back of these Bosch accumulators isn't pressurized. There is a coil spring inside it that backs up the diaphragm and provides the "accumulation" function as it retracts under main fuel pressure on the wet side. The air inside flows in and out of that back fitting when the diaphagm moves.

So I'll modify my earlier note a bit to say that if somebody is running a DeLorean with an accumulator without a fitting for the safety return hose on it then they should hunt down and reliably plug the safety return line that used to go to the factory accumulator. Otherwise you are running with an open line into the fuel tank. Venting, odor and - maybe - a fire hazard there....

[Jonathan]

The example I'm thinking of might be just what Dermot is referring to, with the water treatment industry or process piping industry at large using this type of device.

We call them water hammer arrestors or surge protectors or pulsation dampeners. It's not much more than a small cylindrical tank on a tee, in the line where the tank is connected to the process fluid and has a bladder in it. The other side of the bladder that is contained in the vessel/tank is charged with nitrogen typically.

If a forwarding pump kicks on upstream, it can send a pretty powerful shock wave through the piping system and the idea of the surge protector is to dampen the force of the wave by letting it expel the energy through the nitrogen on the other side of the bladder.

That's the theory anyway.

You can get away without them sometimes if you've designed the system in a way that valves or pumps open/close or turn on/off slowly. You also need to ensure the nitrogen is recharged at set intervals as part of your maintenance program, for if it all escapes one way or the other, all you're left with is a piece of pipe in a tee full of water adding to the places you could see a leak or failure. Not to mention whatever application needed the water/fluid downstream isn't going to be getting any if you just blew your piping all over the room.

[NightFlyer]

Are you sure this VW wasn't running a later iteration, like KE-Jetronic?

Not exactly sure to be honest. But here's (one of) the fuel accumulator(s) on an '87 Testarossa (they didn't upgrade to KE-Jet until the 1988.5 models), which featured a standard K-Jetronic system, and it's the same setup as the VW, with no provision for a hose coming off the accumulator's dry side:

http://www.ferrarilife.com/forums/attachments/trs-testarossa-f512m/37889d1321979451-new-tr-owner-clutch-accumulator1.jpg

[Rich]

Good info.

Thanks.

Not exactly sure to be honest. But here's (one of) the fuel accumulator(s) on an '87 Testarossa (they didn't upgrade to KE-Jet until the 1988.5 models), which featured a standard K-Jetronic system, and it's the same setup as the VW, with no provision for a hose coming off the accumulator's dry side

[David T]

Good info.

Thanks.

One of the things the fuel accumulator does is dampen the pulses from the fuel pump. It doesn't matter if it is a spring or a compressed gas which acts like a spring or both, the purpose is to maintain some pressure for a while to restart the car when it is hot to prevent the fuel from boiling. Do NOT use a plastic filter, they are not made to handle the pressure and can burst. The Bosch fuel injection system came in all kinds of iterations for the different cars and years it was used. Many of the parts were used differently than in the K-Jet on a Delorean. Many of the parts look the same but are not. Some can be modified to be used for different cars, some not. The best advice is to try to keep the system as stock as possible so you know all of the parts will work together properly.