# fuel accumulator



## Burnt clutch (Aug 22, 2003)

I got a '81 rocco with a leaky fuel accumulator. Its leaking on the back side of it at the screw. Is there a reason for the screw on the back? Is there a preferred way to replace the acummulator? I hope this wasnt a rare factory option...








-Karl


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## WackyWabbitRacer (Apr 24, 2001)

*Re: fuel accumulator (Burnt clutch)*


_Quote, originally posted by *Burnt clutch* »_I got a '81 rocco with a leaky fuel accumulator. Its leaking on the back side of it at the screw. Is there a reason for the screw on the back? Is there a preferred way to replace the accumulator? I hope this wasn't a rare factory option... 

Karl, the accumulator is essentially a rubber diaphragm with a spring that dampens the fuel pulses from the CIS high pressure fuel pump. The end of the accumulator is "vented" (ie rivet in end) so the diaphragm can move.
After many cycles of movement, the rubber diaphragm will rupture allowing gas to leak from the end of the accumulator.
All CIS fuel systems use an accumulator so it is not a rare part. To replace the accumulator, turn off the engine and let the CIS System Pressure bleed down over night. Then disconnect the hoses to the accumulator and replace it. 
If you don't want to wait for the System Pressure to bleed off, just slightly loosen a fitting on the accumulator and place a rag around the fitting as you loosen it.
Cheers, WWR.


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## ABA Scirocco (May 30, 2001)

*Re: fuel accumulator (Burnt clutch)*

FWIW, the accumulator is not an absolutely critical part of the CIS system, it can be removed or bypassed usually without any serious side effects. I ran my previous Scirocco without one for a few years and if the accumulator in my current car sprung a leak I wouldn't hesitate to do it again.


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## marcm (May 19, 2007)

*Re: fuel accumulator (ABA Scirocco)*


_Quote, originally posted by *ABA Scirocco* »_FWIW, the accumulator is not an absolutely critical part of the CIS system, it can be removed or bypassed usually without any serious side effects. I ran my previous Scirocco without one for a few years and if the accumulator in my current car sprung a leak I wouldn't hesitate to do it again.

Ghetto fix http://****************.com/smile/emthdown.gif


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## ABA Scirocco (May 30, 2001)

*Re: fuel accumulator (marcm)*

True enough, but it works well.


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## iamdagerman (Feb 19, 2006)

*Re: fuel accumulator (ABA Scirocco)*

If you don't get another one your car will be a pain in the ass to start after it's hot> I know because I sealed my leaking one with JB weld but it would take me about 30sec-1 minute of constant cranking to restart when the engine was hot. So I bit the bullet and brought a used one for $25


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## ABA Scirocco (May 30, 2001)

*Re: fuel accumulator (iamdagerman)*


_Quote, originally posted by *iamdagerman* »_If you don't get another one your car will be a pain in the ass to start after it's hot> 

I've heard that from several other people too but that wasn't my experience, I ran my car without an accumulator that for almost 3 years, it started just fine hot or cold, summer and winter.


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## Burnt clutch (Aug 22, 2003)

*Re: fuel accumulator (ABA Scirocco)*

I bought one from here late thursday
http://shop.autopartsfair.com/...&y=16
-not sure if its the right one though. Are these somewhat interchangeable between different models of VW for this year? Thanks to all for your replies!
-K


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## wclark (Mar 28, 2001)

*Re: fuel accumulator (ABA Scirocco)*

Like all accumulators, the main purpose is to reduce cycling and thus stress on the fuel pump and lengthen its life. A side effect if the fuel pump output check valve isnt perfect is a longer period when there is residual pressure which affects ease of restart. I suspect this would go a long way toward explaining differences between experiences when operating without an accumulator.


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## ABA Scirocco (May 30, 2001)

*Re: fuel accumulator (wclark)*

Thanks Walter, that makes sense. Every time the subject of accumulators comes up I always wondered why some people have had such different experience from me, you may have the answer.


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## WackyWabbitRacer (Apr 24, 2001)

*Re: fuel accumulator (ABA Scirocco)*


_Quote, originally posted by *ABA Scirocco* »_Thanks Walter, that makes sense. Every time the subject of accumulators comes up I always wondered why some people have had such different experience from me, you may have the answer.

I did not use an accumulator on my SCCA WackyWabbit production car and had no problems with a cold or hot start. 








Both the Carter low pressure pump and the CIS high pressure pump were hard-wired on toggle switches. My normal startup procedure was to turn both toggle switches on and let the pumps cycle for several seconds prior to pushing the starter button.
Cheers, WWR.


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## Burnt clutch (Aug 22, 2003)

*Re: fuel accumulator (Burnt clutch)*

Okay, I got the part today, and it is noticeably different, the main thing being that it is a smaller size. The part # of the original accumulator was 0438170 0027, and the part # of what I got is 0438170 001. I bolted it in, fired up the car, and it seems to run fine at idle, and when I peg it at my normal highway RPMs (3200). Does anyone have a reason why it wouldn’t work? Is the real test to see how it restarts when the engine is warm in the summer? 
-Karl


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## ABA Scirocco (May 30, 2001)

*Re: fuel accumulator (Burnt clutch)*

The accumulator is a very simple devise even though the appearance may be different, internally and in function it would be very similar to the original one, so as long as the fitting are the same I can't see any reason it wouldn't work okay.


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## stealthmk1 (Aug 17, 2001)

*Re: fuel accumulator (ABA Scirocco)*

I was under my 4000 last night diagnosing a fuel leak and I also noticed my accumulator had been bypassed by a previous owner. I have owned the car for about 3 years and I don't remember any particualrly hard starts, but there was once that it failed to start entirely. Left it for a weekend and it has been fine since. The car gets driven mostly in the winter. However, looks like my check valve is the source of my leak (VERY crusty), so that along with the banjo fitting is getting replaced tonight.


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## almstVW (Aug 24, 2002)

*Re: fuel accumulator (stealthmk1)*

i have the accumulator bypassed on two of my cars an '86 4000Q, and a '91 2.0L 16V, just the 16V has an issue starting, mostly when it's hot or it was just run and the motor is hot... the 4000Q doesn't seem t care...


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## 77whtrocco (Nov 17, 2006)

Does anyone know if the accumulator is tucked under the passenger side fender on a 77 Scirocco?
I have a fuel soaked dripping hose that appears to be coming from this area. It looks like there's another hose from this thing over to the charcoal canister. I'm trying to figure out if it's a problem with the accumulator or what. Sorry if this is completely unrelated.


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## ABA Scirocco (May 30, 2001)

*Re: (77whtrocco)*


_Quote, originally posted by *77whtrocco* »_Does anyone know if the accumulator is tucked under the passenger side fender on a 77 Scirocco?
I have a fuel soaked dripping hose that appears to be coming from this area. It looks like there's another hose from this thing over to the charcoal canister. I'm trying to figure out if it's a problem with the accumulator or what. Sorry if this is completely unrelated.

Do you mean front or back?, The accummulator is the right rear wheel. Follow the fuel line that comes from the outlet of the pump, the first you come to after the pump is the accumulator.


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## 77whtrocco (Nov 17, 2006)

*Re: (ABA Scirocco)*

Okay, I found the accumulator. The thing I'm not sure about is up in the driver side front fender. I don't want to hijack though. Thanks.


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## 16vDigiGti (Aug 23, 2005)

the thing behind the front pass. fender is a vapor catch can isn't it? i've replaced those a few times due to broken/leaky ones. you might have a leaky one. and yes it is gas.


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## WackyWabbitRacer (Apr 24, 2001)

*Re: (16vDigiGti)*

The container at the top of the passenger side fenderwell is an Expansion Tank which is a part of the Evaporative Emissions Control (EEC) system.
The purpose of the Expansion Tank is to collect gas vapors via the Gravity Breather valve which is connected to the gas tank. The outlet of the Expansion Tank is connected to the Charcoal Canister that is normally in the driver side fenderwell.
Cheers, WWR.


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## coocheese (Aug 5, 2004)

*Re: fuel accumulator (wclark)*


_Quote, originally posted by *wclark* »_Like all accumulators, the main purpose is to reduce cycling and thus stress on the fuel pump and lengthen its life. A side effect if the fuel pump output check valve isnt perfect is a longer period when there is residual pressure which affects ease of restart. I suspect this would go a long way toward explaining differences between experiences when operating without an accumulator. 

I thought it was the other way around...holds the pressure and as a bonus feature helps dampen pulses.. hence "fuel pressure accumulator"... I could be wrong though.. And mostly for the hot start in high temp areas because of the maintained higher pressure in the system raises the vapor point of the fuel in the lines...kinda like what a radiator cap does to the cooling system.


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## ABA Scirocco (May 30, 2001)

*Re: fuel accumulator (coocheese)*

You are correct, the accumlator isn't there to reduce cycling of the fuel pump, the fuel pump doesn't cycle as it's on a 100% duty cycle. The accumulator is there to dampen the pulses and together with the check valve, to maintain a residual pressure which helps hot restarting eliminating the formation of vapor blocks in the fuel lines.


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## wclark (Mar 28, 2001)

*Re: fuel accumulator (coocheese)*

Yes, I am wrong and ABA's description is correct.


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## FeatherFrog (Oct 15, 2007)

*Re: fuel accumulator (wclark)*

main point of having an accumulator + check valves is to hold line pressure for a specific time--to allow injectors some residual fuel pressure during restarts--especially when hot...back in the day remember having to match MK 1 injectors with proper accum or if accum is rated too high (-c) --could cause injectors to "bleed down" on their own--therefore defeating the purpose of the accum---had to match -23 injectors with -c accum for example


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## A2JettaGLI18 (Oct 2, 2002)

*Re: fuel accumulator (FeatherFrog)*

I wanted to bring this up again. 

Where Can I buy a brand new fuel accumulator for my Mk2 Jetta? I want OEM or very close so it works correctly. I am having trouble with starting the car after a few hours and it takes a long time (10 seconds or more) to start when HOT.


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## ABA Scirocco (May 30, 2001)

*Re: fuel accumulator (A2JettaGLI18)*

The accumulator is a VERY simple piece of kit, so much so that if it isn't leaking, it's almost certainly working properly. Get a set of CIS gauges and see how quickly your residual pressure bleeds down, the problem may not be the accumulator, it might be the check valve, or leaky injectors. If you do need a an accumulator, I've ordered stuff through THESE GUYS before, reasonable prices, good service.

_Modified by ABA Scirocco at 3:32 PM 7-10-2008_


_Modified by ABA Scirocco at 3:33 PM 7-10-2008_


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## vwovw (Apr 2, 2004)

*Re: fuel accumulator (ABA Scirocco)*

http://www.autohausaz.com/sear...lator


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