Fuel accumulator removal / bypass

[FABombjoy]

I just finished bypassing the accumulator and wanted to share my thoughts.

First, totally worth removing. I now have a rubber-free fuel system. I replaced the accumulator in 99 or 2000 and it was leaking into return port. It serves no meaningful purpose with EFI. It just sits there threatening to leak-through and bypass fuel back in to the tank, taking rubber shrapnel with it. It makes strange noises when you turn the car off.

If I did it again I would not spend the time & money on parts to adapt the stock fuel feed line, especially having to work through the accumulator port. The lack of space and strategic use of impact tools, pry bars, and short-length wrenches to keep the stock lines from kinking make it challenging. Two lengths of nylon fuel tubing ran in tandem with the heater core lines would be far easier.

After removing the accumulator & fittings, I used Eaton p/n 15.163-6-6 to adapt the feed elbow to -6AN
https://i.imgur.com/OmXLZ2f.jpg

Before:
https://i.imgur.com/Kqdsv1u.png

After:
https://i.imgur.com/vmoRU1H.png

A new braided hose routed where the stock hard line was. I'm sure if I spent more time I could have found fittings that would mate to the "bulk ring" 24 degree flare, but the 2 or 3 that I purchased would not fit correctly. Initially I'd hoped to run new aluminum hard line but the routing of it wasn't going to work without drilling a hole through the frame or removing the body. So a new braided line was the quickest way to finish the job.
https://i.imgur.com/0mweCMT.jpg

New fuel filter, bottom fitting converted from elbow to banjo. Allows any style of K-jet filter to be used.
If I'd converted to nylon lines, a quick disconnect EFI filter could be used.
https://i.imgur.com/lL4uVHx.jpg

To plug the return line, a chunk of original hard line (I think from the old fuel return pipe) w/ the bulk ring/olive/ferrule & nut was used. I just soldered in a random bolt and screwed it back in to the return T. Low fi but free. You can see it dangling there in one of the above photos too. Really a piece of rubber line could have been attached and plugged but I didn't want some vestigial rubber appendix threatening to leak.
https://i.imgur.com/vFdUVeX.png

Peace of mind, and the only cost is that I will reek of gasoline for the next few days.

[powerline84]

Looks nice man. To piggy back on Luke I ended up doing a similar bypass and accumulator removal when I first went to the efi conversion on the prv. The reason was we figured out on the Dyno that the accumulator had failed in a way that it was bypassing so much fuel back to the tank it couldn't maintain a consistent fuel pressure and was causing starvation issues on high demand runs inconsistently.

So...I would say if you do an efi swap you absolutely should just ditch the accumulator and avoid the Hassles...it may prematurely solve a problem you have not yet discovered lol.


I also switched to the Delphi pump and ditched the Houston huko.

[Tom_hd02]

Luke,
Excellent write up. I just removed the fuel accumulator a few days ago in preparation for EFI, but I couldn't find the appropriate fittings to connect the fuel lines. I ended up cutting the male fittings off the fuel accumulator and welding them together , creating a male-male fitting, but I'd like to eliminate that short rubber/nylon hose from the feed line. Where did get the an-6 fitting?

[Bitsyncmaster]

Do any modern cars use an accumulator? One function of the accumulator is to smooth out the pressure pulses of the fuel pump.

[powerline84]

Do any modern cars use an accumulator? One function of the accumulator is to smooth out the pressure pulses of the fuel pump.

A few modern ls Cars use a regulator/filter combo . Most people who want a simple fuel system for an ls swap or many other swaps use a 2003 Corvette ls wix or ac Delco filter regulator....puts out 58psi constant and also filters the fuel.

[FABombjoy]

One function of the accumulator is to smooth out the pressure pulses of the fuel pump.
I suspect this is DeLorean folklore. I guess I've never seen anyone pressure log just the fuel pump & no injection but I'd suspect it's fairly smooth.

CIS being continuous would be less susceptible to pressure spikes at the engine compared to solenoid injectors. For EFI that seems to typically be handled by fuel pressure dampers rather than something as large as the accumulator.

[AugustneverEnds]

Question: Where did you get your braided line from? I believe my rear feed hard line is leaking (#30 https://store.delorean.com/parts/fuel-emissions/2-1-0-tank-hoses-pump-accumulator-etc.html) and it seems like there is no way to remove it without lifting the body from the frame. My plan was to have a custom line made. I'm researching where to buy from and what fitting I need on each end.

[FABombjoy]

Its Eaton/Aeroquip FCC0606-06 with matching Aeroquip steel AN fittings.

You can remove 106989 without separating the body but putting a new hard line in its place will be challenging. Not sure what (if any) fitting would be available for the accumulator connection. You can easily use AN for the fuel filter along with a corresponding banjo fitting on the bottom in place of the stock elbow. This also will allow for the use of all fuel filters, including the ones with a captive nut on the bottom rather than just the DMC compatible filters.

As an addendum, I did end up installing a different fuel filter and all straight-through connections. I have an "August" EFI problem with heat and efficient, long highway drives that causes fuel pump cavitation once the cooling pipes have heated the gasoline. Removing the 90 degree fittings and installing insulation on the cooling pipes helped, but will soon implement PWM control to slow the pump down and limit cavitation.

[AugustneverEnds]

You really think 106989 can be replaced without separating the body? I'm not confident I have the skill to pull that off but maybe I will have to try.

Jonathan posted DMCMW sold him a flexible line to replace 106989 with the correct fittings for the accumulator and filter so fingers crossed they or another vendor still have some on hand.

If that fails I guess my next move will be to inquire about having a custom line made.

Thanks for the info. I was going to wish you best of luck with your EFI issue but sounds like you already have it solved :thumbup:

[FABombjoy]

You really think 106989 can be replaced without separating the body? I'm not confident I have the skill to pull that off but maybe I will have to try.
Not at all :D I know you can remove the old one, breaking clips in the process, and it will be bent out of shape. Getting the new one in place and in usable condition will be likely not possible.


If that fails I guess my next move will be to inquire about having a custom line made.

Thanks for the info. I was going to wish you best of luck with your EFI issue but sounds like you already have it solved :thumbup:
IIRC the fittings on the accumulator direct are some kind of metric size. With a little research you should be able to find the matching hose fitting, then use 6AN and banjo on the fuel filter. If a vendor has one that's great but you shouldn't have to rely on one for a single fuel hose.

Depending on where it's leaking you may be able to cut & install a repair fitting in place, too.

The fuel heat issue affects all DMCs really. I'm surprised hasn't been properly solved yet. A replacement tank closing plate that separates the hard lines for example.

[AugustneverEnds]

I was just looking through some plumbing stuff I have laying around and a 3/8" compression nut on a toilet fill line fits like a glove. Wonder if the 7/8" end will fit on a fuel filter :hysterical:

Looks DMC was prepared for cheapass owners trying to use plumbing supplies to keep their cars running

[Helirich]

Not at all :D I know you can remove the old one, breaking clips in the process, and it will be bent out of shape. Getting the new one in place and in usable condition will be likely not possible.

I haven’t looked at it, but if it can’t be replaced in the stock location, it would seem like it can’t be that hard to run a line in another location. Of course, I’m not a “factory only” kind of guy.

[AugustneverEnds]

I haven’t looked at it, but if it can’t be replaced in the stock location, it would seem like it can’t be that hard to run a line in another location. Of course, I’m not a “factory only” kind of guy.

I will probably end up using some type of alternative to the hard line routed slightly differently to the way it is. I'm not concerned with originality here just need a leak free connection.

[Coppertank]

Hello!

Sorry that this is a bit of a necro post, but I'm curious if this will benefit my car.

I'm running a TEC-II ECU for EFI on a 3.0L Eagle Premier engine in #2860. I cannot pin any sort of pattern down, but the car will sometimes outright refuse to prime. I've checked all the wiring and relays and haven't come across anything sketchy. I've hooked a multimeter up to right where the TEC-II runs to the fuel pump. When it's not priming, there is no power at all. I've basically narrowed it down to the ECU itself thinking it needs replaced or re-tuned, but lately I've been thinking maybe the pump won't prime if theres too much pressure in the accumulator? I can hear what I think is the accumulator making a sound when the pump primes and sometimes when I turn the engine off.

[Ron]

(Assuming you confirmed that the ECU is getting the signal to prime during failures...)

I'd say that the ECU is the better bet since normal D rest pressure is less than 50psi [3.3 Bar], and, the PPR will keep it <= 75.4 psi (5.2 Bar).
Next time it fails to prime, you might try jumping 12V to the ECU pump terminal...

[FABombjoy]

When it's not priming, there is no power at all. I've basically narrowed it down to the ECU itself thinking it needs replaced or re-tuned, but lately I've been thinking maybe the pump won't prime if theres too much pressure in the accumulator?
I'm not familiar with this ECU but there may be some control over priming when the engine is warm vs cold.

It's also possible there is a fuel pressure sensor that's part of the pump control but this is less common.

EFI cars do not need an accumulator but this isn't the source of your situation, and removing it won't change anything.


the PPR will keep it <= 75.4 psi (5.2 Bar).
Next time it fails to prime, you might try jumping 12V to the ECU pump terminal...
The PPR is likely on another car :D Should be closer to 45psi (less when engine running).

Don't put 12v at this terminal. EFI ECUs almost always are switched ground.

[Ron]

The PPR is likely on another car :D Should be closer to 45psi (less when engine running).

Don't put 12v at this terminal. EFI ECUs almost always are switched ground.LOL - Yeah, I guess the PPR wouldn't have anything to do with since it's eliminated along with the FD.

I think I'll ban myself from the EFI section...:bang:

[Coppertank]

I'm not familiar with this ECU but there may be some control over priming when the engine is warm vs cold.

It's also possible there is a fuel pressure sensor that's part of the pump control but this is less common.

EFI cars do not need an accumulator but this isn't the source of your situation, and removing it won't change anything.


The PPR is likely on another car :D Should be closer to 45psi (less when engine running).

Don't put 12v at this terminal. EFI ECUs almost always are switched ground.

I very much appreciate input from both of you! It's great to hear input that basically validates what I've been headed towards. This has been an uphill battle for the last half of a year. I just bought a Windows XP with a built-in serial port off of ebay so that I can talk to the damn thing (I did get it running with a modern laptop and a serial-to-usb adapter, but didn't feel like lugging my main laptop around). Yesterday, I was able to run a "datalog" file which basically shows that the idle starts bouncing between 700-800 once the coolant reaches about 140F. Definitely worth investigating if it's a setting that adjusts based on the temp. After I ran the datalog, I turned the car off and tried priming it a few times. The pump would kick on and then stop more abruptly than usual. Normally it primes for about 15-20 seconds or so before it stops.

Today, I took a look at the car without starting it. I disconnected the fuel pump relay and hooked in a multimeter. When I turn the key on, power runs through it every single time. Forgive me if this sounds silly, because I am a computer guy and not a mechanic; Is there anything that could be telling the ECU that there's "enough gas" and so it just doesn't prime? If I jump the relay, the pump kicks on without fail. But it won't start if I don't have the relay in.

[FABombjoy]

A fuel pressure sensor combined with ECU fuel pump driver module or solid-state relay. This is really not common at all on basic EFI conversions.

There are a host of reasons that the idle would oscillate but the fuel pump isn't likely one of them. You should start a new thread and post some data or a recording of the car & gauges visible on the laptop.

[Coppertank]

A fuel pressure sensor combined with ECU fuel pump driver module or solid-state relay. This is really not common at all on basic EFI conversions.

There are a host of reasons that the idle would oscillate but the fuel pump isn't likely one of them. You should start a new thread and post some data or a recording of the car & gauges visible on the laptop.

Good thinking! Sorry to momentarily hijack your thread. It's good to know that deleting the accumulator wouldn't resolve it. It's still something I may do down the road if it's not needed for EFI anyway. Thanks again!

[FABombjoy]

Good thinking! Sorry to momentarily hijack your thread. It's good to know that deleting the accumulator wouldn't resolve it. It's still something I may do down the road if it's not needed for EFI anyway. Thanks again!
All good! Maybe someone else has a similar problem down the road, would make it easier to find w/ its own thread.

If the bad running happens at a certain temp, it's likely some part of the tune. For example:
-Closed-loop idle control engages but settings are not correct
-Idle target drops and now you're operating in an area of the fuel map that isn't tuned correctly