Accumulator function

[Helirich]

I just replaced the accumulator and I have some questions about it’s operation. I know it is a spring loaded diaphragm that should keep the fuel pressure up for awhile after the car is shut down. What I don’t quite follow is the lines to it. There are three. I would assume one comes from the pump and another goes on to the engine. What is the third for? It looks like it comes off the back of the diaphragm. Is it just a vent? That hose on mine had a leak and fuel was coming out. I don’t understand why there is fuel even there to leak. Of course my diaphragm could have a leak, but I assume it’s not supposed to leak. What doesn’t that hose dump overboard?

[Michael]

I just replaced the accumulator and I have some questions about it’s operation. I know it is a spring loaded diaphragm that should keep the fuel pressure up for awhile after the car is shut down. What I don’t quite follow is the lines to it. There are three. I would assume one comes from the pump and another goes on to the engine. What is the third for? It looks like it comes off the back of the diaphragm. Is it just a vent? That hose on mine had a leak and fuel was coming out. I don’t understand why there is fuel even there to leak. Of course my diaphragm could have a leak, but I assume it’s not supposed to leak. What doesn’t that hose dump overboard?

I believe the single port on the slender end is a vent but I don't know if it vents back to the tank or the pump or ??

[Bitsyncmaster]

It is a vent that goes back to the fuel tank. It would only have fuel if the internal balder was leaking. Maybe if you overfill the fuel tank some fuel can back feed into that line.

[David T]

It is a vent that goes back to the fuel tank. It would only have fuel if the internal balder was leaking. Maybe if you overfill the fuel tank some fuel can back feed into that line.

The 3rd port is when the diaphragm leaks, the fuel can go back to the tank. If you take the hose off, it is tee'd into the line that is the return from the fuel pressure regulator and fuel returning to the tank will leak out of that line. The accumulator also softens the pulses from the fuel pump besides holding up "Rest Pressure" for the fuel injection. When it is bad it is one of the three usual things that cause the hard hot start syndrome. The other 2 being a bad fuel pump check valve and a leaky fuel pressure regulator (or a leak in a fuel line or connection).

[Ron]

It and the return line (12) from the FD-FV join a Tee (11), which eventually dumps into the tank (via 68 ).

68344

[Helirich]

The 3rd port is when the diaphragm leaks, the fuel can go back to the tank. If you take the hose off, it is tee'd into the line that is the return from the fuel pressure regulator and fuel returning to the tank will leak out of that line. The accumulator also softens the pulses from the fuel pump besides holding up "Rest Pressure" for the fuel injection. When it is bad it is one of the three usual things that cause the hard hot start syndrome. The other 2 being a bad fuel pump check valve and a leaky fuel pressure regulator (or a leak in a fuel line or connection).

Ahhh, that would explain why it leaked after I installed the new accumulator. Seems like that would fill the back side of the diaphragm with fuel. (The lines are above so the air would bleed out) I guess that doesn’t hurt anything.

I’ve had a gas smell for a long time when I apply the brakes. Everything I read said I had a leak at the fill tubes or fuel pump. But I checked that multiple times and it was all dry. I believe now that this leak was the source of the smell. I think the gas was leaking in my frame and would slosh forward when I hit the brakes. I will be testing this soon. (It only did it after a fairly long drive)

[David T]

A fuel smell is often a problem with the fuel tank. On one car the rivets in the sender were leaking when the tank was full. On another the gasket was missing from the sender unit. Very common for the boots for the fuel pump to leak on the old style fuel pump. The inner boot MUST be dry, if it leaks you will get a fuel smell even if the outer (upper) boot is good. On some cars there is a small leak on the fittings for the fuel filter. On my car the gas cap would not seal properly anymore so I replaced it and fixed the smell. Keep looking and you will find it. Replace that small hose from the accumulator 3rd port if the hose looks cracked.

[Michael]

Ahhh, that would explain why it leaked after I installed the new accumulator. Seems like that would fill the back side of the diaphragm with fuel. (The lines are above so the air would bleed out) I guess that doesn’t hurt anything.

I’ve had a gas smell for a long time when I apply the brakes. Everything I read said I had a leak at the fill tubes or fuel pump. But I checked that multiple times and it was all dry. I believe now that this leak was the source of the smell. I think the gas was leaking in my frame and would slosh forward when I hit the brakes. I will be testing this soon. (It only did it after a fairly long drive)
There are two areas to still check.
First the gas cap seal can cause a strong odor in the cabin. The fuel isn't leaking, but the vapor can if the seal is bad and the cabin air pickup is practically right beside the cap.

Another area is the fuel gauge sender cap. This can leak especially with a full tank and under braking. The fuel is forced forward under braking causing more pressure than normal on the cap, and it can leak but it's hard to see unless you are looking for it. Fill it up and give it a few hard brakes and a little cornering. Immediately turn wheel to full right and look through the left side front wheel well at the top of the tank, you should see the top of the tank and the sensor cap and any fuel that has leaked. It could also very well be the pump seal but if you have already eliminated that possibility, chances are if you see raw gas on the tank, it's the sender cap.

One more possibility is the hard lines above the accumulator that can only be accessed, (without removing the accumulator) from the top. It only takes a SMALL leak to cause a big smell in the cabin. You must remove the center console and remove the cover that has been glued in place to get on the fittings. Maybe try running the car while watching the fitting connections to verify a leak.

[Bitsyncmaster]

I had problems getting a good seal at the sender cap. I could not get the DMCH cap that is used to block the sender hole to seal. My tank had a notch cut in the lip (not sure if that is normal). My car did have the Zilla sender when I bought it. I ended up cutting a metal disk with a gasket and using the old sender ring to get it sealed.

I tested mine by filling the tank right to the top of the fill cap. I was testing the capacity and sender resistance values anyway but that proved everything was tight.

[Helirich]

What I had done previously was remove the access panel to the fuel pump. Filled the tank and drive the car hard. (Braking and turning) Checked the tank/pump/fill hose and cap multiple times. Nothing wet and no smell.

There’s one particular restaurant my wife and I go to almost weekly. It is an hour away. About 1/2 hour down a highway, it tees into another highway. I’m usally doing about 70 and have to brake hard at the tee. Then I make a hard left excellerating turn. Right than is when we almost always smell the fuel. My theory is the accumulator hose was leaking all the while. After 1/2 hour, there’s a puddle in the frame. When I brake it sloshes forward to make the smell. On short drives it hasn’t leaked enough to make the puddle, so no smell.

Although, looking at this, you might think it would leak a ton, but when the hose is bent in the curve at the accumulator, it closes up all these cracks.

68353

We will be going to our favorite restaurant soon. (Maybe today) I’ll see. I’m hopping for better gas mileage too.

One thing I’ll mention. After changing the accumulator with the old hoses still in place, I only turned the key on and off a few times and this hose was dripping. Assuming the new accumulator was not leaking through the diaphragm, that fuel must have come from the return line. That tells me there is quite a bit of fuel going back to the tank. Also, it probably doesn’t take long to fill the backside of the accumulator with fuel.

[Bitsyncmaster]

There is a lot of returned fuel. I had run a test on my new pump just by measuring the amount of fuel returned. That test showed me the pump rate at 75 PSI. I will have to look for my post on those tests I did. The return rate only drops with the rate of fuel the engine uses.

[Bitsyncmaster]

I found that post. Here is the return result.

I ran a flow test. This is the amount from the return line with the pump running for 60 seconds. This was with 5 gal. in the tank. Flow was just a little less than 2 quarts for 60 seconds. So that is the flow at 75 PSI since my primary pressure regulator has been calibrated for 75 PSI.

[Bitsyncmaster]

I found that post. Here is the return result.

I ran a flow test. This is the amount from the return line with the pump running for 60 seconds. This was with 5 gal. in the tank. Flow was just a little less than 2 quarts for 60 seconds. So that is the flow at 75 PSI since my primary pressure regulator has been calibrated for 75 PSI.

So my pump setup results in 30 gal/hour which would be consumption around 300 HP. I would guess if you needed more GPH you would need larger fuel lines and a higher power pump.

[David T]

So my pump setup results in 30 gal/hour which would be consumption around 300 HP. I would guess if you needed more GPH you would need larger fuel lines and a higher power pump.

There are several reasons for a high flow rate. The flow rate needs to exceed the maximum demand of the motor. You want a decent recirculation flow to distribute heat. You want enough flow to pressurize the system so you don't vaporize the fuel when it is hot. By recirculating the fuel you filter out any contamination that may accumulate. You also mix the fuel to prevent any separation and keep water in suspension. Over time the flow rate can be reduced by the filters building up contamination so you oversize things to maintain a minimum flow rate even as things start to age. This is not like the older carburated systems that did not recirculate and only provided enough pressure and flow to get the fuel to a carburetor. Newer direct injection systems run at even higher pressures and flow rates, more like diesel systems. Because of the high flow rate that is why you see the pick-up hose (suction hose) on the fuel pump collapse when they get old and soften. On Deloreans we only have the one fuel pump. In many fuel injection systems they use 2 pumps. One is basically a transfer pump to get the fuel out of the tank. A second, external pump gets the pressure up for the injectors. Finally, with a high flow rate it enables you to build up pressure quickly to get the motor started during a short cranking cycle. A lot of factors go into designing a fuel system. Just for an example, look at a fuel system on a dragster. They have to pump gallons of fuel in seconds. Everything is LARGE, the pipes, the pumps, everything to get all of that fuel to the motor in seconds. An extreme example is in rockets. They have to move thousands of pounds of fuel every second so it is on a whole different scale!

[Helirich]

So I drove to our favorite restaurant today and the fuel smell was as bad as ever. So I need todo some more searching. On a good note, the car starts hot better than ever.

[Helirich]

So I jacked up the car, removed the fuel pump access panel in the spare tire well. Started the car and turned on the AC. I ran it like that for at least 20 minutes. I crawled under and checked the accumulator multiple times. Went over the fuel pump, lines at the tank and engine. Everything is dry. I couldn’t smell anything. I couldn’t smell fuel when I put my nose to the open fill tube. I don’t know what to do.

How about the triangle frame cover under the tank. Can I just unbolt that? Or will the frame need to be supported to keep it from spreading? Am I going to see anything of use under it? Will the tank try to drop out? Are there any parts of the tank that get holes by ware?

[Bitsyncmaster]

It may be only when the gas in the tank sloshes that you get a leak. One great test for that is to fill the tank right to the top of the filler neck. Then inspect the sender and pump locations.

[WHO1DMC]

So I jacked up the car, removed the fuel pump access panel in the spare tire well. Started the car and turned on the AC. I ran it like that for at least 20 minutes. I crawled under and checked the accumulator multiple times. Went over the fuel pump, lines at the tank and engine. Everything is dry. I couldn’t smell anything. I couldn’t smell fuel when I put my nose to the open fill tube. I don’t know what to do.

How about the triangle frame cover under the tank. Can I just unbolt that? Or will the frame need to be supported to keep it from spreading? Am I going to see anything of use under it? Will the tank try to drop out? Are there any parts of the tank that get holes by ware?

You should have no problem with taking off the fuel tank cover. The fuel tank is usually tightly wedged in there so it shouldn't move. Not saying it can't move I just know that when I took mine of 5 years ago to have it powder coated mine didn't move. Also at the time I didn't know how much fuel was in it.


Dave B.

[Michael]

If you absolutely can't find a raw fuel leak, then you might want to consider the possibility of a vent leak in the evap system. Maybe the vent hose at the filler neck has come loose or any number of vent hoses around the cabin area may be split or loose or maybe even the roll over valve itself.
The thing with fuel vapor is it can travel and the scent can work it's way from almost anywhere so don't assume it must be around the cabin or cabin air intake, but it's a good place to start.

PS I doubt you will find anything by removing the closing plate. The plate does keep the tank in place but it's a tight fit and the neck should prevent it from falling out but I wouldn't count on it, especially if there is any amount of fuel in the tank so use a jack and a protective shield to prevent the tank from being punctured and support the tank once the closing plate is off. Again the only thing you will have access to there are some coolant pipes.

[WHO1DMC]

I was thinking if you disconnected the hose at the evap tank that goes to the fuel tank and put a little air in to see if there is a leak. Preferably a leak detection machine would work best.



Dave B.

[Helirich]

Boy, you guys get up early! I’m going to look in to the vent hose. I do think it’s from fuel sloshing, but I don’t think it’s coming out at the top of the tank. One thing we noticed yesterday was the smell is stronger when I have the AC on normal. (I usually have it on max)

Edit, I don’t see a vent on Ron’s diagram. (Except for the fill vent) Is that all there is?

[Rich]

Edit, I don’t see a vent on Ron’s diagram. (Except for the fill vent) Is that all there is?

No, that's not all there is.

Ron showed you where the accumulator 'safety return' hose is. That diagram doesn't include the evap control system (https://store.delorean.com/parts/fuel-emissions/2-4-0-evaporative-control-systems.html). That's what some of the earlier posts today are pointing you to.

Remember that the "vents" we talk about in the fuel and evap systems don't vent directly to atmosphere. The "venting" is only through the charcoal canister in the left pontoon. It traps fuel vapor for later combustion.

The connections, hoses and components shouldn't be loose or cracked in any bits of the fuel or evap systems. You can see on the evap diagram there are 4 hoses and at least 3 components (fuel filler neck, rollover valve, gas fill cap) up front (and not on the fuel diagram) that could leak fuel vapor.

When A/C is set to MAX much less air is routed from the exterior intake grille to the cabin so keep looking up front to start with since smell is worse in NORM mode.

[Helirich]

No, that's not all there is.

Ron showed you where the accumulator 'safety return' hose is. That diagram doesn't include the evap control system (https://store.delorean.com/parts/fuel-emissions/2-4-0-evaporative-control-systems.html). That's what some of the earlier posts today are pointing you to.

Remember that the "vents" we talk about in the fuel and evap systems don't vent directly to atmosphere. The "venting" is only through the charcoal canister in the left pontoon. It traps fuel vapor for later combustion.

The connections, hoses and components shouldn't be loose or cracked in any bits of the fuel or evap systems. You can see on the evap diagram there are 4 hoses and at least 3 components (fuel filler neck, rollover valve, gas fill cap) up front (and not on the fuel diagram) that could leak fuel vapor.

When A/C is set to MAX much less air is routed from the exterior intake grille to the cabin so keep looking up front to start with since smell is worse in NORM mode.

I wish I saw this earlier. In any case, I found the evap system in the manual. I removed all the access panels again. I checked all the hoses again. The pump hoses are almost new when I installed the pump. They look and feel good. The pump and sensor cover were tight. The fill hose looks and feels new. There is a short small hose from the fill to the roll-over. It also looked new. I removed the roll over and tested it. It does not leak. The short hose clamp was not really tight, but I doubt it is the problem. The long hose from the roll over does not look as good as the others, but I can’t say I found any real problem.

I got to looking at the intake for the HVAC. It is sealed from the trunk, but open to the fuel fill section. In fact, it almost seems like it’s designed to pull any fumes from that area. Lol. Anyways, there’s only two sources of fumes there. One is the gas cap and the other is a general vent from under the trunk. (My rubber cover to the clutch master is in good shape, so no fumes coming from there.)

I inspected my gas cap again and it looks good. The spring is tight and the rubber seems to be in good shape. Since I’m grabbing straws, I cut a new rubber gasket and installed it on the cap in addition to the stock one. The cap is serious tight now. I’m going to take a ride with my wife when she gets home. She has a nose that can smell anything. I still have the panels off, so I will be doing some irrational driving to see if I can make it leak. The tank is over half full. In my garage, I drove about 10 mph and slammed on the brakes. I couldn’t make any fuel come out of the filler even with the cap off.

[Rich]

Some thoughts about your test drive.

In looking back at when you smell fuel:

1. You report it's only after a long drive. That could be a fuel vapor leak due to improper tank pressurization when hot causing vapor to leak out of the tank or any of the components. Smells the same as spilled fuel.
2. You don't report seeing any fuel pooling anywhere nor spilling onto the ground. Be sure to check thoroughly. If there is no fuel spilling/pooling then as with #1 you are chasing a vapor leak.
3. It happens (only?) when you apply the brakes. That points to something near the front of the tank. You report the fuel pump boot and connection is good. Further ahead than that boot is the fuel sender/cap. David T mentioned it's a leak source.

I'd say #3 is the next thing to test. Keep all the fuel access covers off up front. Do your braking thing, then immediately turn off the engine and look/smell closely for signs of wet fuel at the fuel sender or the pump boot (again). You have to check quickly before the fuel vaporizes. You can add more fuel to be sure you're making a worst-case test.

After that try testing for tank pressurization. After a 15-20 min drive (to heat/expand the fuel) turn off the engine. Immediately pop the fuel cap off. You shouldn't hear or smell vapor/air whooshing out. The vapor in the tank and the low-side hoses is meant to be routed to and through the charcoal canister. A pressurized tank means your evap system isn't working and it makes what would otherwise be a small vapor leak act like a bigger (smelly) vapor leak. You might also see the pump boot puffed up in that case.


....I’ve had a gas smell for a long time when I apply the brakes. Everything I read said I had a leak at the fill tubes or fuel pump. But I checked that multiple times and it was all dry. I believe now that this leak was the source of the smell. I think the gas was leaking in my frame and would slosh forward when I hit the brakes. I will be testing this soon. (It only did it after a fairly long drive)

[Michael]

I said to start looking at the evap system if you were sure there wasn't a raw fuel leak but just to reiterate the possibility of a fuel leak at the accumulator....
You should remove the center console and the top cover on the underbody and watch closely while the engine is running. If there is even a tiny leak at one of the flare fittings above the accumulator, it might not show under the car because the rolled edges of the frame might catch any fuel, but it would certainly flood the cabin with a fuel smell.

[Ron]

$.02


...
After a 15-20 min drive (to heat/expand the fuel) turn off the engine. Immediately pop the fuel cap off. You shouldn't hear or smell vapor/air whooshing out. The vapor in the tank and the low-side hoses is meant to be routed to and through the charcoal canister. A pressurized tank means your evap system isn't working and it makes what would otherwise be a small vapor leak act like a bigger (smelly) vapor leak.
I'm thinking pressure can be in the system if the throttle is closed when you shut it off and it can build up afterwards - It purges only when the engine is running.

"2. Due to the design of the fuel injection system,it will be normal to have a slight amount of
pressure in the fuel tank. This pressure will be
noticed when removing the fuel filler cap." WSM, D:06:02, 2.

======

IIRC, you have a smoke machine...If you strike out up front, maybe try putting it on the Vent and Purge hoses at the canister.

[Helirich]

Some interesting things to report.

So, I put my extra rubber gasket on the gas cap. Loaded up the wife and went for a ride. First thing I notice is the fuel gauge is reading beyond full. In fact, the needle is straight up. I know the tank is only about 3/4 full. I had the door open for a couple hours and the alternator was struggling to change the battery. (Belt squealing a little) I figured that maybe the low voltage effected the gauge. I had the AC on also, so that wasn’t helping the alt catch up.

Anyways, I got it up to 70 mph and slammed on the brakes. No smell. This was with the AC on normal. (Should be the most likly to smell) I did it again and this time, I jumped out and opened the trunk. (All the access panels are off) I looked at everything and no wet spots. Felt all the hoses also. My wife still didn’t smell anything so I thought I would remove the gasket from the gas cap and try again. When I undid the cap, my wife said the fuel gauge went to 3/4 full right then. (From the off the scale reading) Hmmmm.

So I put the cap on with out the extra gasket and closed the trunk. I did a left u-turn to go back and before I even got up to speed, my wife said she could smell fuel. I did a couple more hard stops and she said it didn’t seem to get any stronger.

So I have a couple conclusions. My gas cap must be bad even though it seems good. The only thing that I could say about it is the rubber is kind of hard. I will order another tomorrow. I’m wondering if I have a problem with the canister/purge system. Like, how come a seal tank reads high fuel? The car was running when I removed it, so I can’t say if it was under pressure or vacuum. I don’t really understand how that effects the fuel gauge. I have the new fuel pump/gauge sender from Houston.

There is one other interesting thing I found out. I installed the access panel on the spare tire and the brake master, but left the fill tube access open. I turned on the key with the AC still on. Of course the fans started and air was blowing out the access hole. I’m guessing when I install the fill tube access cover, the air flow will be focused to the small vent next to the gas cap. So if there is any fumes, they will be sent right to the intake of the HVAC.

At this point,I really think my problem (with smell) is the cap. But when I get a good seal there, I may have an additional problem with my canister or lines. The manual mentions several problems from pinched lines and such. I’m probably going to have to let Micheal say “I told you so” because I think he told me to check the cap a long time ago in another thread. It looks like Rich is on to something about the pressuration. Tomorrow I plan to undue both ends of the long line and run some compressed air through it. If it’s open, maybe I have an issue with my canister. Is there any test for that?

I had a prior appointment tonight so I didn’t get to do much after the ride with my wife. I did put the extra gasket on the cap and start it again. This time the gauge was unelected. I’ll up date as I know more.

[Rich]

Two comments about your plan.

Comment A is about checking that line with compressed air - or not. That test is done with the entire line connected to the canister. You just want to verify any flow to start with.
Comment B points to checking the rollover valve with both of its hoses free before testing the main canister line. Seems like the likeliest point of blockage. Or just get a new one when you order the new gas cap.

A. Try running a vacuum test on it (with a brake bleeder pump?) rather than using compressed air unless your compressor has a low-pressure regulator on it that's set to maybe 5psi. That line is mostly metal tubing but you don't want to fail a hose or the canister. You can test the line from the front - keep the entire line connected to the canister until you know you need to get to the canister.
B. Take notice of this info from the DMCH description of the Rollover Valve p/n 101402:
"The rollover valve is designed so that in the unlikely event that you should "roll" your DeLorean, this prevents liquid fuel from leaking out of the fuel tank and travelling through the vapor hose to the canister. Sometimes we'll see where a bad one can contribute to fuel smells from the front of the car, or in the passenger compartment."




Tomorrow I plan to undue both ends of the long line and run some compressed air through it. If it’s open, maybe I have an issue with my canister. Is there any test for that?

[Helirich]

Two comments about your plan.

Comment A is about checking that line with compressed air - or not. That test is done with the entire line connected to the canister. You just want to verify any flow to start with.
Comment B points to checking the rollover valve with both of its hoses free before testing the main canister line. Seems like the likeliest point of blockage. Or just get a new one when you order the new gas cap.

A. Try running a vacuum test on it (with a brake bleeder pump?) rather than using compressed air unless your compressor has a low-pressure regulator on it that's set to maybe 5psi. That line is mostly metal tubing but you don't want to fail a hose or the canister. You can test the line from the front - keep the entire line connected to the canister until you know you need to get to the canister.
B. Take notice of this info from the DMCH description of the Rollover Valve p/n 101402:
"The rollover valve is designed so that in the unlikely event that you should "roll" your DeLorean, this prevents liquid fuel from leaking out of the fuel tank and travelling through the vapor hose to the canister. Sometimes we'll see where a bad one can contribute to fuel smells from the front of the car, or in the passenger compartment."


I ended up working on something else today.

On your comments,

I did check the roll over valve. It’s good.

On the line test, how would you test it with it hooked to the canister? Unhook the line to the engine? I don’t have a brake bleeder pump and I’m not sure how low I can regulate my compressor. I think I have a 12volt vacuum pump. In the manual, it says the canister is unserviceable. If it’s bad, replace it. But it doesn’t really tell you what goes bad. Not sure what’s in it. A filter maybe?

[WHO1DMC]

I ended up working on something else today.

On your comments,

I did check the roll over valve. It’s good.

On the line test, how would you test it with it hooked to the canister? Unhook the line to the engine? I don’t have a brake bleeder pump and I’m not sure how low I can regulate my compressor. I think I have a 12volt vacuum pump. In the manual, it says the canister is unserviceable. If it’s bad, replace it. But it doesn’t really tell you what goes bad. Not sure what’s in it. A filter maybe?

The evap canister is just filled with activated charcoal.
The evap canister has one serviceable part. The bottom of the canister pops off with a screw driver and you will see a filter made of fiberglass that can be changed.
I changed mine a few years ago but it wasn't really that terrible looking. But I did find some dirt in the over flow hose maybe put there by a mud dauber.
I do have filters if you need one.



Dave B.

[Rich]

Yes, unhook the lines to the engine so only the line from the valve is still connected to the canister for the test.

About the flow test, not the canister:

You're just looking for any kind of low air flow such that the tank can't pressurize.

Your 12V vac pump will do. Connect it to the end of the hose you took off the passenger side of the rollover valve and pull air from the canister forward. Check the vac pump exhaust port to detect airflow. Running the air backward shouldn't hurt anything.

You can even try just blowing into the hose at the rollover valve if you dare.

If you get flow thru the hose-canister and if the upstream evap connections, including the rollover valve and the filler neck fitting are all open then the tank cannot pressurize which is one thing you want to rule out for the fuel smell problem.





On the line test, how would you test it with it hooked to the canister? Unhook the line to the engine? I don’t have a brake bleeder pump and I’m not sure how low I can regulate my compressor. I think I have a 12volt vacuum pump. In the manual, it says the canister is unserviceable. If it’s bad, replace it. But it doesn’t really tell you what goes bad. Not sure what’s in it. A filter maybe?