Accumulator function

[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. 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. 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.