[WIP]

Hissing sound???

Ok, noticed on my '84 Spider... a Hissing sound from the engine compartment... am looking all around, notice the Fuel Pump Regulator bolt is lose, tighten it up, notice the hose that connect to the top of same, is showing some cracks... cut off the top 1/2 inch, reconnect... still hissing, not as loud, but still there... if I wiggle the entire regulator, the hissing stops/starts.... not sure if the hissing is coming from somewhere on the rail itself though, as I push the rail around, up down, etc... the hissing stops/starts as well... should I loosen that large bolt at the bottom of the regulator and then reconnect (sigh, if it were only to be that simple)... do ya'll think that there is a problem in the rail somewhere?

Anyone had this happen to them yet, what did you do?

Thanks folks, any advice/suggestions, as always appreciated... and again, am quite a rookie, so please bear with me. Lots to learn still... heck, only way I even knew that that thing was is because of the IAP "Whats that things under me hood" page.

 

[ghnl]

I haven't noticed a hissing sound from the fuel pressure regulator in our '84 Spider. I suspect you still have a vacuum leak. Hopefully from a hose or connection. Hopefully NOT the regulator itself (it'd be easier/cheaper to replace a hose vs the regulator).

The ultimate for new hoses is Greg Gordon's silicone hose kit.

 

[WIP]

Hmmmm

Ok, you were correct... had a vacuum leak... now, here is the fun part, need some more help here folks... sigh...

The leak was coming from the front right side of the plenum... there are 3 nipples on that side nearest to the fender... they are one right on top of the other... the bottom nipple has the hose that is connected to the Fuel Pressure Regulator... the middle one I have no idea... and the top one is the one with the leak... seems that hose is extremely old and brittle... I thought I could simply cut off an inch or so and reconnect to the nipple... nope, kept cracking again... this hose (about a half inch or less in diameter) seems to run from that nipple and disappears into the firewall... from there I have no clue where it goes to???

I may have to replace the entire hose... does anyone know where the other end of this hose goes?

So, end of that hammer head looking plenum that is closest to the passenger fender... three small nipples in a row, top to bottom on the plenum... top one is the culprit. Can you help... where does this lead to?

Thanks again.

Ron F.
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[Tifosi]

The topmost one goes to the fuel pressure regulator
The middle one goes to the oil vapor seperator
The bottom one goes to the fuel vapor recovery tank located behind the panel at the back inside of the right wheelwell

*the nipples are oraficed specifically for where they go and should not be shuffled around*

The one at the back of the plenum under the brake booster hose goes through the firewall and back to the vacuum sensor located right next to the ignition control box in the right vertical panel behind the seat.

 

[WIP]

Ok, hate to ask, but would rather double check... on mine it's like this:

Top - Goes into the Passenger Fender and disappears (the offending leak)

Middle - Goes to Oil Vapor Sep. (we agree on this one)

Bottom - Goes to the Fuel Pressure regulator

Sooooo... again, hate to ask, are you positive? If so, mine are not set up correctly and have not been for at least 5 years. (-;

If you are correct, then step one is to connect these to the correct nipples.

Step two will then be to find that Fuel Vapor Recovery tank you mentioned as this is the one that has the leak...

Please let me know... as I will not proceed until I have double checked - thanks!

 

[Tifosi]

Yes, I'm quite certain that is the correct order.

There's a picture of the vapor recovery tank and where it's located if you click the link in my sig and scroll down a bit. (it's in the 'step 1' section)

There's also a schematic of the hoses a bit further down (still in 'step 1'), the page that confirms what hose goes where.

 

[WIP]

Fantastic! And the photos ROCK! This is exactly what I needed - thank you very much.

Just ran outside and at least connected the hoses up correctly... man, for about 5 years they have been hooked up incorrectly - unreal!

Here is another dumb question... have I "hurt" anything by having it connected as I initially stated it was?

Should it run better, cleaner etc,... with it connected correctly now and when I replace that hose that runs into the "secret" compartment tomorrow? This is gonna be fun, ha ha.

Thanks again!

Ron F.
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[ghnl]

I doubt you've hurt anything.

The difference that a 'small' intake or vacuum leak makes in how well the car runs is amazing. Click here for a thread about finding & fixing air/vacuum leaks in our '84 Spider.

Replace those old, brittle hoses. As I mentioned above the ultimate is Greg Gordon's silicone hose kits - those hoses should outlast anything else available. For now, you can use standard vacuum hoses for the smaller hoses. The larger hoses are harder to find locally - thus you'll appreciate the completeness of Greg's kit.

While you are under the hood replacing hoses, I suggest you also remove the oil vapor separator and give it a thorough (internal) cleaning. Use some solvent (I use carb cleaner spray or lacquer thinner)) to soak the innards and remove the years of accumulated crud (sorry for the technical terms...). Also clean (or replace) the small diameter hose that exits the bottom of the separator and leads down to the bottom of the dip stick tube. This hose can also get clogged.

Here's a neat trick to help figure out if you have found all the intake/vacuum leaks: with the engine idling, lift up the dipstick an inch or so. When you break the dipstick's seal in the dipstick tube the idle should change slightly (for the worse). If it doesn't there is likely still a vacuum leak somewhere.

 

[WIP]

Great idea and will begin these little projects today. Thanks again for all the advice etc... dip stick trick seems to indicate I nailed the leak now... ok, so will attack the Oil Vapor Sep. next.

Thanks for all the help and clarifications - I really appreciate it. Will also be checking that site and most likely ordering the hose kit... my hoses are beyond imagination in terms of not looking too good. Thanks again!

 

[WIP]

ok, I'm back... hmmm... seems I have nailed a leak or two... but NOW... I hear a hissing... sounds like near the rear of the engine, passenger side... ok, I have looked and looked... then I put my head under the car, behind the front passenger wheel... could hear it much louder????

Anything under there???

Much louder under the car, front passenger side, behind that wheel... what the heck could that be??

Thanks again folks... this one is driving me bonkers. Sort of can hear it from the top, slightly... but from underneath... wow! Just sounds like a hissing sound... any ideas?

 

[Tifosi]

Leak at that hidden canister, or the small vac under the brake booster hose has popped loose or cracked/broken mabe?

The vac sensor hose starts out as rubber, then transitions into hard clear/semi-clear plastic near where it shoots into the firewall and continues as such down the door sill til it get's within a few inches of the vac sensor proper where it goes back to rubber.

It's also not beyond the realm of possibility that one or more of the rubber tubes that ties the plenum to the manifold is cracked/broken.

 

[ghnl]

Try using an 18"-24" length of 1/2" hose as a 'stethescope'. Hold one end near any suspect areas and the other end near your ear. That'll help pin down where the sound is coming from.

From the location you are describing, it sounds like the vapor cannister or its hoses need checking. Below is a schematic of the system. Item #12 is located behind the rear splash panel of the right front wheel well. Brush off the dirt and find a few phillips head screws to remove the splash panel. Note there are two hoses running into the engine bay (and then connected to the intake duct & plenum) plus a hose running along the right side inner sill (inside the ****pit) to the back of the car.

There is another hose (plastic tube as Tifosi describes) not shown in the sketch below that runs along the inner sill for the manifold pressure sensor (measures intake vacuum). The sensor is located under the trim panel behind the right side door.

 

[WIP]

Quick Update... thanks for the diagram and the such, very helpful.

I have been all over this thing, and still cannot find that hiss... took apart the panel in the wheel well... all was fine... no hissing in there... strange eh... tried the hose thing, but still no luck... just can't seem to get to it. Now, not sure if one thing has anything to do with the other... but starting is also harder than it has been in the past.... for example... when it is cold, I either can do a bit of cranking (2-5 times) or if I pump the pedal she'll fire up.... now, when she is warm, no sweat.... fires right up if I barely breathe on the starter... but it used to fire right up even when cold.

This hissing can be heard pretty decent when I am in the garage or up close to a building... but I'll be darned if I can find this thing... driving me nuts. again, can't hear in the car unless you are in the garage... but stick your head under the car, passenger side... and it's hiss-city. Went under, used a flashlight... can't pin point. Frustrating at best.

Thanks again folks.... I may have to just "leave it" - hate to do that though, ha ha... it's becoming personal now. (-;

 

[Tifosi]

Does the hiss sound change, or your idle pick up a bit when you step on the brake? (just a reach)

Just for giggles, you might want to pull the inspection plate on the front of the transmission (bolts, quick/easy removal other than being under the car) and see if there's evidence of any rubbing. (the flywheel touching the plate can sorta sound like a hiss if it's a light touch)

Beyond that, I'd say keep chasing around the plenum and all the rubber bits you can find over there as a vac leak can do some pretty nasty things to an engine if it's in the 'right' location.

 

[ghnl]

I do notice that I can hear air rushing through the hose from the AAV to the plenum during cold starts (when the AAV is open). It is not a leak, however.

The other place to check (it has been mentioned - just bringing it up again) are the 4 short hoses between the intake plenum and the intake runners.

You can try this: slightly pressurize the engine by sticking an air hose into the dipstick tube. I used about 10 psi with the oil fill cap off. Then, (engine off) listen to any suspect areas with the 'stethescope' (length of 1/2" hose). Place the palm of your hand over the oil fill to build up some pressure. If there is even a slight leak it'll be more obvious this way.

Once you are sure there are no intake.vacuum leaks if it still is hard to start when cold, investigate the Cold Start System. See the L-jet page in my signature for more info & testing procedure. Our '84 Spider starts right up, hot or cold, no fiddling with gas pedal needed (knock on wood....) On cold starts it should idle up to about 1200 rpm for a few minutes then settle down to normal (900rpm) after a few minutes.

 

[WIP]

Okeedokee... I'll give these things a shot - thanks!

did have one more tidbit of info, was paying close attention at lunch today.... noticed dueing idle... the engine kept going up 3-4 rpm, then back down at intervals of a few seconds... so watching the tach, I could see (as well as hear and feel) this happening... coincidence?

Thanks again!

 

[Tifosi]

When the engine was warmed up or cold?

When warm, it's sometimes a sign there's air bypassing the throttle body. (f'rinstance when the AAV hangs open after warmup, the revs will go up and down quite a bit, usually a couple grand or more though)

What is your average idle speed BTW?

 

[ghnl]

Do you mean the idle is varying by 300-400 rpm? (I don't know how you'd measure 3-4 rpm's...)

If you are certain there are no intake/vacuum leaks, I'd suggest you check for proper operation of the AAV. Remove the AAV and put it in the freezer for 20 minutes. Then look through the device - the passage should be nearly 100% open. Next put it in the oven at 150F (I use a 'toaster oven') for 15-20 minutes. Check the passage again (don't burn yourself!) - it should be 100% (or very nearly so) closed.

While it is warm, check that it actually blocks the passage of air. I had an AAV that looked like it was closing but the car still didn't idle correctly (irregular idle speed). When I checked the AAV after it warmed up in the oven, the internal vane blocked light but I cold still blow air through it. (don't burn your lips...)

If you find the AAV's vane is stuck, you can try freeing it up by washing it out. I used a few squirts of carb cleaner then hot soapy water and a fresh water rinse.

 

[WIP]

Whoops... sorry, yes I meant 300-400 RPMs fluctuation... boy, do I feel stupid (so, what else is new)... I never knew that "AAV" had someting inside of it? I always though it was just a hollow accordian tube of som esort - duh... will pull that as well... and try your tests... neat stuff... this is gonna be fun.

The idle fluct seems to happen at either time and not always... like at lunch it was doing it, but on the ride home this afternoon... was not doing it - like I said, ought to be fun.

Thanks again!