Fuel odor from model e vent

Propane, Butane, LPG, GPL, C3H8, C4H10
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scoutii
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Fuel odor from model e vent

Post by scoutii » Mon Jun 03, 2013 7:05 pm

During my tinkerings with my truck i hooked up a balance line. As an experiment i removed the line while running and noticed that the vent on my model "e" has small pulses of pressure with a fuel smell to them. Im not able to picture how any fuel could be present there without some sort of failure i was pretty suprised at the pressure too. The regulator is pretty new is this normal?

-Sam

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Re: Fuel odor from model e vent

Post by C3H8 » Tue Jun 04, 2013 12:20 pm

The small pulses are easily explained. Picture air flowing through a tube with a flat plate being slid in and out of the tube at the half way mark. This is what the air is doing as it enters your engine and the valves open and close. Air moves into the engine, stops and moves again. Fuel is entering the stream in much the same way as it flows through the mixer. The pulses carry all the way back to the regulator where the diaphgm is moving in and out in time with the air pulses. This causes air in the balance line to pulse.

As for the odour. You can have a smell of propane out the vent. It varies from vehicle to vehicle and is frequently related to the age of the reg. Propane has a powerful odour added to it at the factory to detect leaks. The diaphragm in the reg is quite thin and the odur may be seeping through the diaphragm or through the rivets where the plate is attached. Saying that there is also a possibility of a tiny hole in the diaphragm. I suggest you start the engine, allow it to warm up. Shut it off and pull the balance line off at the mixer and listen at the line, like a stethescope, to see if you can hear a leak. If you don't hear anything the diaphragm is good. The odour could also be left over from propane vapours that have permeated the balance line from propane vapours from the mixer end. When the engines are shut off it is typical for some vapour to be present around the mixer and the rubber line might have absorbed the smell from that end.

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Steptoe
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Re: Fuel odor from model e vent

Post by Steptoe » Tue Jun 04, 2013 5:31 pm

The general leak test used in NZ is soapy water in a squeeze bottle...
If I could smell any raw lpg thats the 1st thing I would be doing regardless where I thought the smell was coming from.
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scoutii
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Re: Fuel odor from model e vent

Post by scoutii » Wed Jun 05, 2013 6:24 pm

Really killer reply ch! Thank you guys for the prompt and informative responses. The fuel smell is not "raw" its more hinty. The line is new and the reg is about a year with less than 3500 miles on it. Not to say it couldnt be faulty. I was surprised the pulses were so noticeable. That mercaptian stuff is pretty vial. Infact its almost a quirk of the truck. If i havent been in it in a while i always catch a slight wiff of it. Ive dumped alot of soapy water on my fittings and found a few leaks over the last couple years but theres always a hint of it under the hood. Even if the tank valve is off and the truck sits for a few days theres always a hint of it under the hood. Im just about to replace the entire propane system. The lines are very old type i lift truck stuff. The lockoff filter is origional etc the tank is way too big etc. so i have a few more threads to start.

A little off topic...
I think theres an improvement in idle quality with the balance line hooked up. I had seen them hooked up before and just assumed it was an offroad thing to keep the vent clean. After reading on this forum i learned a little more. I tried the line in several ports between the mixer and the carb and all of them had too much vacuum (not register-able with a gauge) i had to drill a hole in the top if the air cleaner and make a fitting for it. Whats the benefit of leaving the vent open?

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Re: Fuel odor from model e vent

Post by C3H8 » Wed Jun 05, 2013 9:39 pm

Balance lines have two puroses. The secondary purpose is too keep dirt or water from getting in the vent. The main purpose is to correct the regulator output for a dirty air filter. If you were to look at a gasoline carb you would realize the bowl vents are all inside the air cleaner. There is a pressure drop across an air filter element so if atmosperic pressure is at 14 PSI the air pressure inside a new filter might be 13.9 as an example. As the filter clogs up with dirt the differential increases. A poorly maintained vehicle might see a large pressure drop, say 1 to 2 pounds. Having the vent inside the air cleaner corrects for the pressure differential. Without the balance line the mixtures will get richer and richer as time goes by because the pressure on the top side of the diphragm remains at 14 PSI and the dirty air filter causes the vacuum to increase inside the mixer. It is important that a balance line be at least 3/8" inside diameter and routing can be critical in cold climates. In cold climates condensation can occur inside the line and if there are any low spots in the routing the condensate can collect there and freeze plugging the balance line, which will stop the secondary diphragm from opening. Most IMPCO mixers have a port on them marked "BAL" to indicate the balance line location. It is usually located just below the air claener gasket lip.

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Steptoe
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Re: Fuel odor from model e vent

Post by Steptoe » Thu Jun 06, 2013 12:58 am

Basically my system was 2nd hand and installed mid 1980s... tanks been pulled out a couple times for 10 yr surveys, pulled a good 200K miles and a few other things... but in all that time, I can leave the car in the garage from over night and for even weeks on end... never do I have a smell....
Any leak is unaceptable, and in this country , illegal
Sry about the bluntness...
Think about this... if it was petrol and you could smell it over night, not enough to have a puddle on the ground but enough to leave stains.....where it has evaporated... would that worry u?
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scoutii
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Re: Fuel odor from model e vent

Post by scoutii » Sat Jun 15, 2013 9:54 am

Step ya freaked me out. I completed another thorough leak inspection and found only one leak. The start asssit valve will leak if the primer button is pushed but it does not leak with the engine running. Im not entirely sure it will ever see that kind of pressure under normal conditions so it might not really be a leak at all. I listend to the vent hose and heard no hissing, i even stuck it in a glass of water ( engine off) and saw no bubbles. Sniffing around i did notice that the fuel lines themselves have a hint of odor. Seepage?
Im still planning to install new supply lines fittings and a new lockoff as these items or likely over 20 years old. I have questions about all of this. Should i start a new thread?

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Steptoe
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Re: Fuel odor from model e vent

Post by Steptoe » Sat Jun 15, 2013 7:04 pm

We use a squeeze bottle with a dish washing detergent soln in it, and squirt over anything that could possibly leak...
And if cant reach or what ever use a thick brush and paint the soln on.
I have never had the need for a primer button, so refraining about a smell and when using....thu Im sure if any leak , it would certainly fail and certification inspection
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scoutii
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Re: Fuel odor from model e vent

Post by scoutii » Sat Nov 03, 2018 10:45 pm

While google-ing this ongoing issue I came across my ancient thread. Kinda funny. Ive decided to update this thread seeking advice and for future folks that may have this question/issue. Please note that I have a very sensitive smell reflex.
Ive purchased a cheapy sniffer type leak detector wand and the model e vent ports Ive exposed it to set it off. Im now on regulator number three plus a rebuild kit in one of the previous regulators. Ive even tried tightening the rivets on one diaphragm. I just installed a brand new model-e and it (just like the others) emits enough gas to smell slightly and set off the leak detector. This regulator has like 10 mins of run time on it. Theres more to the story as its been going on for years, but the short of it is; after all this money spent the problem is still there.
So:
A- this is "normal" leakage coming from seepage through the diaphragm material or its rivets. Seems kina odd and shocking. I cant be the only person to ever notice this. If so its probably such a small amount its not significant in fuel loss or as a hazard. It does make me question weather or not I should hook ub a blance line to the mixer.

B- all non impco aftermarket model-e components are defective in this way.

C- there is something Im doing wrong or something wrong with my tank, fuel, or installation.

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Re: Fuel odor from model e vent

Post by jono » Mon Nov 05, 2018 3:35 am

Nice to see you have not blown anyone or anything up with this detectable leak!
Mix up a soapy water solution to fill the atmosphere side of the diaphragm and see if it blows bubbles.
I prefer silicone -2 diaphragms wherever I can avoid the black hydrin ones. Have you got yellow or black diaphragm?
Balance lines have been good to me, and down right pain in my hind :( causing lean bogs . Brrrr !
You can also use a bleed device or just a hole in the balance line or fittings ( best at converter end) to soften the effect the balance line has.
An ideal bleed device would be like a tapered screw and spring to adjust to atmosphere ...just no idea where I would find such device to shove inline

scoutii
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Re: Fuel odor from model e vent

Post by scoutii » Mon Nov 05, 2018 7:03 am

All the diaphragms Ive been through would be the yellow silicone types. I cannot Imagine this just being a stroke of bad luck. The truck gets driven about 3000 miles a year. The last two years the propane system was semi-removed. There were some state political tax nonsenses that made it very hard to get propane for a vehicle. Those issues seem to have blown over. Upon reinstallation the regulator issue forced me to replace everything but the tank.
Could the use of an electric lockoff be hammering these things? I prefur it due to size and my method of dual fuel selectability.
Ive yet to actually diagnose any of the model e's with pressure testing. After dissasembling one these things I thought to mysealf "theres not much to go wrong here". Guess Im wrong. It wouldnt take alot of pressure to push fuel through the rivets of the diaphragm. It really wasnt meant to see easily measured pressures.
Im at a loss. Im going to call Century and see what they say. Maybe I just need to push for a genuine IMPCO warranty replacement. Are the IMPCO generics not right in sume way? I was told they are "quality" knock offs. Parts interchange and the generic stuff seems to be easier to source now than the genuine.

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