Hard starting

Propane, Butane, LPG, GPL, C3H8, C4H10
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Flingarrows

Hard starting

Post by Flingarrows » Sun Jun 26, 2005 9:21 pm

i noticed that after my jeep sits for more than a few hours, i have to crank the engine over quite a bit before it will start. it starts fine withing the first hour.

my E converter is on the passenger side inner fender, with 2-1/2' of low pressure hose to the mixer. the converter is slightly lower than the mixer also.

i have the vacuum from the vff30 connected to a tee with the pcv to manifold vacuum.

it almost seems that it takes a bit of cranking to get fuel from the converter to the mixer.

I tried the idle mixture, and it helped slightly. i read Franks post about hard starting and it turned out to be that on his car. What is a start valve (SV) and do i need that? Any help would be appreciated

George

Frank
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SV - Start Valve

Post by Frank » Tue Jun 28, 2005 7:51 am

This device enriches the fuel mixture when starting. It uses a solenoid that is energized when the starter is engaged (if you wire it properly).

Don't connect the VFF30 to the PCV line. There should be a nipple on the adapter to provide the VFF30 with manifold vacuum. The PCV line won't provide enough vacuum because it is somewhat open to atmospheric pressure from the inside of the engine.

Try a dedicated source of manifold vacuum and see it that works better.

Flingarrows

Post by Flingarrows » Tue Jun 28, 2005 6:21 pm

Ok thanks. ill change it to a dedicated manifold vacuum

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Starting

Post by C3H8 » Sat Sep 10, 2005 12:29 am

Primer advice is great but a VFF30 only needs 1.5" of water column vac to open all the way. Using full manifold vac is hard on the diaphragm and seal between the lquid and vac chamber. Full manifold is OK in cold climates but in warmer climates the air valve vacuum at the base of the mixer is more then adequate. Also once the seals start to leak full manifold vac will suck propane directly into the manifold and cause very rich mixtures and very strong odours.

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Post by fordCourier » Wed Oct 12, 2005 12:27 am

Very good tip c3h8! I'm going to replumb my vff30 tomorrow morning.

I have a start valve (SV) installed and it helps, but it should start fine without it. Its only function is it assist when the engine is hot, making an intial mixture a bit leaner. If the converter leaks it can empty, leaving the vff30 to fill it up when you go to restart.

1st thing you should do is depress the primer button on the converter to make sure you have propane there. If thats okay, you have other problems.

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Re: Starting

Post by Eskimo » Wed Oct 12, 2005 9:40 am

C3H8 wrote:in warmer climates the air valve vacuum at the base of the mixer is more then adequate. .
Air valve vacuum (port)? anyone got a picture of which one this refers to? I'm using a port that's on my q-jet baseplate currently, but I don't want to damage the diaphragm.
"the FJ" - 1970 Toyota FJ-305 rock crawler - Chevy 305, now running on BBQ juice.. http://www.rnrfab.com/rich/05build

"FJ Hauler" - 1998 Dodge Ram Cummins 3500, B20 fueled, 300hp/700tq at the wheels..

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Air Valve Vacuum

Post by C3H8 » Wed Oct 12, 2005 11:22 pm

AVV can be found on all IMPCO mixers if you remove one of the silver screws that screws into the side of the mixer at the base. The hole under the screw will pass through the body into the mixer just below the air gas valve. The screw is a 1/4" x 28 thread. Ported vacuum is usually found at the base of a throttle body and its port is just barely above the throttle plates. The difference is AVV will only reach a vacuum of about 30" water column maximum (about 1" mercury). Ported vacuum can be as high as manifold under certain conditions.

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Diaphragm damage

Post by C3H8 » Wed Oct 12, 2005 11:29 pm

Just as a note, you likely won't damage a VFF30 diaphragm with full manifold vacuum unless it is an older designed unit. The main issue is the tendency to suck propane past the pin seal into the vacuum side of the lock off and this fuel then bypasses the mixer. In the end it screws up the fuel mixtures and results in the misdiagnosis of components when there is nothing wrong with them. I have seen many mixers condemmed and convertors rebuilt when the only problem was fuel bypassing the system through the lock off seal.

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Post by Eskimo » Thu Oct 13, 2005 12:05 pm

Thank you VERY much. I understand you saying that it won't necessarily hurt anything, but heck, it's free (or nearly so), and the "right" way to do it.. Why not go for it? :wink:
"the FJ" - 1970 Toyota FJ-305 rock crawler - Chevy 305, now running on BBQ juice.. http://www.rnrfab.com/rich/05build

"FJ Hauler" - 1998 Dodge Ram Cummins 3500, B20 fueled, 300hp/700tq at the wheels..

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