Mucked with propane system

Propane, Butane, LPG, GPL, C3H8, C4H10
Rattlenbang
Posts: 12
Joined: Wed Oct 05, 2016 9:46 pm

Re: Mucked with propane system

Post by Rattlenbang »

Its hard to read the fancy font but I believe the brand is "Dual Curve" Ford integrated engine management. There are a number of modules under the dash but there's no ECU on the passenger kickpanel, just a bunch of connectors and a relay and fuel cutoff switch. Nothing under the seats, either.Perhaps the dual curve unit - which is disconnected - played that role?

Rattlenbang
Posts: 12
Joined: Wed Oct 05, 2016 9:46 pm

Re: Mucked with propane system

Post by Rattlenbang »

Also couldn't one tweak the mixture setting on the mixture? I set it midway as per instructions, but could one just drop it off to lean a bit? Or does that cause driveability and heating issues? It seems a pretty crude adjustment. I'll be towing a vehicle back today the same 500k and it'd be nice to have it get the best mileage possible.

C3H8
Posts: 1129
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Mucked with propane system

Post by C3H8 »

OK. That provides some of the information I needed. Autotronics Dual Curve units were used on most if the conversions once fuel injection became common on engines. In your case the factory ECU is definitely still on the vehicle. I just may have the location of the ECU wrong. It was commonly behind the right or left kick panel. Most times you can see a large electrical connector going through the firewall. The ECU is on the inside where that connector is.

I need you to do two things. Take a close look at the front of the Dual Curve unit. There will be a 4 digit model number. Something like 8795 or 5914 or 5916 or 5918. If it is the 59 series the mixer has a rich gas valve in it and it will have to be changed to a standard gas metering valve. The other option is to reconnect the Dual curve which will then electronically control the fuel mixtures. The Dual Curve integrated module also has some timing control capability and check engine light controls. The little three port solenoid in your picture is what controls the fuel mixture curves if you have what is called an FB300. With that disconnected the mixtures would be quite rich at cruise speeds.

Second I need you to send me a PM (Private message) with an email that will allow me to send you the instructions for your dual curve unit. It is too hard to explain how to hook t up in a post.

If you choose not to use the dual curve you will need to check the part number of your gas valve. Again, to make sure you find it I need an email address to send you the 300 schematic with an itemized list of components and the proper part numbers. If you have the 300-20 series mixer the standard (non feedback) gas valve is V2-11. If it is the gas valve commonly used with a dual curve unit it will be a V2-39. This number is printed right on top of the gas valve. To check it you have to take the vapour inlet fitting off and remove the gas valve by unscrewing the mixture adjustment screw completely and lifting it out. Prior to doing this you have to carefully mark the existing setting. Once marked screw the adjuster all the way in until it bottoms out while counting the number of turns. The remove the assembly and take the gas valve off the stem. The part number is inscribed on the top of the metering valve.

No, you cannot just lean the mixture out by closing the power valve so it is leaner. IMPCO metering valves have three adjustments. An idle area. A cruise area determined by the angle of the metering valve and a wide open throttle area that will allow you to adjust the maximum fuel at WOT. The 300 is fairly forgiving though and you can turn your mixture adjustment under the hex cap down slightly. This will place the cruise portion in a slightly leaner location throughout it's range. As long as the idle and starting are OK leaning this valve is OK. You can also lean the WOY setting as long as it does not result in a loss of power. A loss in power will just cause you to push on the gas pedal harder resulting in the same fuel usage and also a drop in the available power.

The key here prior to any major changes is knowing that gas valve number. If the mixer has the rich gas valve you will be consuming unnecessary fuel and the combustion temperatures will be increased.

Rattlenbang
Posts: 12
Joined: Wed Oct 05, 2016 9:46 pm

Re: Mucked with propane system

Post by Rattlenbang »

Part no 5910. PM sent. I've just driven about 300k hauling 4500lbs worth of vw van and man, it's burning the fuel. I think our combined weight is around 12000#, all being hauled by a six. Do you lose HP and torque burning propane, or just fuel economy? This is an old old truck and I'm surprised she's holding up under this load.

C3H8
Posts: 1129
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Mucked with propane system

Post by C3H8 »

:shock: 12,000 lbs!!!! Pretty good with a 6 cylinder with your KM's. Lots of torque with the 4.9 but that weight would tax any engine economy wise. I would keep the speed down as much as is safely possible to improve the economy. Most big block V8's suck on economy with that much load also. They will usually do better then a 6 cylinder though because they don't work as hard to maintain the speed or climb hills.

5910 is a fuel control system and timing control system. I'll get the instructions to you. Hooking the module up properly will help your mileage as long as the Oxygen sensors are functioning properly. These modules are designed to control mixtures properly unless the mixtures go so far out of whack that they can't. In that case the box will basically quit trying and allow the ECU to set a code that says it can't maintain proper control. As soon as control is restored the box goes back into operation.

You will have to hook up the control solenoid again to get proper fuel control. The key is proper placement of the vacuum lines along with dialing in the fuel mixtures after by following the instructions precisely. It is still important to verify the correct gas valve is installed. The gas valves are quite cheap by the way. If for any reason the box does not work you can revert to the lean valve at a substantially lower cost then locating and paying for a new box.

Rattlenbang
Posts: 12
Joined: Wed Oct 05, 2016 9:46 pm

Re: Mucked with propane system

Post by Rattlenbang »

Got the instructions, thanks. Wow, that's a pretty complicated setup, no doubt implemented due to the same regulations that brought in feedback-loop fuel injection. Trying to reconnect all that - just to find out the module is toast - is a non-starter I think, when I can just replace the gas valve. Given how the system has been hacked up I really doubt anyone replaced the original valve with a proper one. I'll just pull that and swap it. Thanks again for all your help.

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