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Old 08-05-2022, 09:32 AM   #11
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I may have to find a "normal" van to look at, if there's no diagram to be had. It's going to hurt to convert from CNG back to gasoline. I filled up at $1.54 a gallon from SoCal Gas near Hemet, CA yesterday, which is four dollars a gallon cheaper than the factory option.

Can you convert to a dual-fuel system? My friend has a 2012 E350 that CNG and regular gas, with a switch to go back and forth between the two systems.

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Old 08-05-2022, 10:12 AM   #12
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Can you convert to a dual-fuel system? My friend has a 2012 E350 that CNG and regular gas, with a switch to go back and forth between the two systems.
A dual-fuel system has two sets of injectors and associated wiring. I've looked at them and a conversion from my CNG-only setup would require ripping out what I've got to replace with new. I'd be required to change out my tanks, because installers won't warranty used tanks. I've been unable to find a junkyard that'd let me salvage a hybrid system to put in with my existing tanks. So, we're talking about a whole new system, which isn't worth the money.

I'll just use a dual-van system; using the gasoline van when that's appropriate and the extended range CNG van when I can instead. The CNG tanks have a life limit, at which time they must be replaced (nobody wants a 3600 psi CNG explosion). So, the second CNG van will also eventually be converted back to gasoline as well.

.... or, I've got a couple of 86 kW (110 HP each, for a total of 220 HP in a 4WD system) Bosch motors, controllers, and DC/DC converters that could also go in, although I'd need a trailer to carry all the batteries it'd require.
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Old 08-05-2022, 11:30 AM   #13
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Or long extension cord
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Old 08-05-2022, 05:34 PM   #14
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Or long extension cord
Was talking with Alan a couple of days ago and he was thinking diesel generator. You know, like a diesel-electric train engine. Lots of low end grunt but with efficient fuel usage.
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Old 06-11-2023, 01:03 AM   #15
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I finally did the CNG to gasoline (de) conversion, as part of installing an MG based 4WD lift using an F250 front axle. With the CNG tanks weighing around 1000 pounds, mostly centered around the rear axle, the van had to go on a diet.

The transition was fairly straightforward. I removed the daughter wiring harness that was plugged into the factory harness. This included a box to emulate the fuel level sensor and evap purge valve. I then installed the fuel tank assembly, with fuel pump and evap system. The CNG injectors were installed with wiring pigtails, so it was simple to swap in gasoline injectors. A new evap valve was connected to the engine intake connector, which had been capped because CNG did not need an evap function. I had to make my own fuel lines, since the factory ones aren't available from any parts houses or Ford dealers. I'll swap these out when I run across a set at a "pick a part" junkyard.

The van runs and all functions work, including the fuel gauge. I have an appointment scheduled to remove the CNG fuel mapping tune and return the PCM to factory condition, since it's a bit rich now.

I will miss the low fuel cost and the clean burning CNG lack of engine soot, but won't miss extra weight and stress over finding CNG stations, which limited the places I could go.
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Old 06-14-2023, 09:38 AM   #16
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From CNG back to gasoline

Nearly two hours were spent trying to reprogram the PCM back to factory stock before the guy working on it decided it must have been locked by the CNG installer. About ten minutes after he left, I figured out the PCM line had been disconnected at the OBDII connector by BAF... I guess to discourage reprogramming as part of any service. Twisting the wires back together, I was able to get a firmware load with Forscan 2.4.7 ($12 extended license) and a vScan USB interface ($34 through Amazon). It went from having to take multiple start attempts to get it running to then starting right up. Unfortunately, it then had no power off the line, with power not kicking in until the rpms came up. It went from throwing codes for too rich operation with the CNG mapping to then throwing codes for evap system failures.

Well, called the mobile flashing service guy and he came back by later in the day to get me to the current factory firmware calibration level (Forscan having used the last available it could find instead of the current) but it didn't run any better. Bank 2 was all out of whack with the evap codes continuing.

I think I've got it straightened out now. The vent valve at the canister is still throwing a code but I've unstuck everything else and have a new vent valve showing up today. I cleaned the used injectors before installing but I guess they weren't all flowing the same initially. I'm not having balance issues now. Some De-oxit on the evap system electrical connectors that were left dangling for a dozen years may have also helped.

I've not found any reported case of someone completely converting CNG back to gasoline before. Several people have said they did it, but that it ran like crap on initial startup or had some other issue. I think I can now say that it's not only possible to completely convert back to gasoline but also that it's not that hard or expensive. I probably could have just run with the $50 firmware flash I did myself instead of paying for the $110 reflash service (I couldn't see how to turn on the cruise control with Forscan, so that was worth paying the mobile reflash guy to come back). Even with that, I think the whole thing was done for less than $400.

What's going to hurt is pulling up to a gas pump. CNG can be had for $2 a gallon equivalent in SoCal. Gasoline is nearly three times that, although it will be much more available.
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Old 06-14-2023, 10:09 AM   #17
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I've not found any reported case of someone completely converting CNG back to gasoline before. Several people have said they did it, but that it ran like crap on initial startup or had some other issue. I think I can now say that it's not only possible to completely convert back to gasoline but also that it's not that hard or expensive.
Congratulations, I imagine the worst part is having to wonder if it will ever work the whole time you are fighting it. Once it's done it seems really easy without that overhanging "cloud of doubt"
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