Converted CNG to gasoline
 

Converted a 1998 Ford Van from a CNG to gasoline. Problems with cold starts but runs fine otherwise. Can the computer (ECM) be programed or replaced? Got any suggestions?

Not knowing all the items you changed, you might check with a Ford parts dept and they probably use a different ECM for CNG as compared to Gasoline. Cold start enrichment is most likely different. My ASE certification for CNG vehicles has expired and a lot of things can change in 5+ years.

I also have a 1998 Ford CNG van that I want to switch to gasoline.
I would like to read some more details on what was done Bo470

Great Information Hanky !!

Welcome on a borad GreenMM !!

The reason I changed over is because we live in a rural area and CNG stations are not available. You don't have to change the intake, only the injectors and all the fuel lines, fuel tank and filler neck. Remove all natural gas items, there is a water line that comes out of the back of the engine and you have to plug it off. Went to junk yard and purchased an ECM off gas van with same equipment as the CNG and that cured the cold start. Only problem that I have is the fuel gauge doesn't work. I used all used parts except for fuel pump. Van runs great.
P.S. There is a natural gas control on the left inside fender that doesn't have to be changed, just leave it alone, don't try to disconnect it.

Its really a nice information. Thanks for sharing !!

Awesome stuff! One thousand thanks to you sir!!!!!!
I have been pulling my hair out to find any glean of info how to do this.

Big relief on intake.
Had also read someone did a full wire harness swap (crazy) and read another person did some chopping and splicing on the CNG electrical connectors accessing the Mitchell wiring diagrams...

I wonder what that water line that gets plugged up goes to. (?)


And thank you for the welcome to the site as well!

I am doing a lot more research into this, mostly on my own as no one seems to have done this or comment on this much at all.
Take a look at this. This is official stuff from a write up by multiple Ford engineers.

I am much more active at a much more active forum here:

I would like to convert my 1998 e250 CNG factory 5.4L engine BACK to gasoline!! - Page 3 - Ford Truck Enthusiasts Forums

This is page 3 of a post I've made to try to get the info to swap a CNG only motor back to gasoline only.

To summarize a little more of what I've learned here (please visit above link for much more info),
the valve seats and valves are indeed hardened and different from a stock factory gasoline. But that's fine and actually good. No need for changes there.
That "water line" out of the back of the motor mentioned by o.p. here is in fact a Heating line that goes into the CNG valve to heat it up so the fuel doesn't freeze solid and freeze the line (the high pressure drops temp of the fuel big time). There is a return line there back to the main cooling system. So the active one line TO the CNG valve needs to be disconnected there and (cut back shorter if wanted) and plugged up anywhere along that line so coolant won't leak out. Same for return line.

According to two engineering papers I've been reading on the econoline e250 and e350 and also on the Ford Crown Victoria dedicated CNG vehicles, it appears that the stock gas vehicles have the same PCV valves and same EGR. However, NGV only models don't have a need for "Evaporative" equipment at all, which is the vented canister collector past the gas tank, and the charcoal filter there, and the return SAI line (Secondary Air Injection) to the intake. And this must have a wiring connection to some of these parts to work right, not sure if they are all hanging around and not being used in the CNG only model or if the wiring harness part that connects by the driver side front wheel is actually different. I grabbed that wiring run from the 2006 e350 model and will try to compare it to what's in my 1998 e250 CNG only model (assuming I actually move forward and tear things apart).

Evaporative:
What this basically means is that gasoline tanks must have expansion room and be able to draw in fresh air for gasoline to expand and also the fuel to be drawn out of the tank for use. So they have vents. Pre 1960s tanks used to vent to the air - and pollute. The canister with charcoal the return SAI line cleans the gaseous air and stores it, and then a one way valve opens on start up and the air from the canister is sucked back into a tube running back to the intake on top of the engine and is reburned. This is all for environmental goodness / air quality and also to have your vehicle not stink of fuel, and not spit / burp back gas up the fuel filler when opening the gas cap etc etc... The NGV fuel does not require or need any of the evaporative stuff, the fuel is in a 'closed loop'. There's no need to collect expanded gaseous air, so the system isn't there. What parts are installed and not used or hooked up by Ford factory remains to be discovered. Bo470, can you shed any light on this??

The O.P. here does not mention this at all. I just went and gutted all the gasoline parts off a 2006 e350 gasoline only van and right away noticed all this extra complex stuff I had not even thought would be in the gasoline setup (should have known better, I own a 1995 "California" model motorcycle which also has a collector, a charcoal canister, a liquid separator and return hoses to return the cleaned air and reburn it right at an inlet by the carburetors. Same principle, but there are no wiring connections for that setup and no sensors to trigger a Check Engine Light either.)

I am wondering if he simply vented to atmosphere and didn't concern himself with all this. Once you swap ECU / PCM module in, you would 100% get a CEL (MIL) if this is not installed.

hey were you able to switch your truck I have a 2010 that it’s giving me a headache and wanna change to gasoline