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cng problem

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Old 03-25-2008, 06:30 PM
tomerloy tomerloy is offline
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I was talking to a CERTIFIED CNG TECH today and he told me the Ford E series vans have electronic shut off valves. They need power and ground to open. So to shut off the valves just disconnect the connectors at each tank and run the system dry or disconnect the battery and bleed the pressure from one of the fittings on the high pressure side.
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Old 08-15-2008, 03:54 AM
Sppubadmin28 Sppubadmin28 is offline
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The CNG tanks have electronic valves. When the ignition is off the electronic valves are closed. There are two ways to de pressurize the lines.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
1. With the ignition off, slowly loosen the hex nut on the bottom of the coalescent filter bowl and allow the small amount of CNG to bleed out of the lines. This will take about >1 min. If you have an additional tank inside the vehicle that was not factory, it could have a manual shut off valve similar to a propane tank. Close the valve on any such tanks before depressurizing the lines.<o></o>
2. Second more difficult method. Unplug the two prong wiring harness connected the electric CNG valves. A dedicated CNG van will have 3 tanks standard, two in the back mounted under the van (perpendicular to the length of the van), and a long tank mounted parallel with the frame rail. Some CNG vans came equip with an 4th extended range tank mounted in the back behind the 3rd or 4th row seat. If your van has this tank you will need to disconnect the wiring harness from this tank as well. With the electronic valves disconnected, start the van and let it run out of gas. This will happen in no more than 2 min. if you disconnected all of the electronic wires to the electric valves. After the van is out of gas, loosen the hex nut on the bottom of the coalescent filter bowl, located under the van next to the frame rail on the driver’s side, just behind the driver’s seat. Approximately 40 psi will be remaining in the CNG lines; slowly bleed this pressure so you do not damage your o-ring. Now you may perform the flush procedure listed in the Ford TSB bulletin, or just drain any oil in the bowl and replace the coalescent filter if it is damaged, dirty, or saturated in oil.<o></o>
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Old 09-24-2010, 06:00 PM
pastorkim pastorkim is offline
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I just purchased a 1998 F-250 CNG that was used by Oklahoma Natural Gas. It is duel fuel, but when I flip the dash board switch to put it into CNG mode, it works sometimes, and doesn't other times. Someone told me it could be the electric value that was going bad. Any thoughts from anyone?
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Old 02-28-2011, 12:16 AM
tomerloy tomerloy is offline
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different van this time...98 E-250 dedicated CNG...running bad, throwing codes for a lean bank 2. Bank 2 o2 sensor was reading a constant 90mv. Replaced o2 sensor and no change. removed injectors and cleaned them (used method found on youtube) no change. Ended up being 2 bad coil packs on bank 2 (drivers side). o2 reading normal now ~ 100-900 mv. Note: plugs and coil packs had been changed 10K miles back.
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Old 07-14-2011, 11:46 PM
epyle3 epyle3 is offline
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My 99' F250 CNG 5.4 with 122,000 miles has a short. The # 10 fuse (20 amp)( manual says fuel pump) but, I suppose is for a solenoid blows within 3 seconds .. a 30 amp lasted 8 secs. So, I am assuming a worn wire or maybe a bad solenoid .. any ideas?? I've burned up 8 fuses so far. I am reluctant to undo the wiring harness and look for crossed wires / exposed copper. Did all the plugs recently in 4 hrs with this forum's help, thanks Ed

Update: after disconnecting all solenoids one at a time, the truck ran with the lower tank valve / solenoid off, hence, I will be running for a while on the two tanks in the bed .. now, how to replace the solenoid ?? how to empty the tank? parts???? Jury is still out on CNG .. I've logged 50,000 miles on this used F250. Saved big bucks using cng vs gas ... 3000 gge x about $1.10 difference here locally = $3300++ no smog, 20,000 mile oil changes ... fuel of the future?? tanks expire next 2012

Last edited by epyle3; 07-15-2011 at 04:42 PM. Reason: up and running
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Old 05-09-2014, 11:47 AM
BlumenthalOKC BlumenthalOKC is offline
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CNG Filter Cleaning and Change Out

Only a certified CNG Technician may perform this operation in the State of Oklahoma. Other states may have the same restrictions. Unlike not being certified to change spark plugs, the high pressure of the CNG may harm you, the vehicle and the personnel and property around where you are working. The electronic shut off type cylnders will prevent CNG from leaving the tank if operating properly. Manual valve cylinder heads must be shut off at the cylinder head manually. The gas pressure must be very slowly released from the lines by very slowly unscrewing the inflow fitting at the filter housing. Older systems have an o-ring fitting and failure to allow the gas to bleed off while unscrewing can strip out the treads or pop the o-ring. Compression fittings must be slowly unscrewed and the gas allowed to be released, BUT when reattaching the fitting must be turned tight, then 1/4 of a turn more applied. Leak checking must be done when reapplying by spraying a soap and water solution - make sure the soap contains no amonia. Small bubbles small leak, tighten until gone, large bubbles large leak, tighten but the fitting may need to be changed out. The filter housing unscrews from the bottom. It has two o-rings and the inner o-ring on the housing must be changed and the o-ring lube must be used. The filter will look like a paper roll, some have a platic tip, some do not. Replace the filter with the type that came off. If the filter is saturated or dirt and/or if the housing has compressor oil it must be cleaned using 90% or greater alcohol. Then leave the filter off and fill the vessel with the alcohol, tighten, replace the CNG lines and run the vehicle for 30 minutes at 2000 rpm or so to clean the oil out of the system. Then remove the line, release the cng pressure and dump the alcohol not used, replace the filter and lines, turn ignition to on, but don't start the vehicle. Spray the solution on the fitting to check for leaks. This should tune-up your cng injectors and push the oil through the system and out. Hope this helps.
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