Weird Problem
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Weird Problem
I recently purchased a 1999 F-150 5.4 gas/CNG. The truck is 1, extremely hard to start. 2, It idles rough all the time. The mechanic I bought it from worked on and couldn't fix it and the local dealer gave up. While testing I unhooked the egr and a couple of other sensors and didn't get a trouble. Alittle help please.
Thanks
Lockdoc
Thanks
Lockdoc
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
First some comment.
If you didn't need an engine with this dual fuel option, it would have been much less expensive to keep repaired.
What you have a is "very complex" seperate fuel systems arrangment.
It takes a shop familuar with and service info to even begin to address any issue in depth.
.
There might be codes set to indcate a probable system issue. This is where you start to chase the problem, otherwise a discovery search must be done from service info..
You have no solid info to work with for the moment.
Is it hard starting on gas, NG or both as a starting point.
What does the PCM read for codes and was a good scanner used to take a look at the system once it was running?
I remember an owner in England that bought one and could not get any service on it.
The shop needs to get into a service source on Bi FUEL engines, then into diagnostics and symptoms section, to begin the quest to solve the issue.
There are a number of areas to be looked at.
This is all from referencing my service data disc section on these engine options.
It's far too much data to type out here and be understood.
I wish you good luck, at the least.
If you didn't need an engine with this dual fuel option, it would have been much less expensive to keep repaired.
What you have a is "very complex" seperate fuel systems arrangment.
It takes a shop familuar with and service info to even begin to address any issue in depth.
.
There might be codes set to indcate a probable system issue. This is where you start to chase the problem, otherwise a discovery search must be done from service info..
You have no solid info to work with for the moment.
Is it hard starting on gas, NG or both as a starting point.
What does the PCM read for codes and was a good scanner used to take a look at the system once it was running?
I remember an owner in England that bought one and could not get any service on it.
The shop needs to get into a service source on Bi FUEL engines, then into diagnostics and symptoms section, to begin the quest to solve the issue.
There are a number of areas to be looked at.
This is all from referencing my service data disc section on these engine options.
It's far too much data to type out here and be understood.
I wish you good luck, at the least.
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Here is what I was told - the truck was owned by Piedmont Natural Gas. It went to auction. It was used as a service truck up until 6 mos ago. it has 47k on it. The #3 plug blew out. The entire head and cop was replaced. The only code it show is a lean code. THe service or check engine light is not on. There is NO CNG in the truck. When we pulled some of the vac lines and plugs (EGR, etc) no code was created. Thanks
Lead Driver
Joined: Sep 2006
Posts: 7,907
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Need to know what the code is first.
A code set will light a CEL lamp unless it is burnt out.
If it is a code suggesting an A/F ratio issue, the motor has a good chance of acting the way you discribe.
Don't be concerned about checking for a lamp/code response by disconnecting parts.
Address the code in memory first.
Your problem may not turn out to be that difficult, then you would be lucky.
Owners try to word to death the problems and disreguard the codes.
We live or die by codes because it's most often the only way we know what is or is not happening within a complex computer controlled system.
This is why there are more than 1000 codes in the program, to help id issues.
A code set will light a CEL lamp unless it is burnt out.
If it is a code suggesting an A/F ratio issue, the motor has a good chance of acting the way you discribe.
Don't be concerned about checking for a lamp/code response by disconnecting parts.
Address the code in memory first.
Your problem may not turn out to be that difficult, then you would be lucky.
Owners try to word to death the problems and disreguard the codes.
We live or die by codes because it's most often the only way we know what is or is not happening within a complex computer controlled system.
This is why there are more than 1000 codes in the program, to help id issues.
Fleet Mechanic
Joined: Jul 2010
Posts: 1,354
Likes: 31
From: Winnipeg
Did you check the TSB's from this site? Here's one that might apply; *03-10-2***DRIVEABILITY - COMPRESSED NATURAL GAS (CNG) - ROUGH IDLE OR NO START WHEN COLD - VEHICLES EQUIPPED WITH CNG BI-FUEL ENGINE ONLY.
There are more regarding gas/cng vehicles.
There are more regarding gas/cng vehicles.
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Junior User
Joined: Jul 2010
Posts: 95
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From: AZ
It sounds like you're saying it's hard starting when running regular gas through it, correct? I'd be wondering about fuel pressure if so. Here's an ugly thought. I'm not up on these CNG trucks, but I'll assume they have two fuel tanks, if regular gas sat in the system for a long time and varnished there could be a restriction anywhere. I'm thinking this is real possible because it was a natural gas company truck.
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