Rough Idle on Start /Possible Air in Fuel? - Ford Powerstroke Diesel Forum
Powerstroke.org is the premier Diesel Truck Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 06-15-2013, 02:33 PM
Powerstroke.org Rookie
 

Join Date: Dec 2012
Posts: 6
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Rough Idle on Start /Possible Air in Fuel?

The truck: 1995 F250 7.3 Powerstroke. 180k miles, no mods. Recently had new batteries, glowplugs, valve cover gasket, glowplug harness, glow plug relay.

A few months ago I started the truck up, let it idle for maybe 2 minutes and took off. I got about 1/2 a mile and it started shaking and lost power, like it wasn't firing on all cylinders. I pulled over and it died. Waited about 5 minutes, cranked for quite a while and it started up, running rough at first, but then smoothed out and ran fine. No problems for about 2 or 3 weeks and then the exact same thing happened again.

Then it started happening more frequently. At this point, if I start it and idle it, it starts out smooth and then after 2 minutes or so, starts loping wildly. It does this for a while and then smoothes out and becomes drivable. Once the truck is 100% up to operating temperature it drives ok but it still has some loping issues when idling. I'm also noticing the smell of fuel in the cab and around the truck.

I just got it back after four days in the shop with a guy who was recommended to me. He basically said he can't pinpoint the issue and didn't charge me anything but he said he thinks there's air getting into the fuel. This makes sense, as I am also experiencing alot of injector cackle.

Sorry for the long post but I just don't know where to start. Are there any known issues that would go with these symptoms?

Thanks

Matt
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old 06-15-2013, 06:35 PM
Compression Ignition Addict
 

Join Date: Jun 2012
Location: Charlottesville
Posts: 158
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
need more info

Is there fuel in the bowl when it's running rough? I had a problem that sounds almost identical to what you're experiencing, where it would start running rough all the sudden then die, and would start back eventually after a long amount of cranking. I would crank until the fuel bowl was full, then put the filter back in, and start driving, and the problem would happen again. I finally found a pin-hole sized leak where one of the steel fuel lines went to rubber. I hooked up the output of a vacuum pump--low maybe 10-12psi pressure up to the lines and looked for a fuel leak. I just replaced the old section of rubber line with new fuel injection hose and new clamps. Problem solved.


This isn't necessarily your problem, but you might be able to get some insight on your problem.

Last edited by Woodturner Nate; 06-15-2013 at 06:38 PM.
Reply With Quote Quick reply to this message
  #3  
Old 06-17-2013, 10:43 AM
Powerstroke.org Rookie
 

Join Date: Dec 2012
Posts: 6
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Thanks Woodturner,

My symptoms cetainly sound similar. I am wondering why the problem would go away when it gets warm? Matbe because the metal is expanding and sealing up the leak? Also can you discribe the vaccum pump setup a little more? What type and where you hooked it up?
Reply With Quote Quick reply to this message
  #4  
Old 06-18-2013, 10:03 AM
Compression Ignition Addict
 

Join Date: Jun 2012
Location: Charlottesville
Posts: 158
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Quote:
Originally Posted by mattleycrue76 View Post
Thanks Woodturner,

My symptoms cetainly sound similar. I am wondering why the problem would go away when it gets warm? Matbe because the metal is expanding and sealing up the leak? Also can you discribe the vaccum pump setup a little more? What type and where you hooked it up?


The reason I used a vacuum pump for the air source is because I already had a vacuum pump, a fairly good size (1/3HP) one, with an adjustable output. Vacuum pumps can be used either to pull or to push, but they don't make a huge amount of pressure. The output of mine is threaded, so I just put a gauge on it with a bleeder screw and a hose barb, and attached a piece of fuel line to the output. I can bleed off a little pressure and adjust the output pressure with the amount of air I let out. I think it's fairly important to use low pressure on the fuel lines--the supply line isn't pressurized while the engine is running, and I thought I might create more leaks if I put high pressure air to it. I used only 10 psi, but I think even 5psi would be plenty. If you don't have a plug to put in the other end of the hose, you MUST open your fuel tank cap, or pressure will build in the tank, forcing fuel through the supply line and all over whatever is underneath it. Don't ask me how I know. I got under the truck with a headlamp on and traced every connection point where the lines transition from steel to flexible. I was replacing the rear tank at the same time, because it had a very slow leak in it, so I had an easy time making sure the air leak wasn't from the tank connection. You only have to pressurize the supply line. If you have a leak in the return line, it will just drip, but not allow air to enter the fuel system. A diesel drip is another problem all together, but a LOT easier to find and correct.


My leak seemed pretty small to me--just a small wet spot where a factory crimp-clamp wasn't holding tight enough. There was a very slow drip in TWO spots. At the tank switching valve, the supply line is the one closest to the frame rail. You have to be VERY careful with the pollak switching valve connections. The plastic gets brittle after 15+ years, and WILL break if you put any amount of torque on it. I broke mine. Expensive lesson. There is a great supplier of them, Kascar, on ebay, they are the same switching valve used on the military Humvee. Kascar is a supplier to the military. It was under $200, but I shouldn't have broken it. The Ford Dealer wanted something like $350. I don't remember exactly. Anyway, you have to make sure every connection is holding pressure. I replaced every connector to the pollak valve also. It is nearly impossible to remove the factory connectors without breaking them.

The factory line is braided steel covered in some sort of rubber with a teflon liner. Not only is the liner very difficult to keep from bunching up around the hose clamp and bunching up inside the tube, but I simply couldn't get enough clamping force with little worm-gear clamps to keep it from leaking, so I replaced the factory flexible hose with fuel injection hose. Regular old fuel line is not enough. For what it's worth, 5/16" will work for both supply and return lines, you just have to be patient with it and lubricate the barb of the factory steel line as well as the click-lock connectors for the pollak valve. I found that 3/8" i.d. fuel injection hose is too big to get a secure connection around the steel rigid fuel lines. I over-torqued a couple worm gear hose clamps trying to do this. Don't buy cheap hose clamps. You DO have to use 3/8" i.d. line on some of the connections around the fuel bowl. As far as the bowl is concerned, I ordered a complete o-ring kit from dieselorings and covered all possible leak sources at the same time. There's no way to be sure otherwise.



This is a big project, and will take more than a couple hours when you factor in the normal amount of time spent cleaning off the dirt and road grime from the hoses to actually SEE if you have a leak, the unforseen diesel spills, torqued out clamps, and the difficulty of working around the frame rail supports that completely surround the pollak valve. To say it is a pain in the A$$ is putting it mildly. Only one of the two leaks I found was enough to actually show up on the fuel line before I put pressure on it.



I don't know for sure that this is your problem, but the only way you can get air in the fuel line is from a leak. I had to go through all this to ensure there weren't any leaks. To be completely honest, I did this all twice, because the first time I didn't fix my problem completely. That's why I got so obsessive about every single connection. I found the second leak after fixing one, which seemed to make the problem go away, then all the sudden getting stranded on the highway. All it takes is a little tiny leak for air to build up. The diesel shop I went to about my problem told me it was the fuel pump. After replacing it and still having problems, I grabbed the bull by the horns. I don't regret it. Problem gone, and now I know the fuel system very well, and can diagnose other issues a whole lot easier now.

Last edited by Woodturner Nate; 06-18-2013 at 10:12 AM.
Reply With Quote Quick reply to this message
  #5  
Old 06-20-2013, 12:49 PM
Powerstroke.org Rookie
 

Join Date: Dec 2012
Posts: 6
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Update:

Well, it's been a humbling day. The problem is solved and I'm kind of embarrased to post the solution but I figure it's for posterity and maybe it'll save some other guy alot of headache. Turns out I had two seperate problems. Last time I had changed the oil filter I had removed the little appendage to the right of the fuel bowl (the one on the top right that comes off with two 10mm bolts) in order to clean the fuel screen. After removing a bunch of hoses and shining a light way down onto the block I realized that as I had put it back together I had dropped the O ring that goes between the two metal surfaces. Popping it back in took care of the fuel leak. Now to the really embarrasing part.
The more I had been reading about the fuel injection system and how it is so heavily dependant on Oil pressure I started to wonder if the Mazda Dealership I used to work at had used their standard mineral oil instead of full synthetic like I requested when they changed my oil (they billed me for full synthetic). It had been about 10k miles since the last oil change so I figured hey, I'll do an oil change just to be sure. It's due anyway. I bought some Rotella 5w40 and a new filter and as I was going to start the change I pulled the dipstick. It was DRY. I tried a few times, no oil, nada. After slapping my forehead hard enough to cause a welt I changed out the oil, filled to proper level and voila, starts, idles and drives as good as she ever has.

Apparently, the low oil pressure light doesn't get triggered until way below the point where the injectors aren't getting appropriate operating pressure. A secondary cause may have been the use of improper oil that had broken down but of course that would be hard to prove. I could have likely avoided all of this if I had checked the oil level initially but it simply never occured to me that the symptoms displayed could have been caused by a low oil level. Lesson learned.
Reply With Quote Quick reply to this message
  #6  
Old 06-20-2013, 01:50 PM
Compression Ignition Addict
 

Join Date: Aug 2008
Location: Madison, WI
Posts: 2,633
Thanks: 1
Thanked 35 Times in 34 Posts
Feedback Score: 0 reviews
Quote:
Originally Posted by mattleycrue76 View Post
Apparently, the low oil pressure light doesn't get triggered until way below the point where the injectors aren't getting appropriate operating pressure. A secondary cause may have been the use of improper oil that had broken down but of course that would be hard to prove. I could have likely avoided all of this if I had checked the oil level initially but it simply never occured to me that the symptoms displayed could have been caused by a low oil level. Lesson learned.
There is no low oil pressure light. But there might as well be. The oil pressure "gauge" is really just a swinging-needle version of the idiot light. Rather than a light that goes on when there isn't "enough" oil pressure (whatever the trigger point is for the sender switch), the needle settles at the middle when there is "enough" oil pressure. But indeed, that trigger point is actually based on minimum pressure to properly lubricate the engine (functionality basically borrowed from the gasser engines). Our engines need quite a bit more than that to activate the HPOP system. It's a happy coincidence of the HEUI design, really; with insufficient oil pressure to fire the injectors, the engine will quit running long before the lubrication system is dry/weak enough to risk spinning a bearing or the like.

And indeed, 10,000 miles is, er, a bit overextended for dino oil. Even if the level were maintained, oil that old would probably have been so broken down that it would affect the HPOP pressure.
Reply With Quote Quick reply to this message
  #7  
Old 06-20-2013, 02:11 PM
Powerstroke.org Rookie
 

Join Date: Dec 2012
Posts: 6
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
madpogue, you are of course correct. What I should have said is that there was no indication from the oil pressure gauge that op was low. The rest of your post nicely sums up what I learned the hard way. I have no way of knowing whether the oil in there was actually dino oil, it was just a possibility. Either way it's got some good stuff in it now
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Ford Powerstroke Diesel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -8. The time now is 12:17 AM.


Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.6.1
Garage Plus, Vendor Tools vBulletin Plugins by Drive Thru Online, Inc.

vB.Sponsors