1986 f250 4x4 6.9 c6 will crank and run but idles rough.

[Virginia86IDI]

Hi I am 16 and was given a 1986 f250 4x4 6.9 c6 with 133xxx miles on her from my Grandfather. The breaks went out and it sat for about 7 years until he told me i could have it. I replaced the injectors with napa injectors and redid the return lines. It has a new fuel filter and fresh winter diesel. Now it seems that the truck is missing on the #1 cylinder. I checked this by cracking the return lines and listening to the idle. The truck shakes and jumps really bad at idle, but as soon as it revs above a thousand rpm it even outs. I need to change the glowplugs, but was wondering if the glowplugs could cause a miss? Could the lift pump be causing the miss and shaking at idle? Thanks for the help. Lewis

 

[86.9]

The glowplugs are just to get things warmed up for starting. They won't have anything to do with a miss. The lift pump won't be the issue either as it would not just be the one cyl. acting up. I am probably not the person to say, but I would suspect an injector or a mechanical problem in that cyl. Is it the same hot or cold?

Jeff

 

[Saskredneck]

Try swapping injector to a different cylinder, if the miss follows the injector you found your problem. If not I'd be doing a compression test to start checking into other possibilities.

 

[opusd2]

Just wondering, think the injection pump could be at fault here? I ask because I am going through the same thing right now, but low power when riding and cracking all injectors causes the same inconsistency in running. I am more used to dealing with Roosa and inline IH diesels when it comes to the injection system.

 

[Ugly Moosling]

Just wondering, think the injection pump could be at fault here? I ask because I am going through the same thing right now, but low power when riding and cracking all injectors causes the same inconsistency in running. I am more used to dealing with Roosa and inline IH diesels when it comes to the injection system.

Roosamaster became Stanadyne and our pumps are just a different version of what's on your IH tractor! If it's just running rough it could be the injection pump, possibly an advance issue. If it's definitely only one cylinder it's most likely not injection pump related. I like the idea Saskredneck posted about swapping injectors to narrow it down.

 

[icanfixall]

Welcome to the forum. As for swapping injecter around I too will suggest that idea. Now about these injecter from Nappa. I'm betting they are a rebuild injeter. Usually we don't recommend using them because they are nearly as expensive as new injecters. Also nobody can get the parts to rebuild them so whats been replaced in a rebuilt injecter. Nothing but testing and shimming is all that ca be done. Conestoga Diesel in Pa owned by a member her named Mel Agne. His signon name here is agnem. See his web site for information on what he has. Over on the west coast a member named typ4 or russ in Oregon can do the same deal as Mel can. they are a cost effective couple of guys that have helped out many members here. Mel is world renowned for his work with pumps and injecters. He sells to many people around the world. My feelings are you have a bad injecter. Please do try moving the bad injecter and see if the problem follows.