I was driving my truck today everthing was working as normal, stoped at a gas station went in bought a soda. When I came out I noticed the truck was Idleing rough, didnt think much of it till I took off and it sumbles.

It seems to sumble at low rpms and at idle but runs fine up top. I changed the fuel filter hoping thats what it was but it didnt help. It doesnt seem to make any smoke at all, which is normal its all stock. I cracked a few injector lines and there was a noticable difference on all the injectors but #1.

At this point im thinking two things. 1. bad injector or 2. slipped timing.

Im leaning more on the injector but it seems weird that it was fine on minute and bad the next.

Anyone got any ideas what to check next?

 

Man 3 days 36 views and not one person has anything to say? Did I **** some one off or is it just slow from the holiday weekend?

I did a little more diging on this and it seems that the way the fuel sprays out of the line when it is cracked is much weaker on #1 then the rest of the cylinder. do I have a bad pump? I have been doing a lot of reading and Im starting to suspect that.

 

I suppose it is possible, but I would swap the Injector from 1 to 2 and see if it follows. The only thing keeping the pressure back is the Injector, and if 1 is weak on the pop, the fuel would seem like it wasn't as forceful.

 

Unless you want to throw parts at it check the fuel pressure.
Instructions> http://www.cumminsforum.com/forum/94...-12-valve.html

 

This is the very first place I would go, and the liklihood is high that's what's wrong. I carry a spare outlet regulator valve in mine just for this kind of occasion....

 

I orderd up all the parts for a fuel pressure gage, just waiting for them to show. I was just trying to get some other ideas on what to check next if the pressure is good. Im trying to get this solve as quick as possible. Thanks for the help.

 

I am thinking the same as Bill and HammerMTB.
Those fuel return valves go bad, and if the injection pump doesn't get enough fuel it it runs really weak.
Does the motor put out white smoke when it stumbles or loses power.
You might be able to pinch the rubber fuel return line a bit and then rev the engine and see if it stops stumbling.
You then can be pretty sure you need a new valve.
I just bought a truck that stumbled and you couldn't even rev over 2,600 RPM in nuetral because the fuel return valve was shot. It also put out white smoke like the dry ice rolling off the stage at a KISS concert.

 

It doesnt smoke at all, white or black. I can hear the overflow squeck when i prime my pump. I dont know if thats good or bad.

I have a new overflow valve sitting on my bench in the garage and a fuel pressure gauge as well. I figured Im gonna need one (overflow vavle) at some point with this truck, so I might as well buy it now and have it for now or later. Im gonna get the fuel pressure gauge in and see what it has to say first. Hopefully I will have this solved by tomorrow. thanks for all the help.

 

20 psi at idle switched out the old overflow for the new and now its 25 at idle so fuel pressure is not my problem.

Would slipping the gear on the pump and making the timing retarded make it idle rough? Would it also give it a dead injector? Or is the injector or the injection pump bad it self?

Im headed back to the garage to check timing now, and possibly change injectors. Hopefully I can figure this out, and hopefully its not the pump.

 

Just to close this thread out, I found my problem. It must have been a bad injector. I swaped out all 6 to a set of bosch 300 and it runs smooth as silk now.

Im not sure why but the tips of the injectors were realy carboned up bad. I pulled a set of injectors out of a 96 with 200,000 miles on it and they were not as bad. Makes me wonder what the p.o. was running threw this truck.

Oh well just wanted to say thanks to everyone fore the help.

 

Waste veggie oil and ATF are well known for carboning up injectors.