diesel misses/lopes?????

[CenTxk5blazer]

My dad's 94 6.5 TD engine has been loping?? periodically while driving (acts like it's not getting any fuel, stumbles) and sometimes it'll cut out. It did this once or twice before I changed the filter. Now it does it fairly often while driving, but sometimes it'll run great. Since I don't have much experience diesels, any help would be appreciated.

 

[sandawgk5]

Maybe and injector pump problem or injectors I know they had a problem with that on the 6.5tds but I am not sure of what year. It was the year that they converted from mechanical to electronic injectors.

Ira

 

[diesel4me]

Pmd..

They had lots of problems with a thing that controls the injectors on the 6.5's thad had turbos and computers(and non turbo ones too)--the thing is called a "PMD"--but I dont know what the initials stand for..if you go to www.dieseldoctor.com there are many posts on the message boards relating to the "PMD"--I guess they were located too close to a heat source,and they crap out when they get hot,or whenever they feel like it..they sell kits to relocate them,and replacement for OEM ones..

 

[CenTxk5blazer]

diesel4me

I don't think its the PMD. It only does it after initial start up, anywhere between 5-15 minutes after starting it'll act up while accelerating and sometimes stall. After it'll stall I can restart it and it'll run great. I haven't had a chance to work on it yet and am trying to figure out what to look at.

 

[diesel4me]

lift pump?

It must not be air in the lines if it starts quick after sitting overnight,but acts up during warm up..I think some 6.5's had electric fuel pumps,both internal and externally mounted,depending on the year.. if one or the other is cutting out,it will interupt the flow of fuel thru the injector pump.( an injector pump CAN suck the fuel all the way from the tank,even if whatever fuel pump it has is dead or dying,enough to keep it running,but it wont accelerate right or have good power without the volume of fuel it needs)..

A clear hose in the return line will show bubbles if fuel lines are letting air leak in..water in the fuel is a possibility too..my 6.2 sounds like it misses ,and it misfires once in a while-Kinda "lopes" like a hot cam in a gas motor--adding some diesel fuel conditioner made it run much smoother at idle..I would not doubt my fuel is watery from condensation, and old,because I havent driven it much since winter....I've added "dry gas" (isopropanol) and it has the same effect..even a
slight amount of water makes diesel combustion more difficult,and more likely to "misfire"....

 

[Kiwi John]

It did this once or twice before I changed the filter. Now it does it fairly often while driving, but sometimes it'll run great..

There is a clue here maybe?

Do the basic diesel-related stuff first. If you changed the filter, are you sure you bled the fuel system properly since you say you dont have much experience of diesels?
No harm in bleeding it again anyway.
Did you check the old filter for water, debris,dirt ?
Any chance you had dirty hands or got dirt on the IP side of the new filter?

There is a 'sticky' thread somewhere in the diesel forum about how to bleed the fuel system btw.
good luck.

 

[CenTxk5blazer]

I bled the system again yesterday, and when I drove it this morning it still stumbled while trying to accelerate. I didn't see any dirt/debris or indications of water on the old filter. I'll pull the new filter again and check it to see if anything new was shaken loose. I'm going to check the electric pump on the drivers side frame rail. I know I should be getting at least 12 volts from the harness. What kind of reading should I get if I check the pump itself?

 

[Guss]

this thing doesnt have a turbo does it??? are injectors mechanical or electric