cold studder, no power when cold

[DBCooper]

Friend has a '95 with 36k miles and has a problem with a studder and lack of power when cold (cold being 40 to 50), says its almost like a misfire. Runs fine within a couple of minutes of running. I'm thinkin' return line problems, any other ideas? Thanks.

Dan

 

[PUMPERDUDE]

36k milesin 7 years?Thats the problem. Its not broken in yet. He needs a few WOT runs to blow the soot out Jokin aside,You're correct on the return line. It is overdue . Change the supply while youre at it. It might be worth it to check out the overflow valve too. Come to think about it,I'd check the overflow valve first. Its the easiest thing to do. The engine may have never warmed up enough to hurt the hoses

 

[DBCooper]

Thanks. I was thinkin' about the overflow valve, but with so few miles on it, I figured it would be ok. The thing prob'ly hasn't had more than 6 or 8 tanks of fuel thru it Can an overflow go bad with age?

 

[MDKram]

1. At what RPM is the stumble and under what throttle conditions?



2. Is the power really low or is there just poor throttle responce pre boost prior to warm up?



Advancing the timing 1. 5 to 2* will typically eliminate stumble when cold. I used to see this problem when temps fell below freezing. Timing will also eliminate white smoke when cold. In our part of the country, temps from November through February hover around -15 to -25*C.



If the AFC housing is still at the factory setting, try adjusting the star wheel 20 clicks toward the engine or slide the AFC housing toward the front of the engine about 0. 030". This will allow more pre boost fuel which really helps the driveability of a "cold" engine (not to mention a warm engine).



Just a few things that work in our part of country.



Regards, Marc

 

[DBCooper]

Thanks for the reply. The stumble is with moderate to heavy throttle just to get the truck to move with very little exceleration. The truck has quite a bit of black smoke when cold. Everything seems normal besides this little problem.

Dan

 

[PUMPERDUDE]

I dont know if age effects that spring. What I do know is that it is easy to check. Much easier than the supply/return lines:{

The overflow valve sits atop a banjo fitting right on the front of the pump. Put a rag in the crack so the washers dont go south. Take the valve apart to check the spring. (mine was in 2 pieces). It should measure arround 1/2". If that checks out,put it back in and move on to plan B. If its broken,get a hold of Piers for a replacement. Good luck!

 

[DBCooper]

Good point. Thanks. I've got one of Piers' in my truck and it is easier by far than the return line.

 

[illflem]

Usually a bad fuel line or overflow valve will cause a hard start situation. Sounds to me more like your buddy isn't waiting for the grid heater to cycle or they don't work. My 95s will do the same thing as your friend's at 40° or below if I don't cycle the heaters even though they start right up. If his valves and/or timing are out of whack the problem will be compounded.