Engine/Transmission (1994 - 1998) bad miss

[Milk]

My 97 has a bad engine miss when i'm out of gear, engine warm, and when i rev it up. It also does this if i excelerate hard in 1st and 2nd gaer. The motor spits and sputters, shoots a cloud of white smoke out the pipe. its to the point now where i can hardly excelerate until i'm in a gear where i can lug it a bit. I did just have the timing set to 17 degrees, and it made the problem worse. its been doing it for a couple years, but hasn't been an issue until i started messing with the pump. Now the more fuel i add the worse it gets. The truck has a #10 plate, 370 injectors, hx-40 with wastegated 16cm housing, and a AFC spring kit. Could use some help with this very annoying problem, is it my governer adjustment, havn't touched that yet. :{

 

[RHARVEY]

Are you sure the timing is correct?????



Rick

 

[nfox]

With white smoke, i would double check the timing and check the fuel pressure and replace the rubber supply and return hoses behind the injection pump, those might be sucking air possibly. Let us know what you figure out.

 

[Milk]

i just remembered i messed with the return valve back when i first bought it, i stretched the spring because it was giving me trouble. must have gone to far. i just ordered a new one, should be here tomarow, i hope thats it, i'll let you know.

 

[Milk]

O, it was doin this before i adjusted the timing, it was at 11 degrees, now its hopefully at 17 but i will double check.

 

[SEmerson]

Maybe a bad injector?



You definety need a gsk but that is not your problem.

 

[JGheen]

Sounds like a timing issue to me. That 11* of timing was way to low. I would really make sure you have around 17* of timing. It sounds like it is still at 11* or maybe you timed it the wrong way and retarded it some more.

 

[Milk]

I am goin to have it retimed tonight, i'll let you know the results.

 

[bmoeller]

Could've been timed right. But if things weren't clean, it may have been able to slip.

 

[Vaughn MacKenzie]

With white smoke. . . replace the rubber supply and return hoses behind the injection pump, those might be sucking air possibly. Let us know what you figure out.

I have seen this posted a few places but it makes no sense to me.



How can a fuel return line cause air to get into the pump when it is headed back to the fuel tank?



How can a "leak" in the fuel supply line allow air in when it's under pressure? Then it would leak fuel all over the place, not allow air in . . . (unless you're on the throttle hard and/or a weak overflow valve or fuel pump).



Just asking cause I've been slowly working out a light miss and constant moderate blue smoke problem with my truck and haven't had much luck with a new overflow valve, filter, injectors and timing.



Vaughn

 

[mikel]

I have seen this posted a few places but it makes no sense to me.



How can a fuel return line cause air to get into the pump when it is headed back to the fuel tank?

I think most of the problem is caused by the supply line and not the return line, and this part of the problem shows up when the truck is off and sitting. The supply line lets air in and the fuel run back to the tank instead of staying at the lift pump inlet. This causes a hard start condition since the engine has to crank until the fuel is sucked back to the engine from the tank.

How can a "leak" in the fuel supply line allow air in when it's under pressure? Then it would leak fuel all over the place, not allow air in . . . (unless you're on the throttle hard and/or a weak overflow valve or fuel pump).

That's the thing, it isn't under pressure at that location. The supply line is under suction any time the engine is running because of the engine mounted lift pump, so any defect in the hose would tend to let air into the fuel rather than fuel out and even with the engine off there wouldn't be any pressure on the supply line to force the fuel to leak out on the ground which is why most of the time there is no real "evidence" of a bad hose.

Just asking cause I've been slowly working out a light miss and constant moderate blue smoke problem with my truck and haven't had much luck with a new overflow valve, filter, injectors and timing.



Vaughn

Mike

 

[Vaughn MacKenzie]

Thanks for the answer Mike. I was referring to the rubber supply line between the filter canister and the injection pump though, that's the one under pressure because of the lift pump (unless the pump is weak and you're under acceleration, then it may be a vacuum if it can't keep up with demand).



What I was getting at though is people post that if you have an issue with a miss or excessive smoke, the cause is sucking air (true) and that one of the hard-to-get-to hoses behind the pump is at fault (this can't be true, doesn't make sense).



Vaughn

 

[cop0110]

Mine did the same thing. I replaced the metal supply line and cleaned out the pre filter. I was sucking air. . That fixed my problem. . My 2 cents

 

[Milk]

I finally fixed the miss. Turns out the timing gear did slip, all the way to about 9 degrees. Reset the timing to 17, and all is well. runs great, just need to find a good clutch now.