I am doing the truck pulls next saturday (still got tons of work to do) and so I decided to bump my timing up a little more. Since I have it advanced a tooth, I've been running it with the pump retarded a little bit just below the stock line. I just barely advanced it so it was about 1/8" advanced + the tooth jump and now it runs away. It starts and idles at about 1000 rpm and and at about 12-1300 rpm it just takes off on its own.

Before it idled at about 900 rpm and took off pretty fast at about 1200 rpm but didnt runaway. My full power screw is cranked in quite a bit (haven't touched it in years) and I have an Airdog pushin about 13 psi of fuel pressure and a 4200 spring. I did have a little incident the other day while driving to school I was cruisin at about 50 and all of sudden there was a huge puff of smoke and it was takin off like it was running away so i slammed it in neutral and shut it off. I thought the throttle got stuck or something but checked the linkage and all was good, I fired it back up and it has ran normal since. What is causing this? and what does timing have to do with it? I don't like this runaway business...

 

its happened to me, push it too far and it will surge. its kind of odd. pull the timing back a little.

 

yeah when I first advanced it a tooth I lined the marks right up and it would surge at about 2200 rpm while driving and sputter so i backed it off. Should I pull the timing back or back my full power screw out?

 

Timing has nothing to do with fuel so I'm not sure why advance would cause runaway. Thats a new one on me.

 

That's exactly what I thought. I was wondering why it was doing that? Maybe has something to do with the governor weights? I went back out and retarded it about 1/8" and runs just fine and normal like before.

But I would still like to know what causes this? All you other guys that are 1 tooth advanced, have you had anything similar or where do you run your pumps at most the time?

 

When you have the power screw turn way up like that the pump can't de-fuel like it used to(supposed to). That is why they run away. Sounds like, that by adding some more timing it raised the efficiency just enough to cause run away. Like when you add bigger inj. and usually have to turn the idle up since efficiently(at idle) went down slightly. If this is the case backing the PS out just a tad should make it happy with the added timing.

Orrr.....your pump has some problems internally based on your experience while driving. Ever find a good reason why it id that?

My $0.02

 

Me and my dad have kind of come up with a theory. We think that with the timing way advanced, plus more fuel pressure than it used to have (which will also advance it more) that it got to the point where its running a little higher rpm from the timing bump then with more rpm while already being way advanced is advancing it a little more by the governor and with the big 4200 spring (which isn't as tight as the 3200 or stock spring but it is bigger and firmer to pull making things take off quick) is not holding the governor back and so it just fuels and runs where it wants to. I think if I had the tighter 3200 spring back in there that it wouldn't do this... or clip my 4200 spring a bit so it pulls harder at idle and keeps everything down but still keep the firmness of the spring making it quick to react.

Am I kind of right or totally off? I really think this 4200 spring is a big factor with this. I'm sure my full power screw doesn't help either but what do I want for pulling? more timing? or more fuel? I was gonna turn up the regulator a bit on my airdog to get a little more fuel pressure for pulling but I'm not sure if thats a good idea now if it causes more timing advance and a runaway. I seem to have plenty of fuel so I might tear into it again and back off my full power screw a bit and bump my timing back up and see what happens... my full power screw is so buggered up I just hope I can break it loose again to mess with it.

I have wondered if my pump has internal issues. It only ran away while driving that one time and its been fine since. Luckily no one was around but it scared the crap outta me. Supposedly this pump had been changed a while before i go the truck but I am starting to wonder if its one of those recall pumps or something else.

Most you guys that have your pump jumped a tooth run 3200 springs right? or a clipped 3200 spring? anyone else with the gear jumped a tooth and a 4200 spring have this issue before??? This was just very interesting to me...

 

I have a tooth jump with the 3200 spring, but also the timing piston is milled. So I don't any issues like you have since my base timing is back near stock.

 

Alright bringin this back up... and now I'm curious about backin my power screw out a bit and rotating my pump some more to get some more timing out of the ol girl... I don't seem to be lacking for fuel and I think theres a lot left in the timing department I could do even though its jumped a tooth. What do you guys think? I just wanna know if backin my power screw out and bumping it up will still make it run away or not or is there only one way to find out?

 

Turn the timing up, and the fuel screw down....or, put in a more aggressive spring. More timing = more power = more rev-gain

 

Im thinking ill try this in a few weeks after I dyno with pod injectors. I got a 4200 spring now but I am thinking about clipping it a coil or two, what's your thoughts?

 

will clipping it lower the actual governed rpm any or what? I am buying a 3800 spring but I might clip my 3200 spring. But I want fuel right up or last 3500rpm, which is why the 3800spring is on order.

 

In all of my timing escapades, timing has never changed rpms, or induced runaway. "weird pop and smoke" would make me look at fueling or governor. I have read somewhere that 4.2k spring is too long?
I run a 3.2k with 3 coils out. She revs high. Makes power to 35-37ish and revs to 4+

 

Not sure on the clipping yet. All I know is that the 4200 spring is longer than the 3200 spring or stock spring and the spring is bigger in diameter making it have more tension and harder to pull apart. My theory of why the 4200 spring makes the throttle so touchy is that it has so much tension that it starts to pull fuel earlier which is why after about 1200 rpm it just takes right off and goes. But where its a longer spring I'm not sure if its getting enough travel or letting it rev higher than my 3200 spring. I've hit 3500 rpm with my 4200 spring and I could hit that as well with my 3200 spring. Only big difference I could tell is much better throttle response and very touchy with the 4200 spring which makes sense cuz of its tension. So in my theory clipping a coil or two off should make it about the same length or less than a 3200 or stock spring making it rev high but be much more snappy and maybe fuel harder and hopefully rev higher. This is just the way I'm looking at it, I could be totally off. I've heard of guys clipping the 4200 spring but would just like to know the advantages before I pop my pump top off again. I'm thinkin clipping my 4200 spring, less power screw and some more timing should give me a lot more rpm and top end which is what I'm lookin for in the truck pulling business What do you guys think or whats your experience?

I got a pic of a stock spring, 3200 spring and my 4200 spring all lined up somewhere...