how to stopEngine hunting

[Cruiseliner]

Hi,

I have a 90 model valueliner with a 350 4 valve engine with a machanical injector pump.

The problem is it keeps huntting or up and down revs. If you try to hold it at a certain rev it hunts and makes it hard to maintain a certain speed.

It mainy does this anything under 1600, Is there away it fix this.

thanks for any info.

Dan

[br549]

Check the fuel linkage for slack in it, also take the rod loose that hooks to the fuel pump shaft, and see if the spring in the lever is broke or has slack in it, it need to be tight with no slack in it but should be able to give as you push hard on it. Other than that it probably be in the governor and be repair at a pump shop. Is it American Bosch or Robert Bosch pump?

[theakerstwo]

Worn out engine mounts some times will do this.Also cab mounts bad can do it.

[e9500v8]

If it has an air ride cab put new shocks on it that will help a lot !

[jakebrake86]

My '87 R model did it horribly until I had the pump rebuilt. It was in the governor, as br549 stated. I'd definitely start with the easy stuff, though!

[dds92780]

My 89 would always surge slightly when it has hot out in the summer, it made it hard to shift the twin stick smooth i tell you that much. I never did find out what the problem was though

[607t1173]

I've seen people spend a lot of money trying to fix this relatively simple problem on the old mechanical engines.

After all of the professional shops and Mack dealers get thru rebuilding pumps and governors and all of the mounts and anything else they can think of.

About 9 times out of 10 it's the throttle arm on the pump & it's usually either a weak or broken spring in the arm.

The BEST Mack (he started in the 30's) mechanic I ever knew told me 40+ years ago to look at this first when ever I encountered this problem.