Idle RPM? Pump timing or Fuel Screw?

[Idually]

When I bought my 1993 Last year the very first thing that I noticed was the idle speed (No guages yet, Bad, bad. ). I have done nothing to the truck at all (Except Maintenance). I'm still a little shy about doing anything I might regret. I bumped into another 1st Gen owner the other day that commented about the idle. He said it sounded like the fuel screw was turned up. I got home that day a started to inspect the the pump. The marks on the pump are still lined up! So, I have to assume, that the Fuel screw has caused the idle increase(Duh), but is this bad? I thought that turning the pump was the "1st" adjustment? Then fuel from there.

Could there be trouble by leaving it this way? Should I back out the fuel screw or adjust the pump to compensate?



What do you all think?

 

[dpuckett]

READ THE STICKIES RELATING TO THE VE PUMP

I wouldnt mess with the fuel screw to set the idle- you WILL regret that. There is a nut on the back side of the AFC hosuing that controls the idle. It is a real PITA be-atch to get to with a normal wrench, so what many guys here do is use a flat screwdriver and hammer on one of the sides of the jambnut to loosen it, then turn the idle where needed. REtighten the same way you loosened, only go the other way. Do you have an auto or stick? If it is a stick, I'd leave it alone, unless you just cant live with it. If it is an auto, it may cause some hard chunking between D and R.



The marks on the pump are timing related- kind of a guide point. The power screw is behind the back of the pump, normally covered by a tamper resistant cap, though it is easy enough to get off.

Daniel



PS- I bet you paid a pretty penny for that zero in front of the miles, esp in Colo, didnt ya? [I have an aversion to vehicles driven less than 15K per year]

 

[prototech]

turn the idle screw down a bit, you'll mis the power if you turn the fuel screw out, oh and get some gauges and join us BOMBers!!!

Proto

 

[prototech]

Hey while we are on the subject, has any one adjusted the governor screw, I think that's what its called, the one on the opposite side of the pump from the idle screw, I haven" seen it mentioned any where. looks like it would give you more throttle travel? any thoughts or experiences?

Proto

 

[Forrest Nearing]

the only time I'd turn the fuel screw to adjust the idle is if the idle were too low!



Forrest

 

[JLEONARD]

I was able to loosen the idle screw locknut with a cheap $1 13mm wrench... it was a very skinny wrench... I was planning on bending it to fit, but it worked in it's "stock" form.

I've turned up my governor... about 150 rpm... . so I could hit triple digits on the speedometer.

Jay

 

[Idually]

Could have said it better...

Thanks for the responses.



I should have said it better. My truck seems to idle high. I don't have a Tach(I know, I know... ), but the idle is high enough that it will pull my truck up my driveway and not load down the motor any more than sitting on a level surface in gear. My driveway, mind you, is fairly steep.



Some other things to add. Very little smoke on acceleration(even to WOT). MPG is fair at the moment (16mpg on avg).



She moves, don't get me wrong, but I don't know what has been "monkeyd" with, so I can't tell what's up? I know this isn't all she has in her.



Maybe I should take it Cummins and have it put back to stock, so I have a starting point.

 

[LV-CTD]

My 93 W250 auto idles fast enough to hold about 17mph in 1st gear on level ground. I think the idle is a little fast but like you I haven't checked with a tach yet. I found a couple of web sites a while back that had troubleshooting guides on them that mentioned that a fast idle speed might be one reason behind low fuel mileage, mine has been around 16mpg also but my tire pressures have been low to try to smooth out the harsh ride but I recently pumped them back up to 80psi to see how much that helps mileage. I'm going to have to wait a little while for guages since I need to get new tires soon, thinking about going from the 235's I've got now to 285's for better mpg's and hopefully a smoother ride too. Anybody like to comment on the idle and tire changes as well as pump adjustments? Idually and I both may be able to benefit as well as others too. Thanks



Tom