Engine/Transmission (1994 - 1998) Cold Start Issues

[RIT]

My 12V is experiencing cold start issues. My engine idles at 550-600 RPM during a cold start and rev to 750-800 RPM after about a minute and a half. I have tried adjusting the idle speed with limited success. What could be going on here? A possible weak transfer pump perhaps? The valves were reset and new injectors were installed by the factory approximately 20K miles ago.

1997 3/4 ton with 190,000 miles
I have not ran B20 for approx 2000 miles

 

[Joe G.]

How are you trying to adjust the idle? Are you pressing on the pedal a little to start it? Email me at -- email address removed -- for my write up on the 12 valve fuel supply system, how it works and how to fix it.

 

[EKlem]

Joe's article is quite good so I would recommend starting there.

We could also use a little more info on your issue. Are you able to bring the engine rpm up by using the pedal or will it not go any higher when cold? Is there any smoke coming out of the exhaust and if so, what color is it?

All 12V engines will idle pretty low when cold started if you don't use any throttle. That in itself is not a problem. If the truck doesn't want to start even when you give it a little pedal, then you have a problem.

 

[RIT]

I e-mailed Joe and got his documentation. It looks like I adjusted the idle improperly. I had tried setting the idle with the throttle linkage. After reading Joes documentation, I reset my throttle linkage to the previous settings and made the proper adjustments on the injection pump. The idle is now set to 750-800 RPM with the A/C on and in gear. I will now just have to wait for a cold snap to hit so that I can see if this fixed my cold start issues. Thanks for the quick response

 

[RIT]

I got my cold snap this morning and the old 97 started up and ran a little better this morning. The increase in idle speed allowed the truck to run long enough at idle for me to observe erratic behavior in the voltage gauge. It would charge to about 15 and then drop to 9 every 15 seconds or so. The issue only presents itself during the first couple of minutes after running the engine. During that time frame, the engine is very cold and struggles to maintain a constant 650 RPM in park. When the voltage stabilizes the engine will then idle at 850 RPM in gear with the A/C or Heater on high. Is this just a weak alternator and very low idle speed that caused the problems?

 

[BigPapa]

It's the grid heater cycling off and on. It is the way it's supposed to work. It will also get worse as it gets colder. When it's in the 20's, I can drive mine a couple of miles and stop at a light or something and the grid will start cycling again.



Scott

 

[Missouri Mule]

As BigPapa states it is the grid heaters. The grid heaters have a pre-cycle(before engine0 is running and post-cycle (after the engine is running). If you have one your owner manual describes the cycles.