Former VWDieselParts.com Forum

I bought a used pump that was supposed to be rebuilt with only 3000 miles on it. It has an idling problem.

Problem: When first started, with the cold start cable pulled, the motor will not idle (barely runs) and runs very rough. If I give it a little throtte (about 1/8th an inch or so) it stops running rough and will idle smooth at about 1000 rpms after holding the throttle at that spot for about 45 secs or so. Then the engine warms up and will idle nicely but high at 1300-1350 rpms the entire time the motor is used on any trip or venture.

So, in summary, it won't idle when cold on its own and I have to give it some throttle for 45 secs to get it to stabilize and run smooth when cold. When warm, it stays at a high ilde and idles smooth.

Is there a way to adjust the idle for low/cold running and high/warm running? My assumption is that the motor should idle at the same speed regardless of cold or warm temperatures like all my other 84 VW diesels.

This is a naturally aspirated pump from an 82-84 rabbit.

Any suggestions or recommendations?

Is there air in the fuel lines when you start up?

Not that I'm aware of. I'll check my return and feed hoses and see if there is any air in the lines.

Mine idles lower when its colder. Say, 150 RPMs lower or something, especially if I have a big load on it (Blower on full blast, etc)

I have a NA 82 rabbit with recently rebuilt IP. Seems to have symptoms similiar to yours, when engine is cold, (even 65F) idle is slow, but once things warm up something "kicks in" and idle picks up. I live with it and have assumed that for some reason internal govenor in pump isn't doing its job. I'll be following this string with interest... R

How is your timing? Sounds like it may need to be advanced a little. How is your power also? If you you think it has less power than it should, that might confirm the timing too retarded. What position is your cold start lever in all of this?

OK no air in the lines. I checked all the lines, steel and rubber. The pump runs really nice but at a high rpm. Doesn't start smooth unless the throttle is adjusted at a higher setting.

Question: Is there an alternative way to adjust the starting rpm and the operating temp/warm up rpm by taking off the throttle arm, nut and top of the housing of the IP? (vertical shaft with all the springs around it).

OK no air in the lines. I checked all the lines, steel and rubber.

If all your lines are steel and rubber,... how can you tell if there is air in them?

I guess I should have said rubber & steel checked up to the clear line on the banjo fitting.

Still the same results after checking the lines for air and finding none.

Could there be an internal adjustment to bump up the idle that is associated with the governor?

Did you ever check your timing?

Yes, timing is correct. I checked it twice with a dial indicator.

Hmmmm. You say it is a pump from an 82-84 Rabbit, but is it in an 82-84 Rabbit?. The reason I ask is that the cold start throw (the distance in change of the cold start cable from start to finish) is a different distance between a Rabbit and a Mk2 Jetta/Golf. I notice this when I had a Rabbit pump put on my Mk2 Jetta. I would pull the cold start out, but I never notice any change in the running of the car. So, I pulled the cold start all the way out in the cab, then I looked at the pump and the lever on the pump was not all the way over againist the stop. I readjusted it to make sure that it is pulled all the way at the pump. When I did that, I also noticed extra tension when I pulled it out in the cab. That last .5 inch in the cold start really makes a difference. If your Rabbit pump is in a Rabbit, then I am out of ideas.

This is why the Mk2 Pump's cold start also made the engine idle higher too. When I start my car, I always hold down a little on the gas just to keep the dash from rattling apart.

My pump doesn't have the idle adjuster from the M2 Jetta. I'll check the throw and see if its not going its max movement. Good Idea. I overlooked that. Thanks.

The motor is in a Suzuki Samurai. I've done a lot of these in Suzuki's but this pump is stumping me. I think its something to do with its calibration, but I don't know how the diesel shops adjust them and how they meausre the speed on the bench. This is supposed to be a rebuilt pump with only 3K on it.

I give it extra throttle at start up too so I don't loose my teeth! LOL!

After racking my brains along with all your suggestions, I decided to get another pump and bought a brand new pump and installed it today. Problem solved. Idle works great now at high and low rpms for cold and operating temperature.

Thank you for your insights everyone.