603's dying at idle

[LAbioCars.com]

i have two 603's at the shop right now that start hard and die every time the revs go down when the car stops at a light , then starts right up again....
cars have been serviced and have all new filters ... fuel pump maybe ?

[compu_85]

Is the ELR working? Unplug it with the car idling and see if the speed changes.

-Jason

[LUVMBDiesels]

I swapped OVP's with one I had as a spare (turned out it did not work) without the OVP powering the idle control, the engine would run way below 500RPM (no tach so I am guessing) and wanted to stall. In fact it did stall before I swapped OVPs again.

I would check the idle controls as mentioned above and the OVP relay.

[bustedbenz]

Mine is doing the same thing. Exactly. My tentative theory is that somehow it's temperature related, because this only happens to me on hot days after hot drives on hot roads. 90 degrees plus, generally. Are yours similar conditions when they fail in this way?

[Brian Carlton]

I've got a new theory on this.

I recently replaced the line from the pump to the secondary. When running, it's very clear that there is a bunch of air bubbles that run along that line. I'm not clear on exactly where the air is being generated, but the clamps on the primary are suspicious.

I did notice the engine beginning to hunt, ever so slightly, at idle, after a hard run. It hasn't done this in the past and I wonder if it's related to all that air............further investigation is required.

Certainly, it's absolutely clear that the engine can run with a decent amount of air in the line from the fuel pump without any ramifications.

[LAbioCars.com]

one of the cars (350sd) starts sosmetimes and idles fine but then sometimes you start it and it will start but you have to floor it jsut to get it to idle
then shut it on and start it and it will rev up fine but still not idle

i just got a 90 2.5t in and its doing the same thing too ...

when it rains it pours

[pawoSD]

There sure have been a lot 603's with weird issues lately.....just saying....

[awsrock]

I would look into increasing the mechanical idle speed..my car used to drop rpms below 500 briefly when it was cold and I was coming to a stop, most notably if I let go of the pedal rather quickly. I increased the mechanical idle (the small, 6mm screw on the back of the IP, above the ELR connection) to about 550-600ish, and this solved the problem. Well, it does still kind of drop down when cold, but at that rpm it does not have any effect on idle quality- no shakes, no stumbles, etc. Besides, the ELR setting of 4 should have you in the 680 rpm range, and that's with a ~80 rpm boost from the electronics.

[awsrock]

Originally Posted by pawoSD

There sure have been a lot 603's with weird issues lately.....just saying....

It's worth the hassle!

[Brian Carlton]

Originally Posted by LAbioCars.com

one of the cars (350sd) starts sosmetimes and idles fine but then sometimes you start it and it will start but you have to floor it jsut to get it to idle
then shut it on and start it and it will rev up fine but still not idle

i just got a 90 2.5t in and its doing the same thing too ...

when it rains it pours

Just for the hell of it, replace the fuel hose from the pump to the secondary so that you can see the fuel flowing...........it's only $10. or so...........I'm curious if you also see a lot of air.............

[LAbioCars.com]

aniother thing odd that happend
when i had the car floored it would barely idle
I sprayed a touch of starting fluid in and the motor immediately started revving normal until i turned it off again ???!!!
weeeiiirrddd

[LAbioCars.com]

Originally Posted by Brian Carlton

Just for the hell of it, replace the fuel hose from the pump to the secondary so that you can see the fuel flowing...........it's only $10. or so...........I'm curious if you also see a lot of air.............

i have solid fuel in the secondary ......no bubbles

[Brian Carlton]

Originally Posted by LAbioCars.com

i have solid fuel in the secondary ......no bubbles

How do you know........??

[LAbioCars.com]

Originally Posted by Brian Carlton

How do you know........??

the lines are clear no bubbles going in no bubbles coming out

[Brian Carlton]

Originally Posted by LAbioCars.com

the lines are clear no bubbles going in no bubbles coming out

Can you see through the dark amber lines............or have they already been replaced?

The bubbles are very tiny, you'll never see them if the lines are amber colored.