I need some help. I just bought my truck last week, 1989 W250 4x4 Cummins 5 speed 120K miles from the original owner. I just changed the oil, oil filter, air filter, fuel filter and the water in fuel sensor. The wait to start light comes on normally for starting since I replaced the burned out bulb. Problem is after running for a time the wait to start light proceeds to blink at a steady rate until I shut the truck off. It seems to run fine, good power, smooth idle, no smoke. The owner's manual says nothing about the light ever blinking and the Chilton manual I just bought offered no help either. Any help would be appreciated, thanks in advance. ???<br>mr4spd69

 

I have the shop manuals that cover that older control module. The manual says the Wait to Start lamp will blink if intake manifold is open circuit. You will notice two heat sensors, one top and one on side of intake manifold. One on side is analog thermistor that can be measured with an ohm meter, probably somewhere between 4Kohms to 10kohms depending on temperature. Make sure it does not measure open circuit. Remember that it can be corroded connector to module as well so unplug at both ends and look carefully. The other is the KSB thermal switch that is open above 59DegF and closed below 59DegF, it operates advance on injector pump only. Tell us the price difference between a Cummins distributor and dealer on that sensor. I think you will be shocked.

 

Thanks for the advice. I will give that a try and see what happens. I don't even know where the nearest Cummins dealer is, I will have to do some research. Thanks again!<br>mr4spd69

 

Try here:
Cummins Service Locator

Ed

 

Well today I tried what you suggested. I checked the one on the side with my meter set to 200K ohms and got 24.8 on the display, so I guess that is the culprit, or at least I hope. Will keep you posted as I go, thanks again.