cold start intake heater grid

[DThibault]

I just picked up a '93 that gives me a little trouble starting on cold mornings. It goes through the "wait to start" cycle and I here a big click, the light goes out and when I crank, it tries to go but will not stay running. Here is what I notice. My old '91 will cycle the lights dimmer and brighter as the heater grid switches on and off and I see the ampmeter fluctuating up and down simultaneously whereas the 93 shows no sign of that. I was reading in one of the old TDR to check the KSB valve on the injection pump and I am getting 12 V there so I assume the temp sensor is OK. Where do I go from here. Thanks.

 

[KSommer]

I wonder if your relays aren't connecting right, i'd try jumping them, either activating them manualy or bypassing them altogether, also check for resistance at the grids themselves, they could be broken or shorted out.

kinda just guessing, but that's all i can do from here... .

kent

 

[cerberusiam]

Thats the correct operation on the 93. The heaters are not supposed to cycle again until the engine is running or you cycle the ignition. The 91 should be the same way. After the engine is running both should continue to cycle the grids and you can see it in the volt gauge. If the 93 does not continue to cycle after the engine is running you may have a bad IAT sensor, bad grid relay or bad PCM. You will just have to start back tracking to find it.



Have you advanced the timing on the 93? That will make a big difference in starting. My 92 will fire on the first cylinder up all the way to a little below zero. Your 91 is probably already more advanced so it starts a little better.

 

[bgilbert]

Try cycling them twice. Turn the key over, wait for the light to go out and big click, then repeat, turn key over, wait etc etc. Then try starting. If that doesn't help. Might try holding the throttle about 1/4 way down when starting. I bet it would stay running there, you idle might be a bit too low.

 

[sdstriper]

Try cycling them twice. Turn the key over, wait for the light to go out and big click, then repeat, turn key over, wait etc etc. Then try starting. If that doesn't help. Might try holding the throttle about 1/4 way down when starting. I bet it would stay running there, you idle might be a bit too low.

On my 89' w/290,000 the linkage and breakover spring & pin were all worn pretty bad. It starts much easier with new adjusted linkage, I was having to hold the throttle down a little to keep it idling before.



Also, Cummins Operations and Maintenance manuals state to apply full throttle after engaging starter(below 60*), it ensures the VE pump start fuel deliver is sufficient and helps keep the engine operating once started. One pump full throttle should do it, obviously you don't want to rev it up while the oil pressure is building after it starts.

 

[DThibault]

Thats it, I see no fluctuation in the ammeter needle after it does start, thats what makes me think it is not working at all. It started aat 16 degrees with difficulty the other morning so when I get it figured it out I'll never have to worry. Thanks for the help.

 

[WyattEarp]

could be idle needs set up a little bit, i know mine does the big click and it has started at below zero after i come out of work with no plug up, sounds very rough but to me it acts as its only firing on 3 cylinders until it heats up in the combustion chamber then after so many minutes it high idles and im at full power lol... if you have a tachometer or can hook one up check your idle, i believe at idle with a/c on wide open its 750rpm, someone correct me if im wrong...