BC 400 cold starting issuse

It may not be a Frankenstein motor. I t was not uncommon to build an engine to a
different HP/CPL number and not re-stamp the data plate. There are a few things
that can cause hard starting. Fuel draining back from the pump can be caused by
the rubber like material on the disc in the shutdown solenoid deteriorating or worn
seals in the fuel pump. There is a spring and plunger inside the governor weight
shaft called the "weight assist" The weight assist puts pressure on the governor
plunger to increase fuel pressure during cranking and during lift out/clutch engagement.
The weight assist spring wears against the bore and gets weak over time causing
hard starting and weak lift out.
There should be a data plate on the pump, it should have a pump code and CPL
number on it. If a competent Cummins mechanic built the engine a pump shop should
be able to tell you what CPL spec your engine was built to. The CPL or Control Parts
list will identify all the performance parts in the engine.
Take the pump to a fuel system shop and get them to go through it and put it back
on and see how it works before you go any further.

 

You may be able to get away with just pulling the injectors and seeing how the orings are and replacing them.

As far as the injectors go, they'll have a number on them. Without disassembling the engine you have to assume that whoever put those injectors put the correct injectors for that cpl that it is set at. Check the injector number and see what CPL and horsepower that is and if you want to replace the injectors replace them with the same. With an engine that old you don't know what anyone did but that's the only thing that you can go by without disassembling the engine.

When you say they change the coolant system I assume they went from low-flow to high flow. That is a good thing. If that's what they did they did you a favor.

And by the way the fuel lines on these engines can collapse internally. On any truck that's an older truck like that if you think they've never been changed it's something that you should plan on doing soon if you're going to keep this truck. I saw a photo of someone that replaced their lines that were on for however many years and you could literally with the naked eye see the difference in the size of the line because the other older lines had collapsed. Sometimes they can just collapse enough to reduce the fuel flow other times they can collapse enough to almost shut it down.

As far as hard starting that can be a symptom of low compression. It could also be that your pump isn't holding a prime any longer and you're losing prime. You just have to get into it to see what the problem is.

Is the truck hard to start when it's warmed up? Is it hard to start when the weather outside is hot but the engine hasn't been started for a day or two? Does it smoke or miss or have any other problems? Any smoke at idle when the engine is warm?

 

Cold smoke is normal.

Plug it in for easier starting.

 

I fired up a truck with a 400 big cam 3 in it on a Sunday morning at the dealership
where I worked. Someone saw the smoke and called the fire department out. I was
opening the gate to let the owner take the truck when the fire department showed up.

 

You have a very good point about the pump loosing its prme.Had that happen a couple of times.Put a new check valve on the pump and it worked,as far as oil in the antifreeze, could be a bad oil cooler
.I had a 400BC 4 for 12 years

 

Does this BC4 400,have the STC system on it,,,,,,,Step Timing Control,?

 

No the STC came out with NTC444 with truck engines.

 

Mine was a 1987 BC400 with the STC system on it,,,never really cared for that part of it