I am working on a 3126b Serial #7as82380. It will crank no…

Typically what I've seen in the past is that the engine won't start when it's cold without stating fluid then it will run poorly for several minutes until it warms up, during this time it will smoke white to gray and sound like it is not running on all cylinders, after the engine warms up it will start and run fine all day and restart just fine until it cools off again, this is an indication of worn out injectors, the injectors produce such high pressures that as they wear out the tolerances in the plungers and barrels are to loose to be able to make th injectors pop off at cold cranking RPM, the only fix that I know of is to replace all of the injectors. Before I commit you to spending that kind of money there are a couple of other things to check. First, what is the actual fuel pressure, it can be measured at the fuel filter, it needs to be about 20 psi at cranking rpm and about 60-80 psi at high idle. Second, if the truck will not start after it is warm then we need to look at the HEUI oil pressure, it needs to be about 800 psi for the computer to allow the engine to start, sometimes be running the engine on starting fluid it will allow the engine to spin faster and develop that pressure, there is a port in the cylinder head to measure this pressure but it is difficult to find a fitting to fit it, the best way to measure it is with a diagnostic computer. Third, the engine computer needs to have a minimum of about 8 volts supplied to it during cranking if it doesn' it will turn off, by running the engine on stating fluid it will take the starter load from the system and allow the voltage to increase and turn on the ECM, check that the check engine light does not come on after cranking, this will indicate if the ECM has restarted and of course check and clean the small power and ground wires at the battery. I hope this helps, let me know if you need anything else,

Thanks,

XXXXX XXXXX

We need to make sure the fuel pressure is ok before we look at the other items, the fuel transfer pump is very under engineered, it sounds like thats what we need to look at next, the fuel filter base on the engine is under pressure so it shouldn't be sucking air but if it has a primary fuel filter on the frame then that could suck air, you can remove and inspect the fuel transfer pump from the back of the HEUI pump it's a plunger and several cheap plastic check valves, you won't be impressed.

Steve