I have been fighting a starting problem for about 2 years on the boss's f250 since I installed a used engine. Cold starts are almost impossible without the block heater plugged in. I have checked the glow plug relay. It is working and feeding power to the glow plugs. I tested the glow plugs before installing the engine and all tested good but the boss wasn't satisfied and had me install a new set anyway. It didn't help. I have installed a mechanical HP gauge in the HP oil rail to check for pressure and it has good pressure. He had me replace the valve cover gaskets and undercover harnesses. Still no help. I did a compression test on the engine and all 8 cylinders were in the range of 375 to 390 p.s.i. I don't know what the specs are for compression on this engine but I suspect that it is not high enough and that is the primary reason for the hard start. Does anyone know what the compression is supposed to be? Before I installed the engine the compression tested about 100 pounds low on 2 cylinders and a wet test brought them up. I tried to get the boss to make the junkyard give us another engine but he and junkyard insisted that I install it and it has never started right. Now that the weather in Florida is cooling off the block heater has to be plugged in or it will not start at all.

 

not for sure what it is, but i found where someone said it is supposed to be between 350 and 400

7.3 Compression Test Procedure - Ford Powerstroke Diesel Forum

 

The compression is in that range so I guess that is eliminated. The used engine was from a 99. Would the HPOP be enough different to cause the problem? The other thing I would like to do is have the injectors tested. I have an extra set from the other engine but I haven't found anyone yet with a bench tester for the electronic injectors.

 

The injectors aren't electronic they're hydrolic. How is the oil in the HPOP res.? You may have a bad o ring on your injectors causing the HPOP oil to leak back to the engine oil. If the HPOP oil is low fill it up and then try to start see what you get. Also the IPR (injection pressure regulator) could be toast and may be failing. How are your batteries?? May also be something to look at.

 

Actually they are electric over hydraulic but the point I was making is I haven't found someone that can bench test them. I just replaced all the injector o-rings and checked the res. It is full. Two of the top o-rings were bad but it hasn't changed anything from when I first installed the engine and I had put new o-rings on it then also.

 

might need to check and verify the the glow pugs are being energized from the relay.
the other thing is to make sure the truck is primed with fuel.

 

I have pressure tested the fuel and I have about 60 psi and I went so far as to put an ammeter between the relay output and the glow plug feed wire to make sure the current drain is correct, The relay is engaging and the glow plugs are definitely working.