Low compression and hard to start

[6 Nebraska IDIs]

Low mile long block installed before we bought the truck.
Its got low compression on 3 cyl. and it cranks a long time before it starts.
What do you think is wrong?

 

[Diesel JD]

Well, probably either the block really isn't such a low mile long block... it was a redneck rebuild and not so good, or its fine, but the rings are stuck a bit. RLDSL is always saying to try some product autoRX or something if you find the rings sticking in a diesel that's sat around for awhile. Has it sat? How low is the compression? Any bad noises or other obvious problems?

 

[Agnem]

I doubt a few cylinders is going to make it hard to start. I'd check the usual suspects first (air, fuel, glow). You can't get good compression readings on a cold engine, so unless it was hot when you checked it, it don't count. Starter speed may be an issue too.

 

[sassyrel]

I doubt a few cylinders is going to make it hard to start. I'd check the usual suspects first (air, fuel, glow). You can't get good compression readings on a cold engine, so unless it was hot when you checked it, it don't count. Starter speed may be an issue too.

mell--on my 84--ive got two low cyls---and gps work--and when warm pops right off--but not cold--even if the gps are cycled twice---sooooooo

 

[Agnem]

I'd question if all your GP's are working and if your spray patterns are good then. The injector spray goes right onto the glow plug tip, so if the glow plugs are hot, fuel is going to burn and the engine has to run. When they went to the 7.3, they moved the glow plug tip over so as not to be in the line of fire per sey, and this is what makes the 7.3 a little harder to start. Low compression is certainly going to lower the heat in those cylinders, but I'd think it would run rough for a few seconds and then clear up, but still start quickly.

 

[RLDSL]

That AutoRX is some great stuff for sticky rings. If you think the thing may have sat for a while, it's worth a shot, but usually one low hole won't make it that hard to start. Definitely check your battery condition and starter . Slow cranking speed will keep a diesel from starting , and make starting a drawn out event. Sometimes the batts just need a good charge. Most diesels have a time keeping up with charging the batteries, especially if a lot of short trips are made.

--------Robert