I'm currently debating rebuilding my 1997 f350 engine. It doesn't like to start really, even on a 60 degree day it will take a few minutes and multiple cranks on it to get it to fire up. Also when you do fire it up it blows some serious white smoke out of the exhaust, which I'm thinking its uncompressed diesel. Which in my mind would help explain why it doesn't want to fire up maybe? Now I greatly respect these trucks and I'm willing to put a lot of money into this truck due to the fact that I don't want to have to buy another truck EVER. So what the great debate is, is either buy a drop in engine, or pull my engine have it rebored and resurfaced and put some quality pistons, cam, rods etc in it. I want to put great quality into this truck so I never have to do this again. So I can drive it for 500k additional miles and not have to worry about breaking down. Any suggestions are very welcomed as far as quality parts and suggestions on what ya'll would do. Also I don't want this truck to have 800 horse power or anything crazy. I just want it stock but with extremely quality parts. Thanks for the advise in advance.

 

Ok first off have you tested your glow plug relay and glow plugs? Second bad injectors can also cause hard cold starts.

 

I am with Adam. Let's make sure the basics are covered first before you have to rework the engine.
Some things to check first:
Glow plug relay
Glow plugs
How does it run once it warms up?
Any black junk in the fuel filter?
Take the oil fill cap off. Turn it upside down and set it over the hole. If it is not knocked off by blow by then your engine itself is probably just fine. It may rattle off but that is ok

How many miles are on it?

These things can go a LONG way before needing rebuild as long as they are serviced fairly well

If you need some help on how to verify the glow plug system operability just ask and we can help you out

 

I have not checked any of that. I have checked the blow by however and it's pretty bad. The previous owner was a young kid who I don't believe treated it right. I do know however that there are 100 horse injectors in it or that's what I was told. I'm very new to diesel trucks. This is actually my first so I'm trying to learn the ins and outs. It only has 214k on it and it seems to run alright once it warms up. I don't drive it all that much due to me not wanting to tear something up beyond repair before I know what's going on.

 

What do you consider "pretty bad" blowby?

Believe it or not running these trucks hard every once in a while is actually good for them. It gives the motor a chance to heat up and burn all of the crud out of the motor and sort of get everything pumping. Granted the kid was probably just doing hole shots with it.

I would try to fix what you have first if possible, but if i were in your shoes i'd look for a good low miles motor on craigslist or something along those lines. You should be able to pick one up for around a grand. Swap that in, and then drive that and ponder whether or not you want to spend the money fully rebuilding the motor that's currently in your truck.

But then again a good low miles 7.3 motor should go another few hundred thousand miles without any major issues.

200k miles is where you start seeing injector issues, leaking up pipes, fuel leaks, etc, and it's normally a good time to spend some money and freshen everything up and sort of see whats going on with everything.

 

The blow by is bad enough you can actually see it coming out of the blow by tube while driving down the road or parked idle in a parking lot. So I'd say its to the stage of being run ragged or mistreated.

 

How much pressure is behind the blow-by I've.seen where trucks smoke a lot but have no pressure behind the blow by.

 

These trucks are do typically have a lot of blow by, but if you are thinking you have bad compression, then you should do a compression test to verify that.

 

Not sure what "blow-by tube" means, but the customary blow-by test is to remove the oil fill cap, invert it and set it upside down on the fill hole while running. If it rattles off or just jumps a little, good. If it's blown upward, there's enough blow-by to constitute a concern.

 

You may just have a crank case vent issue. Start with the oil cap test and go from there. If you see smoke while idling, pop the hood and track it down. I would start on the driver's just under the air intake hose. Look for a black dog house thing on the valve cover

 

Alright tomorrow I'll go fire her up and look at everything and take a few pictures and see if I can throw them on here so hopefully I can get some more answers or clear a few things up. Thanks guys

 

Pictures of the truck.

 

time too a compression test. From the pic blow by don't seem excessive. A simple test to see which bank it is simply unplug one connector at a time from the VC connectors, could be as simple a bent push rod.

 

The center picture is of what I was told was the "blow by tube", whenever I'm driving and stop at a stop light you can literally see the gas coming from the tube. I mean it doesn't shoot the cap off but there is a bit of pressure behind it. And how do I do a compression test? Totally new to all of this.

 

Yes, in your center picture is the crankcase ventilation tube. Normally, that tube is only a 90 degree elbow tube that is 3 inches long going directly back into the air intake tube before the turbo. This reroutes crankcase fumes back to be burnt/reburnt through the engine.

Many people take the crankcase vent box (doghouse) on the driver side valve cover and turn it around (so the hose fitting is facing the firewall), then put a hose on it like your picture and let it vent to the atmostphere.

The advantage of this is not getting oil in the intake which can seep out the intake tubes near the turbo or dirty up an intercooler if one gets installed later one.

With the hose disconnected like that, you're going to see smoke no matter what. Some people have a lot of smoke from that tube and have no problems. The main thing is to see how bad your oil cap puffs off when you turn the cap upside down and put it back over the hole.

If the pressure is enough to move the cap, you probably do need to look into compression testing. However, if the cap just merely rattles off from the motor vibrating, you should be good. You said there is a bit of pressure behind the cap, but does the cap move any? If not, I'd start diagnosing other things first (glow plugs/valve cover wiring harnesses) before getting too worried about compression testing. However, if the pressure from the oil fill hole does move the cap, then that is something worth looking into.



To do a compression test, you need to remove all the glow plugs and have a special compression test adapter. Harbor freight sells a diesel compression tester, but if doesn't have the correct adapter to work to mount in place of the glow plugs. Many people build their own (like Glenn who is graciously letting me borrow his adapter currently) and use the harbor freight diesel compression tester. Otherwise, you will have to look and see if a better quality compression tester comes with the proper setup to work on these 7.3 trucks.

Perfect compression on these motors will be in the 400-425 range. You should start to worry if you see compression numbers around 320 or lower, OR if you have compression numbers that are more than 15% off.