Slow starting 12.7 Detriot

[farmerlund]

So we have a 90-91 KW T-600 with a 60 series Detroit. It always starts right away with in a couple of revolutions. This spring it started taking longer cranking for it to fire. It cranks fast but is slow to fire off, kind of sounds like the fuel is running back or something. Is there a check valve somewhere I am not seeing? or something else to look at. Runs good once it is running. Starts quick if started right after shutting it off. starts slow overnight or longer time of sittng

Did replace fuel filters and look for leaks or bad fuel lines. I am not real familiar with these engines fuel systems.
Thanks

 

[Truck Shop]

Yes there is a fuel regulator at the back of the head that has a check ball in it. Now that check valve will have a part number relating to that engine probably starting with 235----------
The bad thing is it is in a T600, probably going to be hard to get to. The injector harness will probably be zip tied to the fuel line, because of the age and engine heat be careful moving
the harness around. You don't need a problem with that. Engine serial number will also help getting a new one. Sometimes an injector will start leaking past the o-rings or dribbling fuel
once shut off causing a bleed down in fuel system. Early series 12.7 liters started with GK------- serial numbers. I would think about the fuel lines deteriorating inside just because of age.
And a T600 is no fun to change the fuel hoses on, Pac car installed 500 clamps using 6mm fasteners/10mm that will probably be frozen.

The fuel system is about as simple as it gets. Detroit wasn't stupid like Cat,flowing fuel through the cooler plate behind ECM. It just looks complicated.

Truck Shop

 

[farmerlund]

Thanks TS. I will look back there and check it out.

 

[farmerlund]

Mine doesn’t have anything at rear of head. Just 2 90 degree elbows that fuel lines hook to. There is this filter on the pressure side of pump.

 

[farmerlund]

How about this fitting? It’s on outlet of filter housing. Line goes to rear of head.

 

[Truck Shop]

Take it off, take a look at it but normally it's at the back of head on return fuel line.

 

[RZucker]

It should look like this.

 

[Truck Shop]

Correct. Some were at the filter if frame mounted IIRC. But I don't think I have seen but one of those.

 

[RZucker]

Correct. Some were at the filter if frame mounted IIRC. But I don't think I have seen but one of those.

Honestly, I have never seen any other style. More than once I considered relocating the damn thing to the frame or right at the tank return. Last one was in a late 80's Pete shorthood… GRR.
ETA>>> Bingo, check at the return divider if it has dual tanks. It just hit me.

 

[Truck Shop]

No that is the standard check valve you have in the photo RZ. What I was saying was I've only seen one at the filter before and why it was there I don't know. It could be
at the fuel splitter but that T600 will have the phony Pac Car style fuel splitter that always leaks and I have never seen one installed there, although stranger things have
happened.

 

[RZucker]

No that is the standard check valve you have in the photo RZ. What I was saying was I've only seen one at the filter before and why it was there I don't know. It could be
at the fuel splitter but that T600 will have the phony Pac Car style fuel splitter that always leaks and I have never seen one installed there, although stranger things have
happened.

Oh, ok, the ones I have seen at the filter just keep fuel in the head for an easy restart after changing the filter. But there has to be one in the return too.

 

[Truck Shop]

Well I think he just follows the return he will find it or maybe from the point he was looking at it, it didn't look like it had one. We aren't there so who knows. Hopefully he will prevail.

 

[farmerlund]

So I think we figured out what happened. Last winter we had a local shop replace the clutch. While they were in there they replaced both fuel lines to the back of head. I think someone didn’t put the check valve back in. The truck has been slow starting all spring. We didn’t use it after it came back from shop till a month ago. I fallowed the return to the tank, no check valve. It only has one tank. I will pick one up next week and install it.

Thanks for the help so far.

 

[Truck Shop]

Yes there has to be one. I am assuming by year that engine is a DECC II or early III, make sure it is the correct check. We had five DDEC V's that came from factory with the wrong check.

 

[farmerlund]

I haven't forgot about it. ordered the parts but they didn't come yet. I think the parts guy forgot to send them.

 

[farmerlund]

So upon further investigation I found the check valve. It was 2 feet down the hose wrapped up in insulation under the exhaust pipe. This is what I found.starts like a champ again now. Must not of cleaned out the new hose very well.

 

[RZucker]

Some days I think Kenworth hired the Easter bunny as a part time designer. Anybody that will hide ECM fuses under the cab by the shift tower...

 

[crane operator]

At least you found the issue. There's nothing worse than throwing parts at a intermittent problem and not knowing when you've got it fixed.