DB2: Air bubbles only when cold advance is on?

[WarWagon]

Is the fuel moving too fast to see them when the advance is off? Stopping the engine does not leave air bubbles in the line with advance off. Only when the cold advance solenoid is on do I see a steady stream of very small bubbles. About pinhead size.

Just curious as to why the advance starts the air?

I have extreme hard starting. Glows are good. Fuel pump/lift pump ok. Filter new.

Otherwise I am looking at the IP or injectors. Injectors were rebuilt 30K ago and checked 7K ago.

 

[bison]

Could be a leaking trottle shaft seal(0 ring).The cold advance might somehow put a diff strain on the shaft not seen in normal trottle operation.

Or you got a tiny line leak pre LP.

The hard start might be caused by fuel drain back after sitting.Is the return line full of fuel at all times?

 

[ak diesel driver]

does that have a mech LP or electric? Mech ones are known to suck air.

 

[Acesneights1]

Bison is right. Look around the throttle shaft seals for any wetness. It's a common issue with DB2s although if you use it every day it usually starts ok. My CUCV has bad throttle shaft seals and if I let it sit for a few days it's a MF to start.

 

[WarWagon]

Just one bubble, small as a pin head was in the return line from sitting overnight. It is a real pain to start after 12 hours and "cold" doesn't have much to do with it. It is hard to start when it is 90 degrees out. Hot starts and any other starts appear ok.

Black and blue smoke on starting. And usually requires some throttle to even start.

It will hit a couple and then stall and rely on the starter to keep spinning. RPM is 180 while cranking.

I will look pre-lift pump...
It has a Carter lift pump wired to the ignition - runs with key on - a mod the PO gave me. Since I got it the entire power train was swapped including the pump with my known good stuff from my totaled truck.

The starting problem just appeared... It is like a lift pump failure, but, I have pressure.

 

[iamdave0887]

Sounds like air in the system to me. My blazer did that when the old box style fuel filter housing had an o-ring that started leaking air into the system when the engine was off. Outside temp didn't' matter, it was a bitch to start after sitting for 10+ hours. If it sat for less than that it'd fire up and cough a little, then smooth out and be fine.

 

[bison]

Just one bubble, small as a pin head was in the return line from sitting overnight. It is a real pain to start after 12 hours and "cold" doesn't have much to do with it. It is hard to start when it is 90 degrees out. Hot starts and any other starts appear ok.

Black and blue smoke on starting. And usually requires some throttle to even start.

It will hit a couple and then stall and rely on the starter to keep spinning. RPM is 180 while cranking.

I will look pre-lift pump...
It has a Carter lift pump wired to the ignition - runs with key on - a mod the PO gave me. Since I got it the entire power train was swapped including the pump with my known good stuff from my totaled truck.

The starting problem just appeared... It is like a lift pump failure, but, I have pressure.

It appears there is no drainback,so supply system looks good.

You could have leaking inj nozzles,so fuel press has to be build up before start,and compression press could theoreticly blow back in.

But i would look first for a bad trottle shaft seal.

 

[Acesneights1]

Yep, like in the other thread any wetness around the shaft seals can cause starting problems. The only reason mine starts is the 24v starter spins the bitch over so fast it can reprime itself. These trucks really should have better starters. The 24v one in my CUCV is like night and day. I have long considered using a 24v starter with a series parallel switch on my 6.5s

 

[bison]

Yep, like in the other thread any wetness around the shaft seals can cause starting problems. The only reason mine starts is the 24v starter spins the bitch over so fast it can reprime itself. These trucks really should have better starters. The 24v one in my CUCV is like night and day. I have long considered using a 24v starter with a series parallel switch on my 6.5s

just use the series parallel switch with the 12 v starter.It'll spin twice as fast.The starter wont have time to heat up in the split second it takes for the engine to fire.

 

[WarWagon]

[/B]just use the series parallel switch with the 12 v starter.It'll spin twice as fast.The starter wont have time to heat up in the split second it takes for the engine to fire.

:rof: The same smoke coming out of the exhaust would be coming from the starter. Mix it up during a jump start and it is a show to remember and then you get to pull out a starter... :mad2: Boycee would have given me a 24V starter with my 6.2 just to get it out of their hair...

Here is starting just before the glow light goes out and throttle halfway to the floor, released after it lights. You can hear it trying to start and that is rough on the starter...

[video=youtube;9agx_TwQ6h8]http://www.youtube.com/watch?v=9agx_TwQ6h8[/video]

http://www.youtube.com/watch?v=9agx_TwQ6h8

:???:

 

[bison]

:rof: The same smoke coming out of the exhaust would be coming from the starter. Mix it up during a jump start and it is a show to remember and then you get to pull out a starter... :mad2: Boycee would have given me a 24V starter with my 6.2 just to get it out of their hair...

Here is starting just before the glow light goes out and throttle halfway to the floor, released after it lights. You can hear it trying to start and that is rough on the starter...

[video=youtube;9agx_TwQ6h8]http://www.youtube.com/watch?v=9agx_TwQ6h8[/video]

http://www.youtube.com/watch?v=9agx_TwQ6h8

:???:

I got a belarus tractor and burned out a starter a year for 8 or 9 yrs to get the damn thing to start on 12 volt, to damn slow.
I put a series parallel switch in and been using the last 12 v starter already for 15 yrs,...how is that for burning up 12 v starters on 24 v eh. now the engine usually fires in 2 revolutions,before, it would take forever.

 

[WarWagon]

Throttle shafts look dry. 1st start is the hardest. It will stall w/o cold advance on. Cranking RPM makes no difference as the Powermaster high RPM starter before this current backup starter failed with this ongoing problem. No air in the return line other than the above.

Fair enough on the 24V on 12v starters - learn something new every day. I have not seen the good of it myself rather just the carnage. Usually it is a non starting engine that the 24v smokes the 12v starter on. Seen a lot of: the engine is hydro locked from a cracked head and sitting overnight. Then the 24v boost (12v's disconnected) bends a rod along with starter damage. And sometimes more than 1 starter in this app, heavy equipment at a open pit coal mine. Talk about going through a pallet of heads every month on that old iron...

 

[Missy Good Wench]

Warwagon

As we spoke of on the phone earlier. AIR in the system. Make sure that you are not getting air sucking into the system and that its not draining back.

As a stop gap measure you can install a little check valve between the filter and the IP.
This will stop any drain back due to air leaking in around the throttle shaft on the IP.

Also make sure as I said on the phone to be sure that you are not getting air coming in from the tank to the lift pump.


The blueish smoke as it starts as well as the black stuff does not worry me much.

As you crank the engine the glow plugs cool off and this will add to hard starting.

If the fuel is right there and ready to go, they fire right off.

All it takes is a little bit of air sneaking into the IP after sitting a while to make these suckers a real Beotch to get started.

Missy

 

[ak diesel driver]

I got a belarus tractor and burned out a starter a year for 8 or 9 yrs to get the damn thing to start on 12 volt, to damn slow.
I put a series parallel switch in and been using the last 12 v starter already for 15 yrs,...how is that for burning up 12 v starters on 24 v eh. now the engine usually fires in 2 revolutions,before, it would take forever.

I've had a similar exp as Simon. Starters a fairly robust. As with any starter heat kills them prolonged cranking =heat

 

[bison]

I've had a similar exp as Simon. Starters a fairly robust. As with any starter heat kills them prolonged cranking =heat

There ye go.:agreed:

 

[WarWagon]

Park nose down as was suggested.

Fired right off after sitting 24+ hours.

Looks like the Carter pump will allow drain back and who knows where the small air leak to allow this is.

So a check valve is needed. Hopefully it lasts longer than a stock lift pump...

 

[bison]

IMO Air leak can be some where in the return line too,could even be a worn IP fuel side pump shaft seal.
The fuel supply/return is closed loop,once the lines are full from tank to tank it don't matter if the LP checkvalve is not quite up to par(not to many are),cause fuel draining back to tank would pull fuel back up trough the return.

 

[midniteplowboyy]

I have no answer, but wouldn't the throttle shaft seals leak fuel out when the advance solenoid is on since the whole housing is pressurized then.

 

[bison]

I have no answer, but wouldn't the throttle shaft seals leak fuel out when the advance solenoid is on since the whole housing is pressurized then.

Not nessecairely,press might seal it.

 

[doober]

It sure looks like an air problem to me. It's like it isn't getting enough fuel at all at start up. Then when fuel does get up to the injectors the glows are cooled off therefore causing the smoking issues. Just my 2 cents I guess.