At wits end with this 6.5 Turbo

[DealerDieselGuy]

I have done a search for this, and have not found anything that seems to e any extra information, so I am hopeing that I might get a reply from someone on here with an idea. Here is as much information as I can give:

Truck:
1993
3500 dually
6.5L turbo diesel (VIN F)


Condition: came in hard to start, hot restart, heavy smoke, no glowplug light.

Repairs made:
replaced passenger's side glow plug harness, replaced all 8 glow plugs.

Replaced all 8 injectors due to bleeding down after engine turned off, filling cylinders with raw fuel.

Replaced fuel filter, tested fuel flow and pressure from lift pump, have 5PSI pressure, and good flow.

Had injection pump rebuilt (mechanical pump) due to reluctor ring slipping.

Now here is the problem.... When cold engine starts and runns GREAT. The owner LOVES it. However when he takes his wife to dinner, and the engine sits for more than 25, but less than 50 minutes, the truck has a VERY extended crank. ECT is above threshold of glow plug, so we have no glow plug operation. all data is normal, no DTCs. Fuel supply is present, and after engine DOES start, we get white smoke, just a healthy "puff" from the exhaust which leads us to believe that fuel IS being injected, but not firing off, and when engine DOES start, the unurned fuel gets "smoked" and blown out the tailpipe.

If ANYONE can help me figure this out and get this customer his truck ack I will be eternally grateful!:)

[ronniejoe]

Is this a stock compression engine?

[Robyn]

How is the compression?? 350+ will do fine. All cylinders should be close.

If compression is good then how is the cranking speed?

Any air present in the system?

Another issue could be timing.
If the engine is the original and has not been opened up, the timing chain can be worn A LOT.
This issue will retard the timing a buttload and make semi warm starts a bitch.

These engines with the DB2 IP should pop right off once they are warmed up and even after sitting for an hour should pop off quickly without glow.

Remove the oil fill tube from the timing cover and observe the pump gear while you rock the crank back and forth with a socket and bar on the crank bolt.

If there is very much slop in the chain it will be evident and measures need to be taken.

You can advance the IP some and see if this helps but to get things right the chain will need to be replaced if it is very loose.

You can easily have 10 degrees of error with a sloppy chain and this will wreak havoc with starting especially with no glow. The injection sequence could be way retarded and retarded timing makes starting tough, power poor and mileage go away as well as causing high exhaust temps too.

Here is a simple test to perform.

Rig a temporary 12 Volt supply from the battery and hook it to the cold advance connector on the IP and try a "warm" start. If the engine bangs right off or at least you see improvements then timing is the issue.

Just unplug the wire from the CCA plug on the IP and connect your temp 12V supply.

If all these things fail to turn up anything then the IP even though is has been "rebuilt" is supect.

The Mechanical sytem (DB2) is fairly simple and if there is compression, good cranking speed and fuel present then the little monster should run.


From there you can take remedial action as needed.

Best

Robyn

[DealerDieselGuy]

Thanks for your input. I will check these things. The compression is good, and the engine is factory, with no modifications.

[ToddMeister]

You could also temporarily jumper the glow inhibit switch to force glow plugs regardless of engine temp.

I did this to my old 87 6.2, it also had trouble with intermediate temp starts.

[Kennedy]

How expensive was the pump rebuild? My guess is that the rebuilder skipped right past the problem which is the head/rotor assembly.

I believe MP.s prescription here is to add motor oil up to 10% of fuel volume and see if the improved viscosity helps.