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93 TD HARD COLD START WITH LOTS OF SMOKE

R

REB

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duchesne ut
MY 93 GMC 6.5LTDHAS SOME TROUBLE WITH COLD STARTS. WHEN IT FINALY STARTS IT RUNS ROUGH AND SMOKES ALOT IT SMOOTHS OUT AFTER IT WARMS UP A LITTLE .SOME HAVE SAID LEAKING INJS.IT ALSO SENDS OUT A PUFF OF SMOKE ( I GUESS IT S MORE THAN A PUFF) WHEN I LET UP ON THE THROTTLE AND WHEN I STEP BACK ON.ANY ONE ADVICE ?
 
Check the glow plug system, insure all the plugs are working, replacing them couldn't hurt anything.

A good thing would be to look into the fuel lift pump wiring kit Kennedy offers, it will activate the lift pump with key on and insure the fuel system is primed and stays primed, also a fuel pressure gauge is a good idea to know for sure the lift pump is working.
 
Welcome!
I would follow all the above.
Get the clear tubing at any hardware store. 6" long piece of 1/4" clear tubing and 2 new screw style hose clamps. this replaces the small piece out the front of the ip just behind the oil fill cap in an upside down 'U' shape. 1 small trapped air bubble is ok. a trail of bubbles indicates air intrusion and needs to be addressed.

On the New glow plugs: Only use either AC Delco 60G or Bosch 80034. these are self limiting plugs that don't damage engine if over cycled. always use a little antisieze on the threads. If you unscrew a plug and it doesn't come out easy, STOP! the non self regulating ones can swell up and break off - there is a tool for removing them if this occurs, otherwise it is a pain.
 
THANKS GUYS .I GUESS I SHOULD MENTION THE TRUCK HAS 240.000 MILES AND THE INJS HAVE PROBABLY NEVER BEEN REPLACED.IT HAS BOSCH INJS IN IT.I THINK THEY ARE ORIGINAL.DID GM USE BOSCH INJS?
 
A little advance makes a world of difference on cold starts.

First check the cold start system is working. It's a switch on the thermostat crossover that turn on the advance solenoid and plunger to increase RPM. Quick and dirty: Engine Cold turn the ignition on, then unplug the switch, and you should hear a click from the IP. Use a test light if you can't hear a click. The fast idle solenoid requires throttle movement to set. Green wires. The pink is the engine run wire to the IP.

As you will learn the timing chains stretch out and retard the timing. I bet this has never been timed to correct that and giving you retarded timing always. Best advice is to find an "old school" diesel shop that has the antique equipment to time this engine. And visit them once a year. (By the book adjustments for idle RPM etc. should be done every 6 months.)

Injectors are good for 100K tops. Replace them so you know. A few site vendors on here sell them. Avoid China knock-offs (nozzles) as they have short lives. BOSCH or AC Delco is the body: even God doesn't know what nozzles they may have been rebuilt with.
 
Welcome to thetruckstop REB.
The clear plastic tube is a must for diagnosis, pull and check those glow plugs, I`m putting My bets on the plugs.
240,000 miles is barely broke in, unless it has had some mighty poor maintenance, and or, has been overheated.
 
I'd put my money first on worn injectors, classic symptoms of leak down and poor spray pattern is what you're describing. ESPECIALLY if they are the originals with 240K on them as you suspect! Then, check the glow plugs/wiring/controller system. That many miles on the motor, your timing chain wear must be horrendous by now and no telling where your base injection pump and camshaft timing is in mechanical relationship to the rest of the rotating assembly, either. Then, I would be concerned about the health of your IP with that many miles on it, too. Especially since it was designed to run on high sulphur diesel, not the ultra-low sulphur sold at the pumps now. The sulphur was a lubricant, and if additives to increase lubricity weren't used in its past life (or current) then there is most likely internal wear that affects both timing and pressure to the injectors.

So, being a straight mechanical system, you don't have ECM/PMD issues to contend with, too. When you pull the IP to replace it, go whole hog and pull the timing cover (and the fan and radiator stack, too, and clean the stack out while you're at it) and replace the timing chain set and on reassembly upgrade your water pump and cooling system to the balanced flow system and a better fan, replace the harmonic damper with a Fluidmaster and the drive pulley with Leroy's billet model.

Oh, damn! Suddenly, you have a BIG PROJECT! :eek: Welcome to the forum and the "joys" of 6.5 ownership!
 
Check fuel pressure, glow plug operation, etc.

Lots of little problems add up to a big problem.

Best case, a new OPS and a few glow plugs, worse case a new injection pump and injectors.

Overall, still better than a new pickup if you dont need the power. a full set of 6.5L injectors costs what 1 Duramax injector costs, and a completely rebuilt fuel system is still cheaper than an injector job alone.
 
New injs and glow plugs seems to have been able to fix the cold start problem.but still have lots of smoke.going to do the air test .and install knew lift pump would air or low fuel pressure make it smoke? Also it runs good under load but just to review it up to 2000rpm it starts to cut out and smoke
 
It has been sitting for a week under six inches of snow temps in the twenty's and started nicely but still smokes badly
 
If it runs perfect when warm, my vote is for the cold advance piston in the injection pump is shot. It will need sleeved during a rebuild.

One of many reasons the DB2 does not excite me... :)
 
REB said:
New injs and glow plugs seems to have been able to fix the cold start problem.but still have lots of smoke.going to do the air test .and install knew lift pump would air or low fuel pressure make it smoke? Also it runs good under load but just to review it up to 2000rpm it starts to cut out and smoke

. . . The coolant is always good.Right up to level .it smells like fuel not coolant.
Click to expand...

It seems you have a few of these 6.5's - but the mechanical DB2 will "try" to suck fuel if the lift pump is not doing its job while a DS4 based vehicle will usually just cut off at coast or returning to idle. The DB2 will start and do what you are describing at higher a rpm if it cannot suck enough fuel. Low fuel pressure is taking life out of the IP because there is no fuel for lubrication of the IP. You do not say if the 2000 rpm cut out and smoke is cold or warm.

If the coolant smells like fuel - you may have a head gasket leak - which is popular at the rear cylinders which tend to run hot. A cheap and ugly fix is sodium silicate head gasket seal. But usually most often a head gasket leak means the coolant level will drop over time. You have to check the coolant system pressure to get a better idea when warm.

You say that new injectors and glow plugs fixed the cold start problem, however the first thing to do is get a REAL dependable lift pump on the vehicle.

For instance the AIRTEX E3158 has a spec of 14 psi and that is that is one of the pumps for that vehicle - but I can tell you I have seen four of those pumps in a row loose pumping pressure in 1 week.

Put on a rotary type immersion pump rated at that with a back flow valve - it will work and you can hear it running and know it is pumping because that is a MOTOR pumping through a rotary vane impeller - NOT a solenoid buzzing back and forth using a spring to push fuel.

I hate to rag on this - but the new OEM style lift pumps being produced today do not work and not for long. I have seen them stop pumping pressure in one day.

Otherwise I am with GM Guy from https://www.thetruckstop.us/forum/threads/93-td-hard-cold-start-with-lots-of-smoke.47715/post-564224 that it is the cold start system.

I am also with Husker6.5 at https://www.thetruckstop.us/forum/threads/93-td-hard-cold-start-with-lots-of-smoke.47715/post-563761 that the DB2 should always be run with an additive to add extra lubrication to the fuel because today's ULSD - which is all you can get - is a bit too "dry" to lubricate properly a DB2 for long life.

There are a lot of people who refuse to believe ULSD will harm the older injection pumps - but I have seen the truth - there was a Brand new - not rebuilt - DS4 that seized not even one week into operation and DB2's come in for rebuild with scarred plungers . . .

My two cents
 
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