Engine/Transmission (1994 - 1998) Cold start hesitation

[GJolicoeur]

I have a problem with my 97, 3500, manual, 4 X 4 Cummins. It has about 150,000 miles on it (no upgrades - all stock) and has a problem on cold starts.



While it idles perfectly, any attempt to pull away with a cold engine causes lots of blue smoke and missing when the throttle is depressed anywhere between 1/3 and ½. After a few minutes of driving, I am able to “floor it”, and the blue smoke disappears and the engine roars back to life.



I’ve watched the exhaust as I move the throttle, and the blue smoke only appears when the throttle is between the 1/3 and ½ point - accelerating, and decelerating!?



One reader had mentioned something about timing, but I’ve had nothing done to the pump to alter that - and this problem has slowly been getting worse for the last 2 winters.



Once the engine is warm, there seems to be little indication of the problem. I’ve replaced the fuel & air filter which seemed to improve the situation slightly. I checked for air leaks on the turbo boost side, but can find nothing.



Is it possible that I’ve got something more insidious going on? Like a sticky wastegate, or a problem with the governor? I was concerned that having someone advance the timing may just obscure the real problem.



I’m at the point where I need some expert guidance. Can any of the readers give me a clue? Perhaps someone can point me in the right direction,...



Thanks,



Greg

 

[Dbonzi]

Could be timming has slipped or

it could be dirty injectors. I know what your talking about, I have the same thing going on and its not timming. Mine is set to 16.

My guess its th injectors, We have had John Deere tractors that act the same way, replaced the injectors and the issue clears right up.

Let me know how it comes out.

Dennis

 

[Woodenhead]

Mine does the same thing. It actually seams worse with the installation of the 370's. Since these injectors are new I'm led to believe that's not what's causing my problem.



I've also heard timing could be a cure. A local diesel mechanic told me sometimes the timing gears wear over the years retarding the timing a little and described the same symtoms. The same guy said he advances the timing by scribing a line on the gears/shaft and advancing the timing "about" the width of the scribe lines. I guess once I find a shop to set the timing correctly I'll know for sure.



Sometimes mine will also do this when warm if I wind it up hard in 2nd (not much load high rev).



Take it easy

Mike

 

[dbartos]

Hello, Are you pluging your truck in at night? I was having the same thing, because I didn't want to fool with a cord and the hassel of pluging it in, but I tried it the other night and I couldn't believe the difference. There,s not even a wait to start cycle. This morning it was about 10 degrees and it started great. I'm going to be pluging in whenever possible from now on in cold weather.

 

[Andy Redmond]

Two add'l suggestions to the good advice rendered.



Ck. or have the fuel psi ck'd. A worn overflow valve can cause this symptom (sub-standard fuel psi) s/b at least 20 psi after the filter.



Also cycle the grid heaters twice, if your not using the block heater. The block heater is far easier on batteries and starters.



Of course my truck has seen about five less than 20 deg. F starts in the last several years.





I remember when Dad and I were snowmobiling in Yellowstone several years back we were able to get his 1st gen. truck to Start at minus -15 F. with three wait to start/heat grid cycles. We were lucky maybe.

 

[Ben Rumson]

Originally posted by Andy Redmond



I remember when Dad and I were snowmobiling in Yellowstone several years back we were able to get his 1st gen. truck to Start at minus -15 F. with three wait to start/heat grid cycles. We were lucky maybe.

A single 100 watt light bulb hung appropriately under the hood over night, with the grill covered, can make a hugh difference in starting ability as well.

 

[JJW_ND]

Have timing increase a degree or two!

From what you describe (goes away with heat) I think an increase in timing will make it go away.



I am asuming by your location, a cold engine is air temps at or below zero and not plugged in??



Mine did the same. Now a can cold start below zero with being plugged in (very cold motor) and drive away reving as high as I want without any stumbles. Your stocking timing was 14 degrees or so. I would shot for 15 or even 16. I think slightly higher is more benifitial to cold climate trucks. They start better and deal with cold operation better.



jjw

ND

 

[GJolicoeur]

I always plug the truck in. That does help a great deal. Instead of the stumbling and hesitation and blue smoke lasting for 5-10 minutes - it only lasts for 2-3 minutes until I'm on the highway. In the meantime though, I can't press the throttle past 1/2 or it blows clouds of blue smoke.



It does it in any weather below 50 degrees F. this winter.

 

[HoleshotHolset]

I agree with 'Andy Redmond'... . sounds like a fuel issue to me.



Replacing the rubber fuel feed/return lines, checking fuel pressure, and things of this nature might reveal your issue.



I have never plugged my truck in, nor have I cycled the grid heaters more than once... . and I have started her up in -5°F weather on several occasions with no fuss or muss.



If you're looking for smoke free startups - it's a pipe dream... . but for the low power and inappropriate smoke... improper fuel delivery is usually the culprit.



Matt

 

[GJolicoeur]

Cold Start hesitation solved!

I was able to fix it the day before yesterday.



It was a fuel supply problem as was suggested. Number 1, I had installed in the summer, a large fuel tank that replaces the original (an Aero tank). This tank does not use a vent like the old one, and has to vent "through the cap. " Now most caps only vent on pressure, not on vacuum, so as the fuel was drawn down in the tank (or contracted when the temp's went down in the evening), a vacuum was formed in the tank that the fuel pump had to fight against.



I vent the tank now and that helped, but did not eliminate the problem.



I checked the prescreen next to the fuel filter - I had forgotten about it for the last 100,000 miles, but it was clean as a whistle.



Number 2. I then took off the fuel back pressure valve in the banjo fitting at the front engine side of the fuel pump. I took it apart on the bench - it's a simple thing with 1 spring and a ball bearing - and manually stretched the spring from . 45 in. to . 55 in. and put it back together (the directions in previous posts helped!). This causes the pressure to increase on the low pressure side of the pump.



Tada! Problem solved. No more blue smoke, no more hesitation - I now have low end torque back and find I'm using the lower 1/3 of my throttle as opposed to the upper 1/3. Life is good again!



I guess that I'll have to replace the check valve. Can the part be obtained at the Dodge and Cummins dealers? I'd like to have a choice to compare prices,...



Greg

 

[Andy Redmond]

I don't have the Bosch no. with me, but you want the one that ends in 093.



It is available at DC and Cummins, usually cheaper at Cummins and know I don't have those numbers with me either.



You might call a fellow Canadian, Piers Harry @ Pier Diesel Research and he can fix you up very reasonably.



Good luck,

Andy

 

[Dennis Garrett]

Before you put all your tools away, check voltage to BOTH heater grids. I never plug my truck in here in Kansas, and it always started fine above about 30 deg. Below that, I would get the blue/white smoke, & rough running, but by watching the votage meter, everything looked fine. The colder it got, the worse it got. I finally checked my grid leads with a voltage tester, and found only the top grid was getting current & heating up. Turns out one of the relays on the fender well was bad. They come as a set of two ($65. 00 at dealer) clamped onto a common bracket. The truck will start & run fine on one grid until it get's cold, you'll never notice it in warm weather.