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Why does my truck struggle to start, when its warm outside?

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6.5 diesel
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1.9K views 16 replies 7 participants last post by  DieselMcGee  
#1 ·
I just bought this truck 2 days ago it started rough but I didn’t care because the guy i was buying it off of said it was just the glow plugs (I’ve never owned a diesel but am relatively good at working on vehicles so it didn’t seem like a problem) later on to realize he didn’t know anything about them either. It’s about 55 degrees out and i just ran the batteries nearly dead trying to start it, it blows white smoke until its warmed up and stalls right away if you don't keep giving it gas, then it vibrates a lot while idling but i just give it gas until its at a higher rpm idling and it goes away. I’ve been researching the past two days and now there are like 10 different things it could be and i have a low budget to fix it. It leaks diesel right behind the oil pan idk if that has anything to do with it. I just want to figure out what is failing so i can replace it without having to buy everything it could possibly be. It drives nearly perfect when its warmed up. Any help would be appreciated.
 
#6 ·
Start by going through all grounds: Grounds-Grounds-Grounds The importance of good grounds.....

Inspect your glow plug system. Make sure you have power at the glow plug controller 99 Chevy 6.5 Glow Plugs (no Light on dashboard)

If you do not know the history of the glow plugs then I recommend that you replace them. Use AC/Delco or Bosh brand only
Inspect the glow plug harness going to each plug. make sure there are no broken, worn wires, loose connections, etc.

The fuel leak at the back of the engine is usually the fuel filter manager lines leaking.
The filter manager has 3 rubber lines that will degrade with heat/age and leak
 
#8 ·
6.5’s are hard to start in general. Google how to ohm out 6.5 diesel glow plugs you want to make sure all the glow plugs are functioning. Verify you have voltage after the relay when the glow plug indicator light is on the dash. I got tired of hard starts when I had mine so I wired in a momentary switch across the glow plug relay so I could run them for 5 or so seconds before I cranked it.

FYI The white smoke is unburnt fuel and you don’t have full combustion yet which is why it runs so rough and vibrates. Once the cylinders heat up and combustion is even across all cylinders it smooths out.

I would verify the glow plugs are functioning before you put any other parts into it.
 
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#12 ·
Glow plugs are cheap enough that I would just replace them since you don't know the history. But if money is really tight you can test them first. The resistance test mentioned is a good start. You need to disconnect the harness to test each plug otherwise you will be testing them all at the same time. Just because the resistance checks out does not mean glow plug is good though. I prefer to pull them and watch them glow. The 4 driver side glow plugs are easy to get to. Pull them out and jump battery power to them to see how they heat up. Jumper cables normally work pretty well for this task. The tip should glow red within a second or two of connecting power. The whole tip should glow, not just a little part of it.
 
#13 ·
Best way to seafoam the fuel system is to drain the Fuel filter manager (FFM) Good time to change the filter also. . Then fill with housing with seafoam. Then start and idle for 10 minutes. Do not drive. This will clean the pump and injectors. Engine will run fine on straight seafoam. I do this every time I change the filter.
Someone said 6.5 are "Hard to start in general" That is not true. They should start easily. Unless really cold and not plugged in.
Every 6.5 or 6.2. I have had experience with started fairly easily. Unless there was something wrong.
My 6.5 starts with just a touch of the key. Maybe 1 second or 2 of cranking. No matter if it is Hot or Below 0 cold.
Having the glow plug system in top shape is critical to easy starting. Best to replace all 8 as a set rather than one at a time.
Also you need to find and fix all leaks in the fuel system. Leaks will also cause hard starting.
 
#14 ·
The 92-93 seem to really need a glow plug override for great warm starting. The 92-93 glow plug controller. is made for the OE fast glow plugs and gives little, if any, glow on a warm start. The mechanical injection pumps are a little more tolerant of fuel leaks, but it does effect them. I would test the glow plug harness to be sure there is good power to each glow plug. The harness has fusible wire that can burn out if a glow plug shorts out .
 
#17 ·
I had a 93 and I put in the momentary switch because it was hard to start but after some thought the 6.5s in the Army usually started pretty easily; even on cold FT Lewis mornings unless something was wrong so I probably shouldn’t have said 6.5’s are hard to start in general.

Mine was though and the momentary switch was the easiest way to deal with it. One of the more frustrating things was there seemed to be a dead zone if I drove the truck for 10 minutes to the store that the truck wouldn’t be cold enough to trigger the glow plugs but the truck wasn’t warm enough to start without glow plug assistance. I know this was just the temperature values programmed in to trigger or not trigger the relay. This is also a big reason why I went with the momentary switch.
 
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