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strange 6.2 problems under load or when warm help!

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stoneagemaxx

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last wendsday driving home from work i noticed the burb was runnin a little ruff at idel, within a 1/4 mile it started loseing power rapidly, it took over a mile to reach 40mph then i hit a downhill and it went up to 55, got it home, thought possibly a fuel filter, replaced it and started it up, it started, reved up just fine so we took it for a ride, seemed a little better, went about 11 miles stopped for about 3 min and let it idel, put it in reverse and it died, started it back up and it had no power even worse than before, with some persuesion and manual shifting it would rev up most of the time but not all, so i get it on the e'way and it dident want to go above 50, then dropped to 45, getting off the exit it died again started right back up made it a half mile to the light, ideld though the light with a lil throttle, put it in 1st and it just sluggishly moved dident even get past 5mph, pulled into the fuel station put about 10 gallons in it (cheapest its been in a long time) took a quick look under the hood and under the truck and found nothing, started it back up and put it in first and it took off, reved out fine as long as i manually shifted it went about 2.5 miles and started losing power again, pulling into my drive it lost all power again, i shut it down,pulled into low range and waited 10 min fired up and drove it up the drive to the garage, kinda stumped now, going to check fuel pressure while cranking, but is there any way to check while running, dosent look so to me, sorry about the long post but its my DD and i kinda need it up and running, it is alot worse under load, oh and i fired it up today and the normal puff's of blue/grey smoke dident clear up more so on the right side any help is appreciated. thanks
 
The only fuel pressure that really matters is between the IP and injectors, and not sure how you could check that easily??? From my experience it doesn't matter what the lift pump is doing, and generally when they start going bad the main issue is getting the engine started but after running it doesn't matter that much.

Check and make sure you don't have a leak as it almost sounds like air is sporadically getting into the system. Trace the fuel lines from the tank to the engine, and especially look in the engine galley under the intake as fuel can puddle in there quite awhile before dripping out.

Recently a guy in our club had a similiar sounding issue with his 6.2. It was a CUCV that had sat for several YEARS (not hours that I originally typed) and the diesel had grown algae, after running it awhile it started to break up and was clogging the fuel filter. Flushing the system and changing the filter solved the issue.
 
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Last time I had a similar problem my fuel tank was falling out of the truck and the fuel lines were pinched shut in the process... the more fuel I added to the tank the worse the problem was :doah:

It definitly sounds like you are starving for fuel, a new lift pump would be $15 and a cheap point to start if you don't find any problems with fuel lines.
 
There are two filters on the 6.2's, the primary is bolted to the firewall and the secondary filter hangs off the back of the intake manifold down into the valley. You won't see it unless you take off the air cleaner housing . . .

An easy way to check for air in fuel is to plug a clear line onto the fuel return outlet on the IP--the small rubber hose that comes off the top front--and watch for bubbles.
 
second fuel filter???

I have looked the lines over acouple of times without finding a filter This is a 84 6.2/700r4 4x4 sub/just70k on it.But it has been through (3) IP.s already.
 
Only '82 and '83 models with the spin on filter have 2 fuel filters. '84 and up have a single model 80 filter (retangular) mounted to the firewall.
 
stoneagemaxx said:
yesterday,did you say filters i was only aware of 1 on my '84
Click to expand...

Did the problem start right after you changed the filter? Several years ago I had some issues right after changing the filter and it because the new one didn't seal up right and was sucking air in.
 
I should also ad the 82-83 secondary filter is mounted to the back of the intake manifold and is a bi*ch to change.
 
kennyw said:
I should also ad the 82-83 secondary filter is mounted to the back of the intake manifold and is a bi*ch to change.
Click to expand...

Not really. Not a simple one step process. But still pretty easy. The way I do it is to pull the whole filter assembly. Undo the 2 hard lines, remove the 2 bolts that bolt the assembly to the intake, then remove the filter. Fill filter with diesel and reinstall. Takes maybe 10-15 mins
 
Learn something new everyday.
Click to expand...
ditto, but i'll be looking for blocked or pinched return lines, no the problem started before the filter change that was the reason for the change, also will try the clear hose on the return to see if there is any bubbles, should the return have a steady stream of fuel?
 
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