6.2 diesel has no power/runs rough

[Johnny89345]

Everything on this truck is from the diesel. No mix and match of parts. Sometimes i hit the throttle and its fine then i let off and throttle down and it breaks up. How could i find an air leak? If i had one wouldnt starting be impossible?

 

[Johnny89345]

On a side note i noticed my temp guage reads low. Maybe half way to normal. Is is possible i have a stuck thermostat? The clutch fan seems fine. If theres no computer then would temp not control a/f ratio?

 

[Sparkysikes]

No computer. How many miles on the 6.2? In 89 the 6.2 made like 140 hp and like 280 tq. That's running good. A warm. Diesel is a happy diesel. Check that thermostat! It sounds to me like a lift pump issue. Been there done that... But do clean the CDR. Crankcase decompression regulator valve If stuck open you'll have a lot of oil entering the motor bogging it down and ruining valves. If stuck close you lose the rear main seal and possibly the front seal. Does she fire up ok? Any smoke on fire up? Idle smooth and low throttle response decent?

 

[Sparkysikes]

Also. At front of motor there should. Be bleeder valve. Motor running turn that valve for like 15 seconds. The FFM (fuel filter) is also a water separator. It goes to that valve. Crack it open and get any possible water out. The valve on top of the ffm is really good for priming after a filter swap. I take that fuse and tap it to positive post on the firewall buss bar than at same. Time crack the filter bleeder on top of the ffm to purge any air out.

Have you tried to see if the lift pump is working using this trick?

 

[Johnny89345]

No computer. How many miles on the 6.2? In 89 the 6.2 made like 140 hp and like 280 tq. That's running good. A warm. Diesel is a happy diesel. Check that thermostat! It sounds to me like a lift pump issue. Been there done that... But do clean the CDR. Crankcase decompression regulator valve If stuck open you'll have a lot of oil entering the motor bogging it down and ruining valves. If stuck close you lose the rear main seal and possibly the front seal. Does she fire up ok? Any smoke on fire up? Idle smooth and low throttle response decent?

Actually it has been a little funny starting lately. Have to tap the gas a little for it to fire up and it foes smoke on stsrtup...a big cloud. Idles smooth nost days and the throttle response is good

 

[Johnny89345]

Also. At front of motor there should. Be bleeder valve. Motor running turn that valve for like 15 seconds. The FFM (fuel filter) is also a water separator. It goes to that valve. Crack it open and get any possible water out. The valve on top of the ffm is really good for priming after a filter swap. I take that fuse and tap it to positive post on the firewall buss bar than at same. Time crack the filter bleeder on top of the ffm to purge any air out.

Have you tried to see if the lift pump is working using this trick?

No ill check that tonight once i get home

 

[Johnny89345]

The entire drive has 82k miles

 

[Johnny89345]

Okay so i just got home and checked my tuna can first. Its 100% free flowing. Should there be some type of check valve in this?
2nd i removed the plastic screw on the fuel filter housing and turned the key on woth no fuel spraying out. I cranked fast and fuel came out. Second i got under the car and couldnt hear the pump coming on. I unplugged it both startijg and running that way with no change. Lastly i unscrreqed that t handle with the truck running and no fuel came ojt. But i dont know where it should come out of, i layed under the truck and saw no leaks.

 

[jdla140]

Sounds like your lift pump is only running with the key in the "start" position. Chances are you need an OPS - oil pressure sender. I'd seriously look into signing up to www.dieselplace.com, you'll get better responses over there, not just a bunch of "305 is better" BS.

 

[Sparkysikes]

You need the ops mod. Basically you wire in a relay to key on power. I like that buss assembly on firewall. Use the wire that goes from ops to LP cut it. Use ops side as the trigger and the LP side as the switch. My ops died so I sourced it from the injector pump power.

The ops has 2 circuits. 1 that reads the oil pressure and tells dash how much. The second is a 1 amp trigger for LP. Well the LP draws more than 1 amp.

Go under relay cover on the firewall find the fuse holder. Pull 2 wires containing fuse and wires out. Is fuse good? Turn screw on fuel filter (FFM) than tap the fuse end where you see metal At end of fuse to bus bolt and fuel. Should come out of ffm. Got it?