blueberry

I also wanted to ask if the fan being locked on has anything to do with low power? When its cold I guess the fan clutch couples the fan blade to engine speed until the lubricant warms up.

Brian

win

so your still having problems? is it still intermittent? So am I and I have been through most of what you have done in trying to find the problem. from running clear lines and running pressure and vacuum gauges to trapping air into afc control to get full fuel and no difference. I also did compression check and specs were close to a new engine. the same day I ran it in 4th gear about 20 miles to my house let it idle for 30 minutes and the truck ran great i wish I knew why. good luck
win

blueberry

win, yes...i wonder if the injection pump or a failing head gasket could be the cause of our problems. so the fuel psi and vacuum were good values running down the freeway when you had problems? the only other known issues i have read about is a failing bearing in the transmission. in that case the bearing locked up and spun in the case so they knew what to change.

win

i was reading the manual and was thinking if the engine, fuel system, air and exhaust check out it has to be somthing else. The engine has an excessive parasitic load, or drag. I was reading in the brake section on drag and it was mentioned that the power booster could possibly bind, not fully releasing the brake master cylinder. I have never replaced a power booster so have no idea on the internal workings. It reads that the diesel booster is diferent than the gas. I dont know how to check if the booster is binding it is old bty I have a 89 auto and a 93 manual and both have similar problems. I wonder if it is worth looking into and is it possible. thanks
win

blueberry

the brakes can only drag for so long before they turn to dust. have you noticed that temperature can make the problem better or worse?

dpuckett

I still think you need to hook up a fuel pressure gauge and go for a short run down the road. I had a LP on my 92 that put out 7psi at idle, then sucked down to zero at half throttle in 2nd gear. In other words, it was shot.

Daniel

blueberry

UPS is delevering it today and I'll install it. Its in the 20's all day so it should tell us right away! In the meantime I've disabled the KSB (see other thread).

Brian

win

I have a gauge in a few times and i am reading 5-6 psi after the filter. I have also checked the volume and that is with in spec. I replaced the lift pump about 6 months ago to eliminate it. I had the ip looked at twice by two different people and they told me nothing is wrong with the pump. I dont think there is anything wrong with the engine bcause I checked everything twice and sent the truck out and they could not find anything wrong with fuel, air, exh . temperature outside doese not efect operation but it seems like the longer it idles, or maybe engine, temp I have no idea. blueberry did you run without the belt and there was no change. I was thinking of running w/o the accessory drive just a little dangerouse somthing is draging that engine down

win

its me again, just read through posts again. Brian I have the same symptom with the boost situation higher boost on flat ground, also egt's are higher. Do you experience the throttle pedal harder to push down? or the engine running rough and loud when performance is low and it runs smooth and quiet when it runs good?and does the turbo wind up quicker and rpms quicker while in neutral as well as under load. just trying to get more input i.e symptoms. thanks, win

blueberry

win,

I would say my truck has 2 personalities. The old man that gets there but has to take his time, and the young kid that gets there fast.

I put in my fuel pressure gauge on Thursday night and it was 7 psi at idle and would go up to 9 psi if I revved the motor - it would not even dip as I revved it. The truck had that sound that means its running right. I removed the fuel pressure gauge because it was dripping and I needed to redo the fittings. The next morning I drove to my home in Virginia. For 180 miles it was the young kid. Then on one grade it just turned into the old man. It was like this for the rest of the weekend. It didn't sound as good, and didn't run as good. I even retightened the fuel heater and changed the fuel filter with no real difference.

When I got back to Nashville I put in the fuel pressure gauge again and the gauge was reading about 6 psi and would go up to 7-8 if I revved the motor - and it would dip slightly before increasing. I loosened the fuel filter and retighened and then tried revving again. It seemed to help a little. Then I removed the fuel line at the injection pump waited for most of the gurgling noise to stop and reconnected. Then I ran the truck. Fuel pressure was about 8 at idle and revving it would get to 9.5-10 psi without ever dipping.

I think there was air caught in the fuel lines that was not escaping. I am not sure if these differences are even meaningful since my fuel pressure never dips below 5 psi. I will find out when I drive the truck in the morning.

Brian

blueberry

win,

When I first started working on this problem it was much worse. When it was cold outside it would not have power to push the empty truck faster than 65 MPH and the pedal was very hard to push down. If I was at 5 psi boost and I floored the truck, I would still be at 5 psi boost - no increase - and the truck would slow down going up hill. The problem was the timing. The KSB was advancing the timing too far. On CPL 1579 trucks the KSB is active anytime the manifold < 90 F. I have a 21 mile commute and when it was 20 F outside the KSB was active the entire time to work. I disconnected it at work and have never looked back. To disconnect just disconnect the solenoid on the front of the pump.

Brian

blueberry

win,

The other thing I noticed is that I rarely get maximum boost. The only time is downhill in 4th when it will get to 15 psi and the fuel psi drops to 4 psi. Otherwise when I stomp on the pedal it will slowly increase to 12 psi and stay there, with fuel psi about 6.

Brian

win

brian, when my truck runs good the boost is almost instant to 15psi or over when the pedal is punched and all that is heard is the turbo. When it runs bad it biulds boost going down hill it feels like i have to put the pedal through the floor to get the truck to move. the only thing i am not sure of is i think the fuel finds its way back to the tank but have not checked after work was done to truck and when i had clear tubes allover the place i noticed when i shut truck off the fuel in the line from filter head to ip would fill up the ip. It is like the ip is running, dry? But how could the truck biuld boost and raise egt's w/o fuel? it is like we are running through an engine load or a engine retarder. Have you ever ran your truck from a different fuel source? I got close readings on the gauges the big difference was the inhg it was 2 from container and about 4 from fuel tank.
you dont think the brakes are dragging and youran w/o the belt is it possible that the ps pump or vacuum pump could be cotributing to the problem. This is going to sound strange but the truck steers easier when it runs good. thanks. win
you know, these trucks are not that complicated but this problem is driving me crazy

blueberry

win,

I never drove the truck down the road without the belt. I don't mind the fan not running but I think the water pump should be turning! I've ony run it without the belt stationary in the driveway.

I was sitting at a stoplight last night wondering if my steering was harder to turn but I'm not sure at this point. We have had days of 50 F and now its 18 F outside or something like that so that is a variable also. I have trouble thinking the steering or vacuum pump could drag down the engine that much, I'd tend to think the trans could. I have had a water pump cause an intermittant vibration in a Honda and know others who've had that vibration problem in a Mercedes, but not a power loss. For example my fan hub bearing is notchy and could use replacing but if it was causing problems it'd probably burn the belt before it caused a power loss.

The pump rebuilder can think of nothing internal to the pump that would cause the problem. And the way I keep finding fuel issues I'm not yet convinced I don't have a fuel-air problem.

I just have to do more testing.

Stay tuned. PM me your email if you want to take this outside the forum.

Brian

blueberry

I think my problems with intermittant low power are gone. Now I just want more power

I had the pump timing about 1/8" advance (measured to 1.6 mm of lift). As soon as I retarted the timing down to 1.4 mm of lift things got better - smoother, more power, more boost. I can do 72 MPH up the steep hills and still have pedal left to accelerate (slowly).

I also have replacement fuel line from tank to engine and a new in-tank sock. I used Weatherhead 350 PSI line suited for pretroleum products and sealed the fittings with Permatex #2. Previously I had been sucking some air from the original in-tank sock and very likely some air from the aging quick disconnect fittings.

I am glad this is behind me. Now I can spend time on more productive things like lighting, mirrors, sound system, better grill, and modest power improvements suitable for towing 7-10K across the mountains in the Eastern U.S.

Brian