Engine/Transmission (1994 - 1998) What Can it Be?

[Dave Remillard]

From idle until around 1500 rpm's there is virtualy no power. Just enough to get out of the driveway. This is most noticable after the rig has sat out in the cold all day and not plugged in. After being in the shop and plugged in all night, it is still a problem, but not as bad. I'm still waiting for the fuel pressure gauge I've ordered, but have to a degree eliminated that as the problem. My reasoning being that once I get to the 1500 range I have plenty of power. I also recently replaced the following items... lift pump, overflow valve, supply and return fuel lines, new fuel filter, and serviced the pre-filter. I don't think it's timing either because as I understand it, I would have low end power and lose top end, and my problem is just the opposite. Any ideas???? Thanks

 

[rjones]

maybe a small turbo hose leak to where you get enough until at higher rpm,s... ... if it only does it when its cold grid heater may be a factor..... Rick

 

[Deezul1]

Are the grid heaters cycling?

 

[Dave Remillard]

I'll pay more attention to the alternator indicater this afternoon. It occured to me this morning that maybe the pre-heater isn't working, but I'm not certain how much effect that could have on performance. Based on your responses thus far, I need to confirm both the pre-heater and grid heater operation. My only other concern is that even after driving and getting the engine warmed up, it's still a bit of a dog at lower rpm's. I just put the #10 plate in about the same time this started, so my question would be what kind of low rpm performance should the # 10 give me?

 

[rjones]

Did you use the template to set up the plate? is it in the original location?... ... Rick

 

[Dave Remillard]

The plate is full forward and governor lever set per Piers. AFC housing 3/4 forward.

 

[rjones]

HMMM... . Well check out those grid heaters and let us know... .....

 

[Deezul1]

Double check the lever setting. When my GSK went in it was so gutless it was pitifull. After the lever adjustment it went on the dyno and did 50hp more than I thought it would.

 

[Dave Remillard]

The grid heater is working, so thats out. My fuel pressure gauge showed up finally, so I will get to check that out tomorrow. Still looking for ideas. Thanks

 

[Robin]

Loss of power

This may not be relevant to your situation:



Last November I was towing the trailer in the mountains of West Virginia. Had about 32 lbs boost and 1300 degrees ET. All of a sudden the boost dropped and the temp went sky high with extreme power loss.



Fortunately I was approaching the truck stop near Beckley, WV, limped in and had plenty of room to park. The turbo hose that connects to the input of the intercooler had slipped out of its clamp. Not completely, just enough to make a small opening to the atmosphere. The clamp is heavy duty, but was not very tight. There are four of these clamps in the boost circuit, all were only medium tight. I make a point of checking them, what with up to 35 lbs boost.



BTW, once I had reason to disconnect the preheaters for a short time and could see no difference in the power at low speed.

 

[Dave Remillard]

Thanks for the ideas. I have checked the clamps from the inner-cooler to the intake and turbo, and all is good and tight. I'm beginning to wonder if the overflow valve is bad. It is new however that may not make it in the best working condition. I'll be calling Piers on Monday after I check fuel pressure. If pressures are good going into the fuel pump it only seems logical that the overflow is bad.

 

[danandamy]

Originally posted by Six. Shooter

The plate is full forward and governor lever set per Piers. AFC housing 3/4 forward.

First, check the boost fitting and boost line that connects to the AFC housing, make sure you don't have a leak there. A small leak might cause it not to sense boost until you really get to honkin' on it. While you're there, go ahead and slide the AFC housing all the way forward. Do those two things, I bet you'll be in good shape.



dan

 

[Dave Remillard]

Well, I tried as danandme suggested, but still have the problem. I also did not get the fuel pressure gauge connected because the banjo fitting bolt that Cummins N. W. sold me was not the correct size, thus I'll need to exchange that first. It was suggested by Deezul1 to set governor lever. It is set now to be slightly higher than flush with the bottom of the plate. Similar to the directions and pictures on Piers site. Can anyone with a #10 plate discribe where their lever is set?

 

[Berrigan]

Sounds like the AFC is not seeing low end boost. When I put my #11 in I wanted to set it up smokey for power reasons but didnt want to see the smoke. So what I did was set the housing and star wheel forward (smoke maker) then put in a 12 volt by pass valve on the AFC line. When I want to blow away a Frrd the electric valve sends the actual boost pressure signal to the AFC and it smokes and goes like a bat out of h===. Then for most all of my driving I turn on the switch and bleed a small amount the boost signal, the afc sees low boost and holds back fuel at low end and the smoke is gone. The hole the bleed goes thru is very very small, and it behaves just like you say your truck is, doggy intil higher rpm.



I think you have a small leak on the line going to the afc. Remove the fitting at the intake manifold and pressurize the whole thing to afc and to the waste gate with about 20 psi air and I bet you have a leak. Could even be the wastegate or afc diaphrams.



Let us know!!!

 

[Deezul1]

On some of these trucks the AFC line from the engine to the housing is plastic and can get hot, burn through and leak.

 

[Dave Remillard]

I replaced the line from the AFC to the intake manifold this past weekend, however I didn't pressurize the line at all. Perhaps it's time to remove the AFC again and take a look at the diaphram and check for possible leaks. I'm confident the line from the maifold to the AFC is good. Is diaphram failure a possility? I don't recall reading about this in the past.

 

[Rammin On]

Where does your wastegate get it's signal? off the turbo? or the AFC? if off the AFC check the hard line across the top of the engine - esp where the standoff bracket is on your ex manifold . . those lines are prone to cracking in that area ...

 

[Berrigan]

Six. Shooter



I dont know how common diaphram failure is on afc or turbos but my buddy just had to do his diaphram on his wastgate last month.

 

[Andy Redmond]

Turn your pre-boost screw on the back of the AFC cover in one turn. If that helps, you may have it to far out (counter-clockwise) after the afc spring install. I know the instructions say just touching, but I've found some auto trans trucks that will hardly move w/a low stall converter. Turning it in one turn, did the trick. If you are a misquito fogger at idle (visibly seeing smoke) you have gone to far.



A holey diaphram could cause probs.



Have we a fuel psi reading yet?



You want the overflow valve that ends in 093 (Bosch number).

You might have the one that ends in 086, my 95 did.



You might try taking the overflow valve out, disassy it and stretching the spring to . 550 or so, if that helps you had low fuel psi (going thru the injec. pump and thru the return line).



Bottom line step thru everything before it became doggy and then eliminate things one at the time. Let us know.



Good luck

Andy

 

[Dave Remillard]

Good idea Andy. I first noticed it when I replaced the overflow valve, but it wasn't even close to as bad as it is since installing the #10 plate. As far as fuel pressure goes, I just haven't had the time at the end of the day to play with it. It's looking like the only chance I'll have next is Saturday. I have all the parts, but I'm hesitant to start the install, have something go sour and not be able to drive it the next day. Hopefully I will have time this evening to pull the overflow valve and stretch the spring to see if that improves it at all. How critical is it if the spring was stretched more that the . 550. Do I need a caliper to measure length more accurately? While I'm at it, I'll try to locate the number as you suggest. Thanks again to all for the ideas.