Truck a bit slow? Don't know why.

[Jeff H]

Truck seams have more lag. I check fuel pressure. The pressure meets the spec. I did pinch the fuel return line twice to see how high it would spike. It hit about 70 psi. when I released the return line the 1st time the pressure dropped fast. The 2nd time I released it. The pressure fell slowely. I can top out at 30 psi boost. But is a little slower at doing it. My mileage is still the same. I begining to think something is going on inside the afc housing. Or if timing may have slipped a bit. I could use some thought or ideas on this. Thanks Jeff H.

 

[Evan A. Beck]

What's your fuel pressure under load @ 2,000-2,400 RPM? Any smoke?



Also, if you timing has slipped, and is more retarded, you'll see more blue smoke on cold startups... Do you have this?



Check for boost leaks too, and maybe slide the cam plate a few thousanths forward.

 

[BillGotthelf]

Try loosening up all the clamps on your turbo lines (intercooler) and move rubber boots around and retighten clamps. ould be a slight leak.

 

[Missouri Mule]

Jeff,

I noticed you lost your muffler, was your cat wearing it when it was lost ?

Thinking along lines of restriction of new air or used air.

But need to think about why your fuel pressure fell off quick first time and slower the next time

 

[Jeff H]

Evan

Truck has always kicked out blue smoke. But only at start up.

I'll get back to ya with the pressure readings.

I pretty sure the cam plate is full forward. But might have to look at it.

Going down the road at 60 mph. the boost is at about 4-6 psi.

EGT running between 400 to 450 degrees.

Missouri Mule the cat has been permantly fixed. Thanks

Bill looks like I'll be check clamps and anything else. Thanks

 

[Jeff H]

Readings

Ok I did fuel pressure check again today. I ran it under load. From 1500 to 2500 rpm foot to the floor. The pressure dropped to about 24 to 25 psi at around 1700 rpm and stayed there up to 2500 rpm.

After that I looke at the star wheel in the afc. I was able to click the wheel forward about 8 or 9 clicks. Should have been all the way ahead when was turned up last year. Wonder if it could have backed off a little. Have not driven it yet after star wheel adjustment.

I checked and tightended the clamps for the turbo ducting. Seamed o. k.

My max egt is at about 750 degrees. Used to be able hit 1000 degrees when floored.

 

[Missouri Mule]

Jeff,

The difference in degrees seems to be not enough fuel getting to cylinders.

Double check fuel return valve, either by using primer button to build up enough pressure so it opens/closes as you pump (my method) or take it out and visually check spring for correct length (measure it).

Your transfer pump should be OK if it got your fuel pressure gauge to 70 psi.



Only other thing I can I think of besides a bad injector pump is that your injectors are clogged up a little.

 

[Blakers]

Try loosening up all the clamps on your turbo lines (intercooler) and move rubber boots around and retighten clamps. ould be a slight leak.

Has anyone made a fitting to attach an air compressor hose to check for leaks in the ductwork? It seems to be a very common problem and not easily detected.



Blake

 

[R.ebel]

Sounds like the timming has possibly slipped.

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[Alaskaskiff]

Had low power problems (mostly slightly lower boost) and after checking for leaks, etc, found low fuel to be 18, adjusted spring length to bring back to 23 (at idle). Truck ran better, but pyro looked hot, so, hooked a 1/4" air hose w/ a pressure regulator set to 20 lbs to test wastegate (I thought maybe it was hanging up), and I had blown the bellows in the actuator. I don't think you could tell with the engine running and checking for a leak due to other air disturbance from the fan. Replaced it and wow! Cummins Part # 3536211

 

[Jeff H]

timing

I think the timing has slipped a little. The truck just does not have any pep anymore. When I hit 4th and 5th gear she smokes pretty good and does not get up and go like it used too. I've checked everything that I could check. So next is to the shop to get timing checked and what ever they can check.

I timing is off? Where should I have the mechanic set it at? I was thinking somewhere around 14 to 15 degrees btc.

 

[Alaskaskiff]

timing spec

Mine was set to 14. 5 per revised timing spec for a 96 w/5spd. Runs better than ever that way

 

[Evan A. Beck]

Blakers,



We have the equipment you speak of at our shop. We use them on a daily basis to check Fords, Dodges, etc. I would say 80-85% of all the trucks have a boosi leak of some sort. Very rarely do we ever see a tight system.



Jeff,



Your fuel pressure sounds about right. I wouldn't worry about it. Instead of adjusting the start wheel, try moving the entire AFC housing a few thousandths forward. Watch your pyro before and after you do this, and be sure to scribe the housing/pump body so you know how much you are moving it. Also, you may even want to do the same thing with the plate--a few thousandths toward the front. After you do that, adjust the AFC, and you should be OK. If this doesn't solve your problem, your timing has probably slipped. The blue smoke at 1,800 RPM on a cold start is a good indicator of retarded timing. Also, does it not sound as "clacky" as before?



750° is a little low on the pyro, that's why I am saying make the fuel plate adjustements first before doing any AFC adjustment.



Keep us posted!