Exhaust question

[NH2112]

As most of you probably know, I just finished swapping a 6.5l TD into my 85 C1500. I'm having a problem with it right now, most of the time it will stall and die when I come to a stop. It always starts immediately, either on the initial start or after stalling, and there's more than enough fuel volume squirting from both filters when I open the bleeder (primary was replaced today, secondary installed new on Saturday.)

Now, my thought is that it's an exhaust problem. Due to lack of funds I used a couple adapters to reduce from 3" (downpipe size) to 2 1/4", and have the exhaust running through the old passenger-side muffler and pipe. Could I just be developing so much backpressure that it's choking my engine? I do notice a LOT of blowby coming out the dipstick tube, which gives me more reason to believe it's an exhaust issue.

Either way, I'm going to make a new exhaust ASAFA (As Soon As Funds Appear LOL) - 3" from downpipe to a new muffler with 3" input & output, with a 3" turndown right after the muffler. Hopefully this will take care of the problem, and work till I can get a Flowmaster and run the pipe all the way to the back.

[Philsky]

Hey Phil,

My Suburban just went through the same problems that you are having, the cure for me was a new injection pump, but for you it might just be a bad , PMD, I'd have it checked. Those symptoms are a real ****er huh, oh well. I pick up my sub tomorow with a new ID pump and a bunch of other work. I am now 1630 dollars lighter, man I love that truck. Good Luck.

[NH2112]

It's a mechanical pump, with only about 50K miles on it. The guy I bought the engine from bought a 99 longblock but put a mechanical pump on it. I think I'm going to make the new exhaust anyway, and also drop the fuel tank and take that DAMN sock off the sender. I've had that tank out several times to clean slime off the sock and I've had enough. Actually, I'm going to put a new fuel tank in, and I'll probably cut the drain plug off an old oil pan and weld it to the new tank so I can drain the tank bottom periodically.

[john8662]

Does sound like a fuel delivery problem.

But you're getting pressure at the air drain petcocks, hmm.

A fuel pressure gauge comes in handy for things like this, thats how I diagnosed a failed lift pump on the 83 van that had the same symptoms you're describing, it would stall, but not always.

I agree though, it isn't a PMD problem tongue.gif

A good exhaust system will surely help, I'd recommend the 3.5" route using a 3" downpipe.

You're going to have some fun with the fuel tank from the sound of things, do you think that the old tank is just crud filled and thats what has been causing you trouble again and again?

The blow-by is concerning. I can't say with any authority that too much exhaust pressure would cause it to have blow-by.

Sounds like rings haven't been able to bite from the engine sitting. I had this happen on a 6.2 that I had sitting for awhile before installing it into a project truck, it had LOTS of blow-by. I just ran it for awhile, and little by little it went away, things had to become accustomed to one another again.

[NH2112]

I've had this fuel tank out 3 or 4 times this year, drained as completely as possible each time, all lines blown out in both directions, and each time I blew back through the sock on the sender too. I just started a new job that will have me working 6 or 7 day workweeks, 10-12 hour days, so time to mess with the truck will be hard to come by, but when I get some time the tank's coming out and the sock's coming off. I also need to check the timing because it does seem to develop a little bit too much white smoke, and I can see it "chugging" out puffs now & then while going down the road. I think I'm also going to run stainless fuel line all the way from the tank to the injector pump, no rubber at all (I'll just flare the pipes on the sender and use female fittings on them.)

As far as the blowby is concerned, I'll replace the CDRV and ensure its hose is clear. I have to install the air filter I bought and weld a fitting for the CDR hose to a 3" tube to go between turbo and air filter, too. I could always unbolt the turbo when I make my exhaust and see if the blowby decreases, too.

[john8662]

What are you using for air filtration now?

How is your CDR routed now, since you mentioned a need to plumb the output hose from the CDR in between the air filter element and the intake on the turbo (where it's supposed to be).

I don't think that it would be necessary to re-plumb the fuel system with stainless.

So where are you getting your fuel as to get so much buildup on the pickup sock in the fuel tank?

I understand the NO time thing, working 40 hours a week, then immediatly after the 8am - 5pm shift going to night classes from 6pm to 10pm, getting kind of old! I have plenty of things to work on too...

[NH2112]

What I'm using for an air filter now is the Lexus (I think) filter the guy I bought it from had been using. It's a cylinder about 10" long and 6" across with an elbow built into it that's clamped to the turbo inlet. The CDR is plugged into a hole the guy cut in the plastic elbow, it fits tightly but I siliconed it just to be safe. I'll get an oil analysis done sometime, but I doubt the engine's dusted considering how much power the engine has. I mean, this thing is SCARY fast! It has to have good compression.

I get fuel at whatever high-volume stations is where I happen to be at the time I need fuel LOL. I try to go to separate truck islands whenever possible, because I figure they draw from a different tank than the diesel pumps at the car islands do.

Actually, I've only found slime (fungus) on the sock once, but maybe the other times it just wasn't a black mess LOL. I just decided that if I have a fungus problem again I'd rather deal with it by changing the primary filter than by dropping the tank.

[john8662]

It's more likely to be algae, but I'd suspect that more in fuel where you're getting water and in a warm environment.

There are diesel fuel treatments that you can run that provide this kind of protection. Stanadyne makes it, I just run their all season conditioner, but they have another product for this.