Ok, so I've read though a lot of other posts here and I can't find a situation quite like mine so I'm looking for a little guidance. I have a 94 F250 4x4, auto, 7.3 IDI turbo with about 160,500 miles. I bought it this summer, and it ran fine (had a little smoke at start), but I've been having some smoke issues that I'm trying to pinpoint.

The truck starts fine (even in colder 40 degree weather) and is almost smokeless, but as soon as the high idle drops, it smokes like a straw house on fire. If I don't want to smoke out my neighbors, I have to start driving before it gets warmer and the idle drops, and keep it above 900-1000 RPM until the engine warms up completely, and then it doesn't smoke that much at idle. However, if I turn it off and restart it when it's still warm, it still smokes until I drive it for a while and heat it back up to normal operating temp. It's WHITE smoke, and smells very rich, so I'm thinking it's not oil... I've also been watching the oil and it's NOT burning any.

The following has been replaced:
- Glow plugs with relay (not sure which brand, but it starts smoothly and doesn't smoke when cold, so i don't think it's the plugs)
- Injectors (from Accurate Diesel in MI)
- Injector lines (but there is a small diesel leak in one of the lines, I'm not sure if it's letting air into the fuel system, I'll bleed the fuel lines again to be sure, but it smoked a lot immediately after I bled it before)
- Fuel filter, which was bled twice along with the injectors when replaced


I'm trying to figure out my next step. Honestly, I just want to sell the truck, so I'm not trying to put a lot into it if I don't have to. I originally thought it was the rings, but that's me being a pessimist. Any advice or guidance would be greatly appreciated.

 

Advance your timing by rotating the injection pump a dimes width towards the passenger side. Do a search on timing by ear, make very slight adjustments.

 

Yup, I second this. Smoke issues and missing are usually retarded timing.
(Note that as the IP wears, the timing tends to slowly get more retarded over time, which is why this problem can get worse over time)

 

Ok, so I had planned on adjusting the IP as stated above...however, I think I have a new problem. Twice in the past two days the truck wouldn't start when cold. It took a lot of cranking to get it to start, and once it caught, I had to pretty much floor the gas (for a few seconds) until it started running properly. I let the pressure out of the fuel filter schrader valve as a buddy was cranking the engine to see if there was air in the fuel filter system. There was a (very) tiny bit, but it still wouldn't start... it finally started just as the battery was about to die. After I got it started, it ran fine, but chug/sputtered at one stop light on the way home, like it wasn't getting enough fuel, I had to press the gas a bit again to keep it going. The day before, it died at a light and took a while to restart.

The strange thing is, as it was starting it would puff out some smoke like I described previously, but once it was running there was no smoke at all. It ran like it should... even after the idle dropped. It was no longer billowing out smoke at all, except for the initial start, and if I punched the pedal. If I pressed it slowly, or normally, there was no smoke at all. It's completely unlike it was a few days ago.

I did not adjust anything with the fuel system...

I checked the GP system, and it's working properly, and it was certainly drawing a lot of power from the batteries, so I know it's working enough that the engine should have started without too much trouble.

I'm wondering if the IP is just bad/worn out? The truck has (at least recently) all the symptoms of a bad IP (bad fuel economy, rich exhaust, a lot of smoke, low power).

Is there any way to test the IP to see if it's actually going out? Or do you think it's best to just replace it?

 

Sounds like air intrusion to me, pumps usually fail in a no run fashion. The day my pump died it required ether to start and when it did it spewed white smoke like you wouldn't believe (clouds). It then died while rolling down the highway.

 

I'm going to fiddle with it this afternoon, I was just more surprised that when it finally did start running there was no smoke at all. It was running like I've been wanting it to... minus the whole engine dying thing. Is there a way to test the IP to see if it's bad?

 

Your IP is basically just a hydraulic pump. Either the seals and components build enough pressure to fire injectors (and motor) or they don't. The only impending sign that it is going out is hot start troubles, in this case it seals enough when cold to start but only delivers enough pressure to run (poorly) when hot.

 

A worn IP will mess with the timing, however, ending up being retarded. This is usually the most common problem, and one few people notice.

Advance it and it may help a number of problems, including cold starting(due to the injection being earlier, when the air charge is hotter, it should fire off easier).

 

ive actually ran my truck at -9 degrees, didnt smoke one bit.
my vote is on weak, or a leaky injector or 3.

be carefull of places that sell injectors, most of them are scams,
IMO only 3 places to get them.
Typ4
CDI
R&D

 

Agreed, but in terms of a working (worn) pump vs a "bad" pump its pretty much all or nothing right?

 

Alright. I've done a investigating and I've found at least part of the problem.

My injector line into injector 1 is leaking. It's not on correctly, and I think air is getting into the line. It's having a real hard time starting (I have to crank it almost until the battery dies... not all at once, but in 30 second intervals), and as it starts it blows out a lot of smoke, but once it starts it runs fine (no smoke). However, it like so sputter at stop lights, so I have to keep my foot on the accelerator to keep the RPM up. I think IDIoit's hunch might be correct, however, I think there's still something wrong with the IP. I'm about to go fix that leaky injection line and I'll see what that does. It might just be air in the lines all along, but the timing could use an adjustment, so I'll look at that as the next step.

 

Have you let atf or diesel kleen sit in the pump overnight yet? If so do, it can't hurt. Hard starts followed by running fine is air intrusion. Which by the looks of the return line cap it appears you have. Does the crank time increase based on time that it's parked?

Is the injector line nut on square? Unless it is cross threaded at an angle it can only leak because it's loose.

 

I put diesel kleen in every fill up. The crank time *is* based on how long it sits. If it's overnight, it takes a long time to crank. If I'm driving around, and stop at a store, it will start right back up, albeit very roughly and I have to floor the pedal to keep it going once it catches.

I ended up not being able to fix it today, but I'm going to readjust that nut on the injector line tomorrow. No, it's not on square, but it's tight, so I'm not sure if it's broken. I'll have to loosen it and see. It's definitely leaking though.

The thing that's stumping me the most is the fact that the symptoms have changed significantly over the past two weeks. It went from running alright, but smoking a lot, to not smoking at all but hard starting (and long cranking) and sputtering at lights (which is getting worse every day). I know there's definitely air in the line, and that will be fixed tomorrow, but I'm going to take the truck on a 1400 mile trip soon, and I'm worried about the IP and lift pump. I know a bad lift pump can kill the IP. From the smoke, and just the smell of the exhaust, you can tell it's just dumping fuel into the engine and not burning everything, so I'm thinking the IP is going out anyway? The chugging and sputtering at lights could be an indication of air in the line, but they could also be indicating a bad fuel supply somewhere... and the only real options besides air intrusion is a worn out lift pump/IP. Considering the air, it's still pretty bad, and only one injector is leaking. 1 injector of 8 shouldn't be enough to kill the engine without stomping the pedal.

Tomorrow I'm going to fix the injector line and bleed the system again. If that doesn't solve all the problems, I'll have to look at replacing the pump. It has 161k miles of hard towing, so it's not the worst idea. And the lift pump is $20, so there's no real harm in replacing that too... The lift pump, btw, is extremely dirty. It's caked in grime and fuel/oil. Like, caked.... it's a ball of grime, you can't even really see the pump because it's so covered. I'd be surprised if it wasn't leaking a bit of fuel.

 

Unfortunately if the line isn't on square then the threads are probably fubar and depending on how bad need rethreaded or injector replaced.

If you're going on a long trip I'd pick up aa new/rebuilt pump from a good store, not a chain store. Also I'd drop some money on a good electric fuel pump, delete the mechanical and be happy. The e-pump can bleed the system without stressing batteries, starter, wires, etc. If you have the money I'd throw new/rebuilt injectors in as well. This will give you a good running truck, peace of mind, and reliability.

 

I'm not looking to keep the truck. I have 3 trucks, so I'm trying to get rid of two, this being one of them. So, I don't want to spend a lot of extra money upgrading. The next owner can do that.

However, the injection line was on square, so I just tightened it... and there doesn't seem to be anymore air intrusion. It starts up with much less smoke. However, I think the lift pump is bad and/or the IP is about to go out. It drives fine when my foot is on the pedal, but when it idles for a while (at a light) it still sputters, and upon further listening, there are some funny sounds coming form the engine at the time it starts to sputter... almost like an electrical buzz or whir. I'm just going to replace the lift pump for starters, then work my way to the IP.