7.3 IDI NA White smoke and misfiring on cold start and under load

[AmboIDI]

Hello fine petroleum burning strangers of the internet. Avid reader and first time poster here. Hoping that all you well seasoned folk can help a newbie out with a rather sticky issue I've encountered.

I have a 1994 E350 Ambulance with a 7.3l IDI (relatively new to me) that recently started misfiring under load accompanied with white/blue smoke to match the misfires. It also has become hard(er than before) starting when cold and once its starts it pukes white smoke and runs quite rough for 30-60 seconds depending on the temps. It'll blow some white/blue smoke driving around until it gets up to operating temp. Once its warm it idles and rolls around town with no troubles or smoke until you punch it.

I have within the last 6 months replaced the GP's, controller (which I hard wired to a momentary switch), replaced the injectors and turned down the IP (which was cranked to the moon) by 2 flats, new batteries and a new starter.

Before this issue arose it was pretty hard starting when cold in lower temps(under 30deg) even with all the new additions (worn out IP?). Also at high elevation (above 7000ft) it would blow black smoke when under a heavier load.

The misfire started after a particularly rough hill climb that involved a lot of black smoke for an extended period of time(about 5 miles). Not the best practice I know. I don't have a pyro but I'm sure the egts were above the recommended daily dose.

I'm suspecting either the IP is wearing out and the timing is off, or I have an exhaust valve or a valve guide that is not working properly. What do all of you figure? I want to do a compression test but don't have the proper tools or a shop I can trust for sure near me.

I am currently in Steamboat Colorado at the moment but am on a road trip from Canada so I don't have anywhere to work on this that's not a parking lot. Naturally I'm looking for reputable mechanics or a shop within a couple hundred miles at most that I can work in. I have some tools with me but not everything I need.

Any help/information you guys might have is greatly appreciated! Thanks for tuning in.

Bill

 

[BrianX128]

Where did you get the parts you have replaced? mainly the injectors. Timing could be off, you could have air getting in the system pre-ip causing some of the "misfiring" issues hence what you said with it running ok until you punch it and it runs out of fuel and the air starts getting in.

 

[AmboIDI]

I got everything off of Rock Auto. Delphi injectors and beru plugs.
Could I check if there is air getting in the fuel system with the Schrader valve that's before the IP?

 

[BrianX128]

Yeah but if your only getting some bubbles of air that effects it at wide open throttle it will be hard to tell without replacing a portion of fuel line with clear line to see the bubbles.

Do you still have a stock fuel system ie mechanical fuel pump on side of engine pumping fuel up to the fuel filter and steel line from there to the IP?

 

[Oledirtypearl86]

When is the last time you changed you fuel filter also what is your route if your heading north through Montana I'm west of Bozeman I'm in Whitehall

 

[Macrobb]

You changed your injectors with ones that aren't worn. This means that instead of the pump trying to push into, say, 1200psi, it's pushing into 1800 PSI. This obviously retards the timing much more than it was before(which was retarded).

Get a new IP and time it correctly. Good timing is the single most important part of making an IDI run good.

Alternately, you can pry up the IP cover and "skip" the IP gear forward a tooth to give an extra 7 degrees of advance. In a pinch, this works decently well. Just make sure to only skip it one tooth, mark where you are at and go from there. I've posted about how to do this before.

 

[AmboIDI]

Steel lines to and from the fuel filter but I'm not too sure where the lift pump lives so I don't know if its stock or not. I imagine it is though. Do you know where the lift pump is on the e series idis?

The plan is to head south and west actually. Eventually I'll be up in that neck of the woods but not for a couple months!

 

[AmboIDI]

I have not changed the fuel filter since I've owned it. Seems like a logical starting point that certainly cant hurt!

I'm not sure its air in the fuel line because that wouldn't cause a smokey unburnt fuel flavor of misfire would it?

As for the IP I might give the timing a go unless I can track down a good IP for a decent price in the next couple days here. I'm sitting at ~190k miles so it is probably due anyhow.

 

[Oledirtypearl86]

Macrobb is right timing might be retarded a little and the lift pump is on the passenger side front of the engine will me goldish if not smothered in oil and .Pretty easy swap 2 bolts and 2 fuel lines

 

[Oledirtypearl86]

~190k miles so it is probably due anyhow.

Usually 100k miles is life of IP on thease

 

[Oledirtypearl86]

Pic of lift pump front pass side of motor

You must be registered for see images attach

 

[AmboIDI]

Right on. I'll definitely be swapping the fuel filter. For the moment I'll give advancing the timing on the IP a go to hopefully get it running better until I'm in the right spot to swap it out.

Anybody know of or have a good shop in CO??

 

[AmboIDI]

Definitely the mechanical lift pump. Thanks for the pic!

 

[Oledirtypearl86]

Not sure of any shops in Co if your heading south to Texas might be worth a shot to talk to Wes aka @Thewespaul he rebuilds them pretty sure he will be on later or tomorrow but there are other members here on ob from Co ohoh the is a shop in aroura co I can't remember the name been a few years but it will come to me tonight hopefully .

 

[Christian9112]

Replace the stock lift pump and avoid the head ache. I have a class 3 ambulance. It also came with the smoke and hard starting. First i replaced all the parts that injected air to the system. Installed a black holley pump with adjustable voltage for pressure. Then replaced all the injectors. old ones were popping at 1800 psi. new ones popped higher. smoked a lot more. I advanced the timing as much as I could 1/16 at a time until the white smoke disappeared at idle. It smokes black uphill when I lay the hammer down. then I got a pyro and found out it was going above 1200f. It starts like a dream now.