RV Engine blowing oil through exhaust.

[atpalmer]

I Have a 1987 Ford E350 chassis motorhome with the 7.5L Carburated engine with headers. On the last trip to Pismo Dunes the oil filter cracked and the oil pressure dropped while i limped it off the highway into a gas station. After I replaced the filter it ran fine with no noticable loss of power.

After the trip I replaced all the belts and did some electrical work. I left the smog pump unbelted because the mount cracked.

Since then I've only driven in and out of my driveway and it runs very rough at low rpm and black smoke pours out both exhaust pipes. It also blows a fine spray of black oil from each exhaust.

I'm guessing this means that the headgasket is bad or multple piston rings are leaking. Could it be something simpler like fouled plugs or misrouted spark plug wires?

Any help or troubleshooting points would be greatly appreciated.

Thanks.

[steveG]

As I understand it, the engine ran fine until you replaced the belts. Is that right? If so then go over all your work, install ALL the belts and see what it does. Black smoke is a fuel issue that is probably curable.

[atpalmer]

Do you think the oil spray could be fuel issue?
And yes it ran fine until i replaced the belts.
I also replaced the spark plugs before the last trip.

[steveG]

Sorry, I missed that part. Are you sure it's oil? It could be carbon and condensation. If it is oil then that's definitely not good.

The part I'm hung up on is the fact that it ran OK until you replaced the belts.

[atpalmer]

I am pretty sure its oil. It sprayed my patio furniture and I wiped it with my finger and looked just like the dipstick oil, but dirtier. I seem to remember that it ran rough until it warmed up before the belt work. But the oily smoke is new.

[FABRICATOR]

Fouled plugs or crossed plug wires won't send raw oil out the exhaust. I'd do a compression check and look for collapsed or stuck piston rings, collapsed valve springs, wasted valve guides or valve seals. Some engines can suck oil if an intake manifold gasket lets go.

[TNT race photo]

to much oil? how long has it been sitting

[atpalmer]

Last long trip was in July, since then its been run in and out of the driveway about once a month, not around the block or more.

Could it be that it was always leaking oil internally but now with some pistons not firing the oil isn't burning in the exhaust?

[amr126]

I could see your theory, but it would still belch black smoke with or without it being burnt. You could do a simple compression test to see if the rings are shot. I would pull the plugs for each cylinder and take a look. If ones pitch black and the others are fine, then you narrowed down the mystery. If they all well like the soaking in black crap then thats a good indication that oil is seeping into the cylinder. Overall, the first step would be to check the plugs. This would give you a chance to check your wiring while your at it.

[TNT race photo]

one bad spark plug.you may have valve guide seals problem or stuck lifter, first change plugs

[JEFFRPM]

The thing has a holly carb on it. when is the last time you FULLY warmed it up? If you have been just moving it in and out of the driveway for months it's loaded up pretty bad. If the floats are a little high, the power valve leaks, the choke sticks. Does your oil smell like gas? the "Oil" coming out the exaust is more than likley condensation and soot from the inside of your exaust system. warm the thing up drive it around for half hour or more. if it is oil you will be making more smoke than a crop duster.

[atpalmer]

Hasn't gone past 5 mph since july. The smoke isn't thick, but there are oil spots on the wall where i give it some gas while maneuvering.

I will start looking at the spark plugs. Can anyone recommend what compression gage to get? A couple of the spark plugs are extremely hard to get to.

[steveG]

Any compression tester will work. Even if it's not very accurate, you can at least see if the cylinders are even. If there is one cylinder that's way off then you know you have a problem

When I park my Bronco (carbureted) close to a wall, start it cold and let it idle (high cold-idle, condensation in the exhaust) it will leave black soot splattered all over the wall... in other words, I'm still not convinced what you've got coming out of the tailpipe is oil.

[bajaruner11]

This sounds like a classic case of excessive condensation in the exhaust, and possibly bad plugs, and an out of adjustment carb.
What you are seeing blowing out is most likely a mixture of black exhaust soot, condensation, and some oil build up in the top end
from not operating the engine at full temp, YUCK! Oil generally does not "splatter" out of an exhaust pipe unless you have a serious
failure, oil comes out as smoke.
Motorhomes have a very long exhaust system generally with large mufflers, by you starting it and stopping it without driving, you’re doing
doing more harm than good.
Every time you half way warm it up, then shut it down it builds more and more
condensation in the exhaust system and in the engine oil. Take off your oil cap and look down inside the hole, I would not be surprised if
it was all milky white with condensation from inadequate temps. Nevertheless the only way to burn off condensation in an engine and fully warm it up
is to go for a 30 minute drive down the freeway, up a hill is good too. This is to fully heat the oil and burn off excessive deposits from the valves and piston tops, while also
burning any garbage build up out of the exhaust pipes, just letting it run in the driveway until the water temp gauges says it's up to temp does nothing.
One more thing, if your engine is in fact burning oil the tell tale sign is hovering bluish colored smoke from the exhaust pipe, somewhat like the color of a two
stroke engine exhaust only a lot lighter in color.
Last thing check all your vacuum lines, it's easy to accidentally crack one while replacing belts. That could be the cause of the rough running.

[atpalmer]

I finally got to work on the engine. On closer inspection there was condesnation and soot blowing out the exhaust with some light smoke. I replaced the smog pump which eliminated the smoke. It still ran rough at idle and on the freeway. I checked compression, all cylinders were 100-120 psi. Spark plug routing was correct. The spark plugs were all very black and dry with soot.
I just rebuilt the carb this weekend. After the rebuild the engine starts much easier and doesn't stall at idle anymore and misses less. But it still blows a lot of soot and coats the sparkplugs and runs rough. It also still backfires & pops sometimes when I floor it. The popping is heard in the carb area. on the rebuild I maintained the prior setting for the idle screws and other adjustments. I think as this point it may just need to be tuned.

Can anyone recommend a shop that can tune it in the Pomona, Upland area?

[Ol' Curmudgeon]

Before you take it in, try decarbonizing the motor by slowly and carefully pouring water into the carb as you work the throttle with the motor running. IIRC, it used to take Dad about 10-12 oz, and about 15 minutes on his old 312. It will make a ton of smoke, more than an old smudge pot.

As to the popping, I think you may have a faulty power valve or leaking accelerator pump, but I've forgotten more than I knew when it comes to carbs. Good luck, the closest shop I can recommend is MD Automotive in beautiful downtown Riverside. Talk to Darol or Kirk over there (951)781-7728.

[Camperdave]

The water trick does work - but make sure the engine is at full operating temperature. The idea is the hot carbon deposits on the valves and pistons will "shatter" so to speak and blow out the exhaust as cold water is applied. Just slowly trickle the water through both front carb venturies while holding the gas above idle. Did you replace the power valve? When you pull one of the float bowls off, there is a metering block between it and the carb body. The power valve screws right into the center of the metering block. Often times - over the years - carb kit manufacturers have started supplying only one valve for all kits. Motorhomes do not like this universal approach. Cams in these engines have very different vacuum characteristics than a standard truck engine. The power valve has a number stamped on it - may want to compare to new valve. If different, this could be the cause. (assuming the back fire was not there before)

[FABRICATOR]

Before you take it in, try decarbonizing the motor by slowly and carefully pouring water into the carb as you work the throttle with the motor running. IIRC, it used to take Dad about 10-12 oz, and about 15 minutes on his old 312. It will make a ton of smoke, more than an old smudge pot.

As to the popping, I think you may have a faulty power valve or leaking accelerator pump, but I've forgotten more than I knew when it comes to carbs. Good luck, the closest shop I can recommend is MD Automotive in beautiful downtown Riverside. Talk to Darol or Kirk over there (951)781-7728.

Oh no. I thought that ended for good at least 25 years ago. 10-12 ounces?? I had a friend who did that to his 455 Trans-Am and his 455 flat bottom, quite often. I'm not kidding, with some throttle, it would ingest all you could get from a wide open garden hose. I was never convinced it did any good. Not recommended.

If all else is right, back firing when you tromp on it is almost always an indication of retarded timing.

Strange that hooking up the smog pump would stop the smoking. Time to send it out.

[Ol' Curmudgeon]

Oh no. I thought that ended for good at least 25 years ago. 10-12 ounces??

Well, Dad did get rid of the 312 in early '64. He usually used Mom's 10oz Pepsi bottle, but sometimes a 12oz Coke bottle. He was convinced it was to the good, not sure that the neighbors did. And it's hard for me remember since the coma in '68 and a few concussions since.:confused:

[HardCharger81]

My old man used to do what he called an "Okie Rebuild".

He'd take a Pepsi can full of diesel, and have me, at 7 or 8 years old, start the truck and run it wide open till he was done pouring the diesel down the carb.

Those old government Dodge's always seemed to run better after that. ;)

[Camperdave]

Fabricator is right - the water trick is antiquated. Definetly don't try it on a newer vehicle. Tight tolerances, aluminum heads, sensors, etc. won't like it. Another thought if you haven't taken this to a shop, could be an EGR problem. Could try disconnecting the vacuum hose to the valve and road test - see if the pop goes away.

[JEFFRPM]

Sounds like flat cam to me they will compression test and leakdown test fine but when running they will pop out the intake. also sticky valve guide will do it also.

[arqangel67]

get some top engine cleaner from the dealership if ford has it i know chevy does and pour it down the carb also if it does have sticky valve go to autozone and pick up some motorflush it works and the change your oil of course . hoped this helps ,good luck!:D