mfi putting gas in my oil?

racemor · 02-04-2004, 07:32 AM

Hey guys, I'm having a problem that seems to be gas mixing with my oil. I read the thread below and my symptoms seem exactly the same as tspringer's:

Gasoline in the oil ! Help !

Before the problem started the warm up regulator on the pump had been cleaned for the first time in who knows how long. It was completely stuck together according to my mechanic. I know this could easily create a situation where the car is running rich now, which according to this thread, could be causing the oil/gas problem.

Has anyone else besides Terry and myself had this problem? I think at this point the course of action is to change the oil, lean the motor out some and see what happens. Any better ideas?

Zeke · 02-04-2004, 07:50 AM

I didn't do the link, so I might be a little off base here. To me, there are 2 ways for gas to get in the oil. One is by gas getting by the MFI pump pistons and being picked up by the oil circulating throught he pump. The other is by gas getting past the rings.

On the second one, it seems as if it would take a serious flooding situation for gas to pass the rings and get into the oil. Not that it doesn't happen, but your car would have some serious runnnig problems. That's way rich for enough of the gas not burning to be pushed passed the rings and drip into the sump. This would not be a good thing for your cyls.

I had the pump problem and it dumped a fair amount of gas into the oil. The motor had been idle for a few years. At Tyson's advice, along with a couple others, I ran it hard for a decent time (say 20 miles) a few times and it got much better. I still monitor the oil for gas. And I always run the car to very warm, if not hot, and for at least a few miles to evaporate the gas and water in the oil. Just good practice.

Tspringer · 07:57 AM

My problem is still not fixed. Of coarse I have not run the car in 6 months since Im doing tons of suspension work to it.

I used a Gunson gas tester on mine to test how rich it was running. At idle when warm, it was around 5% - 6%. At 3000rpm it was around 15%. Now 15% is way too high and I am going to adjust the MFI to bring that back in line, but 15% is not rich enough to cause fuel washing past the rings in a quantity to actually raise the oil level significantly in less than 1000 miles.

The only real explanation I came up with was a leaky injector. The MFI injectors "fire" at very high pressure. If an injector or two were messed up and leaky, they could be dripping fuel into the combustion chamber all the time. This fuel would wash past the rings on the non-compression stroke and into the oil. Then under the high pressure it fires fine. Thus, the car runs great but is dumping fuel into the oil.

I bought all new injectors. When I get it running again, Ill post on whether this fixed the problem or not. If not.... Im really going to be stumped!

Zeke...... on my car the MFI pump does not share oil with the engine. Racing style, that connection has been removed. Gus at Pacific Fuel injection told me he actually prefers this setup. Apparently the oil feed to the pump is very low pressure anyway. Gus said just change the pump oil every 50K miles or so and dont worry about it. So, that leaves only oil going past the rings as a possible explanation on my car. The question is how and why?

Terry

Zeke · 02-04-2004, 07:59 AM

Good point about the leaky injector. Still, it seems that the residual gas in the one cylinder would cause that cylinder to run very rich nad foul the plug. Which brings us to the next question, how are the plugs?

racemor · 02-04-2004, 09:46 AM

Zeke, I need to check the plugs again.

Another part of the story that might have something to with it is this. Back in December when the warm-up regulator was fixed there was a big scare when the #3 cylinder was not showing any compression. When my mechanic called to tell me I told him that he must be wrong, the car was not running well, but not nearly that bad. He check again and now there WAS compression. We were both stumped until he figured that there was a chunck of carbon or something holding a valve open. He put some Mavel Mystery oil in and everything seemed fine for a few weeks.

The car then went into the body shop in early January for a couple of weeks. When I picked it up, it smoked like crazy for a couple of miles. Then it stopped and the oil level on the meter was pegged, which it never is. I thought that someone was being "helpful" and added oil when it was not needed but they said no. I checked the level when the car was good and warm and it showed just past the full mark. The oil seemed thin and smelled a little of gas. I've not driven it since.

zotman72 · 02-04-2004, 10:06 AM

This is a common and vexing problem with MFI. Gas in the oil can not be a good thing for bearing wear surfaces. Smelling gas in your oil tank or when you change your oil (you do change it yourself right?) is very unsettling. I saw it on my MFI T motor and on my current MFI S powerplant. Different pumps still the same situation. I am inclined to think that is the injectors leaking after shutdown. Warren (Sman) mentioned a means to clean injectors with ultrasound tank and Carb cleaner a couple years ago, I have yet to try that. I also have not sealed off my pumpline either. Two projects to try. However, I do change my oil about every 1500 miles now, even shorter during track season. HTH

Grady Clay · 02-04-2004, 10:15 AM

C’m on guys.

Every MFI tends to put gas in the oil in cold weather.

The two main issues are: Every time you start the car it should be driven and up to temperature for a sustained period. Everything in the system must be working properly; no drips, no runs, no errors.

Change the oil a LOT, particularly if you have a front cooler.

If the fuel were leaking in the pump (unlikely) it would overflow in your situation. I would recommend going back to the pressured oil stock plumbing and just change the oil more often. If you worry about your pump, put an in-line filter in the oil supply hose.

If there were leaky injectors then the issue would be hard starting when/after hot and poor idle.

Cold start solenoids have been known to stick in the open position or lag in closing. Could this be the problem?

Tom,
When the warm-up regulator was stuck (off?), could the mixture have been set rich to compensate? If so, it is now really rich on warm-up and the gas goes past the rings and dilutes the oil with fuel.
Milt,
The engine will run great with huge amounts of gas (way to rich) when cold and with clean (hot) sparkplugs. All that fuel washes off the oil film on the cylinder and passes (with the combustion gasses and water) into the sump.
Tom,
When you solve the problem, make sure you don’t have way too hot plugs that were used to mask the problem.

YES!
Re your latest post. The body shop probably started the car every time they moved it. Each time it got a cold-start shot and was running on the thermostat. It was NEVER brought up to temperature. Next time pay a little more and have them NEVER start it.

Best,
Grady

racemor · 02-04-2004, 12:39 PM

Grady, I did not think about them starting the car so often. That could have a lot to do with it. As for the oil changes, it is changed very often, 3000 or less. This oil change only has about 200 miles, it was changed at the same time as the warm-up regulator issue. And this is my 4th winter with the car and have not seen this happen before.

I tend to think you are right with the setting being too rich having compensated for the stuck regulator. That plus the cold and often start-ups would make for a bad combo, especially if the cold start is not working right. I'll look into the injector possibility if these adjustments don't help.

Thanks.